[ { "id": "authors:fe1qr-prx57", "collection": "authors", "collection_id": "fe1qr-prx57", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170213-162656555", "type": "article", "title": "Intermediate-mass Asymptotic Giant Branch Stars and Sources of ^(26)Al, ^(60)Fe, ^(107)Pd, and ^(182)Hf in the Solar System", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Karakas", "given_name": "Amanda I.", "orcid": "0000-0002-3625-6951", "clpid": "Karakas-A-I" }, { "family_name": "Lugaro", "given_name": "Maria", "clpid": "Lugaro-M" } ], "abstract": "We explore the possibility that the short-lived radionuclides ^(26)Al, ^(60)Fe, ^(107)Pd, and ^(182)Hf inferred to be present in the proto-solar cloud originated from 3\u20138 M_\u2299 asymptotic giant branch (AGB) stars. Models of AGB stars with initial mass above 5 M_\u2299 are prolific producers of ^(26)Al owing to hot bottom burning (HBB). In contrast, ^(60)Fe, ^(107)Pd, and ^(182)Hf are produced by neutron captures: ^(107)Pd and ^(182)Hf in models \u227e 5 M_\u2299, and ^(60)Fe in models with higher mass. We mix stellar yields from solar-metallicity AGB models into a cloud of solar mass and composition to investigate whether it is possible to explain the abundances of the four radioactive nuclides at the Sun's birth using one single value of the mixing ratio between the AGB yields and the initial cloud material. We find that AGB stars that experience efficient HBB (\u2265 6 M_\u2299) cannot provide a solution because they produce too little ^(182)Hf and ^(107)Pd relative to ^(26)Al and ^(60)Fe. Lower-mass AGB stars cannot provide a solution because they produce too little ^(26)Al relative to ^(107)Pd and ^(182)Hf. A self-consistent solution may be found for AGB stars with masses in between (4\u20135.5 M_\u2299), provided that HBB is stronger than in our models and the ^(13)C(\u03b1, n)^(16)O neutron source is mildly activated. If stars of M < 5.5 M_\u2299 are the source of the radioactive nuclides, then some basis for their existence in proto-solar clouds needs to be explored, given that the stellar lifetimes are longer than the molecular cloud lifetimes.", "doi": "10.3847/1538-4357/836/1/126", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2017-02-10", "series_number": "1", "volume": "836", "issue": "1", "pages": "Art. No. 126" }, { "id": "authors:sr8sm-fgr37", "collection": "authors", "collection_id": "sr8sm-fgr37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170105-083356029", "type": "article", "title": "Effects of the s-process on Fe-group elements in meteorites", "author": [ { "family_name": "Trippella", "given_name": "O.", "clpid": "Trippella-O" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Palmerini", "given_name": "S.", "clpid": "Palmerini-S" }, { "family_name": "Frondini", "given_name": "F.", "clpid": "Frondini-F" }, { "family_name": "Petrelli", "given_name": "M.", "clpid": "Petrelli-M" }, { "family_name": "Zucchini", "given_name": "A.", "clpid": "Zucchini-A" } ], "abstract": "In the present paper we investigate the possible connection between s-process nucleosynthesis occurring during the asymptotic giant branch (AGB) phase of low-mass stars (LMS) and the isotopic anomalies of the \"Fe-group\" elements observed in several macroscopic samples of meteorites or in grains formed as circumstellar condensates (hereafter CIRCONs). The available measurements of chromium, iron, and nickel are well reproduced by stellar models, which account for the largest shifts in the heaviest isotopes of each element: in particular ^(54)Cr, ^(58)Fe, and ^(64)Ni. Moreover, many circumstellar condensates reflect ^(50)Ti excesses and some production of ^(46, 47, 49)Ti, as predicted by slow-neutron captures in AGB stars. Nevertheless, some difficulties are found in comparing theoretical calculations of s-process nucleosynthesis with calcium, silicon, and zinc isotopic anomalies.", "doi": "10.1088/1742-6596/703/1/012027", "issn": "1742-6588", "publisher": "IOP Publishing", "publication": "Journal of Physics: Conference Series", "publication_date": "2016-04-14", "volume": "703", "pages": "Art. No. 012027" }, { "id": "authors:g1v28-jm808", "collection": "authors", "collection_id": "g1v28-jm808", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151106-151257984", "type": "article", "title": "In memory of Ernst Kunibert Zinner (1937\u20132015)", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The death of Ernst Kunibert Zinner brings great sadness to the community of cosmochemists and astrophysicists. He pioneered the isotopic and chemical study of grains formed in ejecta from very diverse stars that exploded before the Solar System formed. The identification of the chemical compounds, which he found in grains of circumstellar condensates, and their isotopic compositions has permitted great advances in our understanding of stellar nucleosynthesis. Ernst Zinner was Research Professor at Washington University, where he was supported by research grants from NASA and some from the NSF.", "doi": "10.1016/j.gca.2015.10.002", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2016-02-01", "volume": "174", "pages": "362-364" }, { "id": "authors:wxjyx-mx827", "collection": "authors", "collection_id": "wxjyx-mx827", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150828-160513973", "type": "article", "title": "Forsterite-Bearing Type B CAI with a Relict Eringaite-Bearing Ultra-Refractory CAI", "author": [ { "family_name": "Krot", "given_name": "A. N.", "orcid": "0000-0002-2278-8519", "clpid": "Krot-A-N" }, { "family_name": "Nagashima", "given_name": "K.", "clpid": "Nagashima-K" }, { "family_name": "Ma", "given_name": "C.", "orcid": "0000-0002-1828-7033", "clpid": "Ma-Chi-Geology" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Forsterite-bearing Type B (FoB) Ca,Al-rich\ninclusions (CAIs) are a rare type of coarse-grained igneous CAIs\nfound almost exclusively in CV3 chondrites [1\u20135]. Here we\ndescribe the mineralogy, petrography, and oxygen-isotope\ncompositions of a FoB CAI Al-2 from Allende containing a relict\neringaite-bearing ultra-refractory (UR) inclusion. Eringaite is a\nSc-rich garnet [Ca_3(Sc,Y,Ti)_2Si_3O_(12)] that has been recently\nidentified in a cluster of UR inclusion fragments within an\namoeboid olivine aggregate in Vigarano [6].", "doi": "10.1111/maps.12501", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2015-08", "series_number": "S1", "volume": "50", "issue": "S1", "pages": "Art. No. 5308" }, { "id": "authors:1k4ab-nbg02", "collection": "authors", "collection_id": "1k4ab-nbg02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150514-073838250", "type": "article", "title": "Isotope Anomalies in the Fe-group Elements in Meteorites and Connections to Nucleosynthesis in AGB Stars", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Trippella", "given_name": "O.", "clpid": "Trippella-O" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" } ], "abstract": "We study the effects of neutron captures in AGB stars on \"Fe-group\" elements, with an emphasis on Cr, Fe, and Ni. These elements show anomalies in ^(54)Cr, ^(58)Fe, and ^(64)Ni in solar system materials, which are commonly attributed to supernovae (SNe). However, as large fractions of the interstellar medium (ISM) were reprocessed in AGB stars, these elements were reprocessed, too. We calculate the effects of such reprocessing on Cr, Fe, and Ni through 1.5 M\u2299 and 3 M\u2299 AGB models, adopting solar and 1/3 solar metallicities. All cases produce excesses of ^(54)Cr, ^(58)Fe, and ^(64)Ni, while the other isotopes are little altered; hence, the observations may be explained by AGB processing. The results are robust and not dependent on the detailed initial isotopic composition. Consequences for other \"Fe group\" elements are then explored. They include ^(50)Ti excesses and some production of ^(46,47,49)Ti. In many circumstellar condensates, Ti quantitatively reflects these effects of AGB neutron captures. Scatter in the data results from small variations (granularity) in the isotopic composition of the local ISM. For Si, the main effects are instead due to variations in the local ISM from different SN sources. The problem of Ca is discussed, particularly with regard to ^(48)Ca. The measured data are usually represented assuming terrestrial values for ^(42)Ca/^(44)Ca. Materials processed in AGB stars or sources with variable initial ^(42)Ca/^(44)Ca ratios can give apparent ^(48)Ca excesses/deficiencies, attributed to SNe. The broader issue of galactic chemical evolution is also discussed in view of the isotopic granularity in the ISM.", "doi": "10.1088/0004-637X/805/1/7", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2015-05-20", "series_number": "1", "volume": "805", "issue": "1", "pages": "Art. No. 7" }, { "id": "authors:fgb9c-10f33", "collection": "authors", "collection_id": "fgb9c-10f33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141219-130341226", "type": "article", "title": "Calcium-aluminum-rich inclusions with fractionation and unknown nuclear effects (FUN CAIs): I. Mineralogy, petrology, and oxygen isotopic compositions", "author": [ { "family_name": "Krot", "given_name": "Alexander N.", "orcid": "0000-0002-2278-8519", "clpid": "Krot-A-N" }, { "family_name": "Nagashima", "given_name": "Kazuhide", "clpid": "Nagashima-K" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Papanastassiou", "given_name": "Dimitri A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Davis", "given_name": "Andrew M.", "clpid": "Davis-A-M" }, { "family_name": "Hutcheon", "given_name": "Ian D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Bizzarro", "given_name": "Martin", "clpid": "Bizzarro-M" } ], "abstract": "We present a detailed characterization of the mineralogy, petrology, and oxygen isotopic compositions of twelve FUN CAIs, including C1 and EK1-4-1 from Allende (CV), that were previously shown to have large isotopic fractionation patterns for magnesium and oxygen, and large isotopic anomalies of several elements. The other samples show more modest patterns of isotopic fractionation and have smaller but significant isotopic anomalies. All FUN CAIs studied are coarse-grained igneous inclusions: Type B, forsterite-bearing Type B, compact Type A, and hibonite-rich. Some inclusions consist of two mineralogically distinct lithologies, forsterite-rich and forsterite-free/poor. All the CV FUN CAIs experienced postcrystallization open-system iron-alkali-halogen metasomatic alteration resulting in the formation of secondary minerals commonly observed in non-FUN CAIs from CV chondrites. The CR FUN CAI GG#3 shows no evidence for alteration. In all samples, clear evidence of oxygen isotopic fractionation was found. Most samples were initially ^(16)O-rich. On a three-oxygen isotope diagram, various minerals in each FUN CAI (spinel, forsterite, hibonite, dmisteinbergite, most fassaite grains, and melilite (only in GG#3)), define mass-dependent fractionation lines with a similar slope of \u223c0.5. The different inclusions have different \u0394^(17)O values ranging from \u223c\u221225\u2030 to \u223c\u221216\u2030. Melilite and plagioclase in the CV FUN CAIs have ^(16)O-poor compositions (\u0394^(17)O \u223c\u22123\u2030) and plot near the intercept of the Allende CAI line and the terrestrial fractionation line. We infer that mass-dependent fractionation effects of oxygen isotopes in FUN CAI minerals are due to evaporation during melt crystallization. Differences in \u0394^(17)O values of mass-dependent fractionation lines defined by minerals in individual FUN CAIs are inferred to reflect differences in \u0394^(17)O values of their precursors. Differences in \u03b4^(18)O values of minerals defining the mass-dependent fractionation lines in several FUN CAIs are consistent with their inferred crystallization sequence, suggesting these minerals crystallized during melt evaporation. In other FUN CAIs, no clear correlation between \u03b4^(18)O values of individual minerals and their inferred crystallization sequence is observed, possibly indicating gas-melt back reaction and oxygen-isotope exchange in a ^(16)O-rich gaseous reservoir. After oxygen-isotope fractionation, some FUN CAIs could have experienced partial melting and gas-melt oxygen-isotope exchange in a ^(16)O-poor gaseous reservoir that resulted in crystallization of ^(16)O-depleted fassaite, melilite and plagioclase. The final oxygen isotopic compositions of melilite and plagioclase in the CV FUN CAIs may have been established on the CV parent asteroid as a result of isotope exchange with a ^(16)O-poor fluid during hydrothermal alteration. \nWe conclude that FUN CAIs are part of a general family of refractory inclusions showing various degrees of fractionation effects due to evaporative processes superimposed on sampling of isotopically heterogeneous material. These processes have been experienced both by FUN and non-FUN igneous CAIs. Generally, the inclusions identified as FUN show larger isotope fractionation effects than non-FUN CAIs. There is a wide spread in UN isotopic anomalies in a large number of CAIs not exhibiting large fractionation effects in oxygen, magnesium, and silicon. The question of why some FUN CAIs show more extreme UN isotopic effects is attributed by us to limited sampling and not a special source of isotopically anomalous material. We consider the majority of igneous CAIs to be the result of several stages of thermal processing (evaporation, condensation, and melting) of aggregates of solid precursors composed of incompletely isotopically homogenized materials. The unknown nuclear effects in CAIs are common to both FUN and non-FUN CAIs, and are not a special characteristic of FUN inclusions but represent the spectrum of results from sampling a very heterogeneous medium in the accreting Solar System.", "doi": "10.1016/j.gca.2014.09.027", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2014-11-15", "volume": "145", "pages": "206-247" }, { "id": "authors:q944h-vtd38", "collection": "authors", "collection_id": "q944h-vtd38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131213-114705797", "type": "article", "title": "Short lived ^(36)Cl and its decay products ^(36)Ar and ^(36)S in the early solar system", "author": [ { "family_name": "Turner", "given_name": "G.", "clpid": "Turner-G" }, { "family_name": "Crowther", "given_name": "S. A.", "clpid": "Crowther-S-A" }, { "family_name": "Burgess", "given_name": "R.", "clpid": "Burgess-R" }, { "family_name": "Gilmour", "given_name": "J. D.", "clpid": "Gilmour-J-D" }, { "family_name": "Kelley", "given_name": "S. P.", "clpid": "Kelley-S-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Variable excesses of ^(36)S have previously been reported in sodalite in the Allende and Ningqiang meteorites and used to infer the presence of ^(36)Cl in the early solar system. Until now no unambiguous evidence of the major decay product, ^(36)Ar (98%), has been found. Using low fluence fast neutron activation we have measured small amounts of ^(36)Ar in the Allende sodalite Pink Angel, corresponding to ^(36)Cl/^(35)Cl = (1.9 \u00b1 0.5) \u00d7 10^(\u22128). This is a factor of 200 lower than the highest value inferred from ^(36)S excesses in sodalite. High resolution I\u2013Xe analyses confirm that the sodalite formed between 4561 and 4558 Ma ago. The core of Pink Angel sodalite yielded a precise formation age of 4559.4 \u00b1 0.6 Ma. Deposition of sodalite containing live ^(36)Cl, seven million years or so after the formation of the CAI, appears to require a local production mechanism involving intense neutron irradiation within the solar nebula. The constraint imposed by the near absence of neutron induced ^(128)Xe is most easily satisfied if the ^(36)Cl were produced in a fluid precursor of the sodalite. The low level of ^(36)Ar could be accounted for as a result of residual in-situ ^(36)Cl decay, up to 1\u20132 Ma after formation of the sodalite, and/or later diffusive loss, in line with the low activation energy for Ar diffusion in sodalite.", "doi": "10.1016/j.gca.2013.06.022", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2013-12-15", "volume": "123", "pages": "358-367" }, { "id": "authors:mj3rw-02g28", "collection": "authors", "collection_id": "mj3rw-02g28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131206-093814685", "type": "article", "title": "Heterogeneity of Mg Isotopes and Variable ^(26)Al/^(27)Al Ratio in FUN CAIs", "author": [ { "family_name": "Park", "given_name": "C.", "clpid": "Park-C" }, { "family_name": "Nagashima", "given_name": "K.", "clpid": "Nagashima-K" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Davis", "given_name": "A. M.", "clpid": "Davis-A-M" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Krot", "given_name": "A. N.", "orcid": "0000-0002-2278-8519", "clpid": "Krot-A-N" } ], "abstract": "CAIs with fractionation and unidentified nuclear effects (FUN CAIs) are characterized by low initial ^(26)Al/^(27)Al ratios, large mass-dependent fractionation in Mg (F_(Mg)), Si, and O isotopes, and nucleosynthetic anomalies in several elements (e.g., Ca, Ti). Most Mg-isotope studies of FUN CAIs were performed more than 30 years ago with TIMS. Here we report high-precision Mg-isotope data of individual minerals from the Axtell 2271, BG82DH8, EK1-4-1, C1, TE, and CG14 FUN CAIs measured with the UH Cameca ims-1280. We followed the procedure described in [2]. Measured Mg-isotope data were correct-ed for fractionation using terrestrial standards assuming that their isotopic compositions are the same as values of [3], and an exponential law with a coefficient \u03b2 = 0.514. The overall conclusions of this study do not change with the choice of \u03b2.", "doi": "10.1111/maps.12165", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2013-07", "series_number": "S1", "volume": "48", "issue": "S1", "pages": "A277" }, { "id": "authors:qctff-tas65", "collection": "authors", "collection_id": "qctff-tas65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131025-151036188", "type": "article", "title": "Mg isotopic heterogeneity, Al-Mg isochrons, and canonical ^(26)Al/^(27)Al in the early solar system", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Wimpenny", "given_name": "Josh", "clpid": "Wimpenny-J" }, { "family_name": "Yin", "given_name": "Qing-Zhu", "clpid": "Yin-Q-Z" } ], "abstract": "There is variability in the Mg isotopic composition that is a reflection of the widespread heterogeneity in the isotopic composition of the elements in the solar system at approximately 100 ppm. Measurements on a single calcium-aluminum-rich inclusion (CAI) gave a good correlation of ^(26)Mg/^(24)Mg with ^(27)Al/^(24)Mg, yielding an isochron corresponding to an initial (^(26)Al/^(27)Al)_o = (5.27 \u00b1 0.18) \u00d7 10^(\u22125) and an initial (^(26)Mg/^(24)Mg)_o = \u22120.127 \u00b1 0.032\u2030 relative to the standard. This isochron is parallel to that obtained by Jacobsen et al. (2008), but is distinctively offset. This demonstrates that there are different initial Mg isotopic compositions in different samples with the same ^(26)Al/^(27)Al. No inference about uniformity/heterogeneity of ^(26)Al/^(27)Al on a macro scale can be based on the initial (^(26)Mg/^(24)Mg)_o values. Different values of ^(26)Al/^(27)Al for samples representing the same point in time would prove heterogeneity of ^(26)Al/^(27)Al. The important issue is whether the bulk solar inventory of ^(26)Al/^(27)Al was approximately 5 \u00d7 10^(\u22125) at some point in the early solar system. We discuss ultra refractory phases of solar type oxygen isotope composition with ^(26)Al/^(27)Al from approximately 5 \u00d7 10^(\u22125) to below 0.2 \u00d7 10^(\u22125). We argue that the real issues are: intrinsic heterogeneity in the parent cloud; mechanism and timing for the later production of ^(16)O-poor material; and the relationship to earlier formed ^(16)O-rich material in the disk. ^(26)Al-free refractories can be produced at a later time by late infall, if there is an adequate heat source, or from original heterogeneities in the placental molecular cloud from which the solar system formed.", "doi": "10.1111/maps.12014", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2012-12", "series_number": "12", "volume": "47", "issue": "12", "pages": "1980-1997" }, { "id": "authors:hdcsc-x1b53", "collection": "authors", "collection_id": "hdcsc-x1b53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120420-132643048", "type": "article", "title": "Supernova-driven outflows and chemical evolution of dwarf spheroidal galaxies", "author": [ { "family_name": "Qian", "given_name": "Yong-Zhong", "clpid": "Qian-Yong-Zhong" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a general phenomenological model for the metallicity distribution (MD) in terms of [Fe/H] for dwarf spheroidal galaxies (dSphs). These galaxies appear to have stopped accreting gas from the intergalactic medium and are fossilized systems with their stars undergoing slow internal evolution. For a wide variety of infall histories of unprocessed baryonic matter to feed star formation, most of the observed MDs can be well described by our model. The key requirement is that the fraction of the gas mass lost by supernova-driven outflows is close to unity. This model also predicts a relationship between the total stellar mass and the mean metallicity for dSphs in accord with properties of their dark matter halos. The model further predicts as a natural consequence that the abundance ratios [E/Fe] for elements such as O, Mg, and Si decrease for stellar populations at the higher end of the [Fe/H] range in a dSph. We show that, for infall rates far below the net rate of gas loss to star formation and outflows, the MD in our model is very sharply peaked at one [Fe/H] value, similar to what is observed in most globular clusters. This result suggests that globular clusters may be end members of the same family as dSphs.", "doi": "10.1073/pnas.1201540109", "pmcid": "PMC3324010", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2012-03-27", "series_number": "13", "volume": "109", "issue": "13", "pages": "4750-4755" }, { "id": "authors:65pnp-adb73", "collection": "authors", "collection_id": "65pnp-adb73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111005-101306666", "type": "article", "title": "Extremely Na- and Cl-rich chondrule from the CV3\n carbonaceous chondrite Allende", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Al\u00e9on", "given_name": "J.", "clpid": "Al\u00e9on-J" }, { "family_name": "Ramon", "given_name": "E. C.", "clpid": "Ramon-E-C" }, { "family_name": "Krot", "given_name": "A. N.", "orcid": "0000-0002-2278-8519", "clpid": "Krot-A-N" }, { "family_name": "Nagashima", "given_name": "K.", "clpid": "Nagashima-K" }, { "family_name": "Brearley", "given_name": "A. J.", "clpid": "Brearley-A-J" } ], "abstract": "We report on a study of Al3509, a large Na- and Cl-rich, radially-zoned object from the oxidized CV carbonaceous chondrite Allende. Al3509 consists of fine-grained ferroan olivine, ferroan Al-diopside, nepheline, sodalite, and andradite, and is crosscut by numerous veins of nepheline, sodalite, and ferroan Al-diopside. Some poorly-characterized phases of fine-grained material are also present; these phases contain no significant H_2O. The minerals listed above are commonly found in Allende CAIs and chondrules and are attributed to late-stage iron-alkali-halogen metasomatic alteration of primary high-temperature minerals. Textural observations indicate that Al3509 is an igneous object. However, no residual crystals that might be relicts of pre-existing CAI or chondrule minerals were identified. To establish the levels of ^(26)Al and ^(36)Cl originally present, ^(26)Al\u2013^(26)Mg and ^(36)Cl\u2013^(36)S isotopic systematics in sodalite were investigated. Al3509 shows no evidence of radiogenic ^(26)Mg\u2217, establishing an upper limit of the initial ^(26)Al/^(27)Al ratio of 3 \u00d7 10^(\u22126). All sodalite grains measured show large but variable excesses of ^(36)S, which, however, do not correlate with ^(35)Cl/^(34)S ratio. If these excesses are due to decay of ^(36)Cl, local redistribution of radiogenic ^(36)S\u2217 after ^(36)Cl had decayed is required. The oxygen-isotope pattern in Al3509 is the same as found in secondary minerals resulting from iron-alkali-halogen metasomatic alteration of Allende CAIs and chondrules and in melilite and anorthite of most CAIs in Allende. The oxygen-isotope data suggest that the secondary minerals precipitated from or equilibrated with a fluid of similar oxygen-isotope composition. These observations suggest that the formation of Al3509 and alteration products in CAIs and chondrules in Allende requires a very similar fluid phase, greatly enriched in volatiles (e.g., Na and Cl) and with \u0394^(17)O ~ \u22123\u2030. We infer that internal heating of planetesimals by ^(26)Al would efficiently transfer volatiles to their outer portions and enhance the formation of volatile-enriched minerals there. We conclude that the site for the production of Na- and Cl-rich fluids responsible for the formation of Al3509 and the alteration of the Allende CAIs and chondrules must have been on a protoplanetary body prior to incorporation into the Allende meteorite. Galactic cosmic rays cannot be the source of the inferred initial ^(36)Cl in Allende. The problem of ^(36)Cl production by solar energetic particle (SEP) bombardment and the possibility that ^(36)Cl and ^(41)Ca might be the product of neutron capture resulting from SEP bombardment of protoplanetary surfaces are discussed. This hypothesis can be tested comparing inferred \"initial\" ^(36)Cl with neutron fluencies measured on the same samples and on phases showing ^(36)S\u2217 by Sm and Gd isotopic measurements.", "doi": "10.1016/j.gca.2011.06.004", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2011-09-01", "series_number": "17", "volume": "75", "issue": "17", "pages": "4752-4770" }, { "id": "authors:pt4sm-fmx93", "collection": "authors", "collection_id": "pt4sm-fmx93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-091701431", "type": "article", "title": "Evidence for Extinct ^(36)Cl from Excess ^(36)Ar in Allende Sodalite", "author": [ { "family_name": "Turner", "given_name": "G.", "clpid": "Turner-G" }, { "family_name": "Burgess", "given_name": "R.", "clpid": "Burgess-R" }, { "family_name": "Kelley", "given_name": "S. P.", "clpid": "Kelley-S-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Introduction: Excesses of ^(36)S have previously been reported in sodalite (Na_8Al_6Si_6O_(24)Cl_2) and wadalite (Ca_6Al_5Si_2O_(16)Cl_3) in CAI andchondrules from the Allende and Ningqiang meteorites and used to infer the presence of ^(36)Cl (half-life 3 x 10^5 a) in the early solar system. In spite of the fact that ^(36)Cl decays predominantly (98%) to ^(36)Ar, all attempts to locate the very large amounts of ^(36)Ar implied by these ^(36)S excesses have been negative. Here we present results of a new method to identify ^(36)Ar from ^(36)Cl decay, based on low fluence fast neutron activation.", "doi": "10.1111/j.1945-5100.2011.01221.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2011-09", "series_number": "S1", "volume": "46", "issue": "S1", "pages": "A5103" }, { "id": "authors:wb5jj-r8g78", "collection": "authors", "collection_id": "wb5jj-r8g78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141106-110646817", "type": "article", "title": "Comment on \"AGU Statement: Investigation of Scientists and Officials in L'Aquila, Italy, Is Unfounded\"", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "In regard to the recent statement by AGU defending our Italian colleagues' statement on earthquake predictions (Eos, 91(28), 248, 13 July 2010), it is my view that there is something more positive that AGU might do than just defend our colleagues. The fundamental problem is that we cannot, with any reasonable certainty, predict earthquakes. This problem applies to many other areas as well. It follows that any statements scientists make should be moderated by that simple fact.", "doi": "10.1029/2010EO420006", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "2010-10-19", "series_number": "42", "volume": "91", "issue": "42", "pages": "384" }, { "id": "authors:yqc5z-6tb70", "collection": "authors", "collection_id": "yqc5z-6tb70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100806-080351974", "type": "article", "title": "^(40)K\u2013^(40)Ca isotopic constraints on the oceanic calcium cycle", "author": [ { "family_name": "Caro", "given_name": "G.", "clpid": "Caro-G" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The contributions of crustal silicates to the oceanic calcium cycle are investigated using high-precision ^(40)K\u2013^(40)Ca measurements in Archean and Proterozoic carbonates, river waters, and a series of terrestrial and extraterrestrial mafic/ultramafic samples. Using a multidynamic data collection scheme with strict controls on instrumental mass fractionation, we show that a reproducibility of 0.35 \u03b5-units (2\u03c3) is obtained for the ^(40)Ca/^(44)Ca ratio using the ThermoFinnigan Triton. This represents an improvement by a factor of 3 compared with previous generations of data. Well-defined excesses of ^(40)Ca from ^(40)K decay were found in river waters draining the Himalayas, but not in the Mississippi and Columbia Rivers. All marine carbonate samples ranging in age from Archean to recent show no discernable effects of ^(40)K decay to within the limit of \u00b1 0.35 \u03b5-units (2\u03c3) in ^(40)Ca/^(44)Ca. Our results, therefore, indicate that the Ca isotopic composition of seawater has remained constant and indistinguishable from that of the mantle for the past 3.5 Ga, despite the influx of radiogenic calcium delivered by weathering of the high K/Ca components of the continental crust. Thus, over most of geologic time, the contributions of the high K/Ca sources from the continents are far below the contributions of hydrothermal sources. Mass balance constraints indicate that unless the present-day contribution of continental silicates is much less than 8% of the river Ca flux, the total hydrothermal flux of calcium must exceed the input from high-temperature vents at ridge axes by at least one order of magnitude. The present-day oceanic mass balance requires a high input of calcium [(4\u201315) \u00d7 10^(12) mol Ca/yr] at low-temperature hydrothermal sites.", "doi": "10.1016/j.epsl.2010.05.001", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2010-07-15", "series_number": "1-2", "volume": "296", "issue": "1-2", "pages": "124-132" }, { "id": "authors:3nr0y-2eb24", "collection": "authors", "collection_id": "3nr0y-2eb24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100706-105934248", "type": "article", "title": "Ruthenium endemic isotope effects in chondrites and differentiated meteorites", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report on the abundances of Ru isotopes in (1) iron meteorites, (2) stony-iron meteorites (pallasites), (3) ordinary and carbonaceous chondrites, and (4) in refractory inclusions from the carbonaceous meteorite Allende. We have developed improved Multiple-Collector, Negative-ion Thermal Ionization Mass Spectrometric (MC-NTIMS) techniques for Ru, with high ionization efficiency of 4% and with chemical separation techniques for Ru, which reduce mass interferences to the ppm level, so that no mass interference corrections needed to be applied. Our data were normalized to ^(99)Ru/^(101)Ru to correct for mass-dependent fractionation. We find no Ru isotopic effects in the ordinary chondrites and group IAB iron meteorites we have measured. There are significant effects (deficits) in the pure s-process nuclide ^(100)Ru, in the Allende whole-rock and in refractory inclusions of up to 1.7 parts in 10,000 (\u03b5u). There are also endemic deficits in ^(100)Ru in iron meteorites and in pallasites of up to 1.1 \u03b5u. The Ru data suggest a wide spread and large scale heterogeneity in p-, s-, and r-process components resulting in a deficit in s-process nuclides or enhancements in both p- and r-process nuclides, in refractory siderophiles condensing in the early solar nebula. In contrast, the data on bulk Murchison suggest an excess in ^(100)Ru and in ^(104)Ru, which are distinct from the rest of the measured patterns. Our results establish the presence of significant isotopic heterogeneity for Ru in the early solar nebula. The observation of endemic Ru effects in planetary differentiates, such as iron meteorites and pallasites, must reflect the siderophile nature of Ru and the preservation in condensing FeNi metal of refractory metal condensate grains formed in the early solar nebula. Once incorporated in the metal phase, the refractory siderophiles remained in the metal phase through the melting and differentiation of planetesimals to form FeNi cores and silicate mantles and crusts.", "doi": "10.1016/j.gca.2010.04.013", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2010-07-01", "series_number": "13", "volume": "74", "issue": "13", "pages": "3851-3862" }, { "id": "authors:e2kts-1mq80", "collection": "authors", "collection_id": "e2kts-1mq80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-090456536", "type": "article", "title": "A ^(40)K-^(40)Ca perspective on the oceanic calcium cyle", "author": [ { "family_name": "Caro", "given_name": "G.", "clpid": "Caro-G" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "This study uses the decay of ^(40)K to ^(40)Ca to investigate the contributions of weathering and hydrothermal fluxes in the oceanic Ca budget. Because of its high K/Ca ratio, the silicate upper crust delivers radiogenic Ca to the oceans, while hydrothermal reactions deliver unradiogenic Ca from the mantle.", "doi": "10.1016/j.gca.2010.04.028", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2010-06", "series_number": "S12", "volume": "74", "issue": "S12", "pages": "A143" }, { "id": "authors:5v7vy-bcq31", "collection": "authors", "collection_id": "5v7vy-bcq31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141106-124437501", "type": "article", "title": "Ardis H. Nier, 1921\u20132009", "author": [ { "family_name": "Nier", "given_name": "Keith A.", "clpid": "Nier-K-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Ardis Hovland Nier died on December 16, 2009.\nArdis was a great friend of the Meteoritical Society and\nendowed its Nier Prize in celebration of the remarkable\ncontributions of Alfred Nier to meteorite research. She\nvery much enjoyed meeting many interesting and\nfriendly people at the society's meetings. She was by\nnature curious, intelligent, and good spirited, and she\ntried to find humor and optimism in whatever situation\nor condition she faced throughout her 88 years.", "doi": "10.1111/j.1945-5100.2010.01048.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2010-03", "series_number": "3", "volume": "45", "issue": "3", "pages": "447-448" }, { "id": "authors:15zf4-42y02", "collection": "authors", "collection_id": "15zf4-42y02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091013-105721958", "type": "article", "title": "Chemical Evolution of the Juvenile Universe", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Qian", "given_name": "Y. -Z.", "clpid": "Qian-Y-Z" } ], "abstract": "Models of average Galactic chemical abundances are in good general agreement with observations for [Fe/H] > \u20131.5, but there are gross discrepancies at lower metallicities. Only massive stars contribute to the chemical evolution of the 'juvenile universe' corresponding to [Fe/H] \u2272 \u20131.5. If Type II supernovae (SNe II) are the only relevant sources, then the abundances in the interstellar medium of the juvenile epoch are simply the sum of different SN II contributions. Both low-mass (~8\u201311 M_\u2299) and normal (~12\u201325 M_\u2299) SNe II produce neutron stars, which have intense neutrino-driven winds in their nascent stages. These winds produce elements such as Sr, Y and Zr through charged-particle reactions (CPR). Such elements are often called the 'light r-process elements', but are considered here as products of CPR and not the r process. The observed absence of production of the low-A elements (Na through Zn including Fe) when the true r-process elements (Ba and above) are produced requires that only low-mass SNe II be the site if the r process occurs in SNe II. Normal SNe II produce the CPR elements in addition to the low-A elements. This results in a two-component model that is quantitatively successful in explaining the abundances of all elements relative to hydrogen for \u20133 \u2272 [Fe/H] \u2272 \u20131.5. This model explicitly predicts that [Sr/Fe] \u2265 \u20130.32. Recent observations show that there are stars with [Sr/Fe] \u2272 \u20132 and [Fe/H] < \u20133. This proves that the two-component model is not correct and that a third component is necessary to explain the observations. The production of CPR elements associated with the formation of neutron stars requires that the third component must be massive stars ending as black holes. It is concluded that stars of ~25\u201350 M_\u2299 (possibly up to ~100 M_\u2299) are the appropriate candidates. These produce hypernovae (HNe) that have very high Fe yields and are observed today. Stars of ~140\u2013260 M_\u2299 are completely disrupted upon explosion. However, they produce an abundance pattern greatly deficient in elements of odd atomic numbers, which is not observed, and therefore they are not considered as a source here. Using a Salpeter initial mass function, it is shown that HNe are a source of Fe that far outweighs normal SNe II, with the former and the latter contributing ~24% and ~9% of the solar Fe abundance, respectively. It follows that the usual assignment of of the solar Fe abundance to normal SNe II is not correct. This leads to a simple three-component model including low-mass and normal SNe II and HNe, which gives a good description of essentially all the data for stars with [Fe/H] \u2272 \u20131.5. We conclude that HNe are more important than normal SNe II in the chemical evolution of the low-A elements from Na through Zn (including Fe), in sharp distinction to earlier models.", "doi": "10.1071/AS08058", "issn": "1323-3580", "publisher": "CSIRO Publishing", "publication": "Publications of the Astronomical Society of Australia", "publication_date": "2009-09-04", "series_number": "3", "volume": "26", "issue": "3", "pages": "184-193" }, { "id": "authors:8nxwa-32p77", "collection": "authors", "collection_id": "8nxwa-32p77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-142216849", "type": "article", "title": "Pink Angel: argon and xenon diffusion, I-Xe chronology, and the ^(36)Cl problem", "author": [ { "family_name": "Turner", "given_name": "G.", "clpid": "Turner-G" }, { "family_name": "Crowther", "given_name": "S. A.", "clpid": "Crowther-S-A" }, { "family_name": "Burgess", "given_name": "R.", "clpid": "Burgess-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Kelley", "given_name": "S. P.", "clpid": "Kelley-S-P" }, { "family_name": "Gilmour", "given_name": "J. D.", "clpid": "Gilmour-J-D" } ], "abstract": "The reported presence in Allende Pink Angel sodalite of excess ^(36)S [1] attributed to ^(36)Cl decay is at odds with the apparent absence of a corresponding excess of ^(36)Ar, which is the major decay product of ^(36)Cl. In an attempt to throw light on the problem we have reviewed new and existing data on the diffusion of Ar and Xe in sodalite, carried out new high resolution I-Xe analyses of Pink Angel, and devised a new methodology for searching for small excesses of ^(36)Ar from ^(36)Cl decay.", "doi": "10.1111/j.1945-5100.2009.tb01099.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2009-07", "series_number": "S7", "volume": "44", "issue": "S7", "pages": "A207" }, { "id": "authors:hv143-7vp13", "collection": "authors", "collection_id": "hv143-7vp13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-081956707", "type": "article", "title": "Citation for presentation of 2008 Nicholas J. Shackleton award to R. Lawrence Edwards", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Nick Shackleton is widely recognized for his major discoveries connecting the isotopic record preserved in foraminifera (Fig. 1) that grew in the oceans and the mass of ice\nstored in ice sheets during periods of continental glaciations. He was awarded the Crafoord Prize of the Royal Swedish Academy for his pioneering discoveries on glaciations & climate change (Fig. 2). In addition to his scientific accomplishments, Nick was an excellent musician and collected\nold instruments that are both played and greatly valued by musicians. Remarkably, the musical community\nknew him as a musician and had no idea of his scientific activities (Fig. 3).", "doi": "10.1016/j.gca.2009.05.036", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2009-06", "series_number": "13", "volume": "73", "issue": "13", "pages": "S15-S16" }, { "id": "authors:rcgad-4a652", "collection": "authors", "collection_id": "rcgad-4a652", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-084324522", "type": "article", "title": "Citation for presentation of the 2007 V.M. Goldschmidt Award to Guenter W. Lugmair", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Victor Moritz Goldschmidt is considered, along with V.I. Vernadsky, to be the founder of modern geochemistry. He was born in Zurich, Switzerland, in 1888, and died on his return from England to Oslo after World War II. Following on the compilation of elemental abundances in igneous rocks by Frank Wigglesworth Clarke, Goldschmidt sought the principles by which the chemical elements were distributed in minerals, igneous rocks, sedimentary rocks, the \"bulk earth\", and the \"cosmos\". He completed his PhD Thesis in 1911 on \"Die Kontact metamorphose in Kristiansgebeit\" (now Oslo) and at age 26 was appointed director of the Mineral Institute of Oslo (see Fig. 1). Goldschmidt had a deep understanding of theory and the necessity of good data with \"modern techniques\" on the right samples. He had quick recognition of the connections between different areas of science, of new developments (crystal structure, ionic radii!) and of new technologies, which he applied to a host of problems in the earth sciences. Goldschmidt was appointed Professor of Mineralogy and Petrology in Gottingen, Germany, in 1929, where there was an extremely high level of scientific research in physics, chemistry and mathematics. He benefited enormously through interaction with other great scientists and persuaded the physicist R. Mannkopf to build him a high sensitivity optical spectrograph, which opened the door to revolutionary new studies. Goldschmidt was then driven out of Germany a few years later with the rise of Nazism with the accompanying violent anti-Semitism. After receiving a special edict relieving him of his duties to the Prussian State with a special edict signed by Adolph Hitler in \"the name of the third Reich\", he returned to Oslo in 1935. After the German invasion of Norway, he escaped to England via Sweden with the help of the Norwegian underground.", "doi": "10.1016/j.gca.2009.05.042", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2009-06", "series_number": "13", "volume": "73", "issue": "13", "pages": "S1-S2" }, { "id": "authors:vhk5x-f4a89", "collection": "authors", "collection_id": "vhk5x-f4a89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090812-202757707", "type": "article", "title": "A search for nickel isotopic anomalies in iron meteorites and chondrites", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report Ni isotopic data, for ^(58,60\u201362)Ni, on (1) FeNi metal and sulfides in different groups of iron meteorites, (2) sulfides and a whole rock sample of the St. S\u00e9verin chondrite, and (3) chondrules from the Chainpur chondrite. We have developed improved, Multiple-Collector, Positive ion Thermal Ionization Mass Spectrometric (MC-PTIMS) techniques, with Ni+ ionization efficiency at 1\u2030, and chemical separation techniques for Ni which reduce mass interferences to the 1 ppm level, so that no mass interference corrections need be applied, except for ^(64)Ni (from ^(64)Zn, at the 0.1\u2030 level), for which we do not report results. We normalize the data to ^(62)Ni/^(58)Ni to correct for mass dependent isotope fractionation. No evidence was found for resolved radiogenic or general Ni isotope anomalies at the resolution levels of 0.2 and 0.5 \u03b5u (\u03b5u = 0.01%) for ^(60)Ni/^(58)Ni and ^(61)Ni/^(58)Ni, respectively. From the ^(56)Fe/^(58)Ni ratios and \u03b5(^(60)Ni/^(58)Ni) values, we calculate upper limits for the initial value of (^(60)Fe/^(56)Fe)0 of (a) <2.7 \u00d7 10^\u22127 for Chainpur chondrules, (b) <10^\u22128 for the St. S\u00e9verin sulfide, and (c) <4 \u00d7 10^\u22129 for sulfides from iron meteorites. We measured some of the same meteorites measured by other workers, who reported isotopic anomalies in Ni, using Multiple-Collector, Inductively-Coupled Mass Spectrometry. Our results do not support the previous reports of Ni isotopic anomalies in sulfide samples from Mundrabilla by Cook et al. [Cook D. L., Clayton R. N., Wadhwa M., Janney P. E., and Davis A. M. (2008). Nickel isotopic anomalies in troilite from iron meteorites. Geophy. Res. Lett. 35, L01203] and in sulfides from Toluca and Odessa by Quitt\u00e9 et al. [Quitt\u00e9 G., Meier M., Latkoczy C., Halliday A. N., and Gunther D., (2006). Nickel isotopes in iron meteorites-nucleosynthetic anomalies in sulfides with no effects in metals and no trace of ^(60)Fe. Earth Planet. Sci. Lett. 242, 16\u201325]. Hence, we find no need for specialized physical\u2013chemical planetary processes for the preservation of different Ni isotope compositions, between FeNi metal and sulfides in the same iron meteorites, as proposed by the above reports nor for complex astrophysical scenarios to provide the very peculiar Ni isotope anomalies reported by these workers for sulfides.", "doi": "10.1016/j.gca.2008.11.040", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2009-03-01", "series_number": "5", "volume": "73", "issue": "5", "pages": "1461-1471" }, { "id": "authors:m3954-k9n31", "collection": "authors", "collection_id": "m3954-k9n31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141111-100526668", "type": "article", "title": "Gerald J. Wasserburg Awarded 2008 William Bowie Medal", "author": [ { "family_name": "Jacobsen", "given_name": "Steven B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Gerald J. Wasserburg was awarded the 2008 William Bowie Medal at the AGU Fall Meeting Honors Ceremony, held 17 December 2008 in San Francisco, Calif. The medal is for \"outstanding contributions to fundamental geophysics and for unselfish cooperation in research.\"", "doi": "10.1029/2009EO010007", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "2009-01-06", "series_number": "1", "volume": "90", "issue": "1", "pages": "5-6" }, { "id": "authors:dhxgn-3rt03", "collection": "authors", "collection_id": "dhxgn-3rt03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:QIAapj08", "type": "article", "title": "Abundances of Sr, Y, and Zr in metal-poor stars and implications for chemical evolution in the early galaxy", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have attributed the elements from Sr through Ag in stars of low metallicities ([Fe/H] \u227e -1.5) to charged-particle reactions (CPRs) in neutrino-driven winds, which are associated with neutron star formation in low-mass and normal supernovae (SNe) from progenitors of ~8-11 M\u2299 and ~12-25 M\u2299, respectively. Using this rule and attributing all Fe production to normal SNe, we previously developed a phenomenological two-component model, which predicts that [Sr/Fe] \u2265 -0.32 for all metal-poor stars. This is in direct conflict with the high-resolution data now available, which show that there is a great shortfall of Sr relative to Fe in many stars with [Fe/H] \u227e3. The same conflict also exists for the CPR elements Y and Zr. We show that the data require a stellar source leaving behind black holes and that hypernovae (HNe) from progenitors of ~25-50 M\u2299 are the most plausible candidates. If we expand our previous model to include three components (low-mass and normal SNe and HNe), we find that essentially all of the data are very well described by the new model. The HN yield pattern for the low-A elements from Na through Zn ( including Fe) is inferred from the stars deficient in Sr, Y, and Zr. We estimate that HNe contributed ~24% of the bulk solar Fe inventory while normal SNe contributed only ~ 9% (not the usually assumed ~33%). This implies a greatly reduced role of normal SNe in the chemical evolution of the low-A elements.", "doi": "10.1086/591545", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2008-11-01", "series_number": "1", "volume": "687", "issue": "1", "pages": "272-286" }, { "id": "authors:7h41q-1ax43", "collection": "authors", "collection_id": "7h41q-1ax43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090518-075933248", "type": "article", "title": "Magnetic mixing in red giant and asymptotic giant branch stars", "author": [ { "family_name": "Nordhaus", "given_name": "J.", "clpid": "Nordhaus-J" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Blackman", "given_name": "E. G.", "clpid": "Blackman-E-G" }, { "family_name": "Palmerini", "given_name": "S.", "clpid": "Palmerini-S" } ], "abstract": "The available information on isotopic abundances in the atmospheres of low-mass red giant branch (RGB) and asymptotic giant branch (AGB) stars requires that episodes of extensive mixing occur below the convective envelope, reaching down to layers close to the hydrogen burning shell (cool bottom processing). Recently, it was suggested that dynamo-produced buoyant magnetic flux tubes could provide the necessary physical mechanisms and also supply sufficient transport rates. Here, we present an \u03b1-\u03a9 dynamo in the envelope of an RGB/AGB star in which shear and rotation drain via turbulent dissipation and Poynting flux. In this context, if the dynamo is to be sustained throughout either phase, convection must resupply shear. Under this condition, volume-averaged peak toroidal field strengths of \u2243 3 \u00d7 10^3 G (RGB) and \u2243 5 \u00d7 10^3 G (AGB) are possible at the base of the convection zone. If the magnetic fields are concentrated in flux tubes, the corresponding field strengths are comparable to those required by cool bottom processing.", "doi": "10.1086/591963", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2008-09-01", "series_number": "1", "volume": "684", "issue": "1", "pages": "L29-L32" }, { "id": "authors:8hqre-hsg50", "collection": "authors", "collection_id": "8hqre-hsg50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091026-115718450", "type": "article", "title": "Can Extra Mixing in RGB and AGB Stars Be Attributed to Magnetic Mechanisms?", "author": [ { "family_name": "Busso", "given_name": "Maurizio", "clpid": "Busso-M" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Nollett", "given_name": "Kenneth M.", "clpid": "Nollett-K-M" }, { "family_name": "Calandra", "given_name": "Andrea", "clpid": "Calandra-A" } ], "abstract": "It is known that there must be some weak form of transport (called cool bottom processing, or CBP) acting in low-mass red giant branch (RGB) and asymptotic giant branch (AGB) stars, adding nuclei, newly produced near the hydrogen-burning shell, to the convective envelope. We assume that this extra mixing originates in a stellar dynamo operated by the differential rotation below the envelope, maintaining toroidal magnetic fields near the hydrogen-burning shell. We use a phenomenological approach to the buoyancy of magnetic flux tubes, assuming that they induce matter circulation as needed by CBP models. This establishes requirements on the fields necessary to transport material from zones where some nuclear burning takes place, through the radiative layer and into the convective envelope. Magnetic field strengths are determined by the transport rates needed by CBP for the model stellar structure of a star of initially 1.5 M_\u2299, in both the AGB and RGB phases. The field required for the AGB star in the processing zone is B_0 ~ 5 \u00d7 10^6 G; at the base of the convective envelope this yields an intensity B_E \u227e 10^4 G. For the RGB case, B_0 ~ 5 \u00d7 10^4 \u2013 4 \u00d7 10^5 G, and the corresponding B_E are ~450-3500 G. These results are consistent with existing observations on AGB stars. They also hint at the basis for high field sources in some planetary nebulae, and the very large fields found in some white dwarfs. It is concluded that transport by magnetic buoyancy should be considered as a possible mechanism for extra mixing through the radiative zone, as is required by both stellar observations and the extensive isotopic data on circumstellar condensates found in meteorites.", "doi": "10.1086/522616", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2007-12-10", "series_number": "1", "volume": "671", "issue": "1", "pages": "802-810" }, { "id": "authors:8b7dd-vm376", "collection": "authors", "collection_id": "8b7dd-vm376", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-140326534", "type": "article", "title": "The absence of nickel isotopic anomaly in iron meteorite metal and sulfide", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Evidence for ^(60)Fe (\u03c4^(1/2) = 1.5 Ma) has been reported in eucrites and chondrites [1-4], consisting of excesses in ^(60)Ni, in phases with high Fe/Ni. Recent work on iron meteorites, using MC-ICP-MS, indicates a complex picture. Quitt\u00e9 et al. [5] analyzed FeNi and sulfide from iron meteorites and found no ^(60)Ni effects in the FeNi at \u00b10.3 \u0454u. However, in some sulfides, they found large and correlated effects in \u0454^(60)Ni and \u0454^(61)Ni. In irons, Bizzarro et al. [6] claimed small shifts in ^(60)Ni and ^(62)Ni. Cook et al. [7]\nshowed shifts of -0.5 \u0454u in ^(60)Ni in several sulfides and up to -2.4 \u0454u in Mundrabilla sulfide.", "doi": "10.1111/j.1945-5100.2007.tb00601.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2007-08", "series_number": "S8", "volume": "42", "issue": "S8", "pages": "A29" }, { "id": "authors:j0sy3-w0c63", "collection": "authors", "collection_id": "j0sy3-w0c63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131120-095534133", "type": "article", "title": "Where, oh where has the r-process gone?", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a review of the possible sources for r-process nuclei (r-nuclei). It is known that there is as yet no self-consistent mechanism to provide abundant neutrons for a robust r-process in the neutrino-driven winds from nascent neutron stars. We consider that the heavy r-nuclei with mass numbers A>130 (Ba and above) cannot be produced in the neutrino-driven winds. Nonetheless, the r-process and the neutrino-driven winds may be directly or indirectly related by some unknown additional mechanism, which, for example, could provide ejecta with very short dynamic timescales of \u227e0.004 s. This undetermined mechanism must supply a neutron source within the same general stellar sites that undergo core collapse to produce the neutron star. Observational data on low-metallicity stars in the Galactic halo show that sites producing the heavy r-nuclei do not produce Fe or any other elements between N and Ge. Insofar as a forming neutron star is key to producing the heavy r-nuclei, then the only possible sources are supernovae resulting from collapse of O\u2013Ne\u2013Mg cores or accretion-induced collapse of white dwarfs, neither of which produce the elements of the Fe group or those of intermediate mass (above C and N). Observational evidence on s and r-nuclei in low-metallicity stars with high C and N abundances shows that the r-process is also active in binary systems.\nThe nuclei with A\u223c90\u2013110 produced by charged-particle reactions (CPR) in the neutrino-driven winds are in general present in metal-poor stars with high or low abundances of heavy r-nuclei. The CPR nuclei and the heavy r-nuclei are not strongly coupled. Some metal-poor stars show extremely high enrichments of heavy r-nuclei and have established that the abundance patterns of these nuclei are universally close to the solar abundance pattern of heavy r-nuclei.\nUsing a template star with high enrichments of heavy r-nuclei and another with low enrichments we develop a two-component model based on the abundances of Eu (from sources for heavy r-nuclei) and Fe (from Fe core-collapse supernovae). This model gives very good quantitative predictions for the abundances of all the other elements in those metal-poor stars with [Fe/H]\u2272-1.5 for which the Eu and Fe abundances are known. We attribute the CPR elements such as Sr, Y, and Zr to reactions in the neutrino-driven winds from a nascent neutron star and the heavy r-nuclei to the hypothecated true \"r-process\". The CPR nuclei should be produced whenever a neutron star is formed regardless of whether heavy r-nuclei are produced or not. Using the two-component model we estimate the yield of the CPR element Sr to be \u223c10^(-6)M_\u2299 for a single neutron star formation event. Self-consistent astrophysical models are needed to establish that the CPR nuclei are common to the neutron stars produced in both sources for the heavy r-nuclei and those for Fe. We show that the observational data appear fully consistent with the two-component model. The specific mechanism and site for the production of heavy r-nuclei remains to be found.", "doi": "10.1016/j.physrep.2007.02.006", "issn": "0370-1573", "publisher": "Elsevier", "publication": "Physics Reports", "publication_date": "2007-04", "series_number": "1-6", "volume": "442", "issue": "1-6", "pages": "237-268" }, { "id": "authors:nrkjz-q8r66", "collection": "authors", "collection_id": "nrkjz-q8r66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131120-090059030", "type": "article", "title": "Short-lived nuclei in the early Solar System: Possible AGB sources", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Gallino", "given_name": "R.", "clpid": "Gallino-R" }, { "family_name": "Nollett", "given_name": "K. M.", "clpid": "Nollett-K-M" } ], "abstract": "The abundances of short-lived radionuclides in the early Solar System (ESS) are reviewed, as well as the methodology used in determining them. These results are compared with the inventory estimated for a uniform galactic production model. It is shown that, to within a factor of two, the observed abundances of ^(238)U, ^(235)U, ^(232)Th, ^(244)Pu, ^(182)Hf, ^(146)Sm, and ^(53)Mn are roughly compatible with long-term galactic nucleosynthesis. ^(129)I is an exception, with an ESS inventory much lower than expected from uniform production. The isotopes ^(107)Pd, ^(60)Fe, ^(41)Ca, ^(36)CI, ^(26)AI, and ^(10)Be require late addition to the protosolar nebula. ^(10)Be is the product of energetic particle irradiation of the Solar System as most probably is ^(36)CI. Both of these nuclei appear to be present when ^(26)AI is absent. A late injection by a supernova (SN) cannot be responsible for most of the short-lived nuclei without excessively producing ^(53)Mn; it can however be the source of ^(53)Mn itself and possibly of ^(60)Fe. If a late SN injection is responsible for these two nuclei, then there remains the problem of the origin of ^(107)Pd and several other isotopes. Emphasis is given to an AGB star as a source of many of the nuclei, including ^(60)Fe; this possibility is explored with a new generation of stellar models. It is shown that if the dilution factor (i.e. the ratio of the contaminating mass to the solar parental cloud mass) is \u0192_0\u223c4\u00d710^(\u22123), a reasonable representation for many nuclei is obtained; this requires that (^(60)Fe/^(56)Fe)_(ESS) \u223c 10^(\u22127) to 2\u00d710^(\u22126). The nuclei produced by an AGB source do not include ^(53)Mn, ^(10)Be or ^(36)CI if it is very abundant. The role of irradiation is discussed with regard to ^(26)AI, ^(36)CI and ^(41)Ca, and the estimates of bulk solar abundances of these isotopes are commented on. The conflict between various scenarios is emphasized as well as the current absence of an astrophysically plausible global interpretation for all the existing data. Examination of abundances for the actinides indicates that a quiescent interval of \u223c10^8 yr is required for actinide group production. This is needed in order to explain the data on ^(244)Pu and the new bounds on ^(247)Cm. Because this quiescent interval is not compatible with the ^(182)Hf data, a separate type of r-process event is needed for at least the actinides, distinct from the two types that have previously been identified. The apparent coincidence of the ^(129)I and trans-actinide time scales suggests that the last heavy r contribution was from an r-process that produced very heavy nuclei but without fission recycling so that the yields at Ba and below (including I) were governed by fission.", "doi": "10.1016/j.nuclphysa.2005.07.015", "issn": "0375-9474", "publisher": "Elsevier", "publication": "Nuclear Physics A", "publication_date": "2006-10-17", "volume": "777", "pages": "5-69" }, { "id": "authors:xw9j5-70738", "collection": "authors", "collection_id": "xw9j5-70738", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-104958848", "type": "article", "title": "An experimental study of trace-element partitioning between Ti-Al-clinopyroxene and melt: Equilibrium and kinetic effects including sector zoning", "author": [ { "family_name": "Lofgren", "given_name": "Gary E.", "clpid": "Lofgren-G-E" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Equilibrium and dynamic crystallization experiments were used to determine distribution coefficients (D-values) for the REE and the trace elements Sc, V, Rb, Sr, Y, Zr, Nb, Ba, Hf, Th, and U between Ti-Al-clinopyroxene and melt. Equilibrium values for D correlate well with previous studies where values have been determined. The D-values were also studied as a function of cooling rate. Increased cooling rates produce higher growth rates. At growth rates that exceed the diffusion rates in the crystals, the D-values increase to near unity and the HREE D-values exceed unity only at the most rapid crystal growth rates. The increase in D-values is the result of the inclusion of components into the growing pyroxene from the boundary layer that develops at the crystal-melt interface because of the disparity between the growth and diffusion rates. The origin of sector zoning is best explained as an interplay of primarily crystallographic control with kinetic effects.", "doi": "10.2138/am.2006.2108", "issn": "0003-004X", "publisher": "Mineralogical Society of America", "publication": "American Mineralogist", "publication_date": "2006-10", "series_number": "10", "volume": "91", "issue": "10", "pages": "1596-1606" }, { "id": "authors:7jzj2-vmc44", "collection": "authors", "collection_id": "7jzj2-vmc44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131211-141250305", "type": "article", "title": "A Late Episode of Irradiation in the Early Solar System: Evidence from Extinct ^(36)Cl and ^(26)Al in Meteorites", "author": [ { "family_name": "Hsu", "given_name": "Weibiao", "clpid": "Hsu-Weibiao" }, { "family_name": "Guan", "given_name": "Yunbin", "orcid": "0000-0002-7636-3735", "clpid": "Guan-Yunbin" }, { "family_name": "Leshin", "given_name": "L. A.", "clpid": "Leshin-L-A" }, { "family_name": "Ushikubo", "given_name": "Takayuki", "clpid": "Ushikubo-Takayuki" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Late-formed halogen-rich phases in a refractory inclusion and a chondrule from the Allende meteorite exhibit large ^(36)S excesses that linearly correlate with the chlorine concentration, providing strong evidence in support of the existence of the short-lived nuclide ^(36)Cl (mean life of 0.43 Myr) in the early solar system. The inferred ^(36)Cl/^(35)Cl ratios at the time when these phases formed are very high (~4 \u00d7 10^(-6)) and essentially the same for the inclusion and the chondrule and confirm the earlier report of ^(36)S excess in another meteorite. In addition, the ^(36)Cl is decoupled from ^(26)Al. The observed and any possible higher levels of ^(36)Cl cannot be the result of a supernova or AGB stellar source but require a late episode of energetic particle bombardment by the early Sun, in support of the arguments based on the previous discovery of ^(10)Be. It is now clear that a blend of several sources is required to explain the short-lived nuclei when the solar system formed.", "doi": "10.1086/500043", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2006-03-20", "series_number": "1", "volume": "640", "issue": "1", "pages": "525-529" }, { "id": "authors:qnfv0-c6w46", "collection": "authors", "collection_id": "qnfv0-c6w46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-080816300", "type": "article", "title": "Alastair Graham Walter Cameron - Obituary", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Alastair Graham Walter Cameron, one of the key discoverers of stellar nucleosynthesis and a founder of modern nuclear astrophysics, died of a heart attack in Tucson, Arizona, on 3 October 2005.", "doi": "10.1063/1.2180186", "issn": "0031-9228", "publisher": "American Institute of Physics", "publication": "Physics Today", "publication_date": "2006-01", "series_number": "1", "volume": "59", "issue": "1", "pages": "68-70" }, { "id": "authors:vwfrd-32h79", "collection": "authors", "collection_id": "vwfrd-32h79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131211-133315514", "type": "article", "title": "Metal Enrichment of the Intergalactic Medium and Production of Massive Black Holes", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A model for the chemical evolution of the intergalactic medium (IGM) is presented using theoretical yields of very massive stars (VMSs; M_(VMS) > 100 M_\u2609) and Type II supernovae (SNe II). It is shown that if [Si/C] is indeed as high as ~0.7 in the IGM, then VMSs (M_(VMS) \u2248 140-260 M_\u2609) associated with pair-instability supernovae (PI-SNe) in low-mass (~10^5 M_\u2609) halos at high redshift must produce at least 50% of the Si. The remainder is from later galactic outflows of SN II debris, which also provide most of the C and O. Both sources are required to account for the metal inventory in the IGM. The early VMS production must continue until redshift z ~ 15 so that the efficiency of VMS formation per low-mass halo is significantly below unity. Contributions from the later galactic outflows mainly occur at z ~ 4-6. Using a Salpeter initial mass function, we infer that the number of VMSs (M_(VMS) \u2248 260-2000 M_\u2609) producing massive black holes (MBHs) with an average mass \u3008M_(MBH)\u3009 ~ 270-550 M_\u2609 is \u22480.72 times the number of VMSs associated with PI-SNe. The amount of metals (particularly Si) in the IGM that is attributable to PI-SNe is thus closely coupled with the total mass of MBHs produced in epochs prior to galaxy formation. Production of ~50% of the Si in the IGM by PI-SNe corresponds to an early inventory of MBHs that constitutes a fraction ~(4-8) \u00d7 10^(-5) of the total baryonic mass in the universe. This is comparable to the global mass budget of the central supermassive black holes (SMBHs) in present-day galaxies. The corresponding occurrence rates in each halo of ~10^5 M_\u2609 during the epoch of VMS formation at z \u2273 15 are ~0.9 Gyr^(-1) for VMSs associated with PI-SNe and ~0.6 Gyr^(-1) for the concomitant more massive stars producing MBHs. These rates may be of use to studies of H_2 dissociation and reionization and to models of SMBH formation.", "doi": "10.1086/497615", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2005-12-20", "series_number": "2", "volume": "635", "issue": "2", "pages": "845-852" }, { "id": "authors:xtk5v-vs561", "collection": "authors", "collection_id": "xtk5v-vs561", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-085600954", "type": "article", "title": "Sources for Metals in the Intergalactic Medium", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a discussion of possible sources of C, O, and Si in the intergalactic medium (IGM) using the yields of very massive stars (VMSs) and Type II supernovae (SNe II). The chemical evolution of the IGM is considered on the basis of analytical phenomenological models of hierarchical structure formation and the required metal production rates. Two regimes are considered: one for gas expulsion by VMSs and SNe II in low-mass halos prior to dissociation of H_2 molecules and reionization, and the other for later SN II-driven outflows from intermediate-mass halos. We use recent data on the abundances of C, O, and Si in the IGM inferred from two UV background (UVB) models. We show that the values of [C/O]_(IGM) and [Si/C]_(IGM) inferred from the UVB model using quasars only cannot be explained by any existing stellar models. To account for the elemental ratios in the IGM by stellar models requires that a softer UVB model be used in calculating the elemental abundances from the data on ionic species. This then permits a solution using the yields of VMSs and SNe II. The results, in particular [Si/C]_(IGM), show that VMSs must provide \u227315% of the C in the IGM. The preferred scenario is that VMSs in low-mass halos provided between 15% and 60% of the C in the regime of very high redshift (z \u227315) and that galactic outflows provided the remainder during later epochs (4 < z \u227e6). Thus, there is a large gap in z between metal production by VMSs very early in the chemical evolution of the IGM and subsequent contributions from galactic outflows. It is not possible to explain the observations by just SN II sources associated with galactic outflows. The observational estimate of [O/H]_(IGM) implies a high [Fe/H]_(IGM) \u2265 -3 for all cases considered (including the case of a pure VMS source). This raises problems with regard to observations of metal-poor stars in the Galaxy. In addition, the [O/Fe] values for SN II models are in conflict with stellar observations, which indicate that the calculated average Fe yields of SNe II are a factor of ~2 too high. These issues and the general problem of relating abundances in the IGM to those in metal-poor stars remain to be investigated.", "doi": "10.1086/428644", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2005-04-10", "series_number": "1", "volume": "623", "issue": "1", "pages": "17-22" }, { "id": "authors:gc9xs-1qm24", "collection": "authors", "collection_id": "gc9xs-1qm24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221115-941547700.2", "type": "article", "title": "Anhydrite and the Sr isotope evolution of groundwater in a carbonate aquifer", "author": [ { "family_name": "Jacobson", "given_name": "A. D.", "clpid": "Jacobson-A-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Major element concentrations and \u2078\u2077Sr/\u2078\u2076Sr ratios were measured in groundwaters and bedrock from the Madison aquifer in western South Dakota. In this region, the Madison aquifer is primarily comprised of dolomite belonging to the Madison Limestone Group. The purpose of the study was to investigate controls on the downgradient evolution of dissolved Sr\u00b2\u207a in a carbonate groundwater system that is recharged by waters with high \u2078\u2077Sr/\u2078\u2076Sr ratios draining Precambrian basement rocks and to establish the sources of Sr\u00b2\u207a added to the waters by reaction with the aquifer lithology. A mass-balance model following previous workers was used to calculate amounts and effective rates of mineral dissolution and precipitation during groundwater transport along a \u223c240-km flow path. Both the calculated reaction rates and data for the Sr isotope geochemistry of the reacting phases were then used to develop a self-consistent and quantitative description of the concentration and isotopic composition of dissolved Sr\u00b2\u207a in the aquifer waters.\nThe major ion chemistry of Madison aquifer groundwater is known to evolve according to dolomite dissolution, anhydrite dissolution, calcite precipitation, and ion-exchange with clay minerals. Dissolved \u2078\u2077Sr/\u2078\u2076Sr ratios in the Madison aquifer decrease downgradient. Input waters draining the igneous Black Hills have \u2078\u2077Sr/\u2078\u2076Sr ratios of \u223c0.723, while highly evolved waters in the aquifer have \u2078\u2077Sr/\u2078\u2076Sr ratios of \u223c0.708. Dissolved Sr\u00b2\u207a concentrations undergo a concurrent increase from \u223c1200 to 66,000 nmol/l. Model results indicate that dolomite dissolution exerts a critical control on the major ion chemistry but is not the primary source of nonradiogenic Sr\u00b2\u207a, as both the dissolution rate and Sr concentration of dolomite are very low. Anhydrite is readily soluble in water, has a low \u2078\u2077Sr/\u2078\u2076Sr ratio (\u223c0.708), and a very high Sr concentration (\u223c50,000 nmol/g). Anhydrite is also greatly undersaturated in the groundwaters, and the downgradient evolution of Sr\u00b2\u207a accompanies an \u223c80-fold increase in dissolved SO\u2084\u00b2\u207b. While anhydrite has a very low abundance in the aquifer rocks, the flow model indicates that anhydrite dissolution provides \u223c300 times more Sr\u00b2\u207a per liter of water relative to dolomite dissolution. These findings suggest that anhydrite dissolution governs the Sr\u00b2\u207a geochemistry of Madison aquifer groundwaters, whereas dolomite dissolution and calcite precipitation control the bulk chemistry. Lastly, it is shown that the calculation of net mineral masses transferred to solution requires very high relative proportions of anhydrite and clay to dolomite. Mineral masses obtained by this approach actually represent bulk contributions without consideration of the intrinsic reaction rates of the phases or their modal abundances in the aquifer rocks. However, consideration of these parameters in a transport equation for flow through porous media shows that the high apparent abundances are not a real requirement. This latter approach is consistent with laboratory experiments and indicates that as little as 0.04 wt.% of very soluble anhydrite and 0.3 wt.% of exchangeable clay in the aquifer rock are sufficient to produce the observed groundwater chemistry in most of the flow path.", "doi": "10.1016/j.chemgeo.2004.10.006", "issn": "0009-2541", "publisher": "Elsevier", "publication": "Chemical Geology", "publication_date": "2005-01-25", "series_number": "3-4", "volume": "214", "issue": "3-4", "pages": "331-350" }, { "id": "authors:jfvc7-a9v70", "collection": "authors", "collection_id": "jfvc7-a9v70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-135959615", "type": "article", "title": "Anhydrite and the Sr isotope evolution of groundwater in a\n carbonate aquifer", "author": [ { "family_name": "Jacobson", "given_name": "A. D.", "clpid": "Jacobson-A-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Major element concentrations and ^(87)Sr/^(86)Sr ratios were measured in groundwaters and bedrock from the Madison aquifer in western South Dakota. In this region, the Madison aquifer is primarily comprised of dolomite belonging to the Madison Limestone Group. The purpose of the study was to investigate controls on the downgradient evolution of dissolved Sr^(2+) in a carbonate groundwater system that is recharged by waters with high ^(87)Sr/^(86)Sr ratios draining Precambrian basement rocks and to establish the sources of Sr^(2+) added to the waters by reaction with the aquifer lithology. A mass-balance model following previous workers was used to calculate amounts and effective rates of mineral dissolution and precipitation during groundwater transport along a \u223c240-km flow path. Both the calculated reaction rates and data for the Sr isotope geochemistry of the reacting phases were then used to develop a self-consistent and quantitative description of the concentration and isotopic composition of dissolved Sr^(2+) in the aquifer waters.\nThe major ion chemistry of Madison aquifer groundwater is known to evolve according to dolomite dissolution, anhydrite dissolution, calcite precipitation, and ion-exchange with clay minerals. Dissolved ^(87)Sr/^(86)Sr ratios in the Madison aquifer decrease downgradient. Input waters draining the igneous Black Hills have ^(87)Sr/^(86)Sr ratios of \u223c0.723, while highly evolved waters in the aquifer have ^(87)Sr/^(86)Sr ratios of \u223c0.708. Dissolved Sr^(2+) concentrations undergo a concurrent increase from \u223c1200 to 66,000 nmol/l. Model results indicate that dolomite dissolution exerts a critical control on the major ion chemistry but is not the primary source of nonradiogenic Sr^(2+), as both the dissolution rate and Sr concentration of dolomite are very low. Anhydrite is readily soluble in water, has a low ^(87)Sr/^(86)Sr ratio (\u223c0.708), and a very high Sr concentration (\u223c50,000 nmol/g). Anhydrite is also greatly undersaturated in the groundwaters, and the downgradient evolution of Sr^(2+) accompanies an \u223c80-fold increase in dissolved SO_4^(2\u2212). While anhydrite has a very low abundance in the aquifer rocks, the flow model indicates that anhydrite dissolution provides \u223c300 times more Sr^(2+) per liter of water relative to dolomite dissolution. These findings suggest that anhydrite dissolution governs the Sr^(2+) geochemistry of Madison aquifer groundwaters, whereas dolomite dissolution and calcite precipitation control the bulk chemistry. Lastly, it is shown that the calculation of net mineral masses transferred to solution requires very high relative proportions of anhydrite and clay to dolomite. Mineral masses obtained by this approach actually represent bulk contributions without consideration of the intrinsic reaction rates of the phases or their modal abundances in the aquifer rocks. However, consideration of these parameters in a transport equation for flow through porous media shows that the high apparent abundances are not a real requirement. This latter approach is consistent with laboratory experiments and indicates that as little as 0.04 wt.% of very soluble anhydrite and 0.3 wt.% of exchangeable clay in the aquifer rock are sufficient to produce the observed groundwater chemistry in most of the flow path.", "doi": "10.1016/j.chemgeo.2004.10.006", "issn": "0009-2541", "publisher": "Elsevier", "publication": "Chemical Geology", "publication_date": "2005-01-25", "series_number": "3-4", "volume": "214", "issue": "3-4", "pages": "331-350" }, { "id": "authors:xqw0q-hpp09", "collection": "authors", "collection_id": "xqw0q-hpp09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131219-102017506", "type": "article", "title": "The Hamburg/ESO R-process Enhanced Star survey (HERES).\n I. Project description, and discovery of two stars with strong enhancements of neutron-capture elements", "author": [ { "family_name": "Christlieb", "given_name": "N.", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Beers", "given_name": "T. C.", "orcid": "0000-0003-4573-6233", "clpid": "Beers-T-C" }, { "family_name": "Barklem", "given_name": "P. S.", "clpid": "Barklem-P-S" }, { "family_name": "Bessell", "given_name": "M.", "clpid": "Bessell-M" }, { "family_name": "Hill", "given_name": "V.", "clpid": "Hill-V" }, { "family_name": "Holmberg", "given_name": "J.", "clpid": "Holmberg-J" }, { "family_name": "Korn", "given_name": "A. J.", "clpid": "Korn-A-J" }, { "family_name": "Marsteller", "given_name": "B.", "clpid": "Marsteller-B" }, { "family_name": "Mashonkina", "given_name": "L.", "clpid": "Mashonkina-L" }, { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Rossi", "given_name": "S.", "clpid": "Rossi-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Zickgraf", "given_name": "F.-J.", "clpid": "Zickgraf-F-J" }, { "family_name": "Kratz", "given_name": "K.-L", "clpid": "Kratz-K-L" }, { "family_name": "Nordstr\u00f6m", "given_name": "B.", "clpid": "Nordstr\u00f6m-B" }, { "family_name": "Pfeiffer", "given_name": "B.", "clpid": "Pfeiffer-B" }, { "family_name": "Rhee", "given_name": "J.", "clpid": "Rhee-J" }, { "family_name": "Ryan", "given_name": "S. G.", "clpid": "Ryan-S-G" } ], "abstract": "We report on a dedicated effort to identify and study metal-poor stars strongly enhanced in r-process elements ([r/Fe]>1 dex; hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey (HERES). Moderate-resolution (~ 2 \u00c5) follow-up spectroscopy has been obtained for metal-poor giant candidates selected from the Hamburg/ESO objective-prism survey (HES) as well as the HK survey to identify sharp-lined stars with ([Fe/H]<-2.5 dex. For several hundred confirmed metal-poor giants brighter than B ~ 16.5 mag (most of them from the HES), \"snapshot\" spectra (R ~ 20,000; S/N ~ 30 per pixel) are being obtained with VLT/UVES, with the main aim of finding the 2-3% r-II stars expected to be among them. These are studied in detail by means of higher resolution and higher S/N spectra. In this paper we describe a pilot study based on a set of 35 stars, including 23 from the HK survey, eight from the HES, and four comparison stars. We discovered two new r-II stars, CS 29497-004 ([Eu/Fe] = 1.64 \u00b1 0.22) and CS 29491-069 ([Eu/Fe] = 1.08 \u00b1 0.23). A first abundance analysis of CS 29497-004 yields that its abundances of Ba to Dy are on average enhanced by 1.5 dex with respect to iron and the Sun and match a scaled solar r-process pattern well, while Th is underabundant relative to that pattern by 0.3 dex, which we attribute to radioactive decay. That is, CS 29497-004 seems not to belong to the class of r-process enhanced stars displaying an \"actinide boost\", like CS 31082-001 (Hill et al. 2002), or CS 30306-132 (Honda et al. 2004b). The abundance pattern agrees well with predictions of the phenomenological model of Qian & Wasserburg.", "doi": "10.1051/0004-6361:20041536", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2004-12-04", "series_number": "3", "volume": "428", "issue": "3", "pages": "1027-1037" }, { "id": "authors:b2568-fps74", "collection": "authors", "collection_id": "b2568-fps74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-092338273", "type": "article", "title": "Rate-controlled calcium isotope fractionation in synthetic calcite", "author": [ { "family_name": "Lemarchand", "given_name": "D.", "clpid": "Lemarchand-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" } ], "abstract": "The isotopic composition of Ca (\u0394^(44)Ca/^(40)Ca) in calcite crystals has been determined relative to that in the parent solutions by TIMS using a double spike. Solutions were exposed to an atmosphere of NH_3 and CO_2, provided by the decomposition of (NH_4)_2CO_3, following the procedure developed by previous workers. Alkalinity, pH and concentrations of CO_3^(2\u2212), HCO_3^\u2212, and CO_2 in solution were determined. The procedures permitted us to determine \u0394(^(44)Ca/^(40)Ca) over a range of pH conditions, with the associated ranges of alkalinity. Two solutions with greatly different Ca concentrations were used, but, in all cases, the condition [Ca^(2+)]>>[CO_3^(2\u2212)] was met. A wide range in \u0394(^(44)Ca/^(40)Ca) was found for the calcite crystals, extending from 0.04 \u00b1 0.13\u2030 to \u22121.34 \u00b1 0.15\u2030, generally anti-correlating with the amount of Ca removed from the solution. The results show that \u0394(^(44)Ca/^(40)Ca) is a linear function of the saturation state of the solution with respect to calcite (\u03a9). The two parameters are very well correlated over a wide range in \u03a9 for each solution with a given [Ca]. The linear correlation extended from \u0394(^(44)Ca/^(40)Ca) = \u22121.34 \u00b1 0.15\u2030 to 0.04 \u00b1 0.13\u2030, with the slopes directly dependent on [Ca]. Solutions, which were vigorously stirred, showed a much smaller range in \u0394(^(44)Ca/^(40)Ca) and gave values of \u22120.42 \u00b1 0.14\u2030, with the largest effect at low \u03a9. It is concluded that the diffusive flow of CO_3^(2\u2212) into the immediate neighborhood of the crystal-solution interface is the rate-controlling mechanism and that diffusive transport of Ca^(2+) is not a significant factor. The data are simply explained by the assumptions that: a) the immediate interface of the crystal and the solution is at equilibrium with \u0394(^(44)Ca/^(40)Ca) \u223c \u22121.5 \u00b1 0.25\u2030; and b) diffusive inflow of CO_3^(2\u2212) causes supersaturation, thus precipitating Ca from the regions exterior to the narrow zone of equilibrium. The result is that \u0394(^(44)Ca/^(40)Ca) is a monotonically increasing (from negative values to zero) function of \u03a9. We consider this model to be a plausible explanation of most of the available data reported in the literature. The well-resolved but small and regular isotope fractionation shifts in Ca are thus not related to the diffusion of very large hydrated Ca complexes, but rather due to the ready availability of Ca in the general neighborhood of the crystal-solution interface. The largest isotopic shift which occurs as a small equilibrium effect is then subdued by supersaturation precipitation for solutions where [Ca^(2+)]>>[CO_3^(2\u2212)] + [HCO_3^\u2212]. It is shown that there is a clear temperature dependence of the net isotopic shifts that is simply due to changes in \u03a9 due to the equilibrium \"constants\" dependence on temperature, which changes the degree of saturation and hence the amount of isotopically unequilibrated Ca precipitated. The effects that are found in natural samples, therefore, will be dependent on the degree of diffusive inflow of carbonate species at or around the crystal-liquid interface in the particular precipitating system, thus limiting the equilibrium effect.", "doi": "10.1016/j.gca.2004.05.029", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2004-11-15", "series_number": "22", "volume": "68", "issue": "22", "pages": "4665-4678" }, { "id": "authors:xtjf3-xhk48", "collection": "authors", "collection_id": "xtjf3-xhk48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-083404445", "type": "article", "title": "Abundances In Very Metal-Poor Dwarf Stars", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Shectman", "given_name": "Steve", "clpid": "Shectman-S" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Ivans", "given_name": "Inese", "clpid": "Ivans-I" }, { "family_name": "Dehn", "given_name": "Matthias", "clpid": "Dehn-M" }, { "family_name": "Karlsson", "given_name": "Torgny", "clpid": "Karlsson-T" }, { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" } ], "abstract": "We discuss the detailed composition of 28 extremely metal-poor (EMP) dwarfs, 22 of which are from the Hamburg/ESO Survey (HES), based on Keck echelle spectra. Our sample has a median [Fe/H] of -2.7 dex, extends to -3.5 dex, and is somewhat less metal-poor than was expected from [Fe/H](HK, HES) determined from low-resolution spectra. Our analysis supports the existence of a sharp decline in the distribution of halo stars with metallicity below [Fe/H] = -3.0 dex. So far no additional turnoff stars with [Fe/H] < -3.5 have been identified in our follow-up efforts. For the best-observed elements between Mg and Ni, we find that the abundance ratios appear to have reached a plateau, i.e., [X/Fe] is approximately constant as a function of [Fe/H], except for Cr, Mn, and Co, which show trends of abundance ratios varying with [Fe/H]. These abundance ratios at low metallicity correspond approximately to the yield expected from Type II supernovae (SNe) with a narrow range in mass and explosion parameters; high-mass Type II SN progenitors are required. The dispersion of [X/Fe] about this plateau level is surprisingly small and is still dominated by measurement errors rather than intrinsic scatter. These results place strong constraints on the characteristics of the contributing SNe. The dispersion in neutron-capture elements and the abundance trends for Cr, Mn, and Co are consistent with previous studies of evolved EMP stars. We find halo-like enhancements for the \u03b1-elements Mg, Ca, and Ti, but solar Si/Fe ratios for these dwarfs. This contrasts with studies of EMP giant stars, which show Si enhancements similar to other \u03b1-elements. Sc/Fe is another case where the results from EMP dwarfs and from EMP giants disagree; our Sc/Fe ratios are enhanced compared to the solar value by ~0.2 dex. Although this conflicts with the solar Sc/Fe values seen in EMP giants, we note that \u03b1-like Sc/Fe ratios have been claimed for dwarfs at higher metallicity. Two dwarfs in the sample are carbon stars, while two others have significant C enhancements, all with ^(12)C/^(13)C ~7 and with C/N between 10 and 150. Three of these C-rich stars have large enhancements of the heavy neutron capture elements, including lead, which implies a strong s-process contribution, presumably from binary mass transfer; the fourth shows no excess of Sr or Ba.", "doi": "10.1086/422576", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2004-09-10", "series_number": "2", "volume": "612", "issue": "2", "pages": "1107-1135" }, { "id": "authors:9p8pp-jjj82", "collection": "authors", "collection_id": "9p8pp-jjj82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-091323698", "type": "article", "title": "Hierarchical structure formation and chemical evolution of galaxies", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present an analytical and phenomenological model for metal enrichment in halos based on hierarchical structure formation. This model assumes that astration of normal stellar populations along with Type II supernovae (SNe II) already occurs at very high redshift. It focuses on the regime of [Fe/H] < -1, in which SNe Ia are not major contributors. The regime of [Fe/H] > -1, in which SNe Ia are major contributors, is also discussed in general. For halos that are not disrupted by SN II explosions, the chemical evolution of the gas and stars is explicitly determined by the rate of gas infall as compared with the astration rate and the corresponding rate of metal production by SNe II per H atom in the gas. This model provides a good description of the data on [Fe/H] for damped Ly\u03b1 systems over a wide range of redshift, 0.5 < z < 5. For all halos not disrupted by SN II explosions, if there is a cessation of gas infall, the metallicities of the stars follow a bimodal distribution. This distribution is characterized by a sharp peak at the value of [Fe/H] corresponding to the time of infall cessation and by a broad peak at a higher value of [Fe/H] corresponding to the subsequent period of astration during which the bulk of the remaining gas forms stars. Such a distribution can be compared with that observed for the Galactic halo stars. If the gas in a halo is rapidly lost on cessation of infall, then an assemblage of stars with a very sharply defined [Fe/H] value will be left behind. This assemblage of stars may be accreted by a larger system and become a globular cluster of the larger system. We discuss the masses and metallicities of the globular clusters in this model considering the criterion for the onset of astration and possible disruption of low-mass halos by SN II explosions. The implications of possible globular clusters with very low metallicities of [Fe/H] \u227e-3 are also discussed.", "doi": "10.1086/422805", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2004-09-10", "series_number": "2", "volume": "612", "issue": "2", "pages": "615-627" }, { "id": "authors:7aknz-vqe42", "collection": "authors", "collection_id": "7aknz-vqe42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-100719911", "type": "article", "title": "Rate controlled fractionation of Ca isotopes in synthetic calcite", "author": [ { "family_name": "Lemarchand", "given_name": "D.", "clpid": "Lemarchand-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Calcium isotopic variations in carbonates, both marine\norganisms and inorganic systems, have recently been\ninterpreted as a possible seawater temperature recorder [1,2].\nIn order to understand the behavior of calcium isotopes during\nprecipitation of Ca-carbonate, synthetic calcite growth\nexperiments were carried out at constant temperature and\nunder various pH and alkalinity conditions.", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2004-06", "series_number": "11", "volume": "68", "issue": "11", "pages": "A208" }, { "id": "authors:yhpf7-kh464", "collection": "authors", "collection_id": "yhpf7-kh464", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-074608283", "type": "article", "title": "Behavior of Sm and Nd in a lateritic soil profile", "author": [ { "family_name": "Viers", "given_name": "J\u00e9r\u00f4me", "clpid": "Viers-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A study of lateritic soils and samples of ground and river waters was carried out in the Nsimi-Zoetele, a tropical watershed in the southern Cameroon. The Nd isotopic compositions and concentrations of Nd and Sm were determined. It was found that the Nd isotopic composition of the river waters was much more radiogenic than the parent rocks, and that the Nd in the waters is not homogeneous but is carried by different dissolved and complexed components that are not isotopically homogenized. The soil profile shows a regular increase in \u03b5_(Nd) going from the parent rock (\u03b5_(Nd) = \u221236) to \u03b5_(Nd) = \u221218 near the top of the profile. The Nd transported in the river is thus not representative of the parent rock but reflects the results of differential weathering of constituent minerals and the redeposition of REE in phosphates and a significant contribution of radiogenic Nd from dust. The concentration of Nd in the river water is far above that found in temperate climate rivers and thus this type of tropical river may play a dominant role in the marine Nd and REE budget. It is suggested that the correlation of REE with DOC is related to DOC fixing some dissolved REE but that the REE in solution is governed by other mechanisms. No major shifts were found in Sm/Nd; however, a regular progression from the parent rock through the lateritic profile was found. The upper laterite profile shows large, almost uniform depletions in all REE below Tb and enrichment above. Complementary behavior was found in the lower part of the section. The concentration of Nd relative to the immobile elements Zr and Ti in the laterite is depleted by a factor of \u223c10. Th, Nd and Sm are enriched in the lowest zone sampled and must reflect redeposition of REE from the upper part of the weathering section and is associated with phosphate formation. It is concluded that the soil evolution involves both differential dissolution of primary phases from the parent rock, significant to major input of REE from atmospheric dust from other regions, and the formation of diagenetic phases, particularly phosphates.", "doi": "10.1016/j.gca.2003.10.034", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2004-05-01", "series_number": "9", "volume": "68", "issue": "9", "pages": "2043-2054" }, { "id": "authors:4a6pt-abj76", "collection": "authors", "collection_id": "4a6pt-abj76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-152304136", "type": "article", "title": "Early solar system radioactivity and AGB stars", "author": [ { "family_name": "Gallino", "given_name": "R.", "clpid": "Gallino-R" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Straniero", "given_name": "O.", "clpid": "Straniero-O" } ], "abstract": "The possible stellar origin of those short-lived nuclei that were shown to be alive in the Early Solar System (ESS) is briefly discussed. The applicability of a close-by AGB star polluting the protosolar nebula depends on the extent to which several nuclei can be explained and in particular the strongly debated problems of the initial amount of ^(60)Fe, as inferred from recent measurements.", "doi": "10.1016/j.newar.2003.11.019", "issn": "1387-6473", "publisher": "Elsevier", "publication": "New Astronomy Reviews", "publication_date": "2004-02", "series_number": "1-4", "volume": "48", "issue": "1-4", "pages": "133-138" }, { "id": "authors:m5zs5-bbz54", "collection": "authors", "collection_id": "m5zs5-bbz54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131113-103654887", "type": "article", "title": "Hierarchical structure formation and chemical evolution of damped Ly\u03b1 systems", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a model for the chemical evolution of damped Ly\u03b1 systems considering the production of \"metals\" by Type II supernovae and infall associated with hierarchical structure formation. The growth of metallicity in these systems is a reflection of the competition between astration and infall. The apparent late turn-on of these systems is due to the late cutoff of infall. The wide range in [Fe/H] at a given redshift is explained by the range of the times for the onset of star formation and the range of the times for infall cessation in different systems. The observed lower bound of [Fe/H] \u2248 -3 follows from the very rapid initial rise of [Fe/H] subsequent to the onset of star formation. To reach [Fe/H] \u2248 -3 from a metal-free initial state requires only ~30 Myr, so the probability of observing lower [Fe/H] values is very small.", "doi": "10.1086/379144", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2003-10-10", "series_number": "1", "volume": "596", "issue": "1", "pages": "L9-L12" }, { "id": "authors:mffp8-syw48", "collection": "authors", "collection_id": "mffp8-syw48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-082121630", "type": "article", "title": "The transport of U- and Th-series nuclides in sandy confined aquifers", "author": [ { "family_name": "Reynolds", "given_name": "B. C.", "clpid": "Reynolds-B-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Baskaran", "given_name": "M.", "clpid": "Baskaran-M" } ], "abstract": "Abundances of ^(238)U, ^(234)U, ^(232)Th, ^(226)Ra, ^(228)Ra, ^(224)Ra, and ^(222)Rn were measured in groundwaters of the Ojo Alamo aquifer in northwest New Mexico. This is an arid area with annual precipitation of \u223c22 cm. The purpose was to investigate the transport of U-Th series nuclides and their daughter products in an old, slow-moving groundwater mass as a means of understanding water-rock interactions and to compare the results with a temperate zone aquifer. It was found that ^(232)Th is approximately at saturation and supports the view of Tricca et al. (2001) that Th is precipitated irreversibly upon weathering, leaving surface coatings of ^(232)Th and ^(230)Th on aquifer grains. Uranium in the aquifer waters has very high [^(234)U/^(238)U] \u223c 9 and low ^(238)U concentrations. These levels can be explained by low weathering rates in the aquifer (w_(238U) \u223c 2 \u00d7 10^(\u221218) to 2 \u00d7 10^(\u221217)s^(\u22121)) using a continuous flow, water-rock interaction model. The Ra isotopes are roughly in secular equilibrium despite their very different mean lifetimes. The ^(222)Rn and ^(228)Ra isotopes in the aquifer correspond to \u223c10% of the net production rate of the bulk rock. This is interpreted to reflect an earlier formed irreversible surface coating of Th that provides Ra and Rn to the aquifer waters. The surface waters that appear to be feeding the aquifer have low [^(234)U/^(238)U] and high ^(238)U concentrations. The flow model shows that it is not possible to obtain the high [^(234)U/^(238)U] and low [^(238)U] values in the aquifer from a source like the present vadose zone input. It follows that the old aquifer waters studied cannot be fed by the present vadose zone input unless they are greatly diluted with waters with very low U concentrations. If the present sampling of vadose zone sources is representative of the present input, then this requires that there was a major change in water input with much larger rainfall some several thousand years ago. This may represent a climatic change in the Southwest.", "doi": "10.1016/S0016-7037(02)01341-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2003-06-01", "series_number": "11", "volume": "67", "issue": "11", "pages": "1955-1972" }, { "id": "authors:cnevt-gcc02", "collection": "authors", "collection_id": "cnevt-gcc02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131113-102732597", "type": "article", "title": "Anthony Leonid Turkevich - Obituary", "author": [ { "family_name": "Economou", "given_name": "Thanasis E.", "clpid": "Economou-T-E" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Anthony Leonid Turkevich, a nuclear radiochemist and physicist and a professor of chemistry at the\nUniversity of Chicago, died in his sleep on 7 September 2002 at his home in Lexington, Virginia. He was\nwidely esteemed for his great intellectual powers, deep physical insight, and personal integrity.\n\nTony was born in New York City on 23 July 1916, the son of a Russian Orthodox clergyman who became a head of the Russian Orthodox Church in both North America and Japan. In 1937, Tony earned a BA from Dartmouth College and, in 1940, a PhD in physical chemistry from Princeton University. His doctoral work was on diffusion determination of molecular structures and dielectric investigations of the motion of organic molecules in the solid state. Shortly after his graduation, he was invited to the University of Chicago as a research physicist in the department of physics; he worked on UV spectroscopy and the radiochemical studies of the fission products.", "doi": "10.1063/1.1595067", "issn": "0031-9228", "publisher": "American Institute of Physics", "publication": "Physics Today", "publication_date": "2003-06", "series_number": "6", "volume": "56", "issue": "6", "pages": "78-78" }, { "id": "authors:4mgha-yya25", "collection": "authors", "collection_id": "4mgha-yya25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131210-154406065", "type": "article", "title": "Stellar Sources for Heavy r-Process Nuclei", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The stellar sites and the complete mechanism of r-process nucleosynthesis are still unresolved issues. From consideration of the observed abundances in metal-poor stars, it is proposed that the production of heavy r-process nuclei (r-nuclei with mass numbers A > 130) is not related to the production of Fe group elements or of elements with lower atomic numbers: Na, Mg, Al, Si, Ca, Sc, and Ti. This requires that the production of heavy r-nuclei not occur in supernovae with extended shell structure but be associated with either bare neutron stars or Type II supernovae (SNe II) in the mass range 8 M_\u2609 < M < 10 M_\u2609. From the observations of stars with [Fe/H] ~ -3 but with high abundances of r-elements, it is clear that these r-process enrichments cannot represent the composition of the interstellar medium from which the stars were formed but must represent very local contamination from binary companions. Further evidence for very high enrichments of s-process elements in metal-poor stars also requires binary systems for explanation. We propose that the accretion-induced collapse (AIC) of a white dwarf into a neutron star in a binary system may be associated with the production of heavy r-nuclei and may provide occasional coupling of high r-process and high s-process enrichments in the envelopes of low-mass stars with low [Fe/H]. If we assume that the bulk of the heavy r-nuclei are produced in AIC events, then these events would have produced ~1.6 \u00d7 109 neutron stars in the Galaxy. A much larger number of white dwarf binaries would have resulted from the evolution of other binary systems. The AIC scenario removes the assignment in our earlier model that SNe II provide the bulk of heavy r-nuclei and relegates r-process production in SNe II to light r-nuclei with A \u227e 130. This new assignment gives Fe yields that are in accord with the observed values for most SNe II.", "doi": "10.1086/374271", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-05-10", "series_number": "2", "volume": "588", "issue": "2", "pages": "1099-1109" }, { "id": "authors:fphrw-mw944", "collection": "authors", "collection_id": "fphrw-mw944", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131210-145233709", "type": "article", "title": "Abundance Analysis of HE 2148\u20131247, A Star with Extremely Enhanced Neutron Capture Elements", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Abundances for 27 elements in the very metal-poor dwarf star HE 2148-1247 are presented, including many of the neutron capture elements. We establish that HE 2148-1247 is a very highly s-process-enhanced star with anomalously high Eu as well, Eu/H ~ half-solar, demonstrating the large addition of heavy nuclei at [Fe/H] = -2.3 dex. Ba and La are enhanced by a somewhat larger factor and reach the solar abundance, while Pb significantly exceeds it, thus demonstrating the addition of substantial s-process material. Ba/Eu is 10 times the solar r-process ratio but much less than that of the s-process, indicating a substantial r-process addition as well. C and N are also very highly enhanced. We have found that HE 2148-1247 is a radial velocity variable; it is probably a small-amplitude long-period binary. The C, N, and the s-process element enhancements were thus presumably produced through mass transfer from a former asymptotic giant branch (AGB) binary companion. The large enhancement of heavy r-nuclides also requires an additional source as this is far above any inventory in the interstellar medium at such low [Fe/H]. We consider that the s-process material was added by mass transfer of a more massive companion during its thermally pulsating AGB phase and ending up as a white dwarf. We further hypothesize that accretion onto the white dwarf from the envelope of the star caused accretion-induced collapse of the white dwarf, forming a neutron star, which then produced heavy r-nuclides and again contaminated its companion. This mechanism in a binary system can thus enhance the envelope of the lower mass star in s- and r-process material sequentially. Through analysis of the neutron capture element abundances taken from the literature for a large sample of very metal-poor stars, we demonstrate, as exemplified by HE 2148-1247, that mass transfer in a suitable binary can be very efficient in enhancing the heavy elements in a star; it appears to be capable of enhancing the s-process elements in very metal-poor stars to near the solar abundance but not substantially above it. The yield of Pb relative to Ba appears to vary among very metal-poor stars.", "doi": "10.1086/374269", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-05-10", "series_number": "2", "volume": "588", "issue": "2", "pages": "1082-1098" }, { "id": "authors:ys74n-5gw03", "collection": "authors", "collection_id": "ys74n-5gw03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111012-140113691", "type": "article", "title": "Isotopic Adventures\u2014Geological, Planetological, and Cosmic", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "When asked to write a summary of my professional life, I had no notion of how\ndifficult it would be. There is the form and the substance, the remembrances and\nthe reality, the discipline and the hope, the frustration of not finding a way, and the\nsatisfaction of finding a trail. Of all of the experiences, the greatest one, the biggest\nturn-on, is the rare feeling that one has some understanding of nature. I have had the\nhonor and privilege of receiving the Crafoord Prize of the Royal Swedish Academy\nfrom the King of Sweden, but my greatest occasions of excitement came when I\nthought I had possibly understood something. The greatest satisfaction comes in\nfeeling that the work I have done or contributed to has some beauty. At the moment,\nI am finishing up a paper on groundwater transport in the Ojo Alamo aquifer,\nhaving just finished a paper with C.T. Lee and Frank Kyte on the chemistry and\ntransport of PGE in the oceans. Just weeks earlier, I returned from an astrophysics\nconference on \"Low Z at low z and high z,\" (low chemical elemental abundances\nat low and high cosmological red shifts) led by Y.-Z. Qian at the University of\nMinnesota. It has been said that the virtue of being \"old\" is that you can live in the\npast as well as the present. Thinking about the past is not my way, except to tell old\nstories over good wines at dinner with friends. However, the truth is that the particular\nproblem that I am working on at any instant is, to me, the most important thing\nin the world. Chasing some particular idea and some observations of nature make\nup the real present and govern my immediate future. In the chase, I met Devendra\nand Aruna Lal. He was fascinated with Indian puzzles and natural puzzles, particularly\nthose cosmic-ray induced. Our mutual interest in natural puzzles has been a\ncontinuous source of entertainment and mutual support. Friendly interaction and\ncritical comments on science and life and what might be true comes regularly from\nKarl Turekian (a Columbia product displaced to Yale). It has been my privilege\nto have had an exciting, productive career that continues to the present day. It is\nmy intent to continue the exploration and the chase. The reader is warned that this report is not chronological, as the actual science in different areas often occurred\nconcurrently.", "doi": "10.1146/annurev.earth.31.100901.141409", "issn": "0084-6597", "publisher": "Annual Reviews", "publication": "Annual Review of Earth and Planetary Sciences", "publication_date": "2003-05", "volume": "31", "pages": "1-74" }, { "id": "authors:354g4-srs15", "collection": "authors", "collection_id": "354g4-srs15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131113-094623693", "type": "article", "title": "Max Planck: closures will damage German science - Cosmochemistry and geochemistry departments should continue their innovative work", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "McKenzie", "given_name": "D. P.", "clpid": "McKenzie-D-P" } ], "abstract": "Your News story \"Max Planck plans double blow to chemistry\" (Nature 422,\n105; 2003), reporting that the Max Planck Society is seriously considering closing its\ndepartments of cosmochemistry and geochemistry in Mainz, is most disturbing.\nInsofar as the Max Planck Society is concerned with pursuing cutting-edge\nscientific research programmes, such action is difficult to understand.", "doi": "10.1038/422469a", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2003-04-03", "series_number": "6931", "volume": "422", "issue": "6931", "pages": "469-469" }, { "id": "authors:68hzy-ma154", "collection": "authors", "collection_id": "68hzy-ma154", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-153534558", "type": "article", "title": "Platinum-group elements (PGE) and rhenium in marine sediments across the Cretaceous\u2013Tertiary boundary: Constraints on Re-PGE transport in the marine environment", "author": [ { "family_name": "Lee", "given_name": "Cin-Ty Aeolus", "clpid": "Lee-C-T-A" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Kyte", "given_name": "Frank T.", "clpid": "Dyte-F-T" } ], "abstract": "The nature of Re\u2013platinum-group element (PGE; Pt, Pd, Ir, Os, Ru) transport in the marine environment was investigated by means of marine sediments at and across the Cretaceous\u2013Tertiary boundary (KTB) at two hemipelagic sites in Europe and two pelagic sites in the North and South Pacific. A traverse across the KTB in the South Pacific pelagic clay core found elevated levels of Re, Pt, Ir, Os, and Ru, each of which is approximately symmetrically distributed over a distance of \u223c1.8 m across the KTB. The Re-PGE abundance patterns are fractionated from chondritic relative abundances: Ru, Pt, Pd, and Re contents are slightly subchondritic relative to Ir, and Os is depleted by \u223c95% relative to chondritic Ir proportions. A similar depletion in Os (\u223c90%) was found in a sample of the pelagic KTB in the North Pacific, but it is enriched in Ru, Pt, Pd, and Re relative to Ir. The two hemipelagic KTB clays have near-chondritic abundance patterns. The \u223c1.8-m-wide Re-PGE peak in the pelagic South Pacific section cannot be reconciled with the fallout of a single impactor, indicating that postdepositional redistribution has occurred. The elemental profiles appear to fit diffusion profiles, although bioturbation could have also played a role. If diffusion had occurred over \u223c65 Ma, the effective diffusivities are \u223c10^(\u221213) cm^2/s, much smaller than that of soluble cations in pore waters (\u223c10^(\u22126) cm^2/s). The coupling of Re and the PGEs during redistribution indicates that postdepositional processes did not significantly fractionate their relative abundances. If redistribution was caused by diffusion, then the effective diffusivities are the same. Fractionation of Os from Ir during the KTB interval must therefore have occurred during aqueous transport in the marine environment. Distinctly subchondritic Os/Ir ratios throughout the Cenozoic in the South Pacific core further suggest that fractionation of Os from Ir in the marine environment is a general process throughout geologic time because most of the inputs of Os and Ir into the ocean have Os/Ir ratios \u22651. Mass balance calculations show that Os and Re burial fluxes in pelagic sediments account for only a small fraction of the riverine Os (<10%) and Re (<0.1%) inputs into the oceans. In contrast, burial of Ir in pelagic sediments is similar to the riverine Ir input, indicating that pelagic sediments are a much larger repository for Ir than for Os and Re. If all of the missing Os and Re is assumed to reside in anoxic sediments in oceanic margins, the calculated burial fluxes in anoxic sediments are similar to observed burial fluxes. However, putting all of the missing Os and Re into estuarine sediments would require high concentrations to balance the riverine input and would also fail to explain the depletion of Os at pelagic KTB sites, where at most \u223c25% of the K-T impactor's Os could have passed through estuaries. If Os is preferentially sequestered in anoxic marine environments, it follows that the Os/Ir ratio of pelagic sediments should be sensitive to changes in the rates of anoxic sediment deposition. There is thus a clear fractionation of Os and Re from Ir in precipitation out of sea water in pelagic sections. Accordingly, it is inferred here that Re and Os are removed from sea water in anoxic marine depositional regimes.", "doi": "10.1016/S0016-7037(02)01135-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2003-02-15", "series_number": "4", "volume": "67", "issue": "4", "pages": "655-670" }, { "id": "authors:014y7-enw52", "collection": "authors", "collection_id": "014y7-enw52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131211-123549723", "type": "article", "title": "Cool Bottom Processes on the Thermally Pulsing Asymptotic Giant Branch and the Isotopic Composition of Circumstellar Dust Grains", "author": [ { "family_name": "Nollett", "given_name": "Kenneth M.", "clpid": "Nollett-K-M" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We examine the effects of cool bottom processing (CBP) on the isotopic ratios ^(18)O/^(16)O, ^(17)O/^(16)O, ^(14)N/^(15)N, ^(26)Al/^(27)Al, C/O, and N/O in the convective envelope during the thermally pulsing asymptotic giant branch (TP-AGB) phase of evolution in a 1.5 M_\u2609 initial mass star of solar initial composition. We use a parametric model that treats extra mixing by introducing mass flow between the convective envelope and the underlying radiative zone. The parameters of this model are the mass circulation rate (\u1e40) and the maximum temperature (TP) experienced by the circulating material. The effects of nuclear reactions in the flowing matter were calculated using a set of static structures of the radiative zone selected from particular times in a complete stellar evolution calculation. The compositions of the flowing material were obtained, and the resulting changes in the envelope determined. No major shifts in the star's energy budget occur from the imposed CBP if log TP < 7.73. Using structures from several times on the TP-AGB, it was found that the results for all species except ^(26)Al were essentially independent of the time chosen if log TP > 7.6. Abundant ^(26)Al was produced by CBP for log TP > 7.65. While ^(26)Al/^(27)Al depends on TP, the other isotopic ratios depend dominantly on the circulation rate. The relationship is shown between models of CBP as parameterized by a diffusion formalism within the stellar evolution model and those using the mass-flow formalism employed here. They are shown to be effectively equivalent. In general, the CBP treatment readily permits calculation of envelope compositions as affected by different degrees of extra mixing, based on stellar structures computed by normal stellar evolution models. Using these results, the isotopic ratios under conditions of C/O < 1 and C/O > 1 are compared with the data on circumstellar dust grains. It is found that the ^(18)O/^(16)O, ^(17)O/^(16)O, and ^(26)Al/^(27)Al observed for oxide grains formed at C/O < 1 are reasonably well understood. However, the ^(15)N/^(14)N, ^(12)C/^(13)C, and ^(26)Al/^(27)Al in carbide grains (C/O > 1) require that many of their stellar sources must have had ^(14)N/^(15)N at least a factor of 4 lower than the solar value. This allows a self-consistent description of all these isotopes in most SiC grains. The rare grains with ^(12)C/^(13)C < 10 cannot be produced by any red giant or AGB source, nor are they reconcilable with novae sources.", "doi": "10.1086/344817", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-01-10", "series_number": "2", "volume": "582", "issue": "2", "pages": "1036-1058" }, { "id": "authors:axfy7-2es10", "collection": "authors", "collection_id": "axfy7-2es10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-134743251", "type": "article", "title": "Al-Mg systematics of CAIs, POI, and ferromagnesian\n chondrules from Ningqiang", "author": [ { "family_name": "Hsu", "given_name": "Weibiao", "clpid": "Hsu-W" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have made aluminum-magnesium isotopic measurements on 4 melilite-bearing calcium-aluminum-rich inclusions (CAIs), 1 plagioclase-olivine inclusion (POI), and 2 ferromagnesian chondrules from the Ningqiang carbonaceous chondrite. All of the CAIs measured contain clear evidence for radiogenic ^(26)Mg^* from the decay of ^(26)Al (\u03c4 = 1.05 Ma). Although the low Al/Mg ratios of the melilites introduce large uncertainties, the inferred initial ^(26)Al/^(27)Al ratios for the CAIs are generally consistent with the value of 5 x 10^(\u22125). There is clear evidence of ^(26)Al^* in one POI and two chondrules, but with considerable uncertainties in the value of (^(26)Al/^(27)Al)0. The (^(26)Al/^(27)Al)_0 ratios for the POI and the chondrules are 0.3\u20130.6 x 10^(\u22125), roughly an order of magnitude lower than the canonical value. Ningqiang shows very little evidence of metamorphism as a bulk object and the (^(26)Al/^(27)Al)_0 ratios in its refractory inclusions and chondrules are consistent with those found in other unmetamorphosed chondrites of several different classes. Our observations and those of other workers support the view that ^(26)Al was widely and approximately homogeneously distributed throughout the condensed matter of the solar system. The difference in (^(26)Al/^(27)Al)0 between CAIs and less refractory materials seems reasonably interpreted in terms of a \u223c2 million year delay between the formation of CAIs and the onset of formation of less refractory objects. The POI shows clear differences in ^(25)Mg/^(24)Mg between its constituent spinels and olivine, which confirms that they are partially reprocessed material from different sources that were rapidly quenched.", "doi": "10.1111/j.1945-5100.2003.tb01044.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2003-01", "series_number": "1", "volume": "38", "issue": "1", "pages": "35-48" }, { "id": "authors:1d5hn-a0119", "collection": "authors", "collection_id": "1d5hn-a0119", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-090812510", "type": "article", "title": "Short-Lived Nuclei in the Early Solar System: A Low Mass Stellar Source?", "author": [ { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Gallino", "given_name": "R.", "clpid": "Gallino-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We discuss possible stellar origins of short-lived radioactive nuclei with meanlife \u03c4 \u2264 100 Myr, which were shown to be alive in the Early Solar System (ESS). We first review current ideas on the production of nuclides having 10 \u2264 \u03c4 \u2264 100 Myr, which presumably derive from the continuous interplay of galactic astration, nucleosynthesis from massive supernovae and free decay in the interstellar medium. The abundance of the shorter lived ^(53)Mn might be explained by this same scenario. Then we consider the nuclei ^(107)Pd, ^(26)Al, ^(41)Ca and ^(60)Fe, whose early solar system abundances are too high to have originated in this way. Present evidence favours a stellar origin, particularly for ^(107)Pd, ^(26)Al and ^(60)Fe, rather than an in situ production by energetic solar particles. The idea of an encounter (rather close in time and space) between the forming Sun and a dying star is therefore discussed: this star may or may not have also triggered the solar formation. Recent nucleosynthesis calculations for the yields of the relevant short-lived isotopes and of their stable reference nuclei are discussed. Massive stars evolving to type II supernovae (either leaving a neutron star or a black hole as a remnant) seem incapable of explaining the four most critical ESS radioactivities in their observed abundance ratios. An asymptotic giant branch (AGB) star seems to be a viable source, especially if of relatively low initial mass (M \u2264 3 M_\u2299) and with low neutron exposure: this model can provide a solution for ^(26)Al, ^(41)Ca and ^(107)Pd, with important contributions to ^(60)Fe, which are inside the present uncertainty range of the ^(60)Fe early solar system abundance. Such a model requires that ^(26)Al is produced substantially on the AGB by cool bottom processing. The remaining inventory of short-lived species in the solar nebula would then be attributed to the continuous galactic processing, with the exception of ^(10)Be, which must reflect production by later proton bombardment at a low level during early solar history.", "doi": "10.1071/AS03035", "issn": "1323-3580", "publisher": "CSIRO Publishing", "publication": "Publications of the Astronomical Society of Australia", "publication_date": "2003-01", "series_number": "4", "volume": "20", "issue": "4", "pages": "356-370" }, { "id": "authors:v84zg-gf278", "collection": "authors", "collection_id": "v84zg-gf278", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-152206137", "type": "article", "title": "Re-Os and Pd-Ag systematics in Group IIIAB irons and in pallasites", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Using improved analytical techniques, which reduce the Re blanks by factors of 8 to 10, we report new Re-Os data on low Re and low PGE pallasites (PAL-anom) and IIIAB irons. The new pallasite samples nearly double the observed range in Re/Os for pallasites and allow the determination of an isochron of slope 0.0775 \u00b1 0.0008 (T = 4.50 \u00b1 0.04 Ga, using the adjusted \u03bb^(187)Re = 1.66 \u00d7 10^(\u221211) a^(\u22121)) and initial (^(187)Os/^(188)Os)_0 = 0.09599 \u00b1 0.00046. If the data on different groups of pallasites (including the \"anomalous\" pallasites) are considered to define a whole-rock isochron, their formation would appear to be distinctly younger than for the iron meteorites by \u223c60 Ma. Five IIIAB irons (Acuna, Bella Roca, Chupaderos, Grant, and Bear Creek), with Re contents ranging from 0.9 to 2.8 ppb, show limited Re/Os fractionation and plot within errors on the IIAB iron meteorite isochron of slope 0.07848 \u00b1 0.00018 (T = 4.56 \u00b1 0.01 Ga) and initial (^(187)Os/^(188)Os)_0 = 0.09563 \u00b1 0.00011. Many of the meteorites were analyzed also for Pd-Ag and show ^(107)Ag enrichments correlated with Pd/Ag, requiring early formation and fractionation of the FeNi metal, in a narrow time interval, after injection of live ^(107)Pd (t_(1/2) = 6.5 Ma) into the solar nebula. Based on Pd-Ag, the typical range in relative ages of these meteorites is \u226410 Ma. The Pd-Ag results suggest early formation and preservation of the ^(107)Pd-^(107)Ag systematics, both for IIIAB irons and for pallasites, while the younger Re-Os apparent age for pallasites suggests that the Re-Os system in pallasites was subject to re-equilibration. The low Re and low PGE pallasites show significant Re/Os fractionation (higher Re/Os) as the Re and PGE contents decrease. By contrast, the IIIAB irons show a restricted range in Re/Os, even for samples with extremely low Re and PGE contents. There is a good correlation of Re and Ir contents. The correlation of Re and Os contents for IIIAB irons shows a similar complex pattern as observed for IIAB irons (Morgan et al., 1995), and neither can be ascribed to a continuous fractional crystallization process with uniform solid-metal/liquid-metal distribution coefficients.", "doi": "10.1016/S0016-7037(02)00952-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2002-11-01", "series_number": "21", "volume": "66", "issue": "21", "pages": "3793-3810" }, { "id": "authors:ax3jd-cec61", "collection": "authors", "collection_id": "ax3jd-cec61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140225-132256052", "type": "article", "title": "Platinum group elements and Re in marine sediments across the K-T boundary: constraints on Re-PGE transport in the marine environment", "author": [ { "family_name": "Lee", "given_name": "C.-T. Aeolus", "clpid": "Lee-C-T-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Kyte", "given_name": "F. T.", "clpid": "Kyte-F-T" } ], "abstract": "The nature of Re-PGE (PGE = Pt, Pd, Ir, Os, Ru) transport\nin the marine environment was investigated using marine\nsediments at and across the Cretaceous-Tertiary boundary\n(KTB) at two hemipelagic sites and two pelagic sites. A\ntraverse across the KTB in a south Pacific pelagic clay core\nfound elevated levels of Re, Pt, Ir, Os and Ru, each of which is\nsymmetrically distributed over ~1.8 m across the KTB. The\nRe-PGE abundance patterns are fractionated from chondritic\nrelative abundances: Ru, Pt, Pd, and Re contents are slightly\nsubchondritic relative to Ir, and Os is depleted by ~95%.", "doi": "10.1016/S0016-7037(02)01011-6", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2002-08-15", "series_number": "S1", "volume": "66", "issue": "S1", "pages": "A440-A440" }, { "id": "authors:k7fjm-tbr97", "collection": "authors", "collection_id": "k7fjm-tbr97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-131138444", "type": "article", "title": "Groundwater weathering rates from U- and Th-series nuclides", "author": [ { "family_name": "Reynolds", "given_name": "B. C.", "clpid": "Reynolds-B-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The transport of U, Th, Ra and Rn nuclides of the ^(238)U and ^(232)Th- decay series has been investigated in a large sandy confined aquifer in New Mexico. Groundwater data are\ncompared with a model of weathering of aquifer grains and\ninteraction with surface coatings, to constrain important\nphysico-chemical parameters that occur within the aquifer,\nprincipally weathering rates, \u03b1-recoil effects, adsorption desorption characteristics, and irreversible precipitation\n(Tricca et al 2001).", "doi": "10.1016/S0016-7037(02)01012-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2002-08-15", "series_number": "15A", "volume": "66", "issue": "15A", "pages": "A637" }, { "id": "authors:ebbd3-16b52", "collection": "authors", "collection_id": "ebbd3-16b52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-110630027", "type": "article", "title": "Excesses of ^(36)S in Sulfide-bearing Ca-Al-rich Inclusions from Allende", "author": [ { "family_name": "Al\u00e9on", "given_name": "J.", "clpid": "Al\u00e9on-J" }, { "family_name": "McKeegan", "given_name": "K. D.", "clpid": "McKeegan-K-D" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Introduction: Having four stable isotopes, Sis a potential tracer of processes such as mass independent chemistry, irradiation and/or the presence of nucleosynthetic anomalies [e.g. 1] in the early solar system. To study these processes, S isotope compositions were measured in 6 refractory metal-rich assemblages (Fremdlinge) from 3 Ca-Al-rich inclusions (CAis) and in 5 massive sulfides in\nchondrules and matrix of the Allende CV3 chondrite, using high precision multiple-collector secondary ion mass spectrometry.", "doi": "10.1111/j.1945-5100.2002.tb00912.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2002-05", "series_number": "S5", "volume": "37", "issue": "S5", "pages": "A10" }, { "id": "authors:6qffa-2fn44", "collection": "authors", "collection_id": "6qffa-2fn44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-114258307", "type": "article", "title": "^(53)Mn-^(53)Cr Systematics in Allende Refractory Inclusions", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Bogdanovski", "given_name": "O.", "clpid": "Bogdanovski-O" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have reported Cr isotope determinations on the Lunatic I and ^(53)Mn-^(53)Cr systematics on Allende refractory inclusions. Achievement of the requisite precision has used multiple mass spectrometric analyses of individual samples and a significant time investment per sample.", "doi": "10.1111/j.1945-5100.2002.tb00912.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2002-05", "series_number": "S5", "volume": "37", "issue": "S5", "pages": "A114" }, { "id": "authors:xptw2-8hg26", "collection": "authors", "collection_id": "xptw2-8hg26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131212-084338577", "type": "article", "title": "The Prompt Inventory from Very Massive Stars and Elemental Abundances in Ly\u03b1 Systems", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Sargent", "given_name": "W. L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "It has been proposed that very massive stars (VMSs) dominated heavy-element production until a \"metallicity\" threshold corresponding to [Fe/H] \u2248 -3 was reached. This results in a prompt (P) inventory of elements, the abundances of which were determined from observations of Galactic halo stars with [Fe/H] \u2248 -3. We calculate \u03a9_P(E) from the P inventory for a large number of elements in the intergalactic medium (IGM). Using the available data on \u03a9(E_(ion)) for C IV, O VI, and Si IV in Ly\u03b1 systems, we find that the ionization fractions calculated from \u03a9(E_(ion))/\u03a9_P(E) are, within reasonable uncertainties, compatible with the values estimated from ionization models for Ly\u03b1 systems. This agreement appears to hold from z ~ 0.09 to ~4.6, indicating that the bulk of the baryonic matter remains dispersed with a fixed chemical composition. We conclude that the P inventory was established in the epoch prior to z ~ 4.6. The dispersal of processed baryonic matter to the general IGM is considered to be the result of energetic VMS explosions that disrupted baryonic aggregates until the \"metallicity\" threshold was reached to permit normal astration. The formation of most galaxies is considered to have occurred subsequent to the achievement of this metallicity threshold in the IGM.", "doi": "10.1086/340641", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2002-04-20", "series_number": "2", "volume": "569", "issue": "2", "pages": "L61-L64" }, { "id": "authors:rn0jg-4rh34", "collection": "authors", "collection_id": "rn0jg-4rh34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131211-120906511", "type": "article", "title": "Determination of Nucleosynthetic Yields of Supernovae and Very Massive Stars from Abundances in Metal-Poor Stars", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We determine the yields of the elements from Na to Ni for Type II supernovae (SNe II) and the yield patterns of the same elements for Type Ia supernovae (SNe Ia) and very massive (\u2273100 M_\u2609) stars (VMSs) using a phenomenological model of stellar nucleosynthesis and the data on a number of stars with -4 \u227e[Fe/H]\u227e-3, a single star with [Fe/H] = -2.04, and the Sun. We consider that there are two distinct kinds of SNe II: the high-frequency SNe II(H) and the low-frequency SNe II(L). We also consider that VMSs were the dominant first-generation stars formed from big bang debris. The yield patterns of Na to Ni for SNe II(H), II(L), and Ia and VMSs appear to be well defined. It is found that SNe II(H) produce almost none of these elements; that SNe II(L) can account for the entire solar inventory of Na, Mg, Si, Ca, Ti, and V; and that compared with SNe II(L), VMSs underproduce Na, Al, V, Cr, and Mn, overproduce Co, but otherwise have an almost identical yield pattern. A comparison is made between the yield patterns determined here from the observational data and those calculated from ab initio models of nucleosynthesis in SNe II and VMSs. We show that the evolution of the \"heavy\" elements in the universe relative to Fe involves three distinct stages. The earliest stage is in the domain of [Fe/H] < -3 and is governed by VMS activities with some small contributions from SNe II, all of which are dispersed in a dilution mass of M^(VMS)_(dil) ~ 10^6-10^7 M_\u2609. The beginning of the second stage is marked by the cessation of VMS activities and the onset of major formation of normal stars (with masses of ~1-60 M_\u2609) at [Fe/H] \u2248 -3. The cessation of VMS activities causes the dilution mass for SN II contributions to drop sharply to M^(SNII)_(dil) \u2248 3 \u00d7 10^4 M_\u2609. The subsequent quasi-continuous chemical evolution until [Fe/H] ~ -1 is governed by SNe II(H), which produce mainly the heavy r-process elements above Ba, and SNe II(L), which produce essentially all the other elements. The third stage starts with the onset of SN Ia contributions to mainly the Fe group elements at [Fe/H] ~ -1. The domain of [Fe/H] > -1 is then governed by contributions from SNe II(H), II(L), and Ia and low-mass stars. It is shown that the abundances of non-neutron capture elements in stars with [Fe/H] \u2264 0 and those of r-process elements in stars with [Fe/H] < -1 can be well represented by the sum of the distinct components in the phenomenological model. The proposed evolutionary sequence is directly related to the problems of early aggregation and dispersion of baryonic matter and to the onset of formation and chemical evolution of galaxies. It is argued that the prompt inventory governed by VMS contributions should represent the typical composition of dispersed baryonic matter in the universe, and that normal galactic evolution should begin in matter with [Fe/H] \u2248 3.", "doi": "10.1086/338277", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2002-03-01", "series_number": "1", "volume": "567", "issue": "1", "pages": "515-531" }, { "id": "authors:5s635-p9790", "collection": "authors", "collection_id": "5s635-p9790", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-073621596", "type": "article", "title": "On the formation of Fe-Ni metal in Renazzo-like carbonaceous chondrites", "author": [ { "family_name": "Connolly", "given_name": "Harold C., Jr.", "clpid": "Connolly-H-C-Jr" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The Fe-Ni metal within chondrites has been postulated to have originated either through condensation or as a byproduct of chondrule formation. To test these hypotheses, we studied metal in three Renazzo-like carbonaceous (CR2) chondrites from three petrographic settings: inside chondrules, on chondrule rims, and in the matrix. Abundances of Fe, Ni, Co, Cr, and P were determined in situ by electron microprobe, and those of Os, Ir, Pt, and Au were measured by a newly developed ion microprobe technique. The refractory platinum group elements Os, Ir, and Pt behave coherently in CR2 metal. They are either all enriched, all depleted, or unfractionated with respect to Fe and cosmic ratios. Metal with approximately CI Os/Fe, Ir/Fe, and Pt/Fe occur primarily in chondrule interiors. All metal grains have essentially CI values of Ni/Fe and Co/Fe. Almost all metal grains have lower-than-CI ratios of the volatile elements, Au and P. We also estimated the bulk compositions via analyses of phases and modal recombination of a subset of the chondrules whose metal we analyzed. The bulk compositions of chondrules are generally unfractionated relative to CI chondrites for elements more refractory than \u223cCr but are depleted in more volatile elements. Abundances of siderophile elements correlate strongly with the metal abundance in the chondrules, which implies that siderophile depletions are due to expulsion of metal from the chondrule melts. The metal most likely originated during melting via reduction of oxides by C that was part of the chondrule precursor. During chondrule heating, molten metal efficiently extracted siderophile elements from the silicate melt. Rim metal consists of two types. One is like metal in chondrule interiors and was in the process of being expelled when the chondrules were quenched. The other shows systematic depletions in Os, Ir, and Pt relative to Fe and higher concentrations of Au and P than interior metal. This metal is attributed to recondensation from a vapor depleted in refractory siderophiles, a vapor most likely derived via evaporation from chondrules. Large, isolated matrix metal grains comprise the same two groups as rim grains and have the same origins. Bulk chondrule compositions and siderophile abundance patterns in metal indicate that the precursors of CR2 chondrules had CI-like abundances of refractory and moderately volatile elements but was likely depleted in the more volatile elements.", "doi": "10.1016/S0016-7037(01)00749-9", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2001-12-15", "series_number": "24", "volume": "65", "issue": "24", "pages": "4567-4588" }, { "id": "authors:dphy8-83f12", "collection": "authors", "collection_id": "dphy8-83f12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-110621703", "type": "article", "title": "Did very massive stars preenrich and reionize the universe?", "author": [ { "family_name": "Oh", "given_name": "S. Peng", "clpid": "Oh-S-P" }, { "family_name": "Nollett", "given_name": "Kenneth M.", "clpid": "Nollett-K-M" }, { "family_name": "Madau", "given_name": "Piero", "clpid": "Madau-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Recent studies of heavy r-process elements in low-[Fe/H] halo stars have suggested that an initial population of metal-free very massive stars (VMSs) may be required to provide early Fe enrichment without coproducing heavy r nuclei. We find similar abundance trends in \u03b1-elements (which should be copiously produced by VMSs) but not in other elements such as carbon (which should not), in agreement with this hypothesis. We then combine the corresponding level of prompt initial enrichment with models of VMS nucleosynthetic yields and spectra to estimate the corresponding ionizing fluxes. The result suggests that there may have been enough VMS activity to reionize the universe. The unusually hard spectrum of VMSs would imply a different reionization history from canonical models. He II could have been reionized at high redshift only to recombine as a subsequent generation of stars formed with a \"normal\" initial mass function.", "doi": "10.1086/337996", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2001-11-20", "series_number": "1", "volume": "562", "issue": "1", "pages": "L1-L14" }, { "id": "authors:xbtph-w6q22", "collection": "authors", "collection_id": "xbtph-w6q22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131211-110040374", "type": "article", "title": "A Model for Abundances in Metal-poor Stars", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A model is presented that seeks to explain quantitatively the stellar abundances of r-process elements and other elements associated with the r-process sites. It is argued that the abundances of all these elements in stars with -3 \u227e[Fe/H] < -1 can be explained by the contributions of three sources. The sources are the first generations of very massive (\u2273100 M_\u2609) stars that are formed from big bang debris and are distinct from Type II supernovae (SNe II) and two types of SNe II, the H and L events, which can occur only at [Fe/H] \u2273-3. The H events are of high frequency and produce dominantly heavy (A > 130) r-elements but no Fe (presumably leaving behind black holes). The L events are of low frequency and produce Fe and dominantly light (A \u227e 130) r-elements (essentially none above Ba). By using the observed abundances in two ultra-metal-poor stars and the solar r-abundances, the initial or prompt inventory of elements produced by the first generations of very massive stars and the yields of H and L events can be determined. The abundances of a large number of elements in a star can then be calculated from the model by using only the observed Eu and Fe abundances. To match the model results and the observational data for stars with -3 < [Fe/H] < -1 requires that the solar r-abundances for Sr, Y, Zr, and Ba must be significantly increased from the standard values. No such changes appear to be required for all other elements. If the changes in the solar r-abundances for Sr, Y, Zr, and Ba are not permitted, the model fails at -3 < [Fe/H] < -1 but still works at [Fe/H] \u2248 -3 for these four elements. By using the corrected solar r-abundances for these elements, good agreement is obtained between the model results and data over the range -3 < [Fe/H] < -1. No evidence of s-process contributions is found in this region, but all the observational data in this region now show regular increases of Ba/Eu above the standard solar r-process value. Whether the solar r-components of Sr, Y, Zr, and Ba used here to obtain a fit to the stellar data can be reconciled with those obtained from solar abundances by subtracting the s-components calculated from models is not clear.", "doi": "10.1086/322367", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2001-10-01", "series_number": "2", "volume": "559", "issue": "2", "pages": "925-941" }, { "id": "authors:7h3x7-fmb54", "collection": "authors", "collection_id": "7h3x7-fmb54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-144256288", "type": "article", "title": "Transport of U- and Th-series nuclides in a Baltic Shield watershed and the Baltic Sea", "author": [ { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Andersson", "given_name": "P. S.", "clpid": "Andersson-P-S" }, { "family_name": "Baskaran", "given_name": "M.", "clpid": "Baskaran-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The transport of Th, Ra, and ^(210)Pb from a continental source region and through an estuarine environment was investigated. Unlike previous studies, here both short- and long-lived nuclide data were obtained for river inputs, river water, and estuarine waters. The mire-rich Kalix River drainage basin was chosen as a typical northern shield area because this river may represent typical waters flowing into the Arctic and northern seas.\nGroundwaters from bedrock and glacial tills have comparable Th isotope concentrations and do not exhibit significant Th isotopic shifts relative to host rocks. The extensive peat deposits of the basin receive groundwater discharges and concentrate Th and U (but not Ba and Ra), which cause high ^(230)Th/^(232)Th ratios in mire waters. However, mire outflows do not have a significant impact on Th and Ra isotopic compositions of the river.\nOverall weathering characteristics for the basin are obtained from the river data. The ^(230)Th/^(232)Th, ^(228)Ra/^(226)Ra, and ^(226)Ra/Ba river ratios are comparable to those of source rocks, consistent with similar release rates of these nuclides from U-, Th-, and Ba-bearing minerals. River ratios of (^(230)Th/^(238)U)_(AR) and (^(226)Ra/^(238)U)_(AR) are <1, so that Th and possibly Ra are accumulating in the weathering regions, and the weathering profile is still evolving. Low (^(228)Ra/^(232)Th)_(AR) and (^(226)Ra/^(230)Th)^(AR) ratios indicate that Th is preferentially retained over Ra. River (^(234)Th/^(238)U)_(AR) ratios are greater than (^(230)Th/^(238)U)_(AR) ratios and suggest that in systems where river inputs are well characterized, these ratios can be used to calculate Th transit times through the watershed. Filtration data indicate that although a dominant fraction of the Th is transported in the river on particles, the rest is almost entirely carried by colloids.\nThe Kalix River discharges into the Baltic Sea. Model calculations for the transport of Th and Ra isotopes in the Baltic Sea show that the high ratios of (^(234)Th/^(238)U)_(AR) found here reflect long Th residence times relative to particle scavenging of \u223c50 d. The water column ^(232)Th budget is dominated by eolian inputs. The ^(226)Ra concentrations may be higher than those of water inflows, with \u226460% derived from underlying sediments. A greater fraction of ^(228)Ra is derived from sediments to balance the decay of ^(228)Ra within the water column during the 35-yr residence time of water in the Baltic. The Baltic (^(228)Ra/^(226)Ra)_(AR) ratios, which are relatively constant over a range of salinities, are fortuitously similar to those of the river inflows.", "doi": "10.1016/S0016-7037(01)00610-X", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2001-08-01", "series_number": "15", "volume": "65", "issue": "15", "pages": "2439-2459" }, { "id": "authors:3c1pr-4aj96", "collection": "authors", "collection_id": "3c1pr-4aj96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140116-084052497", "type": "article", "title": "Aluminum-26 in calcium-aluminum-rich inclusions and chondrules from unequilibrated ordinary chondrites", "author": [ { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "MacPherson", "given_name": "Glenn J.", "clpid": "MacPherson-G-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Russell", "given_name": "Sara S.", "clpid": "Russell-S-S" }, { "family_name": "Srinivasan", "given_name": "Gopalan", "clpid": "Srinivasan-G" } ], "abstract": "In order to investigate the distribution of ^(26)A1 in chondrites, we measured aluminum-magnesium systematics in four calcium-aluminum-rich inclusions (CAIs) and eleven aluminum-rich chondrules from unequilibrated ordinary chondrites (UOCs). All four CAIs were found to contain radiogenic ^(26)Mg (^(26)Mg^*) from the decay of ^(26)A1. The inferred initial ^(26)Al/^(27)Al ratios for these objects ((^(26)Al/^(27)Al)_0 \u2245 5 \u00d7 10^(\u22125)) are indistinguishable from the (^(26)Al/^(27)Al)_0 ratios found in most CAIs from carbonaceous chondrites. These observations, together with the similarities in mineralogy and oxygen isotopic compositions of the two sets of CAIs, imply that CAIs in UOCs and carbonaceous chondrites formed by similar processes from similar (or the same) isotopic reservoirs, or perhaps in a single location in the solar system. We also found ^(26)Mg^* in two of eleven aluminum-rich chondrules. The (^(26)Al/^(27)Al)_0 ratio inferred for both of these chondrules is \u223c1 \u00d7 10^(\u22125), clearly distinct from most CAIs but consistent with the values found in chondrules from type 3.0\u20133.1 UOCs and for aluminum-rich chondrules from lightly metamorphosed carbonaceous chondrites (\u223c0.5 \u00d7 10^(\u22125) to \u223c2 \u00d7 10^(\u22125)). The consistency of the (^(26)Al/^(27)Al)_0 ratios for CAIs and chondrules in primitive chondrites, independent of meteorite class, implies broad-scale nebular homogeneity with respect to ^(26)Al and indicates that the differences in initial ratios can be interpreted in terms of formation time. A timeline based on ^(26)Al indicates that chondrules began to form 1 to 2 Ma after most CAIs formed, that accretion of meteorite parent bodies was essentially complete by 4 Ma after CAIs, and that metamorphism was essentially over in type 4 chondrite parent bodies by 5 to 6 Ma after CAIs formed. Type 6 chondrites apparently did not cool until more than 7 Ma after CAIs formed. This timeline is consistent with ^(26)Al as a principal heat source for melting and metamorphism.", "doi": "10.1111/j.1945-5100.2001.tb01934.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2001-07", "series_number": "7", "volume": "36", "issue": "7", "pages": "975-997" }, { "id": "authors:w2h7n-3z024", "collection": "authors", "collection_id": "w2h7n-3z024", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-085744777", "type": "article", "title": "Inferences on aspects of stellar evolution and the evolution of galaxies", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "In this report we will try to summarize some key observations on isotopic abundances\nof radioactive nuclei in meteorites and their relationship to stellar sources. We will also\ncover the transition from the first generation of supermassive stars to the \"normal\" stellar\npopulation (including supernovae) in a galaxy. Two distinctive approaches are presented.\nThe first is to utilize the observations on meteorites to infer the sources of radioactive\nnuclei in the solar system. We will show that some radioactive nuclides are clearly related\nto production in AGB stars, while others are produced in r-processes in SNII. We will\nshow that there must be at least two distinct types of SNII sites with very different time\nscales for replenishing the ISM with different r-nuclides. This model leads us to a means\nof identifying the first generation of supernovae that contribute to the galactic inventory\nof r-process nuclei and of Fe. This is then related to observations of low metallicity\nstars and connects/disconnects more general r-process abundance patterns with/from Fe\nproduction and points to a first generation of stars having distinct characteristics. This\napproach is the view backward in time. The second approach uses the phenomenological\nmodel derived from the above considerations and applies it to the chronology evolving\nfrom Big Bang toward the present epoch. The latter approach proclaims an \"absolute\"\ntime scale and what the evolutionary path of condensing, star-forming, baryonic matter\nshould be. I am obviously going beyond my own capability in this approach, but it is\nat least interesting and may contain some seeds of truth. The assumption of a universal\nr-process that produces both Fe and r-nuclei in a coupled manner is in violation of the\nobservations that the correlation of r-elements with Fe breaks down at [Fe/H] \u227e - 3 as\nobserved in halo stars. Furthermore, the ab initio approaches to early star formation,\nchemical evolution, and the early universe, have not proven very successful so far. There\nhas been no real success in establishing the relationship between the condensation of cold\ndark matter early in the universe (z \u227310?) with the aggregation of baryonic matter and\nthe formation of the first generation of stars.", "doi": "10.1016/S0375-9474(01)00718-7", "issn": "0375-9474", "publisher": "Elsevier", "publication": "Nuclear Physics A", "publication_date": "2001-05-21", "series_number": "1-2", "volume": "688", "issue": "1-2", "pages": "297C-307C" }, { "id": "authors:qw5ya-rcq87", "collection": "authors", "collection_id": "qw5ya-rcq87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-155623986", "type": "article", "title": "Abundances in the Uranium-rich Star CS 31082-001", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The recent discovery by Cayrel et al. of U in CS 31082-001 along with Os and Ir at greatly enhanced abundances but with [Fe/H] = -2.9 strongly reinforces the argument that there are at least two kinds of Type II supernova (SN II) sources for r-nuclei. One source is the high-frequency H events responsible for heavy r-nuclei (A > 135) but not Fe. The H-yields calculated from data on other ultra-metal-poor stars and the Sun provide a template for quantitatively predicting the abundances of all other r-elements. In CS 31082-001 these should show a significant deficiency at A < 135 relative to the solar r-pattern. It is proposed that CS 31082-001 should have had a companion that exploded as an SN II H event. If the binary survived the explosion, this star should now have a compact companion, most likely a stellar-mass black hole. Comparison of abundance data with predicted values and a search for a compact companion should provide a stringent test of the proposed r-process model. The U-Th age determined by Cayrel et al. for CS 31082-001 is, to within substantial uncertainties, in accord with the r-process age determined from solar system data. The time gap between the big bang and the onset of normal star formation allows r-process chronometers to provide only a lower limit on the age of the universe.", "doi": "10.1086/320266", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2001-04-26", "series_number": "1", "volume": "552", "issue": "1", "pages": "L55-L58" }, { "id": "authors:wq62b-13150", "collection": "authors", "collection_id": "wq62b-13150", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-071952813", "type": "article", "title": "The transport of U- and Th-series nuclides in a sandy unconfined aquifer", "author": [ { "family_name": "Tricca", "given_name": "A.", "clpid": "Tricca-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Baskaran", "given_name": "M.", "clpid": "Baskaran-M" } ], "abstract": "A comprehensive evaluation of the transport of U, Th, Ra, and Rn nuclides of the ^(238)U- and ^(232)Th-decay series in an unconfined sandy aquifer (Long Island, NY) was conducted. Groundwater data are compared with results of a theoretical transport model of weathering of aquifer grains and interaction with surface coatings to establish relationships between the concentrations of the radionuclide activities in the water and flow line distance. The data provide estimates for geochemical parameters including weathering rates and chemical reactivities in both the vadose zone and the aquifer. A theoretical treatment of the transport is presented that considers the reaction between the water and a reactive surface layer. It is found that a model with chemical exchange between the surface layer and the water for all species is not valid, and that the effects of saturation and \"irreversible\" precipitation of Th is required.\nThe water table shows a relatively wide range in U activities, the only element in the U-Th series for which vadose zone input is significant in the aquifer. High weathering of U and recoil inputs of ^(234)U to the water occur in the upper 3 m of the vadose zone, while lower weathering and removal of U from the water occur below. The deeper aquifer has variable ^(238)U activities that can be accounted for by input from the vadose zone and is not a result of non-conservative behavior. The isotopic composition of U is shown to be directly related to the recoil rate relative to the weathering rate. The wide range of ^(238)U in the aquifer waters is a reflection of diverse vadose zone inputs, showing that dispersive mixing is not a dominant effect. The higher values of \u03b4^(234)U in the aquifer reflect the recoil/weathering input ratios from within the aquifer where the weathering rate is lower than the vadose zone. Both high U activities and high \u03b4^(234)U values cannot be obtained in the vadose zone or within reasonable flow distances in the aquifer. Radium isotopes are found to be in exchange equilibrium with the surface layer. ^(224)Ra, ^(228)Ra, and ^(226)Ra have comparable activities throughout the aquifer. In the vadose zone, the dominant input of Ra to groundwater is weathering and recoil. As found elsewhere, the ^(222)Rn in the water is a large fraction (\u223c5%) of the Rn produced in the aquifer rock. This cannot be due to Ra precipitation onto surface coatings in the aquifer as supported by present weathering with Th in exchange equilibrium with the surface layer. It is found that Th is saturated in the waters under oxidizing conditions so that the weathering input is irreversibly precipitating onto surfaces. However, it is shown that under somewhat reducing conditions, Th activities are much higher and the Th/U ratio in the solution is approximately that of the rock. We propose that under oxidizing conditions the source of Rn is a surface coating enriched in ^(232)Th and ^(230)Th. This Th was precipitated in an earlier phase during rapid dissolution of readily weathered phases that contain \u223c10% of the U-Th inventory of the rock, with the associated U carried away in solution. Therefore, the previously precipitated ^(230)Th and ^(232)Th produce daughter nuclides in the surface coating which are the dominant contributors of Ra and Rn to the ground water. In particular, Rn is provided by very efficient losses (by diffusion or recoil) from the surface coating. This then does not require recent, large recoil losses from the parent rock or the presence of nanopores in the rock. The first data of both long-lived ^(232)Th and short-lived ^(234)Th and ^(228)Th in ground water is reported. The Th isotope activities indicate that desorption kinetics are slow and provide the first estimate, based on field data, of the Th desorption rate from an aquifer surface. The mean residence time of Th in the surface coating is \u223c3000 y while in the water it is \u223c1 h. Ra is in partition equilibrium with the aquifer surface layer. However, the strong fixation of Th on surface coatings is very susceptible to changes in oxidation state as is shown by a comparison of two adjacent aquifers. This makes it difficult to define with certainty the retentive characteristics in natural systems. In general, it is shown that the distributions of naturally occurring nuclides can be used to calculate values for transport parameters that are applicable to the transport of anthropogenic nuclides.", "doi": "10.1016/S0016-7037(00)00617-7", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2001-04-15", "series_number": "8", "volume": "65", "issue": "8", "pages": "1187-1210" }, { "id": "authors:hf33s-tke36", "collection": "authors", "collection_id": "hf33s-tke36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141112-072428369", "type": "article", "title": "O'Connell Receives 2000 Inge Lehmann Medal", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "O'Connell", "given_name": "Richard J.", "clpid": "O'Connell-R-J" } ], "abstract": "Richard J. O'Connell was awarded the Inge Lehmann Medal at the AGU Fall Meeting Honors Ceremony, which was held on December 17, 2000, in San Francisco, California. The medal recognizes outstanding contributions to the understanding of the structure, composition, and dynamics of the Earth's mantle and core.", "doi": "10.1029/01EO00091", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "2001-04-10", "series_number": "15", "volume": "82", "issue": "15", "pages": "175-180" }, { "id": "authors:tnb8x-74s33", "collection": "authors", "collection_id": "tnb8x-74s33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131210-143422073", "type": "article", "title": "Evolution of O Abundance Relative to Fe", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a three-component mixing model for the evolution of O abundance relative to Fe, taking into account the contributions of the first very massive stars (with masses of \u2273100 M_\u2609) formed from Big Bang debris. We show that the observations of O and Fe abundances in metal-poor stars in the Galaxy by Israelian et al. in 1998 and by Boesgaard et al. in 1999 can be well represented both qualitatively and quantitatively by this model. We use the representation of the number ratios (O/Fe) versus 1/(Fe/H). In this representation, if there is only a single source with a fixed production ratio of O to Fe beyond a certain point, the subsequent evolution of (O/Fe) is along a straight line segment. Under the assumption of an initial Fe ([Fe/H] ~ -3) and O inventory caused by the prompt production by the first very massive stars, the data of Israelian et al. and Boesgaard et al. at -3\u227e[Fe/H]\u227e-1 are interpreted to result from the addition of O and Fe only from Type II supernovae (SNII) to the prompt inventory. At [Fe/H] \u2273-1, SNII still contribute O while both SNII and Type Ia supernovae contribute Fe. During this later stage, (O/Fe) sharply drops off to an asymptotic value of ~0.8 (O/Fe)_\u2609. The value of (O/Fe) for the prompt inventory at [Fe/H] ~ -3 is found to be (O/Fe) ~ 20 (O/Fe)_\u2609. This result suggests that protogalaxies with low \"metallicities\" should exhibit high values of (O/Fe). The C/O ratio produced by the first very massive stars is expected to be \u00ab 1 so that all the C should be tied up as CO and that C dust and hydrocarbon compounds should be quite rare at epochs corresponding to [Fe/H] \u227e -3.", "doi": "10.1086/319084", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2001-03-01", "series_number": "1", "volume": "549", "issue": "1", "pages": "337-345" }, { "id": "authors:9jk30-cyk97", "collection": "authors", "collection_id": "9jk30-cyk97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-070801709", "type": "article", "title": "The Importance of colloids for the behavior of uranium isotopes in the low-salinity zone of a stable estuary", "author": [ { "family_name": "Andersson", "given_name": "Per S.", "clpid": "Andersson-P-S" }, { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Gustafsson", "given_name": "\u00d6.", "clpid": "Gustafsson-\u00d6" }, { "family_name": "Ingri", "given_name": "J.", "clpid": "Ingri-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Particle-mediated removal processes of U isotopes were investigated during spring flood discharge in the low-salinity zone (LSZ, up to 3 practical salinity units [psu]) of a stable estuary. A shipboard ultrafiltration cross-flow filtration (CFF) technique was used to separate particles (>0.2 \u03bcm) and colloids (between 3000 daltons (3 kD) and 0.2 \u03bcm) from ultrafiltered water (<3 kD) containing \"dissolved\" species. Sediment traps were used to collect sinking material. Concentration of Fe and organic C, which are indicators of the major U carrier phases, were used to interpret the behavior of ^(234)U-^(238)U during estuarine mixing.\nColloids dominated the river water transport of U, carrying \u224890% of the U. On entering the estuary, colloids accounted for the dominant fraction of U to about a salinity of 1 psu, but only a minor fraction (<5%) at 3 psu. A substantial fraction of the total U is removed at <1 psu by Fe-organic rich colloids that aggregate and sink during initial estuarine mixing in the Kalix River estuary. In contrast, at salinities >1 psu, there is a general correlation between U and salinity in all filtered fractions. The ^(234)U/^(238)U ratios in different filtered fractions and sinking particles were generally indistinguishable at each station and showed enrichment in ^(234)U, compared with secular equilibrium (\u03b4^(234)U = 266\u2013567). This clearly shows that all size fractions are dominated by nondetrital U. Consideration of U isotope systematics across the estuary reveals that substantial U exchange must occur involving larger particles at least to 1 psu and involving colloids at least to \u22481.5 psu. Further exchange at higher salinities may also occur, as the proportion of U on colloids decreases with increasing salinity. This may be due to decreasing colloid concentration and increasing stabilization of uranyl carbonate complexes during mixing in the estuary.\nThe results show that although U is a soluble element that shows generally conservative mixing in estuaries, removal occurs in the very low salinity zone, and this zone represents a significant sink of U. Variation in composition and concentration of colloidal particles between different estuaries might thus be an important factor for determining the varying behavior of U between estuaries.", "doi": "10.1016/S0016-7037(00)00514-7", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2001-01-01", "series_number": "1", "volume": "65", "issue": "1", "pages": "13-25" }, { "id": "authors:31df1-yhh13", "collection": "authors", "collection_id": "31df1-yhh13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140415-085757526", "type": "article", "title": "A petrographic, chemical, and isotopic study of calcium-aluminum-rich inclusions and aluminum-rich chondrules from the Axtell (CV3) chondrite", "author": [ { "family_name": "Srinivasan", "given_name": "G.", "clpid": "Srinivasan-G" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Petrographic, compositional, and isotopic characteristics were studied for three calcium-aluminum-rich inclusions (CAIs) and four plagioclase-bearing chondrules (three of them Al-rich) from the Axtell (CV3) chondrite. All seven objects have analogues in Allende (CV3) and other primitive chondrites, yet Axtell, like most other chondrites, contains a distinctive suite of CAIs and chondrules. In common with Allende CAIs, CAIs in Axtell exhibit initial ^(26)Al/^(27)Al ratios ((^(26)Al/^(27)Al)0) ranging from \u223c5 \u00d7 10^(\u22125) to <1.1 \u00d7 10^(\u22125), and plagioclase-bearing chondrules have (^(26)Al/^(27)Al)0 ratios of \u223c3 \u00d7 10^(\u22126) and lower. One type-A CAI has the characteristics of a FUN inclusion. The Al-Mg data imply that the plagioclase-bearing chondrules began to form >2 Ma after the first CAIs. As in other CV3 chondrites, some objects in Axtell show evidence of isotopic disturbance. Axtell has experienced only mild thermal metamorphism (<600 \u00b0C), probably not enough to disturb the Al-Mg systematics. Its CAIs and chondrules have suffered extensive metasomatism, probably prior to final accretion. These data indicate that CAIs and chondrules in Axtell (and other meteorites) had an extended history of several million years before their incorporation into the Axtell parent body. These long time periods appear to require a mechanism in the early solar system to prevent CAIs and chondrules from falling into the Sun via gas drag for several million years before final accretion.\n\nWe also examined the compositional relationships among the four plagioclase-bearing chondrules (two with large anorthite laths and two barred-olivine chondrules) and between the chondrules and CAIs. Three processes were examined: (1) igneous differentiation, (2) assimilation of a CAI by average nebular material, and (3) evaporation of volatile elements from average nebular material. We find no evidence that igneous differentiation played a role in producing the chondrule compositions, although the barred olivine compositions can be related by addition or subtraction of olivine. Methods (2) and (3) could have produced the composition of one chondrule, AXCH-1471, but neither process explains the other compositions. Our study indicates that plagioclase-bearing objects originated through a variety of processes.", "doi": "10.1111/j.1945-5100.2000.tb01520.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2000-11", "series_number": "6", "volume": "35", "issue": "6", "pages": "1333-1354" }, { "id": "authors:rgxyk-vc648", "collection": "authors", "collection_id": "rgxyk-vc648", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-105039012", "type": "article", "title": "High time resolution by use of the ^(26)Al chronometer in the\n multistage formation of a CAI", "author": [ { "family_name": "Hsu", "given_name": "Weibiao", "clpid": "Hsu-W" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" } ], "abstract": "The Allende calcium-rich inclusion (CAI) 5241 has been found to contain distinct initial ^(26)Al/^(27)Al in the three consecutive igneous zones that have been identified by extensive petrogenetic studies to have formed in three distinct crystallization events. The zones in order of sequence of formation from the petrologic observations are: (1) spinel-free islands (SFI) included in (2) a pyroxene\u2013spinel-rich core (SRC) which in turn is included in (3) a melilite mantle (MM). The initial (^(26)Al/^(27)Al) values of these zones are respectively (4.6\u20135.0)\u00d710^(\u22125), 4.3\u00d710^(\u22125), and 3.3\u00d710^(\u22125). It is argued that these distinct (^(26)Al/^(27)Al)0 values are not the result of metamorphism but reflect the relative times of formation by crystallization from melts. Relative to the canonical value of (^(26)Al/^(27)Al)0=5\u00d710^(\u22125), we find the following chronology: t_(SFI)\u22480, t_(SRC)\u224810^5 yr and t_(MM)\u22484\u00d710^5 yr. The three-layer CAI is inferred to have sampled a reservoir with an initial uniform ^(26)Al/^(27)Al ratio that decreased in value due to radioactive decay. From these observations we conclude that we have resolved time differences of a few hundred thousand years at the very early stages of formation of the solar system. The SFI, SRC, and MM zones reflect sequential addition of molten CAI material which crystallized rapidly without seriously metamorphosing the previously formed material. These additions took place over a time of about 400\u2008000 years. We believe that these sequential events are not compatible with condensation in a hot region of the solar nebula. It is proposed that a scenario involving stages of protoplanetary accretion and of melt generation in protoplanetary sites heated by ^(26)Al might provide a possible source for CAIs and chondrules.", "doi": "10.1016/S0012-821X(00)00233-8", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2000-10-15", "series_number": "1", "volume": "182", "issue": "1", "pages": "15-29" }, { "id": "authors:k90f0-y5h90", "collection": "authors", "collection_id": "k90f0-y5h90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-115249837", "type": "article", "title": "Late Eocene impact ejecta: geochemical and isotopic\n connections with the Popigai impact structure", "author": [ { "family_name": "Whitehead", "given_name": "J.", "clpid": "Whitehead-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Spray", "given_name": "J. G.", "clpid": "Spray-J-G" }, { "family_name": "Grieve", "given_name": "R. A. F.", "clpid": "Grieve-R-A-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Late Eocene microtektites and crystal-bearing microkrystites extracted from DSDP and ODP cores from the Atlantic, Pacific, and Indian oceans have been analyzed to address their provenance. A new analysis of Nd and Sr isotopic compositions confirms previous work and the assignment of the uppermost microtektite layer to the North American tektites, which are associated with the 35.5 Ma, 85 km diameter Chesapeake impact structure of Virginia, USA. Extensive major element and Nd and Sr isotopic analyses of the microkrystites from the lowermost layer were obtained. The melanocratic microkrystites from Sites 216 and 462 in the Indian and Pacific oceans possess major element chemistries, Sr and Nd isotopic signatures and Sm\u2013Nd, T_(CHUR), model ages similar to those of tagamite melt rocks in the Popigai impact structure. They also possess Rb\u2013Sr, T_(UR), model ages that are younger than the tagamite T_(CHUR) ages by up to \u223c1 Ga, which require a process, as yet undefined, of Rb/Sr enrichment. These melanocratic microkrystites are consistent with a provenance from the 35.7 Ma, 100 km diameter Popigai impact structure of Siberia, Russia, while ruling out other contemporaneous structures as a source. Melanocratic microkrystites from other sites and leucocratic microkrystites from all sites possess a wide range of isotopic compositions (\u03f5(^(143)Nd) values of \u221216 to \u221227.7 and \u03f5(^(87)Sr) values of 4.1\u2013354.0), making the association with Popigai tagamites less clear. These microkrystites may have been derived by the melting of target rocks of mixed composition, which were ejected without homogenization. Dark glass and felsic inclusions extracted from Popigai tagamites possess \u03f5(^(143)Nd) and \u03f5(^(87)Sr) values of \u221226.7 to \u221227.8 and 374.7 and 432.4, respectively, and T_(CHUR) and T_(UR) model ages of 1640\u20131870 Ma and 240\u20131830 Ma, respectively, which require the preservation of initially present heterogeneity in the source materials. The leucocratic microkrystites possess diverse isotopic compositions that may reflect the melting of supra-basement sedimentary rocks from Popigai, or early basement melts that were ejected prior to homogenization of the Popigai tagamites. The ejection of melt rocks with chemistries consistent with a basement provenance, rather than the surface \u223c1 km of sedimentary cover rocks, atypically indicates a non-surficial source to some of the ejecta. Microkrystites from two adjacent biozones possess statistically indistinguishable major element compositions, suggesting they have a single source. The occurrence of microkrystites derived from a single impact event, but in different biozones, can be explained by: (1) diachronous biozone boundaries; (2) post-accumulation sedimentary reworking; or (3) erroneous biozonation.", "doi": "10.1016/S0012-821X(00)00225-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2000-09-30", "series_number": "4", "volume": "181", "issue": "4", "pages": "473-487" }, { "id": "authors:p5b25-rvx76", "collection": "authors", "collection_id": "p5b25-rvx76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-101539223", "type": "article", "title": "Rhenium-osmium fractionation in group IIIAB iron meteorites", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Group IIIAB is a large iron meteorite group, showing compositional trends suggestive of formation by extensive fractional crystallization of a magma. However, there are problerus in explaining some key IIIAB trends using simple\nfractional crystallization models and published partition coefficients.", "doi": "10.1111/j.1945-5100.2000.tb01796.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "2000-09", "series_number": "S5", "volume": "35", "issue": "S5", "pages": "A39-A40" }, { "id": "authors:erf20-r3d37", "collection": "authors", "collection_id": "erf20-r3d37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131219-100635152", "type": "article", "title": "Calcium-Aluminum-Rich Inclusions from Enstatite Chondrites: Indigenous or Foreign?", "author": [ { "family_name": "Guan", "given_name": "Yunbin", "orcid": "0000-0002-7636-3735", "clpid": "Guan-Yunbin" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "MacPherson", "given_name": "Glenn J.", "clpid": "MacPherson-G-J" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The primary mineral assemblages and initial ^(26)Al/^(27)Al ratios of rare calcium-aluminum\u2013rich inclusions (CAIs) from enstatite (E) chondrites are similar to those of CAIs from other chondrite classes. CAIs from all chondrite classes formed under oxidizing conditions that are much different from the reducing conditions under which the E chondrites formed. Either CAIs formed at an earlier, more oxidizing epoch in the region where E chondrites ultimately formed, or they formed at a different place in the solar nebula and were transported into the E chondrite formation region.", "doi": "10.1126/science.289.5483.1330", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2000-08-25", "series_number": "5483", "volume": "289", "issue": "5483", "pages": "1330-1333" }, { "id": "authors:btvdw-zan72", "collection": "authors", "collection_id": "btvdw-zan72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-095347998", "type": "article", "title": "A Model of Metallicity Evolution in the Early Universe", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" } ], "abstract": "We apply the phenomenological model used to explain the abundances of Fe and r-process elements in very metal-poor stars in the Galaxy to [Fe/H] of damped Ly\u03b1 systems. It is assumed that the first stars that formed after the big bang were very massive and that they promptly enriched the interstellar medium to [Fe/H] ~ -3, at which metallicity the formation of normal stars took over. Subsequent Fe enrichment was provided by Type II supernovae. The range of [Fe/H] at a given redshift z for damped Ly\u03b1 systems is explained by the time t* after the big bang at which normal star formation started in an individual protogalactic system. The average t* is \u224880% the age of the universe for damped Ly\u03b1 systems at z \u2248 1.5-4.5, indicating a long delay between the big bang and the turn-on of protogalaxies. It is inferred that a substantial fraction of the total baryonic matter may not have been aggregated into protogalaxies with normal star formation events until a late time corresponding to z ~ 1.5. The data near z = 2.2 indicate that the rate of turn-on of protogalaxies was initially very low and that it slowly reached a maximum at ~3 Gyr after the big bang. This rate of turn-on of galaxies may be important in understanding the rate of formation of quasars.", "doi": "10.1086/312812", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2000-08-01", "series_number": "2", "volume": "538", "issue": "2", "pages": "L99-L102" }, { "id": "authors:89hk7-21062", "collection": "authors", "collection_id": "89hk7-21062", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131120-074209032", "type": "article", "title": "Stellar abundances in the early galaxy and two r-process components", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present quantitative predictions for the abundances of r-process elements in stars formed very early in the Galactic history using a phenomenological two-component r-process model based on the ^(129)I and ^(182)Hf inventory in the early solar system. This model assumes that a standard mass of the ISM dilutes the debris from an individual supernova. High-frequency supernova H events and low-frequency supernova L events are proposed in the model with characteristics determined by the meteoritic data on ^(129)I and ^(182)Hf. The yields in an H or L event are obtained from these characteristics and the solar r-process abundances under the assumption that the yield template for the high-mass (A>130) nuclei associated with ^(182)W or the low-mass (A\u2264130) nuclei associated with ^(127)I is the same for both the H and L events and follows the corresponding solar r-pattern in each mass region. This choice of the yield templates is justified by the regular solar-like r-process abundance pattern for Ba and higher atomic numbers observed in very metal-poor stars. The abundance of Eu, not Fe, is proposed as a key guide to the age of very metal-poor stars. We predict that stars with log \u03b5(Eu) = - 2.98 to \u22122.22 were formed from an ISM contaminated most likely by a single H event within the first ~ 10^7 yr of the Galactic history and should have an Ag/Eu abundance ratio less than the corresponding solar r-process value by a factor of at least 10. Many of the very metal-poor stars observed so far are considered here to have been formed from an ISM contaminated by many (\u223c10) r-process events. Stars formed from an ISM contaminated only by a pure L event would have an Ag/Eu ratio higher than the corresponding solar r-process value but would be difficult to find due to the low-frequency of the L events. However, variations in the relative abundances of the low- and high-mass regions should be detectable in very metal-poor stars.", "doi": "10.1016/S0370-1573(00)00017-X", "issn": "0370-1573", "publisher": "Elsevier", "publication": "Physics Reports", "publication_date": "2000-08", "volume": "333-334", "pages": "77-108" }, { "id": "authors:t2s62-84e59", "collection": "authors", "collection_id": "t2s62-84e59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131113-093032284", "type": "article", "title": "Osmium isotopes in hydrothermal fluids from the Juan de Fuca Ridge", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hofmann", "given_name": "A. W.", "clpid": "Hofmann-A-W" }, { "family_name": "Butterfield", "given_name": "D. A.", "clpid": "Butterfield-D-A" } ], "abstract": "We present Os data for axial high-temperature and off-axial low-temperature hydrothermal solutions from the Juan de Fuca Ridge. The high-temperature, H\u2082S-bearing axial fluids have unradiogenic Os isotopes pointing to a nearly complete domination of osmium isotopes from the basalts during hydrothermal circulation. The ridge axis fluids typically do not show large enrichment in osmium concentration over seawater although one high-temperature fluid has an Os concentration enhanced by a factor of 4 above seawater. It appears that the Os concentration of high-temperature hydrothermal fluids is typically buffered at roughly the seawater concentration. We suggest that subseafloor precipitation of pyrite from the high-temperature hydrothermal fluids controls the osmium transportation. The axial hydrothermal activity does not supply significant amounts of unradiogenic osmium to the deep oceans. In contrast, a low-temperature off-axis fluid is enriched in non-radiogenic osmium over seawater by a factor of 9, showing much less precipitation of osmium at low temperature. Because a large fraction of the cooling of oceanic lithosphere occurs on ridge flanks, Os from low-temperature, ridge-flank hydrothermal circulation may be a significant contributor to the balance of Os in the oceans. A detailed balance between Os contributions from dissolution of cosmic dust and hydrothermal fluids is still not possible. The low-temperature hydrothermal sample gives \u00b9\u2078\u2077Os/\u00b9\u2078\u2078Os = 0.110 \u00b1 0.001. This extremely unradiogenic osmium can only come from a source that underwent depletion of Re over 2.6 Ga ago. Assuming no contamination during sample collection, this result suggests that the convecting upper mantle contains ancient depleted material that imparted unradiogenic osmium to intruding basaltic melts.", "doi": "10.1016/S0012-821X(00)00099-6", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2000-06-15", "series_number": "1", "volume": "179", "issue": "1", "pages": "139-152" }, { "id": "authors:h9j6t-z5229", "collection": "authors", "collection_id": "h9j6t-z5229", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140115-154423834", "type": "article", "title": "Factors controlling the groundwater transport of U, Th, Ra, and Rn", "author": [ { "family_name": "Tricca", "given_name": "A.", "clpid": "Tricca-A" }, { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A model for the groundwater transport of naturally occurring U, Th, Ra, and Rn nuclides in the ^(238)U and ^(232)Th decay series is discussed. The model developed here takes into account transport by advection and the physico-chemical processes of weathering, decay, \u03b1-recoil, and sorption at the water-rock interface. It describes the evolution along a flowline of the activities of the ^(238)U and ^(232)Th decay series nuclides in groundwater. Simple sets of relationships governing the activities of the various species in solution are derived, and these can be used both to calculate effective retardation factors and to interpret groundwater data. For the activities of each nuclide, a general solution to the transport equation has been obtained, which shows that the activities reach a constant value after a distance \u03f0_i, characteristic of each nuclide. Where \u03f0_i is much longer than the aquifer length, (for ^(238)U, ^(234)U, and ^(232)Th), the activities grow linearly with distance. Where \u03f0_i is short compared to the aquifer length, (for ^(234)Th, ^(230)Th, ^(228)Th, ^(228)Ra, and ^(224)Ra), the activities rapidly reach a constant or quasi-constant activity value. For ^(226)Ra and ^(222)Rn, the limiting activity is reached after 1 km.\nHigh \u03b4 ^(234)U values (proportional to the ratio ^(\u025b234)Th/^(W238)U) can be obtained through high recoil fraction and/or low weathering rates. The activity ratios ^(230)Th/^(232)Th, ^(228)Ra/^(226)Ra and ^(224)Ra/^(226)Ra have been considered in the cases where either weathering or recoil is the predominant process of input from the mineral grain. Typical values for weathering rates and recoil fractions for a sandy aquifer indicate that recoil is the dominant process for Th isotopic ratios in the water. Measured data for Ra isotope activity ratios indicate that recoil is the process generally controlling the Ra isotopic composition in water. Higher isotopic ratios can be explained by different desorption kinetics of Ra. However, the model does not provide an explanation for ^(228)Ra/^(226)Ra and ^(224)Ra/^(226)Ra activity ratios less than unity.\nFrom the model, the highest ^(222)Rn emanation equals 2_\u025b. This is in agreement with the hypothesis that ^(222)Rn activity can be used as a first approximation for input by recoil (Krishnaswamiet al 1982). However, high ^(222)Rn emanation cannot be explained by production from the surface layer as formulated in the model. Other possibilities involve models including surface precipitation, where the surface layer is not in steady-state.", "doi": "10.1007/BF02719153", "issn": "0253-4126", "publisher": "Spinger India", "publication": "Journal of Earth System Science", "publication_date": "2000-03", "series_number": "1", "volume": "109", "issue": "1", "pages": "95-108" }, { "id": "authors:r0xh1-69s65", "collection": "authors", "collection_id": "r0xh1-69s65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-131332141", "type": "article", "title": "Ion probe measurements of Os, Ir, Pt, and Au in individual phases of iron meteorites", "author": [ { "family_name": "Hsu", "given_name": "Weibiao", "clpid": "Hsu-W" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have developed a technique to measure abundances of Os, Ir, Pt, and Au in situ in Fe-Ni metal on a microscale using secondary-ion mass spectrometry. A Cs^+ beam is used to generate negative secondary ions, and interferences from molecular ions are eliminated by a combination of 40 eV of energy filtering and a mass resolution of \u223c1900. Ion yields for Fe, Co, Ni, and the PGEs vary considerably from spot to spot in meteoritic metal samples. Ion yield variations for Os and Ir correlate strongly with the Fe ion yield, that for Pt is weakly correlated, and that for Au is essentially uncorrelated. From ion yields for meteorite standards and the correlations with Fe ion yield, it is possible to obtain concentrations of Os, Ir, Pt, and Au in meteorite samples. Using this technique, a Cs^+ beam current of 10 nA gives a spatial resolution of 10\u201320 \u03bcm and detection limits of less than 1 ppm for Os, less than 0.1 ppm for Ir, and 10\u201320 ppb for Pt and Au. With refinement, it should be possible to measure Rh, Pd, and Ag and to improve the spatial resolution. However, Re, Ru, W, and Hf can only be measured as positive secondary ions.\n\nWe have measured the abundances of Os, Ir, Pt, and Au in kamacite, taenite, and/or plessite in five iron meteorites: Canyon Diablo (IA), Cape York (Agpalilik) (IIIA), Colomera (IIE), Cruz del Aire (Anom), and Wallapai (IID). Our measurements show that Os, Ir, Pt, and Au partition preferentially into taenite relative to kamacite during slow cooling. Measured abundance ratios (taenite/kamacite) range from \u223c1.3 to \u223c2.1 for Os, Ir, and Pt, and from \u223c2 to \u223c6 for Au. These ratios are consistent with those determined recently by laser-ablation ICPMS, but differ significantly from those determined by earlier workers. Low-temperature taenite/kamacite distribution coefficients inferred from our data are \u223c2.1 for Os, \u223c1.6 for Ir, \u223c1.9 for Pt, and \u223c6 for Au. PGEs are not enriched in taenite as much as Ni. Partitioning is controlled by the interplay of the size and electron configuration of Os, Ir, Pt, and Au and the crystal structures of kamacite and taenite. The ion probe can be used to further investigate the distribution and subsolidus redistribution of PGEs and Au in iron meteorites and in the metal in chondrites and stony irons.", "doi": "10.1016/S0016-7037(99)00378-6", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2000-03", "series_number": "6", "volume": "64", "issue": "6", "pages": "1133-1147" }, { "id": "authors:mwspf-we139", "collection": "authors", "collection_id": "mwspf-we139", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-105013874", "type": "article", "title": "Citation for presentation of the 1999 C. C. Patterson Award to R. Lawrence Edwards", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Mr. President, Colleagues, Ladies and Gentlemen:\n\nI received an urgent message that Larry Edwards had telephoned with a request that he should be called at work or at home. My first thought was\u2014what in Heaven's name was wrong? When I reached him, he informed me that nothing was wrong. He was to be awarded the Patterson medal and asked if I would introduce him. That was wonderful news and I was most pleased to accept this happy task. It is a privilege and a delight for me to introduce R. Lawrence Edwards who is to be the recipient of the C. C. Patterson award of the Geochemical Society. This award is for a recent, innovative breakthrough in environmental geochemistry. Having known Claire Patterson since 1948, I have some basis of guessing what his views of Larry Edwards' contributions would be. I think Pud would point a very long, bony finger at Larry Edwards' face and say, \"Edwards, you know I don't like engineers and technologists\u2014but\u2014you have made a scientific breakthrough and do wonderful science,\" and then he would shove the long, bony finger into Larry's chest and say, \"You are a poet and a scientist.\"", "doi": "10.1016/S0016-7037(99)00412-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "2000-02", "series_number": "4", "volume": "64", "issue": "4", "pages": "755-757" }, { "id": "authors:7cc6a-edk49", "collection": "authors", "collection_id": "7cc6a-edk49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-095517692", "type": "article", "title": "Prompt Iron Enrichment, Two r-Process Components, and Abundances in Very Metal-Poor Stars", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Yong-Zhong" } ], "abstract": "We present a model to explain the wide range of abundances for heavy r-process elements (mass number A > 130) at low [Fe/H]. This model requires rapid star formation and/or an initial population of supermassive stars in the earliest condensed clots of matter in order to provide a prompt or initial Fe inventory. Subsequent Fe and r-process enrichment was provided by two types of supernovae: one producing heavy r-elements with no Fe on a rather short timescale and the other producing light r-elements (A \u2264 130) with Fe on a much longer timescale.", "doi": "10.1086/312455", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2000-01-20", "series_number": "1", "volume": "529", "issue": "1", "pages": "L21-L24" }, { "id": "authors:h25kx-z1f44", "collection": "authors", "collection_id": "h25kx-z1f44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-140918131", "type": "article", "title": "Himalayan uplift and osmium isotopes in oceans and rivers", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hofmann", "given_name": "A. W.", "clpid": "Hofmann-A-W" }, { "family_name": "Chakrapani", "given_name": "G. J.", "clpid": "Chakrapani-G-J" } ], "abstract": "Previous studies have shown that ^(187)Os/^(188)Os in seawater has become increasingly radiogenic over the last 40 Ma in a manner analogous to strontium. This rapid rise in the marine ^(187)Os/^(188)Os over the last 17 Ma has been attributed to an increase in the bulk silicate weathering rates resulting from the rise of the Himalayas and/or selective weathering and erosion of highly radiogenic organic rich ancient sediments. The key test of this hypothesis is the ^(187)Os/^(188)Os and the total osmium concentration of the Himalayan rivers. We report the concentration and isotopic composition of osmium in the Ganges, the Brahmaputra, and the Indus rivers. The ^(187)Os/^(188)Os of the Ganges close to its source (at Kaudiyal, 30\u00b005\u2032N, 78\u00b050\u2032E) is 2.65 and [Os] = 45 fM/kg. A second sample of the lower reaches of the Ganges at Patna (25\u00b030\u2032N, 85\u00b010\u2032E) gives ^(187)Os/^(188)Os =1.59 and [Os] = 171 fM/kg. The ^(187)Os/^(188)Os of the Brahmaputra at Guwahati (26\u00b010\u2032N, 91\u00b058\u2032E) is 1.07 and [Os] = 52 fM/kg. A sample of the Indus (Besham, 34\u00b055\u2032N, 72\u00b051\u2032E) has a ^(187)Os/^(188)Os of 1.2 and [Os] = 59 fM/kg. We infer that the Himalayas do not provide either a high flow of osmium or a highly radiogenic osmium component to the oceans. The overall trend for osmium and strontium could be explained by a regularly increasing input of global continental weathering sources but the Himalayas themselves appear not to be the dominant source.", "doi": "10.1016/S0016-7037(99)00305-1", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1999-12", "series_number": "23-24", "volume": "63", "issue": "23-24", "pages": "4005-4012" }, { "id": "authors:d4k1b-wm088", "collection": "authors", "collection_id": "d4k1b-wm088", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131210-113025756", "type": "article", "title": "Probing r-Process Production of Nuclei Beyond ^(209)Bi with Gamma Rays", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Vogel", "given_name": "P.", "orcid": "0000-0003-0587-5466", "clpid": "Vogel-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We estimate gamma-ray fluxes due to the decay of nuclei beyond ^(209)Bi from a supernova or a supernova remnant assuming that the r-process occurs in supernovae. We find that a detector with a sensitivity of ~10^(-7) \u03b3 cm^(-2) s^(-1) at energies from ~40 keV to ~3 MeV may detect fluxes due to the decay of ^(226)Ra, ^(229)Th, ^(241)Am, ^(243)Am, ^(249)Cf, and ^(251)Cf in the newly discovered supernova remnant near Vela. In addition, such a detector may detect fluxes due to the decay of ^(227)Ac and ^(228)Ra produced in a future supernova at a distance of ~1 kpc. Because nuclei with mass numbers A > 209 are produced solely by the r-process, such detections are the best proof for a supernova r-process site. Further, they provide the most direct information on yields of progenitor nuclei with A > 209 at r-process freeze-out. Finally, detection of fluxes due to the decay of r-process nuclei over a range of masses from a supernova or a supernova remnant provides the opportunity to compare yields in a single supernova event with the solar r-process abundance pattern.", "doi": "10.1086/307805", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1999-10-10", "series_number": "1", "volume": "524", "issue": "1", "pages": "213-219" }, { "id": "authors:eqdcr-hpz11", "collection": "authors", "collection_id": "eqdcr-hpz11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131212-080207314", "type": "article", "title": "Circumstellar Hibonite and Corundum and Nucleosynthesis in Asymptotic Giant Branch Stars", "author": [ { "family_name": "Choi", "given_name": "Byeon-Gak", "clpid": "Choi-B-G" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" } ], "abstract": "We report the discovery of two hibonite grains (CaAl_(12)O_(19)) whose isotopic compositions show that they formed in the winds of red giant and asymptotic giant branch (AGB) stars. While hibonite is the second major phase (after corundum, Al_2O_3) expected to condense from stellar ejecta with C/O < 1, it has not previously been found. One circumstellar hibonite grain is highly enriched in ^(17)O and slightly depleted in ^(18)O relative to the solar composition and has large excesses in ^(26)Mg and ^(41)K, decay products of ^(26)Al and ^(41)Ca. The inferred initial values (^(26)Al/^(27)Al)0 \u2248 5 \u00d7 10^(-3) and (^(41)Ca/^(40)Ca)0 \u2248 1.5 \u00d7 10^(-4) of this grain are consistent with models of nucleosynthesis in an AGB star. The other hibonite is enriched in ^(17)O, strongly depleted in ^(18)O, shows no evidence of ^(41)Ca and formed with (^(26)Al/^(27)Al)0 \u2248 2 \u00d7 10^(-2). The low ^(18)O/^(16)O and very high (^(26)Al/^(27)Al)_0 may indicate substantial proton exposure during cool bottom processing in a low-mass parent star. The low upper limit on ^(41)Ca/^(40)Ca (\u2264 3.2 \u00d7 10^(-5)) implies that little or no He-shell material had been dredged into the envelope when this grain formed. We also report isotopic compositions for 12 new circumstellar corundum grains. The compositions of 11 of these grains are consistent with current models for red giant and AGB stars. One corundum grain has extremely high ^(17)O/^(16)O and near-solar ^(18)O/^(16)O and may have formed in a star that was initially enriched in ^(17)O and ^(18)O.", "doi": "10.1086/312239", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1999-09-10", "series_number": "2", "volume": "522", "issue": "2", "pages": "L133-L136" }, { "id": "authors:m69nf-rq471", "collection": "authors", "collection_id": "m69nf-rq471", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BUSaraa99", "type": "article", "title": "Nucleosynthesis in asymptotic giant branch stars: Relevance for galactic enrichment and solar system formation", "author": [ { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Gallino", "given_name": "R.", "clpid": "Gallino-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a review of nucleosynthesis in AGB stars outlining the development of theoretical models and their relationship to observations. We focus on the new high resolution codes with improved opacities, which recently succeeded in accounting for the third dredge-up. This opens the possibility of understanding low luminosity C stars (enriched in s-elements) as the normal outcome of AGB evolution, characterized by production of 12C and neutron-rich nuclei in the He intershell and by mass loss from strong stellar winds. Neutron captures in AGB stars are driven by two reactions: 13C(\u03b1,n)16O, which provides the bulk of the neutron flux at low neutron densities (Nn \u2264 107 n/cm3), and 22Ne(\u03b1,n)25Mg, which is mildly activated at higher temperatures and mainly affects the production of s-nuclei depending on reaction branchings. The first reaction is now known to occur in the radiative interpulse phase, immediately below the region previously homogenized by third dredge-up. The second reaction occurs during the convective thermal pulses. The resulting nucleosynthesis phenomena are rather complex and rule out any analytical approximation (exponential distribution of neutron fluences). Nucleosynthesis in AGB stars, modeled at different metallicities, account for several observational constraints, coming from a wide spectrum of sources: evolved red giants rich in s-elements, unevolved stars at different metallicities, presolar grains recovered from meteorites, and the abundances of s-process isotopes in the solar system. In particular, a good reproduction of the solar system main component is obtained as a result of Galactic chemical evolution that mixes the outputs of AGB stars of different stellar generations, born with different metallicities and producing different patterns of s-process nuclei. The main solar s-process pattern is thus not considered to be the result of a standard archetypal s-process occurring in all stars. Concerning the 13C neutron source, its synthesis requires penetration of small amounts of protons below the convective envelope, where they are captured by the abundant 12C forming a 13C-rich pocket. This penetration cannot be modeled in current evolutionary codes, but is treated as a free parameter. Future hydrodynamical studies of time dependent mixing will be required to attack this problem. Evidence of other insufficiencies in the current mixing algorithms is common throughout the evolution of low and intermediate mass stars, as is shown by the inadequacy of stellar models in reproducing the observations of CNO isotopes in red giants and in circumstellar dust grains. These observations require some circulation of matter between the bottom of convective envelopes and regions close to the H-burning shell (cool bottom processing). AGB stars are also discussed in the light of their possible contribution to the inventory of short-lived radioactivities that were found to be alive in the early solar system. We show that the pollution of the protosolar nebula by a close-by AGB star may account for concordant abundances of 26Al, 41Ca, 60Fe, and 107Pd. The AGB star must have undergone a very small neutron exposure, and be of small initial mass (M <= 1.5 [sols]). There is a shortage of 26Al in such models, that however remains within the large uncertainties of crucial reaction rates. The net 26Al production problem requires further investigation.", "doi": "10.1146/annurev.astro.37.1.239", "issn": "0066-4146", "publisher": "Annual Reviews", "publication": "Annual Review of Astronomy and Astrophysics", "publication_date": "1999-09", "volume": "37", "pages": "239-309" }, { "id": "authors:pqk9z-7fr49", "collection": "authors", "collection_id": "pqk9z-7fr49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140716-153958217", "type": "article", "title": "Calcium-41, aluminum-26, and oxygen isotopes in a circumstellar hibonite", "author": [ { "family_name": "Choi", "given_name": "B.-G", "clpid": "Choi-B-G" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report the discovery of a circumstellar hibonite (CaAI_(12)O_(19)) showing clear evidence of ^(41)Ca and ^(26)Al produced in an Asymptotic Giant Branch (AGB) star and O isotopes that were significantly modified by\nnucleosynthesis in that star.", "doi": "10.1111/j.1945-5100.1999.tb01769.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1999-07", "series_number": "S4", "volume": "34", "issue": "S4", "pages": "A25" }, { "id": "authors:y0pya-ra834", "collection": "authors", "collection_id": "y0pya-ra834", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140204-083216771", "type": "article", "title": "Short-lived nuclei in the early solar system and a diversity of r-processes", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "It is established that Pu-244, Hf-182, I-129, Pd-107, Fe-60, Mn-53, Ca-41, and Al-26 were present\nin the early solar system. Several stellar sources are responsible for producing these nuclei. Short-lived\nAl-26 and Ca-41 require a very late stage injection into the proto-solar nebula and rapid accretion\nof the sun (~7x10^(25)y). I-129 is produced only by the r-process in low abundance, requiring\nlong term contributions to the solar nebula cease ~10^8 y prior to collapse.\n\nIn contrast, Hf-182, with a larger-process component, is in high abundance, requiring a time scale of ~10^7 y. This\ndiscrepancy requires distinctive SN sites for production of the r-process. Furthermore, from\nneutrino interactions competing with beta decays, the two r-processes cannot be produced in a\nsingle scenario. Using the results of Richter, Ott, and Begemann and considering neutrino spallation\nreactions during post processing, we calculate the dynamic scale for SNII to be tau < 0.85 s.", "issn": "0065-7727", "publisher": "American Chemical Society", "publication": "Abstracts of Papers of the American Chemical Society", "publication_date": "1999-03-21", "volume": "217", "pages": "U13-U13" }, { "id": "authors:fdcjb-qy414", "collection": "authors", "collection_id": "fdcjb-qy414", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131120-083121245", "type": "article", "title": "Neutrino Fluence after r\u2010Process Freezeout and Abundances of Te Isotopes in Presolar Diamonds", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Vogel", "given_name": "P.", "orcid": "0000-0003-0587-5466", "clpid": "Vogel-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Using the data of Richter, Ott, & Begemann on Te isotopes in diamond grains from a meteorite, we derive bounds on the neutrino fluence and the decay timescale of the neutrino flux relevant for the supernova r-process. Our new bound on the neutrino fluence \u2131 after freezeout of the r-process peak at mass number A~130 is more stringent than the previous bound \u2131\u227e0.045 (in units of 10^(37) ergs cm^(-2)) of Qian et al. and Haxton et al., if the neutrino flux decays on a timescale hat \u03c4\u227e0.65 s. In particular, it requires that a fluence of \u2131=0.031 be provided by a neutrino flux with hat \u03c4\u227e0.84 s. Such a fluence may be responsible for the production of the solar r-process abundances at A=124-126. Our results are based on the assumption of Ott that only the stable nuclei implanted into the diamonds are retained, while the radioactive nuclei are lost from the diamonds upon decay after implantation. We consider that the nanodiamonds are condensed in an environment with C/O>1 in the expanding supernova debris or from the exterior H envelope. This environment need not have the ^(13)C/^(12)C ratio of the bulk diamonds, since the Te- and Xe-containing nanodiamond grains are too rare to affect that ratio. The implantation of nuclei would have occurred ~10^4-10^6 s after r-process freezeout. This time interval may be marginally sufficient to permit adequate cooling upon expansion for the formation of diamond grains. The mechanisms of preferential retention/loss of the implanted nuclei are not well understood.", "doi": "10.1086/306896", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1999-03-10", "series_number": "2", "volume": "513", "issue": "2", "pages": "956-960" }, { "id": "authors:tdkg9-g1688", "collection": "authors", "collection_id": "tdkg9-g1688", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-142849164", "type": "article", "title": "The Eastern Mediterranean paleoclimate as a reflection of regional events: Soreq cave, Israel", "author": [ { "family_name": "Bar-Matthews", "given_name": "Miryam", "clpid": "Bar-Matthews-M" }, { "family_name": "Ayalon", "given_name": "Avner", "clpid": "Ayalon-A" }, { "family_name": "Kaufman", "given_name": "Aaron", "clpid": "Kaufman-A" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The climate of the Eastern Mediterranean region of the last 60 ky was determined by a high resolution study of the oxygen and carbon isotopic composition (1500 measurement pairs) of speleothems from the Soreq cave, Israel, with chronology provided by 53 precise ^(230)Th\u2013^(234)U (TIMS) ages. The high precision of the speleothem TIMS ages permits us to determine the timing of regional climatic events in the Eastern Mediterranean region and to see if they correlate with global events. During the period from 60 to 17 ky, the \u03b4^(18)O and \u03b4^(13)C values were generally 2\u20132.5\u2030 higher than during the period from 17 ky to present. This is consistent with the climatic transition from glacial to interglacial. Within the 60 to 17 ky period, the Soreq cave stable isotope profile includes four cold peaks (at 46, 35, 25 and 19 ky) and 2 warm peaks (at 54 and 36 ky). In addition, the period <17 ky has two more cold peaks at 16.5 and from 13.2 to 11.4 ky. The ages of four of the six cold peaks correlate well with the ages of three Heinrich events (H1, H2, H5) and with the age of the Younger Dryas. However, the other two Heinrich events are not reflected in the Soreq cave record. Several other isotope peaks which appear during the last 7 ky are contemporaneous with regional climatic events in the Middle East and North Africa.\nIn addition to the drop in \u03b4^(18)O and \u03b4^(13)C observed between the last glacial and the Holocene, sharp simultaneous drops in (^(234)U/^(238)U)_0 ratios, Sr concentrations and in ^(87)Sr/^(86)Sr are also observed, suggesting that the latter are climate related. These variations are interpreted in terms of major changes in the temperature, the mean annual rainfall and its isotopic composition, the isotopic composition of the Mediterranean vapor source, the soil moisture conditions, and in the mixing proportions of sources with different ^(87)Sr/^(86)Sr ratios (sea spray, dust particles and dolomitic host rock).", "doi": "10.1016/S0012-821X(98)00275-1", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1999-02-28", "series_number": "1-2", "volume": "166", "issue": "1-2", "pages": "85-95" }, { "id": "authors:tffhk-vbm29", "collection": "authors", "collection_id": "tffhk-vbm29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131219-093507731", "type": "article", "title": "Presolar Corundum and Spinel in Ordinary Chondrites: Origins from AGB Stars and a Supernova", "author": [ { "family_name": "Choi", "given_name": "Byeon-Gak", "clpid": "Choi-B-G" }, { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Gallino", "given_name": "Roberto", "clpid": "Gallino-R" } ], "abstract": "On the basis of anomalous isotopic compositions of oxygen and magnesium, 14 oxide grains from two primitive meteorites (Bishunpur and Semarkona) have been identified as circumstellar condensates. One corundum grain has a high ^(18)O/^(16)O ratio and isotopic compositions of magnesium, calcium, and titanium that are compatible with a formation in ejecta of a type II supernova that was about 15 times the mass of the sun. The other grains have oxygen, magnesium, and titanium compositions that are consistent with a formation around asymptotic giant branch (AGB) stars with a range of mass and initial composition. The large range of aluminum/magnesium in circumstellar corundum and spinel is considered to reflect various stages of back-reaction between condensed corundum and gaseous magnesium in cooling stellar ejecta.", "doi": "10.1126/science.282.5392.1284", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1998-11-13", "series_number": "5392", "volume": "282", "issue": "5392", "pages": "1284-1289" }, { "id": "authors:ha1tr-zvs89", "collection": "authors", "collection_id": "ha1tr-zvs89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131120-101758761", "type": "article", "title": "Supernovae as the Site of the r-Process: Implications for Gamma-Ray Astronomy", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Vogel", "given_name": "P.", "orcid": "0000-0003-0587-5466", "clpid": "Vogel-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We discuss how detection of gamma-ray emission from the decay of r-process nuclei can improve our understanding of r-process nucleosynthesis. We find that a gamma-ray detector with a sensitivity of ~10^(-7)\u03b3 cm^(-2) s^(-1) at E_\u03b3 \u2248 100-700 keV may detect the emission from the decay of ^(125)Sb,^(137)Cs,^(144)Ce,^(155)Eu, and ^(194)Os produced in a future Galactic supernova. In addition, such a detector may determine the emission from the decay of ^(126)Sn in the Vela supernova remnant and the diffuse emission from the decay of ^(126)Sn produced by past supernovae in our Galaxy. The required detector sensitivity is similar to what is projected for the proposed Advanced Telescope for High Energy Nuclear Astrophysics (ATHENA). Both the detection of gamma-ray emission from the decay of several r-process nuclei (e.g.,^(125)Sb and ^(194)Os) produced in future Galactic supernovae and the detection of emission from the decay of ^(126)Sn in the Vela supernova remnant would prove that supernovae are a site of the r-process. Furthermore, the former detection would allow us to determine whether or not the r-process nuclei are produced in relative proportions specified by the solar r-process abundance pattern in supernova r-process events. Finally, detection of diffuse emission from the decay of ^(126)Sn in our Galaxy would eliminate neutron star-neutron star mergers as the main source for the r-process nuclei near mass number A ~ 126.", "doi": "10.1086/306285", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1998-10-20", "series_number": "2", "volume": "506", "issue": "2", "pages": "868-873" }, { "id": "authors:n2jaa-8kp09", "collection": "authors", "collection_id": "n2jaa-8kp09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-135629045", "type": "article", "title": "Re-Os systematics in chondrites and the fractionation of the platinum group elements in the early solar system", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have investigated the Re-Os system for samples of whole rock, metal, and sulfide from ordinary chondrites. Using closed-system analytical techniques, we found complete exchange between sample and tracer isotopes for silicate-containing samples and obtained precise and reliable Re-Os concentration measurements. Results on two Group IVA iron meteorites and on a silicate-rich iron (Steinbach, IVA-AN) are consistent with the IVA-IVB isochron and support the previous observation that IVA-IVB irons may be slightly older than IIAB irons. Data on whole-rock fragments and metal-rich separates from the St. S\u00e9verin chondrite (LL6) show a large range in ^(1870Re/^(188)Os and in ^(187)Os/^(188)Os, which makes possible, in principle, the determination of a Re-Os internal isochron on a chondrite, for the first time. This Re-Os fractionation may be due to partial melting of FeNiS and macroscopic redistribution of metal and sulfide. The St. S\u00e9verin data show a good correlation line on a ^(187)Re-^(187)Os evolution diagram. If this is considered to represent an internal isochron, it gives an age T = 4.68 \u00b1 0.15 AE [\u03bb(^(187)Re) = 1.64 \u00d7 10^(\u221211) a^(\u22121)] and an initial (^(187)Os/^(188)Os)0 = 0.0953 \u00b1 0.0013. This age is in agreement with but slightly older than the more precise ^(187)Re-^(187)Os age for the IIAB irons as well as for irons from other groups (T = 4.61 \u00b1 0.01 AE). A St. S\u00e9verin sulfide nodule has very low Re and Os concentrations and shows a young Re-Os model age (2.3 AE), indicating recent element remobilization. Whole rock and metal-rich separates of H-Group chondrites (H3 to H6) yield restricted ranges in ^(187)Re/^(188)Os (0.42\u20130.47) and ^(187)Os/^(188)Os (0.128\u20130.133). There is a systematic difference between Re/Os in the metal extracted from a chondrite and the bulk chondrite. This shows that there is a small but significant Re-Os fractionation within subsystems contained in the chondrites. From whole rock samples of H Group chondrites we calculate a mean ^(187)Re/^(188)Os = 0.423 \u00b1 0.007 and ^(187)Os/^(188)Os = 0.12863 \u00b1 0.00046, which may characterize the evolution of an average chondritic reservoir for Re-Os. The ordinary chondrite data plot close to the IIAB isochron, although the deviations found are larger than found for the irons. The Re-Os chronometer in iron meteorites is apparently controlled by the Re-Os fractionation due to fractional crystallization of liquid metal. Re-Os ages of iron meteorites give the time of crystallization of metal segregations and cores of early planetary bodies. In contrast, the behavior in ordinary chondrites, while also dominated by the metal phases, must reflect fractionation and transport on a local macroscopic scale within the chondrites between the metal phases after aggregation, due to partial melting of FeNiS or represent variable Re-Os fractionation of the metal phases prior to the accretion of the chondrites. However, for St. S\u00e9verin, we attribute the major Re-Os fractionation to early heating of the meteorite, above the Fe-FeS eutectic. We do not consider that the Re-Os fractionation observed in other chondrites is due to the redistribution of Re and Os during chondrite metamorphism (including shock) but it may plausibly represent earlier stages of Re-Os fractionation for the different FeNi metal constituents prior to accretion.", "doi": "10.1016/S0016-7037(98)00238-5", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1998-10", "series_number": "19/20", "volume": "62", "issue": "19/20", "pages": "3379-3392" }, { "id": "authors:88qrr-rdr20", "collection": "authors", "collection_id": "88qrr-rdr20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-134635809", "type": "article", "title": "Re-Os systematics in pallasite and mesosiderite metal", "author": [ { "family_name": "Shen", "given_name": "J. J.", "clpid": "Shen-J-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Re-Os data on pallasite metal yield a sufficient range in Re/Os to permit the determination of a whole rock isochron, if pallasites from different groups are considered together. The results are indistinguishable from the data obtained on Groups IAB, IIAB, IID, IIIAB, IVA, and IVB iron meteorites. Pallasite data were obtained on samples of the Main Group, which have been considered related to Group IIIAB irons, and on samples of the distinctive pallasites Eagle Station, Finmarken, and Marjalahti. It appears that iron meteorites and pallasites crystallized within a time interval of 20 Ma. This result is consistent with the evidence from the short-lived chronometers ^(107)Pd-^(107)Ag and ^(53)Mn-^(53)Cr. It is also consistent with the evidence from ^(182)Hf-^(182)W that the time interval over which molten FeNi metal from different iron meteorites equilibrated with and became segregated from silicates was \u223c10 Ma. The well-defined ^(187)Re-^(187)Os whole-rock isochron for pallasites and iron meteorites requires that they were formed in parent bodies that had been partially molten and segregated FeNi metal and FeS and then all crystallized within a 20 Ma time interval. This conclusion appears to apply to members of distinct groups of iron meteorites and pallasites which are viewed as not being cogenetic. The short time-scale requires that the irons and pallasites were formed in small parent planets of \u227210 km radius or near the surface of larger bodies. In contrast to the pallasites, we find that FeNi samples from mesosiderites have a narrow range in Re/Os so that it is not possible to determine a whole-rock isochron for these samples. The mesosiderite data also lie somewhat displaced from the iron meteorite and pallasite isochron indicating a more complex multi-stage evolution. Based on Sm-Nd data on mesosiderite silicate clasts, the Re-Os results on mesosiderite metal are compatible with the model of melted or partially molten FeNi cores or pods still preserved in protoplanetary bodies when these bodies were disrupted up to 150 Ma after early formation and the FeNi was splashed onto the surfaces of other small, differentiated planetesimals.", "doi": "10.1016/S0016-7037(98)00187-2", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1998-08", "series_number": "15", "volume": "62", "issue": "15", "pages": "2715-2723" }, { "id": "authors:zbreh-3p572", "collection": "authors", "collection_id": "zbreh-3p572", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140716-144324335", "type": "article", "title": "Measurement of gas-phase species during Langmuir evaporation of forsterite", "author": [ { "family_name": "Nichols", "given_name": "R. H., Jr.", "clpid": "Nichols-R-H-Jr" }, { "family_name": "Grimley", "given_name": "R. T.", "clpid": "Grimley-R-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Forsterite, the most abundant mineral in meteorites, forms at high temperatures often associated with nebular processes. It evaporates congruently, and its equilibrium evaporation is rather well understood [e.g.]. For these reasons, in part, many recent studies have focused on the\nmore difficult kinetics of the free (Langmuir or nonequilibrium) evaporation of this mineral.", "doi": "10.1111/j.1945-5100.1998.tb01327.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1998-07-27", "series_number": "S4", "volume": "33", "issue": "S4", "pages": "A115-A116" }, { "id": "authors:d1t4h-r9655", "collection": "authors", "collection_id": "d1t4h-r9655", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140716-142351766", "type": "article", "title": "Oxygen, magnesium, calcium, and titanium isotopes in asymptotic giant branch and supernova oxides", "author": [ { "family_name": "Choi", "given_name": "B.-G", "clpid": "Choi-B-G" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We reported O- and Mg-Al-isotopic compositions of eight presolar oxide grains from Semarkona and Bishunpur. Here we report O-, Mg-, Ca-, and Ti-isotopic compositions of additional five presolar corundum grains from Semarkona, which include four AGB grains and one supernova grain.", "doi": "10.1111/j.1945-5100.1998.tb01327.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1998-07", "series_number": "S4", "volume": "33", "issue": "S4", "pages": "A32" }, { "id": "authors:8enm3-enp83", "collection": "authors", "collection_id": "8enm3-enp83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131212-073249454", "type": "article", "title": "A Test of the Supernova Trigger Hypothesis with ^(60)Fe and ^(26)Al", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Gallino", "given_name": "R.", "clpid": "Gallino-R" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" } ], "abstract": "It is shown that if the ^(26)Al inventory of the early solar system, taken as (^(26)Al/^(27)Al)_\u2609 = 5\u00d710^(\u22125), is a result of injection of fresh debris from a Type II supernova (SNII), then ^(60)Fe/^(56)Fe would have to be between 3\u00d710^(\u22127) and 1\u00d710^(\u22125). This inferred correlation of ^(26)Al and ^(60)Fe is based on the observation that both nuclei are produced dominantly in the O/Ne zone and that for SNII ejecta ^(26)Al/^(60)Fe is between 0.6 and 23. A similar correlation applies to ^(41)Ca,^(36)Cl,^(16)O, and ^(18)O, which are also produced in the same zone or in nearby regions. The supernova trigger hypothesis may be tested by determination of ^(60)Ni excesses correlated with Fe in samples where ^(26)Al was demonstrated to be present. From available experimental data, it appears that the observed abundance of ^(60)Fe is too low to be compatible with a supernova trigger that injected the ^(26)Al into the protosolar nebula. The same is true for ^(53)Mn, a short-lived nucleus produced in the outer edge of the Ni core.", "doi": "10.1086/311414", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1998-06-20", "series_number": "2", "volume": "500", "issue": "2", "pages": "L189-L193" }, { "id": "authors:s29v0-84k11", "collection": "authors", "collection_id": "s29v0-84k11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-120901062", "type": "article", "title": "Mg diffusion in anorthite: implications for the formation of early solar system planetesimals", "author": [ { "family_name": "LaTourrette", "given_name": "T.", "clpid": "LaTourrette-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have measured the self diffusion coefficients of Mg, Ca, and Sr in anorthitic plagioclase in order to assess the potential of Mg isotopic heterogeneities in early solar system planetesimals to survive thermal metamorphism. Diffusion couples were constructed from polished single crystals of natural anorthite and synthetic, isotopically enriched anorthite glass. Couples were annealed at atmospheric pressure and 1200\u20131400\u00b0C and isotopic concentration profiles were measured with an ion microprobe. The results show that Mg diffusion in anorthite is surprisingly fast, with D_(Mg) being over 2 orders of magnitude greater than D_(Sr). This indicates that the diffusion coefficient of Mg in anorthite cannot be approximated with that for Sr. Mg diffusion in the c-direction is also slightly faster than in the b-direction, while Ca and Sr diffusion appear to be isotropic. The results provide important constraints on the thermochronological history of anorthite-bearing mineral assemblages that preserve radiogenic ^(26)Mg excesses. In a planetesimal heated by the decay of ^(26)Al, the temperature at any point depends on the planetesimal size, time of formation, thermal conductivity, and depth within the planetesimal. Given sufficient heating, ^(26)Mg heterogeneities produced by the in-situ decay of ^(26)Al in Ca-, Al-rich inclusions (CAIs) and chondrules will be erased by diffusive equilibration. Using the self diffusion coefficient for Mg in anorthite measured in this study, we show that the common occurrence of ^(26)Mg excesses in these inclusions requires that they must be stored in small (\u227215 km) bodies or the outermost rims of larger bodies for the first 1\u20132 million years of the solar system's history. For early formed bodies larger than 15 km, most of the mass will have been heated sufficiently for any radiogenic ^(26)Mg to have been diffusively homogenized in the Mg-rich planetary environment.", "doi": "10.1016/S0012-821X(98)00048-X", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1998-05-30", "series_number": "3-4", "volume": "158", "issue": "3-4", "pages": "91-108" }, { "id": "authors:24m9c-ckw14", "collection": "authors", "collection_id": "24m9c-ckw14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131113-135752590", "type": "article", "title": "U-Th isotope systematics from the Soreq cave, Israel and climatic correlations", "author": [ { "family_name": "Kaufman", "given_name": "A.", "clpid": "Kaufman-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Bar-Matthews", "given_name": "M.", "clpid": "Bar-Matthews-M" }, { "family_name": "Ayalon", "given_name": "A.", "clpid": "Ayalon-A" }, { "family_name": "Halicz", "given_name": "L.", "clpid": "Halicz-L" } ], "abstract": "Precise ^(230)Th-^(234)U ages were obtained on thirty-one growth laminae in speleothem samples which are self-consistent with the detailed layer stratigraphy. Samples with low ^(232)Th/^(238)U ratios give ages with analytical uncertainties of 40 years at 2 ky and 1000 years at 90 ky. Some growth zones with high but variable ^(232)Th/^(238)U were dated by intermal isochrons. This permits the determination of the initial ^(230)Th/^(232)Th assuming equilibrium of ^(232)Th and ^(238)U series in the source of the high ^(232)Th component. This shows initial (^(230)Th/^(232)Th) (in activity units) of from 1.3 to 2.9. The calculated atomic ratios of ^(232)Th/^(238)U for the high ^(232)Th component range from 1.08 to 2.4 which is well below the average crustal value. Speleothem materials with high ^(232)Th/^(238)U are found to exhibit clear correlations of ^(232)Th with Si, Al and Fe, while ^(238)U correlates with Sr and Ba. Analyses of Soreq cave drip waters show that the particulates in the waters have high ^(232)Th concentrations and a ^(232)Th/^(238)U ratio much lower than that found in the high ^(232)Th component in speleothems but with ^(230)Th/^(232)Th) = 1.0 to 2.4. We infer that the trapped high-Th component in speleothems is from particulate matter in water with a large concentration of adsorbed U and not simply from detrital material. The speleothems have only small234U excess The initial ^(234)U/^(238)U)0 show a range of 1.02 to 1.14 that was found to correlate with age over the past 25 ky. The youngest samples have values in the same range as the modern drip waters. There appears to be a correlation of ^(234)U/^(238)U)0 with the \u03b4^(18)O values. There is a drop of \u03b4^(18)O in the time interval 20 to 15 ky which then remains relatively constant to recent times. As the high \u03b4^(18)O values have been related to rainfall and associated climatic conditions, we suggest that the ^(234)U/^(238)U in the speleothem reflects the effects of rainfall and soil weathering conditions on drip-water composition and may provide a proxy for climate change.", "doi": "10.1016/S0012-821X(98)00002-8", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1998-03-30", "series_number": "3-4", "volume": "156", "issue": "3-4", "pages": "141-155" }, { "id": "authors:1hs12-b1e66", "collection": "authors", "collection_id": "1hs12-b1e66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-104855886", "type": "article", "title": "Diverse supernova sources for the r-process", "author": [ { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Vogel", "given_name": "P.", "orcid": "0000-0003-0587-5466", "clpid": "Vogel-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a simplified analysis using equations for the charge flow, which include \u03bd_e capture, for the production of r-process nuclei in the context of the recent supernova hot bubble model. The role of \u03bd_e capture in speeding up the charge flow, particularly at the closed neutron shells, is studied together with the \u03b2 flow at freezeout and the effect of neutrino-induced neutron emission on the abundance pattern after freezeout. It is shown that a semiquantitative agreement with the gross solar r-process abundance pattern from the peak at mass number A ~ 130 through the peak at A ~ 195 and up to the region of the actinides can be obtained by a superposition of two distinctive kinds of r-process events. These correspond to a low frequency case L and a high frequency case H, which take into account the low abundance of ^(129)I and the high abundance of ^(182)Hf in the early solar nebula. The lifetime of ^(182)Hf (\u03c4_(182) \u2248 1.3 \u00d7 10^7 yr) associates the events in case H with the most common Type II supernovae. These events would be mainly responsible for the r-process nuclei near and above A ~ 195. They would also make a significant amount of the nuclei between A ~ 130 and 195, including ^(182)Hf, but would make very little ^(129)I. In order to match the solar r-process abundance pattern and to satisfy the ^(129)I and ^(182)Hf constraints, the events in case L, which would make the r-process nuclei near A ~ 130 and the bulk of those between A ~ 130 and 195, must occur ~10 times less frequently but eject ~10-20 times more r-process material in each event.\n\nAssuming that all of the supernovae producing r-process nuclei represent a similar overall process, we speculate that the usual neutron star remnants, and hence prolonged ejection of r-process material, are associated with the events in case L. We further speculate that the more frequently occurring events in case H have ejection of other r-process material terminated by black hole formation during the neutrino cooling phase of the protoneutron star. This suggests that there is now an inventory of ~5 \u00d7 10^8 black holes with masses ~1 M_\u2609 and ~5 \u00d7 10^7 neutron stars resulting from supernovae in the Galaxy. This r-process model would have little effect on the estimates of the supernova contributions to the non-r-process nuclei.", "doi": "10.1086/305198", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1998-02-10", "series_number": "1", "volume": "494", "issue": "1", "pages": "285-296" }, { "id": "authors:kavrk-p2q61", "collection": "authors", "collection_id": "kavrk-p2q61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-132957570", "type": "article", "title": "An isotopic and petrologic study of calcium-aluminum-rich inclusions from CO3 meteorites", "author": [ { "family_name": "Russell", "given_name": "S. S.", "clpid": "Russell-S-S" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Fahey", "given_name": "A. J.", "clpid": "Fahey-F-A" }, { "family_name": "Greenwood", "given_name": "R. C.", "clpid": "Greenwood-R-C" }, { "family_name": "Hutchison", "given_name": "R.", "clpid": "Hutchison-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have studied the mineralogy and petrology of 229 calcium-aluminum-rich inclusions (CAIs) from ten CO3 meteorites of petrologic types 3.0\u20133.7. Subsets of these inclusions were measured by ion probe for magnesium, calcium, and titanium isotopes and REE abundances. Most CAIs from CO3 meteorites fall into three major types: (1) melilite-rich inclusions, which also contain spinel/hercynite, perovskite, and occasionally hibonite; (2) spinel-pyroxene inclusions; and (3) hibonite-hercynite inclusions. In addition, several isolated hibonite grains, two grossite (CaAl_4O_7) bearing CAIs, two hibonite-fassaite microspherules, and one anorthite-spinel-pyroxene inclusion were found. CAIs from CO3 meteorites exhibit all of the REE patterns commonly seen in inclusions from CV3 and CM2 chondrites. Most exhibit evidence of ^(26)AI, and many have inferred (^(26)AI/^(27)AI)_o \u2248 5 \u00d7 10^(\u22125). The relative abundances of different types of CAIs in CO3 chondrites differ from those in CV3 and CM2 chondrites.\nCAIs in CO3 chondrites have experienced considerable secondary alteration, both before and after accretion. Signatures of nebular alteration include Wark-Lovering rims and the high Fe contents in spinels from all hibonite/hercynite inclusions. Occasionally, melilite and anorthite show evidence of nebular alteration to feldspathoids and pyroxene. The magnesium-aluminum systematics of some melilite-rich inclusions were apparently disturbed prior to final accretion of the parent body. Parent body alteration is indicated by correlations between CAI characteristics and the petrologic type of the host meteorite. Spinel in melilite-rich and coarse-grained spinel-pyroxene inclusions becomes more Fe rich, with the development of relatively homogeneous hercynitic spinel (\u223c50\u201360 mol%) in CAIs from metamorphic grades >3.4. Perovskite has been converted to ilmenite in types >3.4. Melilite-rich inclusions are abundant in CO3.0\u20133.3 meteorites, rare in 3.4 meteorites, and absent meteorites of types 3.5\u20133.7; melilite-rich CAIs are probably replaced by inclusions rich in feldspathoids, pyroxene, and Fe-rich spinel. Isotopic disturbance of the magnesium-aluminum systematics may be more severe in higher petrologic types. Hibonite seems to be unaffected by this level of metamorphism.\nThree isotopically unusual inclusions were found. One single-crystal hibonite, Isna SP16, has a REE pattern strongly depleted in Ce and Y, (^(26)AI/^(27)AI)_o = (2.4 \u00b1 0.3) \u00d7 10^(\u22125), and mass fractionated calcium (F_(Ca) = +12 \u00b1 2\u2030/amu), but no resolvable nuclear anomalies in neutron-rich calcium isotopes. The REE pattern, which is thought to reflect nebular conditions, and mass-fractionated calcium, indicative of evaporation, are similar to those of the FUN inclusion, HAL, and related hibonites, indicating similar formation conditions. The absence in Isna SP16 of the nuclear anomalies observed in HAL and the difference in (^(26)AI/^(27)AI)_o between HAL and Isna SP16 indicate that the processes that produced HAL-type hibonites operated on diverse materials. Two hibonite-bearing microspherules, Colony SP1 and ALH82101 SP15, exhibit nearly flat REE patterns with negative europium anomalies and slightly negative \u03b4^(26)Mg. ALH82101 SP15 has resolved excesses of ^(48)Ca and ^(50)Ti. These characteristics are similar to those of previously described microspherules from Murchison and Lance, implying that the microspherules formed via a single process from related, but not identical source materials.", "doi": "10.1016/S0016-7037(97)00374-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1998-02", "series_number": "4", "volume": "62", "issue": "4", "pages": "689-714" }, { "id": "authors:8ndgx-rkv54", "collection": "authors", "collection_id": "8ndgx-rkv54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-112504419", "type": "article", "title": "Particle transport of ^(234)U-^(238)U in the Kalix River and in the Baltic Sea", "author": [ { "family_name": "Andersson", "given_name": "P. S.", "clpid": "Andersson-P-S" }, { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Ingri", "given_name": "J.", "clpid": "Ingri-J" } ], "abstract": "The role of particles for U isotope transport was investigated in the Kalix River watershed, a particle-poor, Fe/Mn-rich river in northern Sweden, and in the Baltic Sea estuary. Particles >0.45\u03bcm are strongly enriched in U and contain 20-50% of the total riverine uranium budget and <1% of the total U in brackish waters (3-7 PSU). The particles have high \u03b4^(234)U which is close to that of dissolved U in the associated water, indicating that U on particles is dominantly nondetrital and isotopically exchanges rapidly with the ambient dissolved U. Particles at the river mouth are dominated by nondetrital Fe-Mn oxyhydroxides. Uranium and Fe are strongly correlated, clearly demonstrating that secondary Fe-oxyhydroxide is the major carrier of U in river water. There is no evidence for significant association of U with Mn-oxyhydroxide. Apparent U distribution coefficients (K_d^(Fe)) were calculated for U between the authigenic Fe on particles and the solution. These values appear to be relatively constant throughout the year. This suggests an equilibrium between Fe in solution and authigenic Fe-oxyhydroxides on detrital particles. High values of K_d^(Fe) calculated for one summer as well as high U concentrations in brackish waters can be explained by U scavenging by biogenic phases with low authigenic Fe content.", "doi": "10.1016/S0016-7037(97)00342-6", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1998-02", "series_number": "3", "volume": "62", "issue": "3", "pages": "385-392" }, { "id": "authors:qxc6s-cft09", "collection": "authors", "collection_id": "qxc6s-cft09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-141308779", "type": "article", "title": "Osmium isotopic compositions and Re\u2013Os concentrations in\n sulfide globules from basaltic glasses", "author": [ { "family_name": "Roy-Barman", "given_name": "M.", "clpid": "Roy-Barman-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Chaussidon", "given_name": "M.", "clpid": "Chaussidon-M" } ], "abstract": "Sulfide globules present in basaltic glass were analyzed for Re and Os concentrations ([Re], [Os]) and ^(187)Os/^(186)Os from a selection of MORBs and Loihi lavas. The high Re and Os concentrations measured in sulfides confirm the chalcophile character of these elements. The partition coefficients of Re and Os between sulfide globules and silicate melt are estimated to be D_(Re)=43 and D_(Os)=4.8\u00d710^4. The ^(187)Os/^(186)Os of the samples range from 1.054 to 1.387 for MORBs and from 1.091 to 1.146 for the Loihi samples. The low Re/Os ratios of sulfides make correction for in situ ^(187)Re decay negligible. Several sulfide-rich (Os=500\u20131000 ppb) and sulfide-containing fractions from a Loihi sample gave essentially the same ^(187)Os/^(186)Os=1.095, demonstrating the possibility of obtaining very reliable data with our procedure. For some MORBs, shifts in ^(187)Os/^(186)Os for concentrates with low [Os] can be explained by the presence of Fe-oxyhydroxides enriched in Os by co-precipitation from seawater. The radiogenic ^(187)Os/^(186)Os ratios found in several sulfides with high [Os] cannot be explained by post-eruption contamination by Fe-oxyhydroxides or isotopic exchange between sulfides and seawater. We infer that some of the radiogenic ^(187)Os/^(186)Os ratios measured in MORB sulfides reflect the isotopic composition of the lava prior to eruption. Correlations were found between Os and B isotopic compositions and suggest that the radiogenic ^(187)Os/^(186)Os measured in MORBs are mainly due to assimilation of seawater-derived Os by the lavas during their ascent through the altered oceanic crust. MORBs with \u03b4^(11)B\u2264\u221210\u2030 seem to be suitable to study the ^(187)Os/^(186)Os ratio of the mantle. Considering only such `uncontaminated' samples, we still find a significant range of ^(187)Os/^(186)Os ratios (1.054\u20131.093) between two MORBs from the FAMOUS area. This result suggests that the mantle underlying the FAMOUS area is heterogeneous with regard to the Re\u2013Os system and that it may have an Os signature distinct from that of abyssal peridotites collected on the Mid-Atlantic Ridge. Osmium isotopic ratios in Loihi lavas seem less sensitive to contamination than in MORBs. Two Os-rich Loihi basalts have similar isotopic ratios that apparently provide a good estimate of the ^(187)Os/^(186)Os ratio of the Loihi source (^(187)Os/^(186)Os=1.095\u00b10.005).", "doi": "10.1016/S0012-821X(97)00180-5", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1998-01", "series_number": "1-4", "volume": "154", "issue": "1-4", "pages": "331-347" }, { "id": "authors:4ac9k-2x851", "collection": "authors", "collection_id": "4ac9k-2x851", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-101056987", "type": "article", "title": "Osmium in the rivers", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "There is a large uncertainty in our understanding of the behavior of osmium during weathering and transport into deep oceans and the osmium budget of the oceans. The problem stems chiefly from the lack of osmium data on the dissolved load in the rivers and in the estuaries. In this study, the concentration and isotopic composition of osmium have been determined in three North American rivers (the Mississippi, the Columbia, and the Connecticut) and one river draining central Europe and flowing into the Baltic Sea (the Vistula). Osmium concentration in the Mississippi and the Vistula is about 45 femto mol kg^(\u22121); it is about 14 and 15 femto mol kg^(\u22121) for the Connecticut and the Columbia, respectively. The ^(187)Os/^(186)Os ratios estimated for the Mississippi and the Vistula are 10.4 and 10.7, respectively. For the Connecticut and the Columbia ^(187)Os/^(186)Os = 8.8 and 14.4, respectively. Of all the rivers examined, the Mississippi is by far the largest, supplying \u223c1.6% of the total annual world river flow. Its osmium isotopic composition is identical to the upper Mississippi valley loesses (Esser and Turekian, 1993a) indicating (1) congruent dissolution of the bedrock and (2) little or no impact of anthropogenic sources on the osmium isotopic composition of the dissolved load. The latter observation indicates that the upper limit of the anthropogenic input in the dissolved osmium load of the Mississippi outflow is about 250 g yr^(\u22121). While the osmium concentration of the Vistula is high the isotopic composition does not appear to have been affected by substantial pollution.\nThe river data can be used to put limits on the mean residence time of osmium in the oceans (T_(Os) and on the osmium budget of the oceans. If the bulk river influx of dissolved osmium into the oceans is similar to that of the Mississippi, we get a value for the net riverine inflow of osmium of 1680 mol yr^(\u22121). If there were no sequestering of osmium in the estuaries, this would give a value of T_(Os) of = 1.3 \u00d7 10^4 years. As the estuaries may trap a significant amount of river osmium, this is a lower limit so that T_(Os) \u00bb 1.3 x 10^4 years. Using the iridium data by Anbar et al. (1996), the Os/Ir ratio for the Vistula is 2.8. We infer that there is no large fractionation between osmium and iridium during the transport of these elements from the continents into the oceans. It follows that the high Os/Ir ratio (\u223c22) observed in seawater must be related to the different rain out mechanisms of these elements in the estuaries or in the oceans.", "doi": "10.1016/S0016-7037(97)00329-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1997-12", "series_number": "24", "volume": "61", "issue": "24", "pages": "5411-5416" }, { "id": "authors:105f8-gx379", "collection": "authors", "collection_id": "105f8-gx379", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-120310106", "type": "article", "title": "Isotopic systematics of presolar silicon carbide from the Orgueil (CI) chondrite: Implications for Solar System formation and stellar nucleosynthesis", "author": [ { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Hutcheon", "given_name": "Ian D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "One hundred and forty individual SiC grains (1-9.6 \u00b5m) and twenty-two grain aggregates (2.3-7.8 \u00b5m) from the Orgueil (CI) chondrite have been measured by ion microprobe. Silicon and carbon isotopic data were obtained for all individual grains and aggregates, and nitrogen, magnesium,\nand aluminum abundances and isotopic compositions were measured for most grains and aggregates. Abundances of lithium, beryllium, boron, and sodium were measured for some individual grains. Orgueil SiC is remarkably similar to Murchison K-series SiC in the ranges and distributions of silicon and carbon isotopic compositions, the initial abundances of ^(26)AI, the abundances of minor and trace elements, and the proportions of isotopically unusual grains. Higher ^(15)N/^(14)N ratios in 1-4/\u00b5m Murchison K-series SiC grains relative to similar-sized Orgueil grains are inferred to be due to higher amounts of terrestrial nitrogen in the Murchison samples. Higher ^(15)N/^(14)N ratios in 3-6 \u00b5m Murchison KJH SiC grains cannot be explained by terrestrial nitrogen and imply that larger SiC grains sampled a different population of parent stars. SiC aggregates have different average silicon and carbon compositions than individual grains, indicating different source stars for the 0.1-1 \u00b5m constituent grains. However, the aggregates probably formed by clumping of small grains during laboratory procedures, not at the stellar source. Differences between Murchison L-series SiC and SiC from Murchison K-series and Orgueil are due to\nthe presence of terrestrial SiC among L-series grains and to the larger average grain size of L-series SiC. When terrestrial contamination, sample size, and grain size are taken into account, there is no evidence of an intrinsic difference between Orgueil and Murchison SiC. The Orgueil data provide new information about stellar nucleosynthesis and the SiC parent stars. Carbon and nitrogen isotopic compositions indicate that nuclear processing in addition to that described by most stellar models occurs below the convective stellar envelope during the Red Giant and AGB\nphases (Cool Bottom Processing). Grains with high ^(15)N/^(14)N but with other characteristics consistent\nwith AGB source stars indicate that ^(15)N is produced in AGB stars, contrary to the predictions of the standard models. A significantly higher rate for the ^(18)O(\u0251,n)^(15)N reaction than is typically used might reconcile the models with the observations. No data currently rule out a higher reaction rate. Addition of ^(18)O produced via ^(14)N(\u0251, y)^(18)O below the hydrogen shell and burned to ^(15)N in the envelope may also play a role in producing the high ^(15)N/^(14)N ratios observed in some SiC grains. Following previous workers, we take the slope ~2.2 silicon isotope array defined by mainstream SiC grains to reflect the initial compositions of the parent stars due to galactic evolution. A general correlation between ^(12)C/^(13)C and ^(29'30)Si/^(28)Si and more scatter around the silicon array at low ^(29'30)Si/^(28)Si indicate that SiC grains with higher ^(29'30)Si/^(28)Si ratios come from higher-metallicity parent stars. A lack of resolved isotopic effects in ^(25)Mg/^(24)Mg suggests that variations in initial magnesium compositions of the parent stars are at least a factor of three smaller than those in silicon and that the ^(22)Ne neutron source was not significantly activated in the AGB stars that produced SiC grains, in accord with theory. These observations indicate\nthat the parent stars of most mainstream SiC grains were \u22642.3 M_\u2609 and experienced enough Third Dredge-up thermal pulses to supply their envelopes with 2-3% helium.shell material. A few grains have characteristics suggesting that they came from more-massive stars. Most parent stars of > 1 \u00b5m SiC grains apparently had metallicities higher than that of the sun.", "doi": "10.1016/S0016-7037(97)00299-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1997-12", "series_number": "23", "volume": "61", "issue": "23", "pages": "5117-5148" }, { "id": "authors:yz4at-zmj31", "collection": "authors", "collection_id": "yz4at-zmj31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-114514566", "type": "article", "title": "The importance of colloids and mires for the transport of uranium isotopes through the Kalix River watershed and Baltic Sea", "author": [ { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Andersson", "given_name": "P. S.", "clpid": "Andersson-P-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Ingri", "given_name": "J.", "clpid": "Ingri-J" }, { "family_name": "Baskaran", "given_name": "M.", "clpid": "Baskaran-M" } ], "abstract": "The importance of colloids and organic deposits for the transport of uranium isotopes from continental source regions and through the estuarine environment was investigated in the mire-rich Kalix River drainage basin in northern Sweden and the Baltic Sea. Ultrafiltration techniques were used to separate uranium and other elements associated with colloids > 10 kD and >3 kD from \"solute\"\nuranium and provided consistent results and high recovery rates for uranium as well as for other elements\nfrom large volume samples.\nUranium concentrations in 0.45 \u00b5m-filtered Kalix River water samples increased by a factor of 3 from near the headwaters in the Caledonides to the river mouth while major cation concentrations were relatively constant. ^(234)U/^(238)U ratios were high (\u03b4^(234)U = 770-1500) throughout the basin, without showing any simple pattern, and required a supply of ^(234)U-rich water. Throughout the Kalix River, a large fraction (30-90%) of the uranium is carried by >10 kD colloids, which is compatible with\nuranium complexation with humic acids. No isotopic differences were found between colloid-associated\nand solute uranium.\nWithin the Baltic Sea, about half of the uranium is removed at low salinities. The proportion that is lost is equivalent to that of river-derived colloid-bound uranium, suggesting that while solute uranium behaves conservatively during estuarine mixing, colloid-bound uranium is lost due to rapid flocculation of colloidal material. The association of uranium with colloids therefore may be an important parameter in determining uranium estuarine behavior. \nMire peats in the Kalix River highly concentrate uranium and are potentially a significant source of recoil ^(234)U to the mirewaters and river waters. However, mirewater data clearly demonstrate that only small ^(234)U/^(238)U shifts are generated relative to inflowing groundwater. A simple box model of uranium accumulation in peat and transport through the mire that is compatible with the mire data demonstrates that with efficient removal of uranium from solution, only small shifts in ^(234)U/^(238)U ratios can be generated in mirewater uranium. The measurements and model calculations show that mirewaters are not the\nprimary source of the uranium in the river. Bedrock groundwaters with high ^(234)U/^(238)U ratios and uranium\nconcentrations must be the dominant source of riverine uranium.", "doi": "10.1016/S0016-7037(97)00235-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1997-10", "series_number": "19", "volume": "61", "issue": "19", "pages": "4095-4113" }, { "id": "authors:8s6zh-tex12", "collection": "authors", "collection_id": "8s6zh-tex12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-150128545", "type": "article", "title": "The concentration and isotopic composition of osmium in the oceans", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Osmium is one of the rarer elements in seawater. Analytical difficulties have previously prevented the direct measurement of the osmium concentration and isotopic composition in seawater. We report a chemical separation procedure that yields quantitative extraction of osmium standard and of osmium tracer by iron hydroxide precipitation from seawater doped with osmium standard, osmium tracer, and FeCI_3. The iron hydroxide precipitate is processed to extract osmium, using techniques developed for iron meteorites. Utilizing this procedure, water samples from the Pacific and Atlantic oceans were analyzed for osmium concentration and isotopic composition. Direct determination of the osmium concentration of seawater gives between 15 and 19 fM kg^(\u22121). Detailed experiments on different aliquots of one seawater sample from the North Atlantic Ocean, keeping the amounts of reagents constant, yield concentrations from 16 to 19 fM kg^(\u22121). The variability in concentration is outside the uncertainty introduced because of blanks and indicates a lack of full equilibration between the osmium tracer and seawater osmium. The most reliable osmium concentration of the North Atlantic deep ocean water is 19 fM kg^(\u22121) with the ^(187)Os^(186)Os ratio being 8.7 \u00b1 0.2 (2\u03c3). Detailed experiments on one seawater sample from the Central Pacific Ocean indicate that the most reliable osmium concentration of the deep ocean water from the Central Pacific is 19 fM kg^(\u22121) with the ^(187)Os^(186)Os ratio being 8.7 \u00b1 0.3 (2\u03c3). The directly measured osmium isotopic composition of the oceans is in good agreement with that obtained from the analysis of some rapidly accumulating organic rich sediments (Ravizza and Turekian, 1992). A sample of ambient seawater around the Juan de Fuca Ridge gave ^(187)Os^(186)Os= 6.9 \u00b1 0.4. This is distinctly lower than the deep-sea water value and may reflect local hydrothermal activity or some analytical difficulty with this sample. The osmium isotopic composition of the deep oceans indicates that \u223c80% of the osmium is derived from the continents and the rest from extraterrestrial and hydrothermal sources. Using the iridium data of Anbar et al. (1996, 1997) we find that the Os/Ir ratio is \u223c22 for seawater. The mean residence time of osmium (\u03c4_(Os)) cannot be derived directly from these data. However, using the Os/Ir ratio of seawater and the Os/Ir ratio of continental rocks, a lower limit can be established of \u03c4_(Os) \u2265 4.4 \u00d7 10^4 years. The Os/Ir in modern deep sea sediments should be relatively constant and is distinctly less radiogenic than seawater osmium due to limited evaporation (26%) of osmium from infalling cosmic dust. Relative to the cosmic dust infall the hydrothermal sources may, however, play a smaller but significant role in the bulk economy of dissolved osmium and other Platinum Group Elements in the oceans.", "doi": "10.1016/S0016-7037(97)00210-X", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1997-08", "series_number": "16", "volume": "61", "issue": "16", "pages": "3287-3299" }, { "id": "authors:p79da-8b467", "collection": "authors", "collection_id": "p79da-8b467", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131216-141955489", "type": "article", "title": "Determination of Iridium in Natural Waters by Clean Chemical Extraction and Negative Thermal Ionization Mass Spectrometry", "author": [ { "family_name": "Anbar", "given_name": "A. D.", "clpid": "Anbar-A-D" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Methods for the precise, routine measurement of Ir in seawater, riverwater, and estuarine water using isotope dilution negative thermal ionization mass spectrometry (ID-NTIMS) have been developed. After equilibration with a ^(191)Ir-enriched spike, Ir is separated from solution by coprecipitation with ferric hydroxide, followed by anion exchange chromatography using a reductive elution technique. UV irradiation is employed for the decomposition of trace organics, which interfere with negative ion production. IrO_2- ions are produced in the mass spectrometer by heating the sample on a Ni-wire filament in the presence of Ba(OH)_2. Detection efficiencies ranged from 0.1% to 0.3%. We have used these procedures to determine the concentrations of Ir in 4 kg samples from the Pacific Ocean, the Atlantic Ocean, the Baltic Sea, and the rivers supplying the Baltic. Our chemical procedures introduce a total blank of ~2 \u00d7 10^8 atoms per sample. The distribution of Ir in the oceans is fairly uniform, averaging ~4 \u00d7 10^8 atoms kg^(-1). The concentrations in the rivers supplying the Baltic Sea range from (17.4 \u00b1 0.9) \u00d7 10^8 for a pristine river to (92.9 \u00b1 2.2) \u00d7 10^8 atoms kg^(-1) for a polluted river. The distribution, speciation, and transport of Ir in natural waters can now be subjected to intensive study.", "doi": "10.1021/ac961129n", "issn": "0003-2700", "publisher": "American Chemical Society", "publication": "Analytical Chemistry", "publication_date": "1997-07-01", "series_number": "13", "volume": "69", "issue": "13", "pages": "2444-2450" }, { "id": "authors:yqbxx-x5f33", "collection": "authors", "collection_id": "yqbxx-x5f33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-152506716", "type": "article", "title": "Europium valence state distributions in equilibrated ordinary chondrites", "author": [ { "family_name": "Connolly", "given_name": "H. C., Jr.", "clpid": "Connolly-H-C-Jr" }, { "family_name": "Peters", "given_name": "M. T.", "clpid": "Peters-M-T" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "It has been recognized for 30 years that the presence of Eu anomalies in REE patterns is due to the presence of divalent Eu, unique among the REE. However, it has not previously been possible to infer quantitative Eu^(+2)/Eu^(+3) ratios in natural samples. We have used ion probe data for lithophile trace elements for the phases in equilibrated ordinary chondrites [Guareiia (H6), Marion (L6) and St. Sev\u00e9rin (LL6)] to perform mass-balance calculations that yield relatively precise Eu^(+2)/Eu^(+3) ratios.", "doi": "10.1111/j.1945-5100.1997.tb01599.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1997-07", "series_number": "S4", "volume": "32", "issue": "S4", "pages": "A30-A31" }, { "id": "authors:7yxt0-38564", "collection": "authors", "collection_id": "7yxt0-38564", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-150612586", "type": "article", "title": "Rhenium-osmium fractionation and isotopic systematics in ordinary chondrites", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We investigated Re-Os for whole rocks, sulfide, and metal from ordinary chondrites. Reproducible analyses for Re/Os in chondrites are obtained. Data on St. S\u00e9verin (LL6) show a large range in ^(187)Re/^(188)OS (0.31-0.78) and in ^(187)OS/^(188)OS (0.119-0.157).", "doi": "10.1111/j.1945-5100.1997.tb01599.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1997-07", "series_number": "S4", "volume": "32", "issue": "S4", "pages": "A27-A28" }, { "id": "authors:sm9db-77e31", "collection": "authors", "collection_id": "sm9db-77e31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140716-073045286", "type": "article", "title": "Search for nickel-60 excesses in pallasite olivines", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Srinivasan", "given_name": "G.", "clpid": "Srinivasan-G" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have initiated a search in pallasite olivines for possible excesses of ^(60)Ni due to the decay of ^(60)Fe (half-life 1.5 Ma). The search in pallasite olivines was based on the observation of evidence for the in situ decay in pallasite olivine of ^(53)Mn (half-life 3.7 Ma) for Eagle Station and for Omolon; the expectation of high ^(56)Fe/^(58)Ni in pallasite olivines; Re-Os measurements in pallasites that indicate a whole-rock isochron for\npallasites consistent with the whole-rock Re-Os isochron for iron meteorites and possibly early formation; and the discovery of evidence for the in situ decay of ^(60)Fe in eucrites.", "doi": "10.1111/j.1945-5100.1997.tb01599.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1997-07", "series_number": "S4", "volume": "32", "issue": "S4", "pages": "A103-A104" }, { "id": "authors:e9c3s-baa11", "collection": "authors", "collection_id": "e9c3s-baa11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140225-135741132", "type": "article", "title": "Mineralogy and chemical compositions of Colomera (IIE) silicate inclusions", "author": [ { "family_name": "Hsu", "given_name": "W.", "clpid": "Hsu-W" }, { "family_name": "Takeda", "given_name": "H.", "clpid": "Takeda-H" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Irons of groups lAB and IIE contain silicate inclusions. In IAB irons,\nthese inclusions are basically chondritic, but in IIE they vary from chondritic\nto highly differentiated [1,2]. In this work, we present detailed studies\nof mineralogy and trace-element geochemistry of eight silicate inclusions\nfrom Colomera with the goal of better understanding early planetary differentiation and possible genetic relationships between iron and stony meteorites.", "doi": "10.1111/j.1945-5100.1997.tb01599.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1997-07", "series_number": "S4", "volume": "32", "issue": "S4", "pages": "A61-A62" }, { "id": "authors:kds5g-rh468", "collection": "authors", "collection_id": "kds5g-rh468", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-153844843", "type": "article", "title": "Trace-element abundances and the origin of aluminum-26-bearing chondrules in unequilibrated ordinary chondrites", "author": [ { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Russell", "given_name": "S. S.", "clpid": "Russell-S-S" }, { "family_name": "MacPherson", "given_name": "G. J.", "clpid": "MacPherson-G-J" } ], "abstract": "Calcium-aluminum-rich inclusions (CAis) typically contain radiogenic ^(26)Mg (^(26)Mg^*) from the decay of ^(26)Al, with (^(26)Al/^(27)Al); up to 5 x 10^(-5) [e.g., 1]. Some Al-rich chondrules from unequilibrated ordinary chondrites contain detectable ^(26)Mg^*, but (^(26)Al/^(27)Al); is lower [e.g., 2].", "doi": "10.1111/j.1945-5100.1997.tb01599.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1997-07", "series_number": "S4", "volume": "32", "issue": "S4", "pages": "A63" }, { "id": "authors:0ebwc-zyx51", "collection": "authors", "collection_id": "0ebwc-zyx51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140225-133358003", "type": "article", "title": "Precursors of aluminum-rich chondrules from the Axtell (CV3) meteorite", "author": [ { "family_name": "Srinivasan", "given_name": "G.", "clpid": "Srinivasan-G" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Aluminum-rich chondrules are less refractory and have lower ^(26)Al abundance\ncompared to Ca-Al-rich inclusions (CAIs) [1-3]. The presence of\nhibonite grains in a Sharps Al-rich chondrule [2], and of a spinel-fassaite\nfragment in an Allende ferromagnesian chondrule [4] suggest CAIs as plausible\nprecursors of Al-rich chondrules. To investigate this possibility we have\ndetermined major ,-minor-, and rare-earth-element (REE) concentration in\ndominant mineral phases in CAIs and Al-rich chondrules from Axtell. Aluminum-rich chondrules from Axtell have (^(26)Al/^(27)Al)_i \u2264\n 3 x 10^(-6) [1]. Bulk\ncompositions for the chondrules were calculated from modal mineral abundances.", "doi": "10.1111/j.1945-5100.1997.tb01599.x", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1997-07", "series_number": "S4", "volume": "32", "issue": "S4", "pages": "A123-A124" }, { "id": "authors:7fehp-qma51", "collection": "authors", "collection_id": "7fehp-qma51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-110619896", "type": "article", "title": "Negative thermal ion mass spectrometry of oxygen in phosphates", "author": [ { "family_name": "Holmden", "given_name": "C.", "clpid": "Holmden-C" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A novel technique for the precise measurement of oxygen isotopes by negative thermal ion mass spectrometry (NTIMS) is presented. The technique is ideally suited to the analysis of oxygen isotopes in phosphates which form intense PO_3^- ion beams. Since P is monoisotopic, the mass spectrum for PO_3^\u2212 at 79, 80, and 81 corresponds to ^(16)O, ^(17)O, and ^(18)O. Natural and synthetic phosphates are converted and loaded on the mass spectrometer filament as Ag_3PO_4 precipitated directly from ammoniacal solution. To lower the work function of the filament, BaCI_2, is added in a 1:1 molar ratio of PO_4:Ba. Using these procedures, Br^\u2212 mass interference (at 79 and 81 amu) is eliminated for typical analyses. Experiments with ^(18)O-enriched water show less than 1% O-exchange between sample PO_4 and adsorbed water, and there is no O-exchange with trace OZ present in the mass spectrometer source chamber. The ionization efficiency of PO_4, as PO_3^\u2212 is >10% compared to 0.01% for both conventional dual inlet Gas Isotope Ratio Mass Spectrometry (GIRMS) and secondary ion mass spectrometry (SIMS). Therefore, NTIMS offers exceptional sensitivity enabling routine and precise oxygen isotope analysis of sub-microgram samples of PO_4, (<21 nmoles equivalent CO_2 gas) without need for lengthy chemical pre-treatment reproducibility of the sample. Overall external precision is \u00b11%c (2\u03c3) for ^(18)O/^(16)O and ^(17)O/^(16)O with reproducibility of instrumental isotope fractionation (calculated from ^(18)O/^(16)O of \u00b10.5%c amu^(\u22121). Small phosphate samples including single mineral grains from meteorites, or apatite microfossils, can be analyzed by this technique.", "doi": "10.1016/S0016-7037(97)00057-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1997-06", "series_number": "11", "volume": "61", "issue": "11", "pages": "2253-2263" }, { "id": "authors:f9maj-jgr67", "collection": "authors", "collection_id": "f9maj-jgr67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-095721373", "type": "article", "title": "Self diffusion of europium, neodymium, thorium, and uranium in haplobasaltic melt: The effect of oxygen fugacity and the relationship to melt structure", "author": [ { "family_name": "LaTourrette", "given_name": "T.", "clpid": "LaTourrette-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report new measurements of self diffusion coefficients (D) for Mg, Nd, Eu, Th, and U in a haplobasaltic (Fo_(15)Di_(40)An_(45)) melt at 1 atm, 1400\u20131500\u00b0C, and oxygen fugacities corresponding to air and the Fe-FeO buffer. Diffusion couples consisted of isotopically distinct melts of the same chemical composition, and isotopic concentration profiles in quenched couples were measured with an ion probe. The valence state distributions of Eu and U were determined from absorption spectroscopy and model calculations, which demonstrate a shift from Eu^(3+) and U^(5.5+) in air to Eu^(2.5+) and U^(4+) at Fe-FeO. D_(Mg), D_(Nd), and D_(Th) are independent of oxygen fugacity and agree well with our previous measurements. D_(Eu) = D_(Nd) in air and increases by 42% at Fe-FeO, while D_U = D_(Th) in air and shows a possible small increase of \u223c20% at Fe-FeO. The change in D_(Eu) with oxygen fugacity matches the established ionic radius and charge dependence for Mg, Ca, Ba, Nd, Yb, Ti, and Zr, while diffusion coefficients for Zr, Th, U^(4+), and U^(5.5+) are independent of ionic radius and charge. Activation energies for all cations are approximately equal, independent of oxygen fugacity, and approximately match the activation energy for viscous flow. In addition, activation energies and diffusion coefficients recently measured for O and Si in basalt agree well with the present values. The good agreement between the various activation energies and between network modifier and network former diffusivities is consistent with a model in which diffusion of network modifying cations in low viscosity melts is controlled largely by the extrinsic influence of the melt network reorganization, with an additional influence from the intrinsic mobilities of the individual cations. The constant diffusion coefficient defined by the high ionic radius and charge elements is interpreted to represent the characteristic network diffusivity for this composition, which dominates over the intrinsic diffusivities for these elements. Elements with faster intrinsic diffusivities still display a small ionic radius and charge dependence. Diffusion coefficients in high viscosity melts are expected to be decoupled from the network, and thus may display a much greater dependence on ionic radius and charge.", "doi": "10.1016/S0016-7037(96)00377-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1997-02", "series_number": "4", "volume": "61", "issue": "4", "pages": "755-764" }, { "id": "authors:8we2r-cdf62", "collection": "authors", "collection_id": "8we2r-cdf62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-093907366", "type": "article", "title": "The neodymium isotopic compositions and rare earth patterns in highly depleted ultramafic rocks", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A large number of terrestrial and extraterrestrial reservoirs are sampled by ultradepleted rocks containing mainly olivine and orthopyroxene. However, very few attempts have been made to determine the REE contents and neodymium isotopic composition of such samples due to substantial analytical problems in handling large sample volumes. We describe a chemical separation technique with high chemical yield and low contamination suitable for extraction of REEs from depleted ultramafic rocks. After sample dissolution, we use the Fe present in the rock for coprecipitation of REEs while keeping Mg, the dominant major element in an ultramafic rock, in solution. This technique reduces the effective sample size by an order of magnitude, thus permitting the use of existing column techniques to separate the lanthanides. Utilizing this procedure, eight harzburgites and a dunite, associated with the mantle sections of ophiolite complexes, were analyzed for REE and neodymium isotopic composition. The results show the LREE concentrations varying from sub parts per billion to less than 10 ppb; the Yb concentrations representing the HREEs vary from 1 to 70 ppb. The rocks have \u0192_(Sm/Nd) values ranging from \u22120.45 to +3.4 and \u03f5_(Nd)(0) values varying from \u221212.5 to +47.5. The ultramafic rocks can be classified into two groups using their initial \u03f5_(Nd)(t) values. The samples with \u03f5_(Nd)(t) > +7 are derived from depleted MORB mantle and show extreme LREE depletion and HREE enrichment with no hint of a U-shaped REE pattern. However, samples with \u03f5_(Nd)(t) < +7 yield REE patterns that are either U-shaped or flatten towards the LREE end are interpreted as having been contaminated by continental crust. We conclude that the U-shaped REE patterns found in many harzburgites associated with mantle sections of ophiolite complexes are the result of crustal contamination and not the consequence of peculiar fractionation during melting. The HREE depletion shown by the samples with \u03f5_(Nd)(t) > +7 can be modeled with equilibrium fractional melting. However, the observed (La/Sm)_N ratios are several orders of magnitude higher than predicted by the melting model. We suggest that the high (La/Sm)_N ratios in the ultradepleted samples may be a result of refertilization by basaltic melts. The chemical procedure developed in this paper permits a full exploration of ultradepleted rocks from the upper mantle as well as some classes of meteorites that are highly depleted.", "doi": "10.1016/S0016-7037(96)00280-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1996-11", "series_number": "22", "volume": "60", "issue": "22", "pages": "4537-4550" }, { "id": "authors:83mnc-q6f85", "collection": "authors", "collection_id": "83mnc-q6f85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-085601668", "type": "article", "title": "Reply to the comment by S. B. Jacobsen and C. L. Harper Jr. on \"The issue of the terrestrial record of ^(146)Sm\"", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Dymek", "given_name": "R. F.", "clpid": "Dymek-R-F" } ], "abstract": "There is abundant evidence for the widespread occurrence\nof live ^(146)Sm(\u01ac = 149 Ma) in the early Solar System as\nestablished by correlated Sm/Nd and ^(142)Nd/^(144)Nd in meteorites (Lugmair and Marti, 1977; Lugmair et al., 1983; Jacobsen and Wasserburg, 1984; Prinzhofer et al., 1989, 1992; Lugmair and Galer, 1992; Nyquist et al., 1994; Stewart et al., 1994; Sharma et al., 1995).", "doi": "10.1016/S0016-7037(96)90093-9", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1996-10", "series_number": "19", "volume": "60", "issue": "19", "pages": "3751-3754" }, { "id": "authors:24k6p-2tq13", "collection": "authors", "collection_id": "24k6p-2tq13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131216-151319006", "type": "article", "title": "Iridium in Natural Waters", "author": [ { "family_name": "Anbar", "given_name": "A. D.", "clpid": "Anbar-A-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Andersson", "given_name": "P. S.", "clpid": "Andersson-P-S" } ], "abstract": "Iridium, commonly used as a tracer of extraterrestrial material, was measured in rivers, oceans, and an estuarine environment. The concentration of iridium in the oceans ranges from 3.0 (\u00b11.3) \u00d7 10^8 to 5.7 (\u00b10.8) \u00d7 10^8 atoms per kilogram. Rivers contain from 17.4 (\u00b10.9) \u00d7 10^8 to 92.9 (\u00b12.2) \u00d7 10^8 atoms per kilogram and supply more dissolved iridium to the oceans than do extraterrestrial sources. In the Baltic Sea, \u223c75% of riverine iridium is removed from solution. Iron-manganese oxyhydroxides scavenge iridium under oxidizing conditions, but anoxic environments are not a major sink for iridium. The ocean residence time of iridium is between 2 \u00d7 10^3 and 2 \u00d7 10^4 years.", "doi": "10.1126/science.273.5281.1524", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1996-09-13", "series_number": "5281", "volume": "273", "issue": "5281", "pages": "1524-1528" }, { "id": "authors:p8km6-wxp96", "collection": "authors", "collection_id": "p8km6-wxp96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-100505428", "type": "article", "title": "Sm-Nd systematics of a silicate inclusion in the Caddo IAB\n iron meteorite", "author": [ { "family_name": "Stewart", "given_name": "Brian", "clpid": "Stewart-B" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report the first Sm-Nd data from an iron meteorite silicate inclusion. Mineral separates from an inclusion in the Caddo IAB iron define a ^(147)Sm/^(143)Nd age of 4.53\u00b10.02 Ga, and an initial ^(146)Sm/^(144)Sm of 0.0086\u00b10.0021. A plagioclase separate from the inclusion yields the lowest ^(142)Nd/^(144)Nd ratio measured to date, which provides an absolute maximum initial solar system \u03f5_(142) of \u22122.1 \u00b1 0.4. When the ^(146)Sm/^(142)Nd data are combined with the ^(147)Sm/^(143)Nd data, we obtain our preferred initial solar system \u03f5_(142) value of \u22123.2 \u03f5u, which corresponds to an initial ^(146)Sm/^(144)Sm of 0.009. Rare earth element data from the Caddo silicate inclusion suggest that it was derived by partial melting of a chondritic source prior to incorporation into the metal. Therefore, differentiation of the silicate portion of the parent body must have started approximately within the first 30 Ma of solar system history. The data reported here clearly show that IAB meteorites preserve a record of very early planetary differentiation processes. Modeling of element diffusion indicates that, if the silicate material was incorporated into its FeNi host at a time much later than 4.53 Ga, then the mixing must have taken place at shallow levels (i.e., < 50 m) in the parent body, in order to preserve the Sm-Nd systematics. It is more likely that incorporation of the silicate took place at depths greater than 2 km, and that it occurred within the first \u223c 30 Ma of solar system history. This is consistent with estimates of cooling rates determined for IAB irons.", "doi": "10.1016/0012-821X(96)00124-0", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1996-09", "series_number": "1-4", "volume": "143", "issue": "1-4", "pages": "1-12" }, { "id": "authors:d9av7-qcw58", "collection": "authors", "collection_id": "d9av7-qcw58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131113-134356119", "type": "article", "title": "^(238)U-^(230)Th dating of a geomagnetic excursion in Quaternary basalts of the Albuquerque Volcanoes Field, New Mexico (USA)", "author": [ { "family_name": "Peate", "given_name": "D. W.", "clpid": "Peate-D-W" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Geissman", "given_name": "J. W.", "clpid": "Geissman-J-W" } ], "abstract": "We report the ^(238)U-^(230)Th age derived from samples from three basalt flows from the Albuquerque Volcanoes Field, central New Mexico (USA), interpreted to have erupted during one of the Bruhnes Chron geomagnetic field polarity events. Whole-rock samples and magnetite separates from two of the samples define an isochron with an age of 156\u00b129 ka (2\u03c3). It is now possible to determine the ages of geomagnetic excursions with reasonable precision, by the ^(238)U-^(230)Th method, using basalts erupted between possibly 25 and up to 250 ka. Although a strict correlation of the polarity event recorded by the Albuquerque lavas with other high amplitude field phenomena in the latest Quaternary is not yet possible, the Blake and the less well-documented Old Crow and Biwa I/Jamaica events are likely candidates.", "doi": "10.1029/96GL02064", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1996-08-15", "series_number": "17", "volume": "23", "issue": "17", "pages": "2271-2274" }, { "id": "authors:qv78b-ks085", "collection": "authors", "collection_id": "qv78b-ks085", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131218-152816653", "type": "article", "title": "Evidence for Widespread ^(26)Al in the Solar Nebula and Constraints for Nebula Time Scales", "author": [ { "family_name": "Russell", "given_name": "S. S.", "clpid": "Russell-S-S" }, { "family_name": "Srinivasan", "given_name": "G.", "clpid": "Srinivasan-G" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "MacPherson", "given_name": "G. J.", "clpid": "MacPherson-G-J" } ], "abstract": "A search was made for ^(26)Mg (^(26)Mg^*) from the decay of ^(26)Al (half-life = 0.73 million years) in Al-rich objects from unequilibrated ordinary chondrites. Two Ca-Al-rich inclusions (CAIs) and two Al-rich chondrules (not CAIs) were found that contained ^(26)Al when they formed. Internal isochrons for the CAIs yielded an initial ^(26)Al/^(27)Al ratio [(^(26)Al/^(27)Al)_0] of 5 x 10^(-5), indistinguishable from most CAIs in carbonaceous chondrites. This result shows that CAIs with this level of ^(26)Al are present throughout the classes of chondrites and strengthens the notion that ^(26)Al was widespread in the early solar system. The two Al-rich chondrules have lower ^(26)Mg^*, corresponding to a (^(26)Al/^(27)Al)_0 ratio of approximately 9 x 10^(-6). Five other Al-rich chondrules contain no resolvable ^(26)Mg^*. If chondrules and CAIs formed from an isotopically homogeneous reservoir, then the chondrules with ^(26)Al must have formed or been last altered approximately ~2 million years after CAIs formed; the ^(26)Mg^*-free chondrules formed >1 to 3 million years later still. Because ^(26)Mg^*-containing and ^(26)Mg^*-free chondrules are both found in Chainpur, which was not heated to more than approximately ~400\u00baC, it follows that parent body metamorphism cannot explain the absence of ^(26)Mg^* in some of these chondrules. Rather, its absence indicates that the lifetime of the solar nebula over which CAIs and chondrules formed extended over approximately ~5 million years.", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1996-08-09", "series_number": "5276", "volume": "273", "issue": "5276", "pages": "757-762" }, { "id": "authors:jss9s-swg44", "collection": "authors", "collection_id": "jss9s-swg44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131119-095431840", "type": "article", "title": "Abundances of Actinides and Short-lived Nonactinides in the Interstellar Medium: Diverse Supernova Sources for the r-Processes", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Gallino", "given_name": "R.", "clpid": "Gallino-R" } ], "abstract": "Abundances of ^(244)Pu, ^(235)U, ^(238)U, and ^(232)Th in the early solar system are about those expected for uniform production over most of galactic history. The inferred abundance of 182Hf is also compatible with this model. We here associate production of ^(182)Hf with the same r-process SN sources that produce actinides (SNACS). This requires that r-process nucleosynthesis in SNACS took place rather uniformly over the age of the galaxy until ~10^7 yr prior to solar system formation. The low abundance of ^(107)Pd and ^(129)I in the early solar system indicates that SNACS cannot produce these nuclei at the high yields expected from standard r-process models. We propose that there are distinctive SN sources for different r-process nuclei with a sharp distinction in different SN contributions below and above A ~ 140. Abundances in stars with very low metallicities will vary depending on the type of SN contributing to the local region of star formation. A time scale of ~10^7 yr is much shorter than the 108 yr time usually associated with processes in the galaxy and with the last time of r-process injection accounting for ^(129)I, but may be compatible with the rate of SN occurrence. The hypothesis of a nearby SN polluting the protosolar nebula is critically discussed.", "doi": "10.1086/310177", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1996-08-01", "series_number": "2", "volume": "466", "issue": "2", "pages": "L109-L113" }, { "id": "authors:dwpqy-qef89", "collection": "authors", "collection_id": "dwpqy-qef89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-102704356", "type": "article", "title": "Precise Re-Os determinations and systematics of iron meteorites", "author": [ { "family_name": "Shen", "given_name": "J. J.", "clpid": "Shen-J-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The Re-Os system for samples of FeNi, sulphide, and phosphide from iron meteorites was investigated. Techniques were developed which yield reproducible analyses for Re/Os at the 2\u2030 level and which permit complete isotopic exchange between sample and tracer, as is necessary for concentration measurements of Re and Os by isotope dilution. High precision osmium and rhenium isotope data have been obtained using negative ion thermal ionization, with ionization efficiencies of up to 10% for Os and 20% for Re, both for normals and for Re and Os extracted from the samples. Replicate analyses of Re/Os are in good agreement, within \u00b12.5\u2030. The results show a well defined correlation line on a ^(187)Re-^(187)Os evolution diagram for iron meteorites from groups IAB, IIAB, IIIAB, IVA, and IVB, all taken together. This correlation line yields a slope of 0.07863 \u00b1 0.00031 (2\u03c3) and initial ^(187)Os/^(188)Os = 0.09560 \u2213 0.00018 (2\u03c3). If the individual groups of iron meteorites for which there is sufficient dispersion in Re/Os are considered, data on the IIAB and on the IVA irons appear to indicate a difference in age of 60 \u00b1 45 Ma, with the IVA group being older-This age difference is qualitatively the same as obtained for Pd-Ag data but is larger. Sulphides from two IAB iron meteorites show extremely low concentrations of Re and Os and indicate that Re and Os are not partitioned into this phase during planetary differentiation. There is evidence for recent element remobilization or contamination, corresponding to relative enrichment of Re or loss of Os in the sulphides. Schreibersites contain small but significant amounts of Re and Os, with high Re/Os relative to the metal phases and with ^(187)Os/^(188)Os much more radiogenic than in the metal. Model ages for the schreibersites are relatively young (4.3-3.5 AE) and indicate that the schreibersites were open-systems for Re-Os at least 0.5-1 AE after the original formation of the iron meteorites, It now appears possible to use metal-schreibersite pairs to determine internal isochrons. Based on the schreibersite model ages, the cooling rates for the two IAB meteorites are estimated to be ~ 1\u00b0C/Ma, more than an order of magnitude lower than the most recently determined metallographic cooling rates for IAB irons (Herpfer et al., 1994).", "doi": "10.1016/0016-7037(96)00120-2", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1996-08", "series_number": "15", "volume": "60", "issue": "15", "pages": "2887-2900" }, { "id": "authors:c8spa-n4284", "collection": "authors", "collection_id": "c8spa-n4284", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-113712611", "type": "article", "title": "The issue of the terrestrial record of ^(146)Sm", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Dymek", "given_name": "R. F.", "clpid": "Dymek-R-F" } ], "abstract": "Harper and Jacobsen (1992a) have reported a 33 \u03bc (\u03bc = parts per million) ^(142)Nd excess in a 3.8 Ga felsic gneiss (IE 715-28) from Isua, West Greenland. This excess was interpreted as due to a preserved effect in a parent reservoir produced early (between 4.5 and 4.3 Ga) while the short-lived parent of ^(142)Nd (^(146)Sm, T = 149 M\u0251 was still alive. If this result can be substantiated it would indicate an early earth differentiation and generation of parent reservoirs with large Sm/Nd ratios and it would suggest the existence of mechanisms that preserved the ^(142)Nd excess in a 3.8 Ga crustal rock. However, no independent evidence for the ^(142)Nd excesses has been found for other terrestrial samples (Goldstein and Galer, 1992, 1993; McCulloch and Bennett, 1993; Regelous and Collerson, 1995a,b). Inasmuch as the level of the reported effect ( \u223c30 \u03bc excess of ^(142)Nd) requires hitherto undocumented high precision, our efforts have been directed toward addressing the central issue of whether existing high precision mass spectrometers can resolve \u223c30 \u03bc ^(142)Nd excesses. Standards were made up with 0, 30, and 57 \u03bc ^(142)Nd excesses to test the reliability and reproducibility of measuring such isotopic shifts. We used the same model, multicollector mass spectrometer (Finnigan MAT 262) as Harper and Jacobsen (1992a). The data were obtained with 2 \u00d7 10^(\u221211) A ^(142)Nd^+ ion beams, in the static mode. Our experiments show that positioning of the sample filament and ion source focusing potentials can engender large effects (up to 60 \u03bc) and arbitrary shifts in measured '42Nd/'44Nd ratios. We have not been able to identify an a priori method for avoiding these shifts. Under restricted focusing conditions, borne out from our experimentation, it is possible to obtain reproducible results for a short term. Since there is little understanding of what constitutes \"reproducible conditions,\" especially when it comes to ion beam focusing, we believe it is not yet possible to obtain reliable results at the level required. Using restricted focusing conditions, we found strong hints of ^(142)Nd excesses in two rocks from Isua, including the sample analyzed by Harper and Jacobsen (1992a) thereby supporting their claim of an effect. However, we did not find it possible to achieve the level of precision reported by these workers. Moreover, it has not been possible for us to reproduce the results on standards and samples in any regular way. This difficulty has persisted throughout an extensive series of experiments in which considerable care was directed towards identifying optimal instrumental operating conditions. We conclude that further refinements in the experimental techniques are needed to obtain reliable ultra high precision measurements. This is necessary before the issue of a terrestrial record of ^(141)Sm is resolved.", "doi": "10.1016/0016-7037(96)00082-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1996-06", "series_number": "11", "volume": "60", "issue": "11", "pages": "2037-2047" }, { "id": "authors:expk6-cqz57", "collection": "authors", "collection_id": "expk6-cqz57", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-094713692", "type": "article", "title": "^(230)Th-^(232)Th systematics in the central Pacific Ocean:\n The sources and the fates of thorium", "author": [ { "family_name": "Roy-Barman", "given_name": "M.", "clpid": "Roy-Barman-M" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "^(232)Th and ^(230)Th of unfiltered and filtered sea water samples were measured along a depth profile of the central Pacific Ocean using isotopic dilution and thermal ionization mass spectrometry. The ^(232)Th concentration is rather constant from below 25 m down to over 2000 m (45\u201360 \u00d7 10^6 atom cm^(\u22123)) and it then increases rapidly towards the bottom (119\u2013360 \u00d7 10^6 atom cm^(\u22123) at 4000 m). The ^(230)Th concentration increases linearly with depth from 3 \u00d7 10^3 atom cm^(\u22123) at 25 m to 110 \u00d7 10^3 atom cm^(\u22123) at 4000 m. The reproducibility of replicate analyses and the regularity of the profiles demonstrate the reliability of the procedure. However, some lack of reproducibility among different samples from the same depth has to be explained by natural variability or by contamination during sample collection. Due to the very low ^(232)Th concentrations and relatively high ^(230)Th concentrations, the ^(230)Th/^(232)Th ratios can be as high as 1.6 \u00d7 10^(\u22123). The ratio of the amount of Th on particles (> 0.2 \u03bcm) to the amount of Th in solution is significantly higher for ^(232)Th (\u2248 0.37) than for ^(230)Th (\u2248 0.18). These data are interpreted in terms of a model that specifically treats particle transport assuming local equilibrium between particles and sea water. The relatively high ^(230)Th concentrations and ^(230)Th/^(232)Th ratios measured at 25 m are consistent with a mixed layer of about 100 m. The linear increase in ^(230)Th with depth implies that the effect of eddy diffusion is negligible for most of the water column over the Th removal time scale. This profile is consistent with transport of ^(230)Th by reversible uptake on particles settling with a constant velocity. The ^(232)Th data are inconsistent with this model and they suggest that particles carrying ^(232)Th experience 70% of mass loss between the surface and 4000 m and must follow different transport rules. This difference in the transport of ^(230)Th and ^(232)Th demonstrates the distinctive behavior of these isotopes during particle formation and subsequent remineralization and repackaging in the water column. Different speciation of ^(230)Th and ^(232)Th may be explained by their distinctive sources in the ocean (as ^(230)Th is produced in solution and ^(232)Th is carried by detrital material) and by their respective packaging mechanisms, which are not yet known.", "doi": "10.1016/0012-821X(96)00017-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1996-04", "series_number": "3-4", "volume": "139", "issue": "3-4", "pages": "351-363" }, { "id": "authors:y03a5-nnr71", "collection": "authors", "collection_id": "y03a5-nnr71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-111016293", "type": "article", "title": "Self diffusion of Mg, Ca, Ba, Nd, Yb, Ti, Zr, and U in haplobasaltic melt", "author": [ { "family_name": "LaTourrette", "given_name": "T.", "clpid": "LaTourrette-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Fahey", "given_name": "A. J.", "clpid": "Fahey-F-A" } ], "abstract": "We have measured self diffusion coefficients (D) for a wide variety of elements in a Fo_(15)Di_(40)An_(45) melt at 1 bar from 1350\u20131500 \u00b0C. These measurements, including the first reported data for Yb, Ti, Zr, U, and preliminary values for Th and Pb, provide an internally consistent set of self diffusivities for elements covering a wide range in ionic radius and charge. Diffusion couples were formed by juxtaposing isotopically enriched and isotopically normal melts of the same chemical composition, and isotopic concentration profiles were measured with an ion probe. Well-defined diffusion coefficients were determined to within a reproducibility of \u00b115%. The data show good Arrhenian behavior with activation energies ranging from 170 kJ/m for Mg^(2+) to 216 kJ/m for Zr^(4+). The diffusion coefficient for U is interpreted as the weighted sum of variable proportions of U^(5+) and U^(6+), with D_(U5+) > D_(U6+). Activation energies for most elements are similar and agree well with the activation energy for viscous flow, suggesting a structural relationship between diffusion and viscosity. In contrast, diffusion coefficients display a systematic decrease with increasing ionic radius and increasing charge at any given temperature, and at 1400 \u00b0C range from 8.1 \u00d7 10^(\u22127) cm^2/s for Mg^(2+) to 0.9 \u00d7 10^(\u22127) cm^2/s for U^(5\u22126+). These observations suggest that diffusion of network modifying cations in low viscosity melts reflects a combination of the intrinsic mobilities of the individual cations and viscous flow of the melt network. While there is some indication that self diffusion coefficients are influenced by a combination of mechanical and electrostatic effects, a complete physical explanation for the variation of diffusivity with ionic radius and charge does not exist. The width of a boundary layer around a growing crystal is proportional to \u221aD, and hence the small range in diffusion coefficients measured in this study implies that trace element fractionation during crystal growth in basaltic compositions will be minimal.", "doi": "10.1016/0016-7037(96)00015-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1996-04", "series_number": "8", "volume": "60", "issue": "8", "pages": "1329-1340" }, { "id": "authors:g687n-ybr47", "collection": "authors", "collection_id": "g687n-ybr47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-103203157", "type": "article", "title": "Mass transfer of helium, neon, argon, and xenon through a steady-state upper mantle", "author": [ { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have examined the steady-state upper mantle model for helium, neon, argon, and xenon following the mass transfer approach presented by Kellogg and Wasserburg (1990) for helium and Porcelli and Wasserburg (1995a) for xenon. The model explains the available observational data of mantle helium, neon, argon, and xenon isotope compositions and provides specific predictions regarding the rare gas isotopic compositions of the lower mantle, subduction of rare gases, and mantle rare gas concentrations. Rare gases in the upper mantle are derived from mixing of rare gases from the lower mantle, subducted rare gases, and radiogenic nuclides produced in situ. Isotopic shifts in the closed system lower mantle are due to decay of uranium and thorium decay series nuclides, ^(40)K, ^(129)I, and ^(244)Pu over 4.5 Ga, while isotopic shifts in the steady-state upper mantle are due to decay of uranium and thorium series nuclides, and ^(40)K over a timescale of \u223c1.4 Ga. The model predicts that the shift in ^(21)Ne/^(22)Ne in the upper mantle relative to that in the lower mantle is the same as that for ^4He/^3He between the mantle reservoirs. This is compatible with the available data for MORB and ocean islands. Subduction of atmospheric helium and neon is not significant. All of the ^(40)Ar in the lower mantle has been produced by ^(40)K decay in the lower mantle. In the upper mantle, ^(40)K decay further increases the radiogenic 40Ar from the lower mantle by a factor of \u223c3. The calculated minimum lower mantle ^(40)Ar/^(36)Ar ratio is substantially greater than the atmospheric ratio. The inferred rare gas relative abundances of the lower mantle are different from those of the atmosphere and are consistent with possible early solar system reservoirs. Both the calculated ^3He/^(22) and ^(20)Ne/^(36)Ar ratios of the lower mantle are within the range for meteorites with 'solar' neon isotope compositions. The ^(130)Xe/^(36)Ar ratio of the lower mantle is greater than that of the atmosphere, and may be possibly as high as the ratio found for meteoritic \"planetary\" rare gases.\nThe model treats the atmosphere as a separate reservoir with rare gas isotope compositions that are distinct from those in the mantle. If the Earth originally had uniform concentrations of rare gases as represented by those in the lower mantle, then degassing of the upper mantle would have provided only a small proportion of the nonradiogenic rare gases presently in the atmosphere. The remainder may have been derived from late-accreted material with a much higher concentration of rare gases than the lower mantle. However, the amount of radiogenic ^(129)Xe and ^(136)Xe in the atmosphere as well as the lower mantle implies a substantial loss of rare gases. It is most likely that rare gases have been lost during late accretion and/or during; the hypothesized moon-forming impact. The nonradiogenic rare gases in the atmosphere were then supplied by subsequently accreted material with nonradiogenic xenon, possibly in comets. Fractionation of atmospheric xenon isotopes relative to other early solar system components must have occurred either on the late-accreting materials or during subsequent loss from the Earth.", "doi": "10.1016/0016-7037(95)00336-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1995-12", "series_number": "23", "volume": "59", "issue": "23", "pages": "4921-4937" }, { "id": "authors:h446f-0nw53", "collection": "authors", "collection_id": "h446f-0nw53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-092933548", "type": "article", "title": "High ^(143)Nd/^(144)Nd in extremely depleted mantle rocks", "author": [ { "family_name": "Sharma", "given_name": "M.", "clpid": "Sharma-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Quick", "given_name": "J. E.", "clpid": "Quick-J-E" }, { "family_name": "Sharkov", "given_name": "E. V.", "clpid": "Sharkov-E-V" }, { "family_name": "Laz'ko", "given_name": "E. E.", "clpid": "Laz'ko-E-E" } ], "abstract": "Using an iron hydroxide precipitation to concentrate the rare earth elements it was possible to obtain precise Nd isotopic data on ultramafic rocks. Four samples of unserpentinized harzburgite from the Voykar ophiolite, Polar Urals, are characterized by extreme depletion in fertile components including light rare earth elements down to \u223c 1.7 ppb Nd. These samples have f_(Sm/Nd) values > +1 and \u03b5_(Nd)(O) values ranging from +21 to +47, the highest ever measured in terrestrial whole rock samples. Combined \u03b5_(Nd) and \u03b5_(Sr) values of the ultramafic and mafic rocks and a leach indicate that alteration from seawater and/or groundwater is orders of magnitude less than required to produce a detectable change in the \u03b5_(Nd) values even in samples with > 50% serpentine. Three of the harzburgites plot on a Sm-Nd whole rock array along with samples of dunite, websterite, gabbro and diabase from the ophiolite. The slope of the array corresponds to an age of 387 \u00b1 34 Ma and an initial \u03b5_(Nd) = +8.6 \u00b1 1.8. These results indicate that the oceanic crustal rocks and the harzburgites are complementary and come from a MORB source. While the linear ^(147)Sm/^(144)Nd-^(143)Nd/^(144)Nd correlation is consistent with this model, one sample of harzburgite is far removed from the array, indicating the presence of older, depleted mantle material that is unrelated to the crustal section. This must be locally available in the upper mantle for tectonic occlusion during obduction of the ophiolite. Alternatively, this \"aberrant\" sample may represent the original ultrabasic section from older basalt extraction that was permeated by basalts derived from much deeper layers that provided the Voykar ophiolite crust. The major-element and low-REE-compositions of the Voykar harzburgites can be formed by progressive extraction of melt from an undepleted mantle protolith with the requirement that melt separation began in the garnet lherzolite stability field. The extreme chemical and isotopic characteristics of the Voykar harzburgites demonstrate that extraction of partial melt can generate an upper mantle with highly variable \u03b5_(Nd) and very low Nd concentrations. The potential presence of large amounts of such material in the upper mantle poses an intriguing geochemical problem in that its bulk isotopic signature may not be detectably expressed in basalts, which are dominated by sources with higher average Nd concentrations and much lower \u03b5_(Nd) and f_(Sm/Nd).", "doi": "10.1016/0012-821X(95)00150-B", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1995-10", "series_number": "1-4", "volume": "135", "issue": "1-4", "pages": "101-114" }, { "id": "authors:kcnws-py273", "collection": "authors", "collection_id": "kcnws-py273", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BAHrmp95", "type": "article", "title": "Solar models with helium and heavy-element diffusion", "author": [ { "family_name": "Bahcall", "given_name": "John N.", "clpid": "Bahcall-J-N" }, { "family_name": "Pinsonneault", "given_name": "M. H.", "orcid": "0000-0002-7549-7766", "clpid": "Pinsonneault-M-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Helium and heavy-element diffusion are both included in precise calculations of solar models. In addition, improvements in the input data for solar interior models are described for nuclear reaction rates, the solar luminosity, the solar age, heavy-element abundances, radiative opacities, helium and metal diffusion rates, and neutrino interaction cross sections. The effects on the neutrino fluxes of each change in the input physics are evaluated separately by constructing a series of solar models with one additional improvement added at each stage. The effective 1 \u03c3 uncertainties in the individual input quantities are estimated and used to evaluate the uncertainties in the calculated neutrino fluxes and the calculated event rates for solar neutrino experiments. The calculated neutrino event rates, including all of the improvements, are 9.3-1.4+1.2 SNU for the 37Cl experiment and 137-7+8 SNU for the 71Ga experiments. The calculated flux of 7Be neutrinos is 5.1 (1.00-0.07+0.06)\u00d710^9 cm^-2 s^-1 and the flux of 8B neutrinos is 6.6(1.00-0.17+0.14)\u00d710^6 cm^-2 s^-1. The primordial helium abundance found for this model is Y=0.278. The present-day surface abundance of the model is Ys=0.247, in agreement with the helioseismological measurement of Ys=0.242\u00b10.003 determined by Hernandez and Christensen-Dalsgaard (1994). The computed depth of the convective zone is R=0.712R\u2299, in agreement with the observed value determined from p-mode oscillation data of R=0.713\u00b10.003R\u2299 found by Christensen-Dalsgaard et al. (1991). Although the present results increase the predicted event rate in the four operating solar neutrino experiments by almost 1 \u03c3 (theoretical uncertainty), they only slightly increase the difficulty of explaining the existing experiments with standard physics (i.e., by assuming that nothing happens to the neutrinos after they are created in the center of the sun). For an extreme model in which all diffusion (helium and heavy-element diffusion) is neglected, the event rates are 7.0-1.0+0.9 SNU for the 37Cl experiment and 126-6+6 SNU for the 71Ga experiments, while the 7Be and 8B neutrino fluxes are, respectively, 4.5(1.00-0.07+0.06)\u00d710^9 cm^-2 s^-1 and 4.9(1.00-0.17+0.14)\u00d710^6 cm^-2 s^-1. For the no-diffusion model, the computed value of the depth of the convective zone is R=0.726R\u2299, which disagrees with the observed helioseismological value. The calculated surface abundance of helium, Ys=0.268, is also in disagreement with the p-mode measurement. The authors conclude that helioseismology provides strong evidence for element diffusion and therefore for the somewhat larger solar neutrino event rates calculated in this paper.", "doi": "10.1103/RevModPhys.67.781", "issn": "0034-6861", "publisher": "Reviews of Modern Physics", "publication": "Reviews of Modern Physics", "publication_date": "1995-10", "series_number": "4", "volume": "67", "issue": "4", "pages": "781-808" }, { "id": "authors:6tq99-5d879", "collection": "authors", "collection_id": "6tq99-5d879", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131218-102957610", "type": "article", "title": "Observation of Correlated Calcium-41 and Aluminum-26 in CV3 Hibonites", "author": [ { "family_name": "Sahijpal", "given_name": "S.", "clpid": "Sahijpal-S" }, { "family_name": "Srinivasan", "given_name": "G.", "clpid": "Srinivasan-G" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Goswami", "given_name": "J. N.", "clpid": "Goswami-J-N" } ], "abstract": "The demonstration of the presence of ^(41)Ca in the early solar system, based on the observation of excess ^(41)K in Efremovka CAIs [1,2], has led to several attempts that sought to identify plausible stellar sites and processes\nthat could have produced and subsequently injected a host of short-lived radionuclides (e.g., ^(41)Ca, ^(26)Al, ^(60)Fe, ^(53)Mn, and ^(107)Pd) into the protosolar cloud [3-5].", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1995-09", "series_number": "5", "volume": "30", "issue": "5", "pages": "570-571" }, { "id": "authors:2kp6k-s9g94", "collection": "authors", "collection_id": "2kp6k-s9g94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131218-115856514", "type": "article", "title": "A Study of Trace-Element Partitioning Between Pyroxene and Angritic Melt: Equilibrium and Kinetic Effects Including Sector Zoning in Pyroxene", "author": [ { "family_name": "Lofgren", "given_name": "G. E.", "clpid": "Lofgren-G-E" }, { "family_name": "Fahey", "given_name": "A. J.", "clpid": "Fahey-A-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "As part of an ongoing effort to determine partition coefficients, D, for relevant planetary materials, we have determined Ds for REE and Sc, V, Rb, Sr, Y, Zr, Nb, Ba, Hf, Th, and U between fassaitic pyroxene and melt. We have focused on both equilibrium and kinetically controlled partitioning and the application of the data to the petrogenesis of angrites. We used the synthetic ADOR starting material studied by [1], which was doped with trace\nelements at levels of 2 to 600 ppm The experiments were conducted in 1-atm, gas-mixing furnaces with the O fugacity fixed at 1.2 log units above the iron-w\u00fcstite buffer.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1995-09", "series_number": "5", "volume": "30", "issue": "5", "pages": "538" }, { "id": "authors:ys370-mjc97", "collection": "authors", "collection_id": "ys370-mjc97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131218-105845677", "type": "article", "title": "Nitrogen Isotopes in Silicon Carbide: Stellar Nucleosynthesis?", "author": [ { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Nichols", "given_name": "R. H., Jr.", "clpid": "Nichols-R-H-Jr" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Nitrogen in presolar SiC varies over a wide range of concentrations and is typically ^(14)N-rich relative to solar N, consistent with ^(15)N being consumed during CNO processing in stellar envelopes [e.g., 1]. Although C is also heavily processed in the envelopes [1], no clear isotopic correlation exists between C and N [e.g., 2], making N compositions difficult to interpret. Although the same general N features are seen in SiC from many meteorites, clear differences between meteorites have also been observed. In particular, Murchison SiC appears to have systematically higher ^(15)N/^(14)N ratios than Orgueil SiC [2,3]. Among ISN-poor SiC grains for both meteorites, ^(15)N/^(14)N and ^(28)Si/^(l4)N exhibit a positive correlation (Fig. 1).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1995-09", "series_number": "5", "volume": "30", "issue": "5", "pages": "523" }, { "id": "authors:r340n-g4q64", "collection": "authors", "collection_id": "r340n-g4q64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131218-100419787", "type": "article", "title": "Rhenium-Osmium in iron-nickel, sulfide, and phosphide: the possible determination of internal isochrons for iron meteorites", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Shen", "given_name": "J. J.", "clpid": "Shen-J-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "For age determinations of specific events in the evolution of iron meteorites, it is essential to obtain a reasonable range of physical-chemical fractionation of Re-Os. The possible stages of iron meteorite evolution that can, in principle, result in Re-Os fractionation include (1) condensation of PGE and of FeNi in the solar nebula; (2) subsequent oxidation of part of the Fe by reaction with S; (3) segregation and partial removal of massive FeS during\nmelting on parent planetesimals; (4) melting followed by fractional crystallization of the metal phase and crystallization of the remaining FeS; (5) element redistribution during subsolidus phase transformations to produce schreibersite sheaves; and, finally, (6) precipitation or exsolution of minor microphases, e.g., rhabdite, at a later stage.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1995-09", "series_number": "5", "volume": "30", "issue": "5", "pages": "560-561" }, { "id": "authors:aptps-fsg11", "collection": "authors", "collection_id": "aptps-fsg11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131211-143437708", "type": "article", "title": "Deep Circulation in Red Giant Stars: A Solution to the Carbon and Oxygen Isotope Puzzles?", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Boothroyd", "given_name": "Arnold I.", "clpid": "Boothroyd-A-I" }, { "family_name": "Sackmann", "given_name": "I.-Juliana", "clpid": "Sackmann-I-J" } ], "abstract": "The long-standing puzzle of low ^(12)C/^(13)C in low-mass red giant branch (RGB) stars, and the more recent puzzle of low ^(18)O/^(16)O ratios in asymptotic giant branch (AGB) stars and in circumstellar Al_2O_3 grains preserved in meteorites, can be resolved by deep circulation currents below the bottom of the standard convective envelope. These currents transport matter from the nonburning bottom of the convective envelope down to regions where some CNO processing can take place (\"cool bottom processing\"). Modeling circulation with separate downward and upward streams, we found that, to resolve both discrepancies, the base of the extra mixing had to reach a temperature TP close to that of the H-burning shell, namely, \u0394 log T \u2248 0.17 from the base of the H-shell for both RGB and AGB stars. While the envelope composition depends sensitively on TP, it is insensitive to the speed or geometry of mixing. This indicates that our stream circulation model is generic, so that more sophisticated mixing models with the same TP would yield similar results. On the AGB, our models predict that stars with low ^(18)O/^(16)O can be either S or C stars but must have low ^(12)C/^(13)C (~4) and elevated ^(14)N. Cool bottom processing also destroys ^3He, so that galactic (D + ^3He) decreases with time; this removes the strongest lower limit on the baryon density \u03a9_b from big bang nucleosynthesis models.", "doi": "10.1086/309555", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1995-07-01", "series_number": "1", "volume": "447", "issue": "1", "pages": "L37-L40" }, { "id": "authors:tjmxe-47z55", "collection": "authors", "collection_id": "tjmxe-47z55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-152359384", "type": "article", "title": "Mass transfer of xenon through a steady-state upper mantle", "author": [ { "family_name": "Porcelli", "given_name": "D.", "clpid": "Porcelli-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a model of steady-state transport of Xe through the upper mantle with inputs from an undergassed lower mantle by mass transport without fractionation and subducted atmospheric gases. The model is explored using box model mass transport equations for each isotope of Xe coupled with the transport equations for He. The mantle is assumed to have had initially uniform Pu,I, and U concentrations and is divided into two reservoirs. The lower mantle is assumed to have evolved approximately as a closed-system containing initially trapped Xe along with xenon isotopes produced by ^(129)I, ^(244)Pu, and ^(238)U decay. The concentration and present isotopic composition of lower mantle Xe are unknowns. The upper mantle is considered to have inputs of Xe by mass transfer from the lower mantle at hotspots and from the atmosphere by subduction. In addition, the decay of U within the upper mantle contributes radiogenic Xe as well as ^4He. The flows of Xe into the upper mantle are balanced by flows out of the upper mantle at mid-ocean ridges and hotspots, so that the upper mantle Xe concentration is assumed to be in a steady state. In this model, upper mantle Xe reflects the isotopic characteristics of the lower mantle altered by mixing with subducted atmospheric Xe and the present decay of U in the upper mantle. This is in contrast to previous models in which upper mantle Xe is what remains after degassing of the atmosphere, with a present isotopic composition that reflects the integrated history of continuous losses of Xe and grow-in of radiogenic Xe isotopes within the upper mantle. The observed correlation of ^(129)Xe/^(130)Xe and ^(136)Xe/^(130)Xe ratios for MORB found by other workers is interpreted here as reflecting different degrees of atmospheric contamination to a MORB Xe composition.\nConsideration of the production and transport equations yields the following conclusions: (1) radiogenic ^(136)Xe in the lower mantle is dominantly from spontaneous fission of Pu; (2) radiogenic ^(136)Xe in the upper mantle is composed of radiogenic ^(136)Xe from the lower mantle substantially augmented by spontaneous fission of U in the upper mantle; (3) the concentration of Xe in the lower mantle is < 10^(\u22122) that of carbonaceous chondrites; (4) radiogenic ^(129)Xe is stored in the lower mantle, and the ^(129)Xe excesses seen in the upper mantle are due to mass transfer of Xe from the lower mantle to the upper mantle; (5) the residence time of Xe and He in the upper mantle is \u223c1.4 Ga; (6) a substantial portion of nonradiogenic Xe in the upper mantle may be accounted for by subduction of atmospheric Xe; (7) if a large fraction of the total Xe in the upper mantle is subducted atmospheric Xe, then the lower mantle ^(129)Xe/^(130)Xe and ^(136)Xe/^(130)Xe ratios Xe must be large; and (8) the ratio of radiogenic ^(129)Xe to ^(127)I in the lower mantle is about 10^(\u22122) times that seen in meteorites. This indicates that Xe was lost from the Earth \u223c-10^8 years after solar system formation. This occurred either from the fully formed Earth or from Earth-forming materials that accreted late.\nA consequence of the model is that most of the atmosphere was derived from a Xe reservoir with distinct radiogenic isotope characteristics and which is not presently represented within the Earth. In addition to the radiogenic ^(136)Xe and ^(129)Xe contributed to the atmosphere from the upper mantle, Xe from a gas-rich component with Xe/I ratios higher than carbonaceous chondrites is required. One possible source of this component is gas-rich cometary material. If atmospheric Xe has been subject to severe fractionation of the nonradiogenic isotopes due to atmospheric losses to space, as proposed by others, then lower mantle nonradiogenic xenon isotopes will be fractionated with respect to the atmosphere. The extent to which such fractionation is exhibited by upper mantle Xe depends upon the proportion of subducted Xe to lower mantle Xe present in the upper mantle.", "doi": "10.1016/0016-7037(95)00122-0", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1995-05", "series_number": "10", "volume": "59", "issue": "10", "pages": "1991-2007" }, { "id": "authors:gnss3-dd002", "collection": "authors", "collection_id": "gnss3-dd002", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-143158219", "type": "article", "title": "Molecular equilibria and condensation temperatures in carbon-rich gases", "author": [ { "family_name": "Sharp", "given_name": "C. M.", "clpid": "Sharp-C-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Detailed chemical equilibrium calculations were carried out using a number of different C/O ratios, in order to determine the relative condensation sequence of various phases. For C/O > 1, we calculated the condensation temperatures of graphite, TiC, and SiC, and found that the condensation temperature of graphite is strongly dependent on the C/O ratio, but insensitive to pressure, whereas for TiC and SiC, there is a strong dependence on pressure, but almost no dependence on C/O. In all cases, TiC condenses before SiC. For most regions of P-C/O space when C/O > 1, graphite condenses before TiC and SiC, but for a C/O ratio of about 1.2, TiC condenses before graphite for pressures above approximately 30 dyne/cm^2, and this limiting pressure decreases with decreasing C/O ratio.\nWe found that the main species governing the condensation of graphite, TiC, and SiC were the gas phase species H, H_2, C_2H, C_2H_2, Ti, and Si. By identifying the key equilibria involving these species, a few simple analytic formulae were found that estimate the condensation temperatures, which are generally in good agreement with the detailed calculations, with any differences being easily explained by the neglect of some minor species. These results exhibit the basic dependence of the condensation sequence on C/O, pressure, and temperature for C, TiC, and SiC.\nTo form grains in the winds of an AGB star, the gas density must be high enough for grains to form in a reasonable timescale at or below their condensation temperature. From kinetic considerations and stellar models, we argue that grains are most likely to form in the pressure range 0.2 < P < 40 dyne/cm^2. This requires that for TiC to form before graphite, the C/O range is 1.04 < C/O < 1.2. If graphite begins condensing soon after TiC, then the TiC grain will be embedded in abundant graphite before SiC forms at a temperature \u223c170 K lower. These inferences are consistent with previous observations of the presence of TiC crystals embedded in circumstellar graphite spherules found in a meteorite. It is shown that due to the difference between the condensation temperatures of TiC and of SiC, there is a substantial decrease in the amount of available carbon in the gas phase, so that significant graphite condensation will not occur along with SiC. This would appear to explain the occurrence of SiC grains unassociated with graphite in the presolar grain population found in meteorites.\nThe nitrogen chemistry was investigated and it was found that AIN always condenses at a much lower temperature than SiC. However, Al and N are often found in substantial amounts in association with SiC. We infer that these elements must form a solid solution with SiC at higher temperatures. We note that a small amount of SiC forms below the condensation temperature of AIN, due to the formation of CaS grains allowing some Si locked up in gaseous SiS to be released. This additional low temperature SiC could incorporate some AIN.\nFinally, we briefly investigated the equilibria when C/O \u2264 1. When C/O = 1 or slightly smaller, the results are very sensitive to the data. TiC can form at C/O = 0.98 but at lower temperatures than TiN and TiO. Below C/O = 0.98, no SiC forms. For C/O = 0.9, calculations show that this definitely is in the \"oxygen-rich\" regime when oxides and silicates but no carbides form. As SiO is one of the next most tightly bound oxides in the gas phase after CO, it is shown that the whole high temperature condensation chemistry takes on oxygen-rich aspects, when C/O < 0.96 for the solar Si/O ratio.", "doi": "10.1016/0016-7037(95)00069-C", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1995-04", "series_number": "8", "volume": "59", "issue": "8", "pages": "1633-1652" }, { "id": "authors:2x6se-aag51", "collection": "authors", "collection_id": "2x6se-aag51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-152151364", "type": "article", "title": "Hot bottom burning in asymptotic giant branch stars and its effect on oxygen isotopic abundances", "author": [ { "family_name": "Boothroyd", "given_name": "Arnold I.", "clpid": "Boothroyd-A-I" }, { "family_name": "Sackmann", "given_name": "I.-Juliana", "clpid": "Sackmann-I-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A self-consistent calculation of asymptotic giant branch (AGB) evolution was carried out, including nucleosynthesis\nat the base of the convective envelope (hot bottom burning). Hot bottom burning was found to occur for stars between ~4.5 and ~7 M_\u2609, producing envelopes with ^(18)O/^(16)O \u227e 10^(-6) and 10^(-3) \u227e ^(17)O/^(l6)O \u227e 10^(-1). The ^(17)O abundance depends sensitively on the nuclear ^(17)O-destruction rate; this rate is only loosely constrained by the requirement that first and second dredge-up models match O-isotope observations of red giant branch (RGB) stars (Boothroyd, Sackmann, & Wasserburg 1994). In some cases, high mass-loss rates can terminate hot bottom burning before further ^(17)O enrichment takes place or even before all ^(18)O is destroyed. These predictions are in accord with the very limited stellar observations of J type carbon stars on the AGB and with some of the circumstellar Al_2O_3 grains from meteorites. In contrast, precise data from a number of grains and data from most low-mass Sand C AGB stars (\u227e 1.7 M_\u2609) lie in a region of the ^(18)O/^(l6)O versus ^(17)O/^(16)O diagram that is not accessible by first and second dredge-up or by hot bottom burning. We conclude that for AGB stars, the standard models of stellar evolution are not in accord with\nthese observations. We surmise that an additional mixing mechanism must exist that transports material from the cool bottom of the stellar convective envelope to a depth at which ^(18)O is destroyed. This \"cool bottom processing\" mechanism on the AGB is similar to extra mixing mechanisms proposed to explain the excess ^(13)C (and depleted ^(12)C) observed in the earlier RGB stage of evolution and the large ^7Li depletion observed in low-mass main-sequence stars.", "doi": "10.1086/187806", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1995-03-20", "series_number": "1", "volume": "442", "issue": "1", "pages": "L21-L24" }, { "id": "authors:mwzk7-6dd23", "collection": "authors", "collection_id": "mwzk7-6dd23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130821-091940628", "type": "article", "title": "Leonard Medal Citation for A. G. W. Cameron", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "I am very happy that Al Cameron chose to get the Leonard Medal, the highest award of our society, here in the beautiful city of Prague in this magnificent hall of a most ancient university, serenaded by the lovely young Czech ladies. I hope we will not talk too long so that we may hear them sing again, before fainting from the heat of this unusual summer and from boredom. This occasion is graced by the magnificent Baroque architecture of Prague that is also reminiscent in style of so many of Al Cameron's theories. In inspecting the St. Vitus Cathedral, I note that many symbols have been put up in honor of the Meteoritical Society and its activities-stained glass windows with pictures of comets,\nSaturn, the formation of the Earth and the creation of the universe. This city has been the home of great astronomers. It is in this same modest field that Al Cameron has worked. There are many artistic renditions concerning creation myths and cosmology or cosmogony (as Al prefers).", "doi": "10.1111/j.1945-5100.1995.tb01109.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1995-03", "series_number": "2", "volume": "30", "issue": "2", "pages": "131-132" }, { "id": "authors:z8m7h-3n194", "collection": "authors", "collection_id": "z8m7h-3n194", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-145624491", "type": "article", "title": "Injection of freshly synthesized ^(41)Ca in the early solar nebula by an asymptotic giant branch star", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Gallino", "given_name": "R.", "clpid": "Gallino-R" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Goswami", "given_name": "J. N.", "clpid": "Goswami-J-N" }, { "family_name": "Raiteri", "given_name": "C. M.", "clpid": "Raiteri-C-M" } ], "abstract": "We show that ejecta from the envelope of one asymptotic giant branch star of M ~ 3 M_\u2609 may account for many of the short-lived nuclei in the early solar system and also for the recent evidence of the presence of ^(41)Ca (t_(41) = 1.50 x 10^5 yr) in early solar nebular condensates. This would require that the injection into the protosolar molecular cloud took place within a narrow time interval of (5-7) x 10^5 yr before the formation of the solar system. If true, this places extremely tight constraints on the whole process of injection mixing and collapse. The timescales for both ^(41)Ca and ^(26)AI require that the placental medium be a dense molecular cloud (2 x 10^3-8 x 10^3 H cm^(-3)). If the observed residual ^(41)Ca is instead produced by a proton bombardment mechanism within the early solar system, similar to what appears necessary to explain ^(53)Mn, then the time interval is relaxed but would still be (1-2) x 10^6 yr from consideration of ^(26)Al.", "doi": "10.1086/187771", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1995-02-20", "series_number": "2", "volume": "440", "issue": "2", "pages": "L101-L104" }, { "id": "authors:p07yt-rez91", "collection": "authors", "collection_id": "p07yt-rez91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131031-151404860", "type": "article", "title": "^(238)U-^(234)U and ^(232)Th-^(230)Th in the Baltic Sea and in river water", "author": [ { "family_name": "Anderson", "given_name": "Per S.", "clpid": "Anderson-P-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Ingri", "given_name": "Johan", "clpid": "Ingri-J" } ], "abstract": "The concentration (C) of dissolved ^(238)U,^(234)U,^(232)Th and230Th in fresh and brackish waters from the Baltic Sea were determined using TIMS. The brackish waters range in salinity from that of sea water (SW) to 2.5\u2030. C_(238U) in oxygen-saturated, surface waters is well correlated with salinity and shows quasi-conservative behavior, as does Sr. Samples from the redox water interface show depletion in C_(238U), demonstrating that dissolved U is being removed by FeMn oxyhydroxides. From a simple mixing relationship for the brackish water,\u03b4^(234)U^* = 1000\u2030 was calculated for the fresh water source in the northern Baltic. A study of the Kalix\u00e4lven River over an annual cycle yields high \u03b4^(234)U during spring and summer discharge and lower values during fall and winter, showing that different sources contribute to the U load in the river during different seasons. C_(232Th) and C_(230Th) in river water are governed by the discharge, reflecting the importance of the increased abundance of small particles ( < 0.45 \u03bcm) for the ^(232)Th-^(230)Th load at high discharge. ^(232)Th/^(238)U in river water is about 40 times less than in detrital material. In the brackish water, C_(232Th) drops 2 orders of magnitude in the low salinity region ( < 5\u2030), reaching a value close to that of sea water at a salinity of 7.5\u2030. Almost all of the riverine ^(232)Th must be deposited in the low-salinity regions of the estuary.\nThe ^(230)Th/^(232)Th in river waters is about twice the equilibrium value for ^(232)Th/^(238)U (3.8). In the brackish waters, ^(230)Th/^(232)Th is greater by a factor of 10\u2013100 than both river water and SW. The big increase in ^(230)Th/^(232)Th in the Baltic Sea waters over the riverine input indicates that the Th isotopes enter the estuary as a mixture of two carrier phases. We infer that about 96% of ^(232)Th in river water is carried by detrital particles, whereas the other phase (solution, colloidal) has a much higher ^(232)Th/^(232)Th. Entering the estuary, the detrital particles sediment out rapidly, whereas the non-detrital phase is removed more slowly, causing a marked increase in ^(230)Th/^(232)Th in the brackish water. In SW, ^(230)Th/^(232)Th is closer to river input and detrital material than in brackish water. We conclude that in the deep sea, ^(232)Th is almost exclusively dominated by windblown dust and can be used to monitor dust flux. The ^(230)Th excess in Baltic rivers is produced in U-rich, ^(232)Th-poor peatlands and trapped in authigenic particles and transported with the particles. Time scales for producing the ^(230)Th excess are \u223c 2000\u20138000 yr. This is younger than, but comparable to, the time of the latest deglaciation, which ended some 9000 yr ago when the mires were forming. These results have implications for the possible mobility of actinides stored in repositories.", "doi": "10.1016/0012-821X(94)00262-W", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1995-02", "series_number": "1-4", "volume": "130", "issue": "1-4", "pages": "217-234" }, { "id": "authors:s6k67-9cq71", "collection": "authors", "collection_id": "s6k67-9cq71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-111818036", "type": "article", "title": "Trace-element partition coefficients for perovskite and hibonite in meteorite compositions", "author": [ { "family_name": "Kennedy", "given_name": "A. K.", "clpid": "Kennedy-Allen-K" }, { "family_name": "Lofgren", "given_name": "G. E.", "clpid": "Lofgren-G-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The concentrations of 28 elements were measured using an ion microprobe in perovskite, hibonite and coexisting melts, in isothermal crystallization experiments on chemical compositions similar to those of Compact Type A (CTA) Ca-, Al-rich inclusions (CAI) and to a hibonite-glass microspherule. The mineral/melt partition coefficients (D) calculated from the measured concentrations for both minerals define reliable D-values. Perovskite and hibonite D's have ranges of 10^\u22122 for Si to 20 for Th and 3\u00b710^\u22123 for Si to \u223c8 for La, respectively. There are regular relationships between the ionic radius, the valence of the trace element and the partition coefficients in perovskite and hibonite. While there are differences in the D-values between perovskite and hibonite, they follow very similar trends with perovskite typically having D-values that are 5\u201310 times higher for the same element. Perovskite and hibonite D's are almost identical for the divalent cations Ba (0.02 and 0.03, respectively) and Sr (1.1 and 0.8, respectively) in our experiments. D_Mg for perovskite is low, 0.03, when compared with the value for hibonite, 0.5. Mineral/melt D's for the REE decrease continuously from D_La = 6 to D_Lu = 0.03 in hibonite. For perovskite, REE D's increase slightly from D_La = 10 to D_Nd = 15 and then decrease continuously to D_Lu = 1.0 and D's for trivalent cations with smaller ionic radii than the REE are lower, with D_Al = 0.08 and D_Sc = 0.15 lower than D_Cr = 0.8 and D_V = 1.0. With the exception of D_Th and D_Si in perovskite and DSi in hibonite, the D-values for tetravalent cations and Nb, the only pentavalent element, fall within the range of D's for the REE. D_th/D_U equals 3 in perovskite and \u223c 15 in hibonite.\nOur data can be applied to the genesis and evolution of hibonite in refractory meteorite inclusions. For example, low Ba relative to other refractory elements, such as Hf, Zr, La, etc., in hibonite has been observed in some hibonite-bearing inclusions. Since D_Ba \u2aa1 D_Hf, \u2aa1 D_Zr and \u2aa1 D_La in our experiments low Ba may result from the incompatibility of Ba in hibonite rather than the increased volatility of Ba under oxidizing conditions during condensation. In addition, since D_La/D_Lu > 50 for hibonite. LREE/HREE ratios of 1 in hibonite in some CTA CAI from Leoville and Allende are inconsistent with hibonite equilibrating with the melts that formed these inclusions and the hibonite is relict. Similar applications are possible with our perovskite partitioning data. For example, it is likely that high-REE (500\u22121000 \u00d7 chondritic) perovskite with Th/U of 3\u20134 that are found in the outer region of Type B 1 CAI have not been in equilibrium with the CAI melt that contains \u223c 20 \u00d7 ch REE and a Th/U ratio of 3 and they are probably relics that survived the most recent partial melting event.", "doi": "10.1016/0009-2541(94)90139-2", "issn": "0009-2541", "publisher": "Elsevier", "publication": "Chemical Geology", "publication_date": "1994-11", "series_number": "1-4", "volume": "117", "issue": "1-4", "pages": "379-390" }, { "id": "authors:8f8dk-sw836", "collection": "authors", "collection_id": "8f8dk-sw836", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-111855812", "type": "article", "title": "Sm-Nd chronology and petrogenesis of mesosiderites", "author": [ { "family_name": "Stewart", "given_name": "Brian W.", "clpid": "Stewart-B-W" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have obtained Sm-Nd data from four mesosiderite silicate clasts, including three clasts with a variety of textures from the Vaca Muerta type 1A mesosiderite and one gabbroic clast from the Mt. Padbury mesosiderite. The gabbroic Vaca Muerta Pebble 12 and basaltic Pebble 16 yield identical ^(147)Sm- ^(143)Nd ages of 4.48 \u00b1 0.19 AE and 4.48 \u00b1 0.09 AE, respectively, while the highly recrystallized Pebble 5 gives an age of 4.42 \u00b1 0.02 AE; Mt. Padbury yields an age of 4.52 \u00b1 0.04 AE. All clasts show a correlation of ^(142)Nd /^(144)Nd with ^(147)Sm /^(144)Nd , and provide unequivocal evidence for the presence of live ^(146)Sm at the time of their formation. Calculated initial ^(146)Sm /^(144)Sm values range from 0.004 (Pebble 5) to 0.006 (Pebbles 12, 16, and Mt. Padbury) and are generally consistent with the ^(147)Sm- ^(143)Nd ages. However, discordance of whole-rock leach and residue data and some disagreement between ^(146)Sm- ^(142)Nd relative ages and ^(147)Sm- ^(143)Nd absolute ages indicate small but significant disturbances to the Sm-Nd systematics. The ranges of ages and initial ^(146)Sm /^(144)Sm and ^(143)Nd /^(144)Nd values suggest that each of these silicate clasts underwent a separate, protracted evolution on its parent body prior to mixing with metal. Textural and trace element criteria indicate that individual clasts from the same mesosiderite often had very different igneous sources and thermal histories prior to their incorporation in the meteorite. Pebble 12 is extremely LREE depleted, probably a result of several melt extraction events, whereas Pebbles 5 and 16 and Mt. Padbury have nearly chondritic Sm/Nd with bulk REE concentrations higher than chondrites by factors of 5 to 15. In general, the Sm-Nd systematics of mesosiderite silicates require formation of the silicates on a parent planet which underwent relatively early and extreme differentiation. Preservation of diverse, old ages and the presence of ^(146)Sm imply that metal-silicate mixing did not seriously alter the Sm-Nd isotopic memories of these clasts. We present a model for metal-silicate mixing which combines the cooling history with isotopic reequilibration for the case of thermal blanketing. We show that the total amount of isotopic reequilibration in a sample can be related to the initial temperature, depth of burial, grain size, and diffusion parameters. Application of this model to the silicate clasts measured in this study indicates that if the metal and silicate were thermally equilibrated above the metal solidus temperature during mixing, then the clasts must have been buried no deeper than 1-10 m in regolith during the initial high-temperature cooling phase in order to prevent the Sm-Nd systems from being extensively reset. In order to reconcile these results with the slow cooling rates at lower temperatures determined from studies of exsolution in the metal phase, we infer that heat was transferred rapidly from hot metal to cold silicate material during initial metal-silicate mixing, and that the deeply buried portions of the mixture then cooled slowly after reaching thermal equilibrium at ~600-700\u00b0C. The data from this study point to the following history for the mesosiderite parent body: (1) differentiation of a silicate parent body within the first ~50 m.y. of solar system history to form diverse parent magmas;\n\n(2) emplacement of primitive and differentiated mafic magmas near the planetary surface, and extensive differentiation in the near surface environment;\n\n(3) formation and reworking of regolith breccias through impact gardening at the near surface of the body;\n\n(4) mixing of molten Fe-Ni metal with the regolith followed by rapid cooling 100-150 m.y. after the origin of the solar system;\n\n(5) slow cooling from temperatures of ~700\u00b0C to produce the observed nickel diffusion profiles in the iron phase;\n\n(6) mild impact metamorphism and brecciation to obtain the much younger K-Ar ages; and\n\n(7) recent collisions or perturbations sending mesosiderite fragments into Earth-crossing trajectories.", "doi": "10.1016/0016-7037(94)90100-7", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1994-08", "series_number": "16", "volume": "58", "issue": "16", "pages": "3487-3509" }, { "id": "authors:x07sp-v8476", "collection": "authors", "collection_id": "x07sp-v8476", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-112004671", "type": "article", "title": "Oxygen isotopes in circumstellar Al_2O_3 grains from meteorites and stellar nucleosynthesis", "author": [ { "family_name": "Huss", "given_name": "Gary R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Fahey", "given_name": "Albert J.", "clpid": "Fahey-A-J" }, { "family_name": "Gallino", "given_name": "Roberto", "clpid": "Gallino-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have found a ~3 \u00b5m Al_2O_3 grain (B39) in the Bishunpur LL3.1 chondrite that is enriched in ^(17)O by a factor of ~ 6.8 (^(16)O/^(17)O = 385 \u00b1 9) and depleted in 180 by almost 60% (^(16)O/^(18)O = 853 \u00b1 30) relative to solar system oxygen and has an initial ^(26)Al/^(27)Al = 1.7 \u00b1 0.2 x 10^3, ~34 times greater than the initial solar system value. The isotopic compositions of B39 and two other Al_2O_3 grains previously reported from the Orgueil and Murchison meteorites show that these grains formed directly from the ejecta of low-mass AGB stars with C/0 < 1. A simple theoretical analysis is presented showing that the oxygen systematics of the grains are a natural consequence of main-sequence evolution followed by first dredge-up. ^(26)AI is the result of third dredge-up. Circumstellar Al_2O_3 grains provide very precise isotopic data for stellar ejecta that complement spectroscopic observations of oxygen-rich stars. Isotopic differences indicate that the Al_2O_3 grains come from separate stars of different mass and initial oxygen composition that originated in molecular clouds different from the one in which the solar system formed.", "doi": "10.1086/187443", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1994-07-20", "series_number": "1", "volume": "430", "issue": "1", "pages": "L81-L84" }, { "id": "authors:q6efv-g9t38", "collection": "authors", "collection_id": "q6efv-g9t38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-104320418", "type": "article", "title": "Predictions of oxygen isotope ratios in stars and of oxygen-rich interstellar grains in meteorites", "author": [ { "family_name": "Boothroyd", "given_name": "Arnold I.", "clpid": "Boothroyd-A-I" }, { "family_name": "Sackmann", "given_name": "I.-Juliana", "clpid": "Sackmann-I-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We carried out detailed, self-consistent calculations for stars from 1 to 9 M_\u2609 over a wide range of metallicities,\nfollowing the evolution and nucleosynthesis from the pre-main sequence to the asymptotic giant branch (AGB), in order to provide a self-consistent grid for evaluating stellar oxygen isotopic variations. These were calculated for first and second dredge-up, and for some masses also for third dredge-up and \"hot bottom\" convective envelope burning on the AGB. We demonstrate that ^(16)O/^(17)O in red giant envelopes is primarily a function of the star's mass, while ^(16)O/^(18)O is primarily a function of the initial composition. Uncertainties in the ^(17)O-destruction rate have no effect on the ^(16)O/^(17)O ratio for stars from 1 to 2.5 M_\u2609, but do affect the ratios for higher masses: the stellar ^(16)O/^(17)O observations are consistent with the Landr\u00e9 et al. (1990) rates using \u0192 = 0.2 for ^(17)O(p, y)^(18)F and ^(17)O(p, \u0251)^(14)N, and with the Caughlan & Fowler (1988) rates using \u0192 ~ 1. The stellar ^(16)O/^(18)O observations require \u0192 ~ 0 in the Caughlan & Fowler ^(18)O(p, \u0251)^(15)N rate. First dredge-up has the largest effect on the oxygen isotope ratios, decreasing ^(16)O/^(17)O significantly from the initial value and increasing ^(16)O/^(18)O slightly. Second and third dredge-up have only minor effects for solar metallicity stars. The absence of very low observed ^(16)O/^(18)O ratios is consistent with a major increase in the ^(18)O(\u0251, y)^(22)Ne rate over the Caughlan & Fowler (1988) value. Hot bottom burning in stars above about 5 M_\u2609 can cause a huge increase in ^(16)O/^(18)O (to \u227310^6), and possibly a significant decrease in ^(16)O/^(17)O; these are\naccompanied by a huge increase in ^7Li and a value of ^(12)C/^(13)C \u2248 3. The oxygen isotope ratios in the Al_2O_3 grains (Orgueil grain B, the Murchison 83-5 grain, and the new Bishunpur B39 grain) can be accounted for if they originated in stars that did NOT have the same initial\n^(16)O/^(18)O ratio. Thus one cannot assume uniform isotope ratios, even for stars of nearly solar composition. The\ngrains' ^(16)O/^(17)O ratios, together with the ^(26)Mg excesses that indicate grain formation in a ^(26)Al-rich environment, indicate that the Orgueil grain B and Murchison 83-5 grain originated in stars of roughly 1.5 M_\u2609, during third dredge-up on the AGB. The new Bishunpur B39 grain originated in a star of either 2 or of 4-7\nM_\u2609.", "doi": "10.1086/187442", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1994-07-20", "series_number": "1", "volume": "430", "issue": "1", "pages": "L77-L80" }, { "id": "authors:3zjg1-mxb63", "collection": "authors", "collection_id": "3zjg1-mxb63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-144620129", "type": "article", "title": "Problems with Re-Os isochron determinations", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Ngo", "given_name": "H. H.", "clpid": "Ngo-Henry-H-Meteoritics" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have developed closed-system techniques for the equilibration of Os isotopes and for the calibration of Re and Os tracers using high-purity metals [1]. The results show reproducibility of \u00b10.5% for calibrations for Os using different chunks of the same high-purity Os metal produced by vacuum arc melting.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1994-07", "series_number": "4", "volume": "29", "issue": "4", "pages": "515-516" }, { "id": "authors:pftf5-1md90", "collection": "authors", "collection_id": "pftf5-1md90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-115123482", "type": "article", "title": "Mg and Ti isotopes in presolar Al_2O_3", "author": [ { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Fahey", "given_name": "A. J.", "clpid": "Fahey-A-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Previously, we reported O isotopic compositions and initial ^(26)Al/^(27) Al ratios for two presolar Al_2O_3 grains, Orgueil B and Bishunpur B39 [1-3]. In Orgueil B, ^(17)O/^(16)O is about twice the solar value but ^(18)O/^(16)O is normal. In B39, ^(17)O/^(16)O is ~7x higher than solar and ^(18)O/^(16)O is 0.6x the solar value.\nSpectroscopic observations of red giant stars show similar O compositions [4], which result when material that has experienced partial H burning is mixed into the stellar envelope by the first dredge-up [3,5]. The ^(17)O/^(16)O\nratios indicate that Orgueil B originated around a star of ~1.5 M_\u2609, while B39 formed around either a ~2 Me or 4-7 M_\u2609 [3,5]. Both grains formed with ^(26)Al/^(27)Al ratios of ~10^(-3). Aluminum-26 is produced in the H shell after\ncore H burning has ceased and first dredge-up has occurred. It is spread through the envelope by the third dredge-up, which occurs in low- and intermediate-mass stars as a series of mixing events driven by thermal pulses in the He shell. In intermediate-mass stars (3-8 M_\u2609), ^(26)Al can also be brought to the surface by the second dredge-up, which occurs at the end of core He burning.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1994-07", "series_number": "4", "volume": "29", "issue": "4", "pages": "475-476" }, { "id": "authors:jm9ex-16k61", "collection": "authors", "collection_id": "jm9ex-16k61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-103617862", "type": "article", "title": "An Ion Microprobe Study of CAIs from CO3 Meteorites", "author": [ { "family_name": "Russell", "given_name": "S. S.", "clpid": "Russell-S-S" }, { "family_name": "Greenwood", "given_name": "R. C.", "clpid": "Greenwood-R-C" }, { "family_name": "Fahey", "given_name": "A. J.", "clpid": "Fahey-F-A" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "When attempting to interpret the history of Ca, Al-rich inclusions (CAIs) it is often difficult to distinguish between primary features inherited from the nebula and those produced during secondary processing on the parent body. We have undertaken a systematic study of CAIs from 10 CO chondrites, believed to represent a metamorphic sequence [e.g., 1], with the goal of distinguishing primary and secondary features. ALHA 77307 (3.0), Colony (3.0), Kainsaz (3.1), Felix (3.2), ALH 82101 (3.3), Omans (3.3), Lanc\u00e9 (3.4), ALHA 77003 (3.5), Warrenton (3.6), and Isna (3. 7) were examined by SEM and optical microscopy. We have identified 141 CAIs within these samples, and studied in detail the petrology of 34 inclusions.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1994-07", "series_number": "4", "volume": "29", "issue": "4", "pages": "525-526" }, { "id": "authors:ky7hb-dvc44", "collection": "authors", "collection_id": "ky7hb-dvc44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131031-143029161", "type": "article", "title": "Strontium, dissolved and particulate loads in fresh and brackish waters: the Baltic Sea and Mississippi Delta", "author": [ { "family_name": "Anderson", "given_name": "S.", "clpid": "Anderson-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Ingri", "given_name": "Johan", "clpid": "Ingri-J" }, { "family_name": "Stordal", "given_name": "Mary C.", "clpid": "Stordal-M-C" } ], "abstract": "A study was conducted of the isotopic composition and concentration of Sr and of major elements in dissolved and suspended loads of fresh and brackish waters. The purpose was to establish the contributions of different parent rocks and minerals to Sr during weathering and transport and to identify the role of Fe\u2014Mn oxyhydroxides in the redistribution of Sr in the water column during the sedimentary cycle. Studies were conducted on a profile across an oxic-anoxic boundary in the Baltic and on rivers covering behavior over an annual cycle. In general, the 87Sr/86Sr ratios differ between particulate and dissolved loads, with more radiogenic Sr in the particulate loads. These differences are attributed to differential weathering of minerals, where high Rb/Sr minerals dominate the particulate load and low Rb/Sr the dissolved load. There is broad correlation of ^(87)Sr/^(86)Sr with K/Al in the suspended load. The differences in ^(87)Sr/^(86)Sr between suspended and dissolved load are highly variable and are related to the Fe or Mn concentration on the particulates. In samples with high Fe/Al, the difference becomes small. A good correlation was found between Sr/Al and Fe/Al or Mn/Al in the particulates both in brackish and fresh waters. Sr is removed from solution both in rivers and in the Baltic Sea whenever there is formation of Fe\u2014Mn oxyhydroxide particulates. This precipitation greatly diminishes the difference in isotopic composition of the dissolved and suspended loads. As the particles containing Fe\u2014Mn oxyhydroxides settle, they dissolve in anoxic zones and release Sr. This provides a mechanism for Sr redistribution in the water column. Sr is thus only quasi-conservative in environments where Fe\u2014Mn oxyhydroxides form or dissolve. From consideration of the isotopic differences in Sr between dissolved and suspended loads, it follows that the net Sr input depends upon weathering characteristics of the contributing mineral phases. Changes in weathering mechanisms due to climate change may cause Sr isotopic shifts in the marine environment.", "doi": "10.1016/0012-821X(94)00062-X", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1994-06", "series_number": "1-4", "volume": "124", "issue": "1-4", "pages": "195-210" }, { "id": "authors:hhx1t-ger20", "collection": "authors", "collection_id": "hhx1t-ger20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131216-071301846", "type": "article", "title": "Extreme ^(26)Mg and ^(17)O enrichments in an Orgueil corundum: Identification of a presolar oxide grain", "author": [ { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "family_name": "Fahey", "given_name": "A. J.", "clpid": "Fahey-F-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A corundum (Al_2O_3) grain from the Orgueil meteorite is greatly enriched in ^(17)O and ^(26)Mg^*. The measured\n^(16)O/^(17)O is 1028 \u00b1 11 compared to ^(16)O/^(17)O)_\u2609 = 2610. This is the largest ^(17)O excess so far observed in any meteoritic material. The ^(26)Mg excess (^(26)Mg^*) is most plausibly due to in situ decay of ^(26)Al. The inferred\n^(26)Al/^(27)Al)_0 ratio of 8.9 x 10^(-4) is ~ 18 times larger than the 5 x 10^(-5) value commonly observed in refractory inclusions formed m the solar system. The large ^(17)O excess and high ^(26)Mg^*/^(27)Al ratio unambiguously identify this corundum as a presolar oxide grain. Enrichments in ^(17)O and ^(26)Al are characteristic of H-burning and point to red giant or AGB stars as likely sources.", "doi": "10.1086/187319", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1994-04-20", "series_number": "2", "volume": "425", "issue": "2", "pages": "L97-L100" }, { "id": "authors:0b0s1-q6810", "collection": "authors", "collection_id": "0b0s1-q6810", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-132810597", "type": "article", "title": "Asymptotic Giant Branch stars as a source of short-lived radioactive nuclei in the solar nebula", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Busso", "given_name": "M.", "clpid": "Busso-M" }, { "family_name": "Gallino", "given_name": "R.", "clpid": "Gallino-R" }, { "family_name": "Raiteri", "given_name": "C. M.", "clpid": "Raiteri-C-M" } ], "abstract": "We carried out a theoretical evaluation of the contribution of Asymptotic Giant Branch (AGB) stars to some short-lived (10^6 \u2264 \u03c4 \u2264 2 x 10^7 yr) isotopes in the ISM and in the early solar system using stellar model calculations for thermally pulsing evolutionary phases of low-mass stars. The yields of s-process nuclei in the convective He-shell for different neutron exposures \u03c4_0 were obtained, and AGB stars were shown to produce several radioactive nuclei (especially ^(107)Pd, ^(205)Pb, ^(60)Fe, ^(93)Zr, ^(99)Tc, ^(135)Cs, and ^(182)Hf) in different amounts. Assuming either contamination of the solar nebula from a single AGB star or models for continuous injection and mixing from many stars into the ISM, we calculate the ratios of radioactive to stable nuclei at the epoch of the Sun's formation. The dilution factor between the AGB ejecta and the early solar system matter is obtained by matching the observed ^(107)Pd/^(108)Pd and depends on the value of \u03c4_0. It is found that small masses M_(He). of He-shell material (10^(-4)-10^(-7) M_\u2609) enriched ins-process nuclei are sufficient to contaminate 1 M_\u2609 of the ISM to produce the ^(107)Pd found in the early solar system. Predictions are made for all of the other radioactive isotopes. The optimal model to explain several observed radioactive species at different states of the proto-solar nebula involves a single AGB star with a low neutron exposure (\u03c4_0 = 0.03 mbarn^(-1)) which contaminated the cloud with a dilution factor of M_(He)/M_\u2609 ~ 1.5 x 10^(-4). This will also contribute newly synthesized stable s-process nuclei in the amount of ~ 10^(-4) of their abundances already present in the protosolar cloud. Variations in the degree of homogenization (~ 30%) of the injected material may account for some of the small general isotopic anomalies found in meteorites. It is also found that ^(60)Fe is produced in\nsmall but significant quantities that may be sufficient to explain the observations if the time elapsed (\u0394) from\nthe contamination of the ISM to the formation of protoplanetary bodies is not higher than \u0394 = 5 x 10^6 yr. If\n\u0394 is longer, up to 10 x 10^6 yr, this would require the single AGB star to experience enhanced neutron densities\n(n_n ~ 3 x 10^9n cm^(-3)) in the s-processing zone in order to compensate for the branching at ^(59)Fe. The\nalternative model of long-term continuous ejection of matter from many AGB stars does not appear to match the observations. We also estimate the ^(26)Al production from the H-shell and find that the ^(26)Al abundance in the early solar system may be readily explained in a self-consistent manner. Moreover, ^(26)Al from AGB stars\nmay contribute substantially to the galactic ^(26)Al y-source, while no significant y-flux from ^(60)Co (deriving from ^(60)Fe decay) is to be expected.", "doi": "10.1086/173899", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1994-03-20", "series_number": "1", "volume": "424", "issue": "1", "pages": "412-428" }, { "id": "authors:25pdj-52a89", "collection": "authors", "collection_id": "25pdj-52a89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131030-082552961", "type": "article", "title": "Holocene growth history of a reef complex on a cool-water carbonate margin: Easter Group of the Houtman Abrolhos, Eastern Indian Ocean", "author": [ { "family_name": "Collins", "given_name": "L. B.", "clpid": "Collins-L-B" }, { "family_name": "Zhu", "given_name": "Z. R.", "clpid": "Zhu-Z-R" }, { "family_name": "Wyrwoll", "given_name": "K.-H.", "clpid": "Wyrwoll-K-H" }, { "family_name": "Hatcher", "given_name": "B. G.", "clpid": "Hatcher-B-G" }, { "family_name": "Playford", "given_name": "P. E.", "clpid": "Playford-P-E" }, { "family_name": "Eisenhauer", "given_name": "A.", "clpid": "Eisenhauer-A" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Bonani", "given_name": "G.", "clpid": "Bonani-G" } ], "abstract": "The Houtman Abrolhos reefs, situated on the western continental margin of Australia, occupy a transitional position between cool-water shelf carbonate sediments to the south and more tropical environments to the north. Their existence at the outer limits of the geographical range for coral reef growth is a result of the warm, poleward-flowing Leeuwin Current. Though the modern reefs differ ecologically from tropical reefs, their geological characteristics have been little known until recently. Each of the three island groups in the Abrolhos consists of a central platform of Last Interglacial reefs, about which windward and leeward Holocene reefs have developed asymmetrically. In the Easter Group the subtidal windward reef in the west is ca. 10 m thick and is backed by a leeward-prograding, lagoon sand sheet which is 0\u20133 m thick. The emergent parts of the leeward reefs in the east consist of an upward-shallowing sequence comprising reef facies, peritidal rudstone facies, and coral rubble storm ridges. This is underlain by over 26 m of Holocene reef facies. Coring and dating of the Holocene reefs (using both U/Th TIMS and ^(14)C methods) in the Easter Group has shown significantly different lithofacies in the windward and leeward reefs, and has allowed reconstruction of Holocene reef growth and sea-level history. Coralline algal bindstones and interbedded coral framestone facies characterise the relatively slow-growing windward Holocene reefs, whereas the fast-growing leeward reefs consist of coral framestone facies which are dominated by Acropora. The leeward reefs commenced growth about 10,000 U/Th years ago and the Morley reef grew to 0.3 m above present sea level by 6400 U/Th years B.P., recording a relative high sea-level event. This generated Holocene constructional topography characterised by \"blue-hole\" terrain. Windward Holocene reef growth commenced after 8200 U/Th years B.P. following erosion of the windward part of the Last Interglacial platform. High wave energy and competition with macroalgae limited coral growth, and the coralline algal-dominated windward reefs grew more slowly to sea level. The Holocene sea-level record provided by dates from the 26 m core of the Morley reef (a \"keep-up\" reef) is the first such record from the western continental margin of Australia.", "doi": "10.1016/0025-3227(93)90073-5", "issn": "0025-3227", "publisher": "Elsevier", "publication": "Marine Geology", "publication_date": "1993-11", "series_number": "1-2", "volume": "115", "issue": "1-2", "pages": "29-46" }, { "id": "authors:k943h-rhd13", "collection": "authors", "collection_id": "k943h-rhd13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131216-144743114", "type": "article", "title": "Thorium-Uranium Fractionation by Garnet: Evidence for a Deep Source and Rapid Rise of Oceanic Basalts", "author": [ { "family_name": "LaTourrette", "given_name": "T. Z.", "clpid": "LaTourrette-T-Z" }, { "family_name": "Kennedy", "given_name": "A. K.", "clpid": "Kennedy-Allen-K" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Mid-ocean ridge basalts (MORBs) and ocean island basalts (QIBs) are derived by partial melting of the upper mantle and are marked by systematic excesses of thorium-230 activity relative to the activity of its parent, uranium-238. Experimental measurements of the distribution of thorium and uranium between the melt and solid residue show that, of the major phases in the upper mantle, only garnet will retain uranium over thorium. This sense of fractionation, which is opposite to that caused by clinopyroxene-melt partitioning, is consistent with the thorium-230 excesses observed in young oceanic basalts. Thus, both MORBs and QIBs must begin partial melting in the garnet stability field or below about 70 kilometers. A calculation shows that the thorium-230\u2014uranium-238 disequilibrium in MORBs can be attributed to dynamic partial melting beginning at 80 kilometers with a melt porosity of 0.2 percent or more. This result requires that melting beneath ridges occurs in a wide region and that the magma rises to the surface at a velocity of at least 0.9 meter per year.", "doi": "10.1126/science.261.5122.739", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1993-08-06", "series_number": "5122", "volume": "261", "issue": "5122", "pages": "739-742" }, { "id": "authors:bgzmm-yxg45", "collection": "authors", "collection_id": "bgzmm-yxg45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131101-082950155", "type": "article", "title": "High-precision U-series dating of Last Interglacial events by mass spectrometry: Houtman Abrolhos Islands, western Australia", "author": [ { "family_name": "Zhu", "given_name": "Z. R.", "clpid": "Zhu-Z-R" }, { "family_name": "Wyrwoll", "given_name": "K.-H.", "clpid": "Wyrwoll-K-H" }, { "family_name": "Collins", "given_name": "L. B.", "clpid": "Collins-L-B" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Eisenhauer", "given_name": "A.", "clpid": "Eisenhauer-A" } ], "abstract": "The Houtman Abrolhos Islands, situated at the western passive margin of the Australian continent, consist of a series of shelf-edge coral reefs. The central platforms of the reefs are Late Pleistocene in age and are generally some 3\u20135 m above present sea level. The uppermost part of the Last Interglacial reefs normally has an upward-shallowing sequence, consisting of coral framestone, coralline algal bindstone and skeletal grainstone to rudstone. This sequence represents deposition in water depths of less than 2 m, and provides a good indicator of sea level.\n\nHigh-precision mass-spectrometric dates of corals from the Abrolhos reefs, including dates obtained from drill cores, arological, isotopic and stratigraphic criteria are established for the selection of suitable samples for dating and for assessing the reliability of dates. Using the screened dates and the stratigraphic evidence, the timing and character of the sea level variations of the Last Interglacial in the Abrolhos region are examined. The data show that sea level of the Last Interglacial in the Abrolhos was 4 m below its present height by ca. 134 ka BP and probably reached about 2 m above present height at ca. 133 ka BP. The exact time at which sea level reached its peak (6 m above present sea level) cannot be determined from our data. But it is clear that the sea level high stand of the Last Interglacial lasted until ca. 116 ka BP and that for much of the Last Interglacial sea level at the Abrolhos was at a height of about 4 m above its present level.", "doi": "10.1016/0012-821X(93)90173-7", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1993-07", "series_number": "1-4", "volume": "118", "issue": "1-4", "pages": "281-293" }, { "id": "authors:yh9tp-hyd35", "collection": "authors", "collection_id": "yh9tp-hyd35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131031-135703760", "type": "article", "title": "TIMS U-series dating and stable isotopes of the last interglacial event in Papua New Guinea", "author": [ { "family_name": "Stein", "given_name": "M.", "clpid": "Stein-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Aharon", "given_name": "P.", "clpid": "Aharon-P" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Zhu", "given_name": "Z. R.", "clpid": "Zhu-Z-R" }, { "family_name": "Bloom", "given_name": "A.", "clpid": "Bloom-A" }, { "family_name": "Chappell", "given_name": "J.", "clpid": "Chappell-J" } ], "abstract": "The extensive flight of uplifted reef terraces which occurs along the Vitiaz strait on the northern flank of the Huon Peninsula in PNG (Papua New Guinea) contains a particularly good record of sea level changes in the last 250 ky. The Huon terraces were the target of an international expedition which took place in July\u2013August 1988. In particular, we searched for suitable samples for U-series dating in a reef complex designated as VII, which is correlated with the last interglacial episode and high sea level stand. This complex is composed of a barrier reef (VIIb), a lagoon, and a fringing reef (VIIa). Twelve corals from these terraces and two corals from the older reef complex VIII were selected for analysis. The petrography, oxygen and carbon isotope compositions, and magnesium and strontium concentrations were determined along with the concentrations and isotopic compositions of uranium and thorium. ^(230)Th-^(234)U ages of the corals with > 99% aragonite, having primary textures, and which show U/Sr ratios around 0.4 \u00d7 10^(\u22123) and initial \u03b4^(234)U values close to that of present seawater, appear to be reliable. The \"most reliable\" ages from complex VII corals fall in two tight groups centered at 118 ky and 134 ky. Corals with \u03b4^(234)U(T) values higher than 160 and U/SR ratios substantially lower than seawater are assumed to have undergone diagenetic alteration, which appears to be common in this area. The simplest model for sea level height for terrace VII is a continuous rise between 134 and 118 ky. Alternatively, there may have been two periods of rapid sea level rise. In contrast, in the Bahamas, there is evidence that sea level remained rather constant over the time interval 132 to 120 ky. The absence of ages between 132 and 120 ky in PNG could be the result of changes in the local tectonic uplift rates during that time, or erosion that disrupted the continuous record. In any event, we find no basis for accepting a single brief time for the age of the last interglacial and applying this age as a precise chronometer for worldwide correlation, or as a test of climatic models. The older ages reported here precede the Milankovitch solar insolation peak at 128 ky, and the younger ages are ~ 10 ky after this peak. If the present high-precision data are correct, then it will be necessary to reassess the validity of the Milankovitch theory of climatic changes. The fundamental issue which must now be resolved is a means of identifying coral samples that have not been disturbed by diagenetic processes.", "doi": "10.1016/0016-7037(93)90416-T", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1993-06", "series_number": "11", "volume": "57", "issue": "11", "pages": "2541-2554" }, { "id": "authors:zmqks-qte37", "collection": "authors", "collection_id": "zmqks-qte37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120919-094950384", "type": "article", "title": "Laser-induced isotopic effects in titanium resonance ionization", "author": [ { "family_name": "Wunderlich", "given_name": "R. K.", "clpid": "Wundrelich-R-K" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" } ], "abstract": "Titanium isotope ratios have been measured by resonance ionization mass spectrometry (RIMS) with special emphasis on the nature of laser-induced isotopic selectivity. A pronounced wavelength dependence of even mass isotope ratios is caused by large nuclear volume effects near the\nmagic neutron number 28 in ^(50)Ti . Optical isotope shifts, ranging from 0.07 to 0.21 cm^(-l), between ^(50)Ti and ^(46)Ti were measured for several transitions. The ^(50)Ti/^(46)Ti and ^(48)Ti/^(46)Ti ratios, nevertheless, exhibited only mass-dependent fractionation, in which the lighter Ti isotopes were enriched by ~2.5%/amu, when the laser operating parameters were properly controlled. Odd-even mass isotopic selectivity in the resonant ionization process was also examined for several transitions as a function of the laser polarization state and intensity. Under saturating conditions for a \u0394J= +1 transition and a high degree of laser depolarization for a \u0394J = 0 transition, the odd-even isotopic enhancement was reduced below the 2% level. The Ti isotope data agree with our previous results for Os and indicate that, by a careful choice of resonance transitions and laser operating parameters, isotope ratios can be measured accurately and reliably with RIMS.", "doi": "10.1021/ac00058a018", "issn": "0003-2700", "publisher": "American Chemical Society", "publication": "Analytical Chemistry", "publication_date": "1993-05", "series_number": "10", "volume": "65", "issue": "10", "pages": "1411-1418" }, { "id": "authors:42fmb-9fn14", "collection": "authors", "collection_id": "42fmb-9fn14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131030-155148591", "type": "article", "title": "An experimental study of trace element partitioning\n between olivine, orthopyroxene and melt in chondrules:\n equilibrium values and kinetic effects", "author": [ { "family_name": "Kennedy", "given_name": "A. K.", "clpid": "Kennedy-Allen-K" }, { "family_name": "Lofgren", "given_name": "G. E.", "clpid": "Lofgren-G-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The concentrations of 32 elements (major, minor, REE, Ba, Hf, Sc, V, Co, Ni, Sr, Y, Zr, Nb, Ge, Th and U) were measured using an ion microprobe in olivine and orthopyroxene, and in coexisting glass in the run products produced in isothermal and dynamic crystallization experiments on chemical compositions that produce porphyritic olivine, radial pyroxene and barred olivine textures. Cooling rates in the dynamic crystallization experiments ranged from 1\u00b0C/h to 2191\u00b0C/h. The mineral/melt partition coefficients (D) calculated from the measured concentrations for both olivine and orthopyroxene showed very little change between equilibrium experiments and dynamic experiments with cooling rates of up to 100\u00b0C/h. The data appear to define reliable equilibrium D values. Olivine D's range from 2 \u00d7 10^(\u22125) for U to \u223c 10 for Ni, and orthopyroxene D's range from 2 \u00d7 10^(\u22125) for U to \u223c 8 for Mg. There are regular relationships between the ionic radius, the valence of the trace element and the partition coefficients in olivine and orthopyroxene in all experiments. While there are some differences in the D values between olivine and orthopyroxene, they follow very similar trends. For experiments at high cooling rates there is an increase in the measured concentrations for incompatible trace elements in the crystals which yields apparent partition coefficients greater by up to 3 orders of magnitude from the equilibrium values obtained for isothermal equilibrium and slow cooling experiments. In contrast, compatible trace element D values are only slightly sensitive to cooling rate, typically varying by less than a factor of 2. SEM studies showed that melt inclusions were common in orthopyroxenes. It is shown that the increase in apparent D values for pyroxene observed with high cooling rates can be quantitatively explained by trapping of melt inclusions in crystals with equilibrium D values. Incorporation of melt inclusions may also quantitatively explain the increases in apparent D values in olivine at high cooling rates. However, no inclusions of melt were identified in olivine, even at the fastest cooling rate. If the high apparent D values obtained for olivine at high cooling rates were due to incorporation of trace elements in the lattice and not due to entrapment of melt, it would require incorporation of elements independent of valence and ionic radius.", "doi": "10.1016/0012-821X(93)90221-T", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1993-03", "series_number": "1-4", "volume": "115", "issue": "1-4", "pages": "177-195" }, { "id": "authors:ctes8-gat79", "collection": "authors", "collection_id": "ctes8-gat79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131031-134749897", "type": "article", "title": "Late Quaternary evolution of coral reefs on a cool-water carbonate margin: the Abrolhos Carbonate Platforms, southwest Australia", "author": [ { "family_name": "Collins", "given_name": "L. B.", "clpid": "Collins-L-B" }, { "family_name": "Zhu", "given_name": "Z. R.", "clpid": "Zhu-Z-R" }, { "family_name": "Wyrwoll", "given_name": "K. -H.", "clpid": "Wyrwoll-K-H" }, { "family_name": "Hatcher", "given_name": "B. G.", "clpid": "Hatcher-B-G" }, { "family_name": "Playford", "given_name": "P. E.", "clpid": "Playford-P-E" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Eisenhauer", "given_name": "A.", "clpid": "Eisenhauer-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Late Quaternary coral reefs have developed on the southwestern Australian margin, which has otherwise been characterised by cool-water carbonates since the Eocene. The Houtman Abrolhos coral reefs are at the limits of existence, extending, with the assistance of the Leeuwin Current, a poleward-flowing, warm water stream, into a region dominated by more temperate communities. Coring in the Easter Group reefs, supported by high precision dating, by both View the MathML source TIMS and ^(14)C methods, has shown vigorous coral growth, with reefs over 26 m thick in the Holocene and over 15 m thick in the Last Interglacial. Each of the three Abrolhos platforms consists of a central platform composed of Last Interglacial reefs, about which windward and leeward Holocene reefs developed asymmetrically. Reef, peritidal and eolian facies comprise the emergent Last Interglacial limestones which are extensively calcretized, with reef facies up to 5 m above MSL. The Last Interglacial high stand lasted for at least 10 ka from 130 to 120 ka, and possibly 15 ka, from 132 to 117 ka. Holocene reef facies are also emergent by 0.5 m, and are overlain by peritidal and storm ridge facies in an upward-shallowing sequence. Windward (10 m thick) and leeward (26 m thick) Holocene reefs in the Easter Group show contrasting lithofacies. The wave-exposed windward reefs consist of a slow-growing association of coralline algal bindstones and coral framestones, whereas fast-growing coral framestones dominate the more protected leeward reefs. The leeward reefs commenced growth 10,000 years ago and grew to the present sea level by 6500 years ago, generating Holocene constructional topography consisting of 'blue-hole' terrain in the leeward parts of the platforms.", "doi": "10.1016/0025-3227(93)90085-A", "issn": "0025-3227", "publisher": "Elsevier", "publication": "Marine Geology", "publication_date": "1993-03", "series_number": "3-4", "volume": "110", "issue": "3-4", "pages": "203-212" }, { "id": "authors:m2fx0-2pa87", "collection": "authors", "collection_id": "m2fx0-2pa87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131031-115851829", "type": "article", "title": "Holocene sea-level determination relative to the Australian continent: U/Th (TIMS) and ^(14)C (AMS) dating of coral cores from the Abrolhos Islands", "author": [ { "family_name": "Eisenhauer", "given_name": "A.", "clpid": "Aisenhauer-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Bonani", "given_name": "G.", "clpid": "Bonani-G" }, { "family_name": "Collins", "given_name": "L. B.", "clpid": "Collins-L-B" }, { "family_name": "Zhu", "given_name": "Z. R.", "clpid": "Zhu-Z-R" }, { "family_name": "Wyrwoll", "given_name": "K. H.", "clpid": "Wyrwoll-K-H" } ], "abstract": "U/Th (TIMS) and ^(14)C (AMS) measurements are presented from two coral cores from the Easter group of the Houtman Abrolhos Islands between 28\u00b0S and 29\u00b0S on the western continental margin of Australia. The U/Th measurements on the Morley core from Morley Island cover a depth interval from 0.2 m above present sea level to 24.4 m below present sea level and comprise eleven samples. The ages vary between 6320 \u00b1 50 a, at 0.2 m above sea level, and 9809 \u00b1 95 a, at 24.4 m below sea level (all errors are 2\u03c3). The mean growth rate is 7.1 \u00b1 0.9 m/ka. The ^(14)C dates of selected Morley core corals show that the ^(14)C ages are \u223c 1000 a younger than their corresponding U/Th ages, which agrees with previous results. The main purpose of our ^(14)C measurements is to be able to compare them precisely with other coral cores where no U/Th measurements are available. The U/Th measurements of the Suomi core from Suomi Island cover a depth interval from 0.05 m to 14.2 m below present sea level and consist of four samples. The ages vary between 4671 \u00b1 40 a, at 0.05 m below sea level, and 7102 \u00b1 82 a, at 14.2 m below sea level, with a mean growth rate of 5.8 \u00b1 0.2 m/ka. The growth history of both cores is explained by a simple model in which the growth rates of the Morley core can be interpreted as reflecting local rates of sea level rise, whereas the Suomi core is interpreted as reflecting lateral growth during the past \u223c 6000 a. Our results indicate that sea level relative to the western margins of the Australian continent was about 24 m lower than present at about 9800 a B.P. (^(14)C gives a date of 8500 a B.P.). Sea level then rose and reached a highstand, slightly higher than the present position at about 6300 a B.P (14C date: 5500 a). This highstand declined but was still higher than present at 4600 a B.P. This is in agreement with previous observations along the Australian coastal margins and with observations from the Huon peninsula (Papua New Guinea). Our results are very similar to theoretical numerical models, which take into consideration water loading and isostatic compensation and viscous mantle flow. In contrast, coral cores from Barbados show that corals with a ^(14)C age of \u223c 5500 a B.P. are some \u223c 10 m b.p.s.l. We interpret the difference between the Barbados core and the Morley core as resulting from additional \"flooding\" of Barbados by water redistribution, due to changes in the Earth's geoid but not reflecting global sea level rise or major addition of melt waters over the past \u223c 6000 a. The difference in the geoid at Barbados between \u223c 6000 a B.P. and the present will require a refinement in the geophysical models. Precise ^(230)Th (TIMS) measurements on continental coasts will be required to provide an adequate data base for modelling deformation, flow of mantle material and sea-level height.", "doi": "10.1016/0012-821X(93)90081-J", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1993-02", "series_number": "4", "volume": "114", "issue": "4", "pages": "529-547" }, { "id": "authors:4psf8-m2k16", "collection": "authors", "collection_id": "4psf8-m2k16", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-085556113", "type": "article", "title": "Diagenesis of fossil coral skeletons: Correlation between trace elements, textures, and ^(234)U/^(238)U", "author": [ { "family_name": "Bar-Matthews", "given_name": "M.", "clpid": "Bar-Matthews-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" } ], "abstract": "A comparative study of Pleistocene fossil coral skeletons and of modern coral skeletons was carried out using petrographie and trace element analyses on a suite of Pleistocene samples that had previously been studied for ^(234)U, ^(230)Th, and U-^(230)Th ages (Chen et al. 1991). Evidence of a range of diagenetic changes can be recognized by optical (OM) and scanning electron microscopy (SEM). The normal texture exhibited by modern corals under OM consists of fine needles of aragonite forming a radial-fibrous pattern around a central dark line (center of calcification). This pattern can also be seen in many fossil corals. In most cases, the central dark line partially disappears during diagenesis, the radialfibrous pattern is obscured, and there is a distinct coarsening of the radial fabric of aragonite to unoriented platy or equant aragonite crystals. SEM images show diagenetic textures ranging from dense structureless images of the coralline matrix, with sharp boundaries at the septa walls, to the development of (1) a patchy distribution of dissolution micropores partially filled with aragonite fibers in the matrix, (2) aragonite needles coming from selvages in the septa walls which radiate into the septa voids.\nUsing an electron microprobe and SEM, concentrations of Na, S, Sr, and Mg were measured. No other trace elements were detected. Na, S, and Mg contents of the matrix, the fibrous micropores, and radiating needles are highly variable and well correlated. High concentrations of Na, S, and Mg were found in modern living corals with lower concentrations in fossil corals and fibrous micropores, and the lowest value in the radiating needles. The reason for the correlations of Na, S, and Mg and crystal chemistry and the response to diagenesis of these trace elements is not understood. The average concentrations of Na, S, and Mg for each sample, when plotted against the whole coral initial \u03b4^(234)U, are generally correlated (Chen et al., 1991). As all these diagenetic changes involve the recrystallization and deposition of aragonite, we infer that the geologic site of diagenesis both for forming the secondary aragonitic phases and for the enhancement of the ^(234)U content in the fossil corals was the marine environment. It is possible that the textural and Na, S, and Mg trace element contents of fossil corals be used to ascertain the reliability of fossil coral skeletons for U-^(230)Th dating. The basic problem of identifying a priori unaltered coral skeletons for ^(230)Th dating is not yet resolved.", "doi": "10.1016/0016-7037(93)90429-Z", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1993-01", "series_number": "2", "volume": "57", "issue": "2", "pages": "257-276" }, { "id": "authors:r6fbx-kyr89", "collection": "authors", "collection_id": "r6fbx-kyr89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131031-110528692", "type": "article", "title": "The sources and transport of Sr and Nd isotopes in the Baltic Sea", "author": [ { "family_name": "Andersson", "given_name": "Per S.", "clpid": "Andersson-P-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Ingri", "given_name": "Johan", "clpid": "Ingri-J" } ], "abstract": "We have determined the concentration and isotopic composition of Sr and Nd in waters from the Baltic Sea. The Baltic Sea is an intracontinental, stratified, brackish water, estuarine-like system, and the rivers emptying into it drain a suite of terranes ranging from Proterozoic-Archean in the north to Phanerozoic in the south. The sampled brackish waters range in salinity from seawater (SW) at 35.289\u2030 to a minimum of 2.460\u2030 at the surface in the innermost part of the Gulf of Bothnia. The Sr concentrations show generally conservative behavior, indicating a simple two-component mixing. However, small deviations (3\u201370 \u2030) from a perfect mixing line reveal that the imprints from rivers with different Sr concentrations are preserved in the blending. Strontium concentrations from a depth profile across the redoxcline in the Baltic proper indicate that vertical particle transport alters the Sr concentration in the water. Our estimated concentration of Sr in the average freshwater input to the Baltic is \u223c 0.03 ppm, which is only about 0.4% of the SW concentration. The Sr isotopic data range from \u03b5^(Sr)(SW) = 0 in seawater to \u03b5_(Sr)^(BW)(SW) = 7.8 in the least saline Baltic water (BW) sample in the Gulf of Bothnia. The isotopic composition of Sr versus 1/Sr in the Baltic Sea follows an almost perfect mixing line, which shows that seawater Sr is mixed with much more radiogenic components. Calculated end-member values of \u03b5_(Sr)^*(SW) for each sample show that the riverine input into the Gulf of Bothnia has \u03b5_(Sr)^*(SW) = 120\u2013200 and 10\u201350 \u03b5 units in the Baltic proper. These values are in general agreement with direct measurements of river waters in each region. However, the calculated values in the Gulf of Bothnia are lower than the measured river water input in this region, which indicates the presence of less radiogenic Sr, presumably originating from the river waters draining the southern part of the basin which are partially transported northward and mixed with Sr from the Gulf of Bothnia rivers.\nThe Nd concentration in the Baltic Sea is not conservative, varying between 5 and 45 ppt, with the highest concentrations in the bottom waters due to vertical particulate transport. A plot of \u03b5_(Nd)(O) in Baltic water yields a good correlation with the calculated freshwater end member \u03b5_(Sr)^*(SW). The data show that it is possible to unravel the different freshwater sources into the Baltic and to identify the zones of particulate removal of both non-conservative species such as the REE and of quasi-conservative species such as Sr. The use of isotopic tracers in this estuarine environment may provide a much better insight into mixing and element transport. It should also be possible to trace lateral movements of freshwater inputs.", "doi": "10.1016/0012-821X(92)90124-E", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1992-11", "series_number": "4", "volume": "113", "issue": "4", "pages": "459-472" }, { "id": "authors:cq3d1-kg910", "collection": "authors", "collection_id": "cq3d1-kg910", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131030-080832683", "type": "article", "title": "Rhenium in seawater: Confirmation of generally conservative behavior", "author": [ { "family_name": "Anbar", "given_name": "A. D.", "clpid": "Anbar-A-D" }, { "family_name": "Creaser", "given_name": "R. A.", "clpid": "Creaser-R-A" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A depth profile of the concentration of Re was measured in the Pacific Ocean using a technique we have developed for the clean chemical separation and the precise measurement of Re by isotope dilution and negative thermal ionization mass spectrometry (ID-NTIMS). This technique permits Re concentrations to be determined from 200 mL of seawater with a typical precision of \u00b15\u2030. This is an improvement of at least a factor of 100 over the techniques used in previously published determinations of Re in seawater. We obtain a narrow range for Re from 7.20 \u00b1 0.03 to 7.38 \u00b1 0.03 ng/kg for depths between 45 m and 4700 m. This demonstrates that Re is relatively well mixed throughout the water column and confirms the theoretical prediction that the behavior of Re in the oceans is conservative. When examined in detail, both salinity and the concentration of Re increase by approximately 1.5% between 400 and 4700 m, a correlation consistent with conservative behavior. However, Re appears to be depleted relative to salinity by 1.0\u20131.5% at 100 m, and enriched by approximately 4% at the surface. These observations suggest a minor level of Re scavenging in near surface waters, and an input of Re to the ocean surface. This work demonstrates the utility of ID-NTIMS for geochemical investigations of certain trace elements that have not previously been amenable to detailed study.", "doi": "10.1016/0016-7037(92)90021-A", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1992-11", "series_number": "11", "volume": "56", "issue": "11", "pages": "4099-4103" }, { "id": "authors:z3me0-q4n11", "collection": "authors", "collection_id": "z3me0-q4n11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-131452047", "type": "article", "title": "Isotopic Analysis of Os and Re with negative thermal ion mass spectrometry and application to the age and evolution of iron meteorites", "author": [ { "family_name": "Creaser", "given_name": "R. A.", "clpid": "Creaser-R-A" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The ^(187)Re-^(187)Os isotope system has long been recognized as a method by which the age of iron meteorites can be directly determined (Herr et al., 1961). Pioneering work by Luck and All\u00e8gre (1983) established a whole-rock isochron for iron meteorites and the results were used to determine indirectly the half-life of ^(187)Re.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1992-07", "series_number": "3", "volume": "27", "issue": "3", "pages": "212-212" }, { "id": "authors:9dj0a-bp227", "collection": "authors", "collection_id": "9dj0a-bp227", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120912-112611849", "type": "article", "title": "Laser-induced isotopic selectivity in the resonance ionization of Os", "author": [ { "family_name": "Wunderlich", "given_name": "R. K.", "clpid": "Wundrelich-R-K" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Blake", "given_name": "G. A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" } ], "abstract": "Isotope selective effects in resonance ionization mass spectrometry (RIMS) pose a potentially serious limitation to the application of this technique to the precise and reproducible measurement of isotope ratios. In order to identify some of the underlying causes of isotope selectivity in RIMS and to establish procedures for minimizing these effects, we investigated laser-induced isotope selectivity in the resonance ionization of Os. A single-color, one-photon resonant ionization scheme was used for several different transitions to produce Os photoions from a thermal atomization source. Variations in Os isotope ratios were studied as a function of laser parameters such as wavelength, bandwidth, power and polarization state. Isotope selectivity is strongly dependent on laser power and wavelength, even when the bandwidth of the laser radiation is much larger than the optical isotope shift. Variations in the ^(190)Os/^(188)Os ratio of \u224820% for a detuning of 0.8 cm^(\u22121) were observed on a transition with a small oscillator strength. Large even\u2014odd isotope selectivity with a 13% depletion of ^(189)Os was observed on a \u0394J = +1 transition at low laser intensity; the odd mass Os isotopes are systematically depleted. For \u0394J = \u22121 and 0 transitions the isotope selectivity was reduced by polarization scrambling and for strongly saturating conditions. A technique employing the wavelength dependence of even\u2014even isotope selectivity as an internal wavelength standard was developed to permit accurate and reproducible wavelength adjustment of the laser radiation. This technique provides control over laser-induced isotope selectivity for single-color ionization and enabled us to obtain reproducible measurements of ^(192)Os/^(188)Os and ^(189)Os/^(190)Os ratios in the saturation regime for a \u0394J = +1 transition with a precision of better than 0.5%. The application of this wavelength-tuning procedure should significantly improve the quality of RIMS isotope ratio data for many elements.", "doi": "10.1016/0168-1176(92)85037-Z", "issn": "0168-1176", "publisher": "Elsevier", "publication": "International Journal of Mass Spectrometry and Ion Processes", "publication_date": "1992-06-15", "series_number": "2-3", "volume": "115", "issue": "2-3", "pages": "123-155" }, { "id": "authors:jdsf0-ygz71", "collection": "authors", "collection_id": "jdsf0-ygz71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-154702161", "type": "article", "title": "Self-diffusion of magnesium in spinel and in equilibrium melts: Constraints on flash heating of silicates", "author": [ { "family_name": "Sheng", "given_name": "Y. J.", "clpid": "Sheng-Y-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" } ], "abstract": "We have measured Mg self-diffusion in spinel and coexisting melt at bulk chemical equilibrium using an isotopic tracer. The diffusion coefficients were calculated from the measured isotope profiles using a model that includes the complementary diffusion of ^(24)Mg, ^(25)Mg, and ^(26)Mg in both phases with the constraint that the Mg content of each phase is constant. This model also permits the calculation of the diffusion coefficient in one phase from the measured data in a coexisting phase. The activation energy and pre-exponential factor for Mg self-diffusion in spinel are, respectively, 384 \u00b1 7kJ and 74.6 \u00b1 1.1 cm^2/s. These data indicate Mg diffusion in spinel is much slower than previous estimates, probably because earlier measurements included grain boundary transport. The activation energy for Mg self-diffusion in coexisting melt is 343 \u00b1 25 kJ and the pre-exponential factor is 7791.9 \u00b1 1.3 cm^2/s. The results from this study were applied to evaluate cooling rates of Plagioclase-Olivine Inclusions (POI) in the Allende meteorite. Given a maximum melting temperature for POIs of ~ 1500\u00b0C, these results show that a 10 \u03bc radius spinel would equilibrate isotopically with a melt within about 60 min. To preserve Mg isotopic heterogeneity, the POIs must have initially cooled faster than 15 to 250\u00b0C/h depending on the initial temperature of flash heating. The cooling rate must also be slow enough to generate the observed basaltic textures. The inferred cooling rate appears to be comparable or up to ten times greater than those inferred from experimental and textural studies of synthetic CAI systems. The nature of the heating process is thus required to be short with relatively rapid cooling, such as flash heating. However, the relatively rapid cooling cannot be due to radiation into a cold, ~400\u00b0K nebula but would require radiation into a rather stable hot environment.", "doi": "10.1016/0016-7037(92)90207-Y", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1992-06", "series_number": "6", "volume": "56", "issue": "6", "pages": "2535-2546" }, { "id": "authors:b76dv-nqe32", "collection": "authors", "collection_id": "b76dv-nqe32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131031-134904269", "type": "article", "title": "Samarium-neodymium evolution of meteorites", "author": [ { "family_name": "Prinzhofer", "given_name": "A.", "clpid": "Prinzhofer-A" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have obtained Sm-Nd data on two differentiated meteorites, Ibitira, a eucrite with distinct basaltic texture and with evidence of crystallization; and Morristown, a group 3A mesosiderite; as well as on Acapulco, an unclassified meteorite with chondritic chemical composition and a highly recrystallized texture. We have demonstrated the presence of in situ decay of short-lived ^(146)Sm in these meteorites with initial abundance of ^(146)Sm/^(144)Sm from 0.009 to 0.007 for the different meteorites. Precisely defined ^(147)Sm-^(143)Nd internal isochrons were obtained yielding ages of 4.60 \u00b1 0.03 AE for Acapulco, 4.47 \u00b1 0.02 AE for Morristown and 4.46 \u00b1 0.02 AE for Ibitira. The corresponding initial ^(143)Nd/^(144)Nd values obtained were 0.2 \u00b1 0.9, 2.1 \u00b1 0.7 and 1.6 \u00b1 0.8 \u03f5u (epsilon units). Detailed consideration of the coupled ^(147)Sm-^(143)Nd and ^(146)Sm-^(142)Nd systematics and of the elevated initial ^(143)Nd/^(144)Nd values indicates the presence of inconsistencies in the data for the two Sm-Nd parent-daughter pairs in spite of the precise isochrons. We present a model which provides an interpretation of the paired Sm-Nd systematics in terms of an impulsive disturbance. The abundance of phosphate, with large concentrations of REEs, controls the REE economy. Plagioclase, with low REE concentrations is assumed to be susceptible to exchange. Pyroxene is considered to be undisturbed because of the low diffusion coefficients of trace elements. The experimental results can be reasonably explained by this model. The results indicate that three meteorites studied, some with very low REE concentrations, including a mesosiderite, are relatively ancient objects, formed within the first 50 to 100 m.y. of the solar system, by planetary differentiation and impact processes, and were subjected to late metamorphism. The time of late metamorphism is substantially younger than 4.4 AE and possibly as recent as ~3.9 AE. This metamorphism has resulted in partial, very limited reequilibration between plagioclase and phosphate, resulting in the observed shifts in initial ^(143)Nd/^(144)Nd, Sm-Nd model ages, and the ^(142)Nd/^(144)Nd abundances, but preserving the major temporal structures of early original formation and later disturbances. These results show the need for care in the interpretation of the parent-daughter systematics, even when they appear well behaved and the mineral phases are viewed as highly resistant to mild metamorphism.", "doi": "10.1016/0016-7037(92)90099-5", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1992-02", "series_number": "2", "volume": "56", "issue": "2", "pages": "797-815" }, { "id": "authors:c1g6b-a8432", "collection": "authors", "collection_id": "c1g6b-a8432", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131101-091511035", "type": "article", "title": "Neodymium and strontium isotopic study of Australasian tektites: New constraints on the provenance and age of target materials", "author": [ { "family_name": "Blum", "given_name": "Joel D.", "clpid": "Blum-J-D" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Koeberl", "given_name": "C.", "clpid": "Koeberl-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Nd and Sr isotopic studies of Australasian tektites provide information on the age and provenance of the target materials and allow us to characterize the target area and the impact process leading to tektite formation. \u03f5_(Nd) values of australites, splash-form indochinites, and Muong Nong-type indochinites are indistinguishable within analytical uncertainty and average -11.5 \u03f5u. Depleted mantle Nd model ages fall within the narrow range of 1490\u20131620 Ma, indicating that the source material was derived dominantly from a Proterozoic crustal terrane. \u03f5_(Sr) values are variable and are correlated with the geographic location of the tektite samples. Analyses of four Muong Nong-type (or layered) indochinites from a single locality in eastern Thailand yield an isochron age of 167 \u00b1 12 Ma (2\u03c3). A correlation of Rb/Sr fractionation with Sr model ages indicates that the last major Rb/Sr fractionation event experienced by the target materials occurred 175 \u00b1 15 Ma ago. We interpret this age as the time of deposition of sedimentary target rocks and consider the compositional layering observed in Muong Nong-type tektites to reflect compositional variability inherited from Jurassic sediments. The Nd and Sr isotopic data provide evidence that all Australasian tektites were derived from a single sedimentary formation with a narrow range of stratigraphic ages close to 170 Ma. We suggest that all of the Australasian tektites were derived from a single impact event, and that the australites represent the upper part of a melt sheet ejected at high velocity, whereas the indochinites represent melts formed at a lower level in the target material which were distributed closer to the area of impact. The impact site is inferred to be within an area of Jurassic sedimentary bedrock, which spans the geopolitical boundaries between northern Cambodia, southern Laos, and southeastern Thailand.", "doi": "10.1016/0016-7037(92)90146-A", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1992-01", "series_number": "1", "volume": "56", "issue": "1", "pages": "483-492" }, { "id": "authors:y5bvd-xmr05", "collection": "authors", "collection_id": "y5bvd-xmr05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131101-084434768", "type": "article", "title": "U-series ages of solitary corals from the California coast by mass spectrometry", "author": [ { "family_name": "Stein", "given_name": "M.", "clpid": "Stein-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Lajoie", "given_name": "K. R.", "clpid": "Lajoie-K-R" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" } ], "abstract": "The purpose of this study is to evaluate the feasibility of dating fossil solitary corals from Pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity, high-precision U-series technique based on thermal-ionization mass-spectrometry (TIMS). The TIMS technique is much more efficient than conventional a spectrometry and, as a result, multiple samples of an individual coral skeleton, or different specimens from the same bed can be analyzed.\nDetached and well-rounded fossil specimens of the solitary coral Balanophyllia elegans were collected from relict littoral deposits on emergent marine terraces along the California coast at Cayucos terrace (elevation 8 m, previously dated at 124 and 117 Ky by \u03b1 counting), Shell Beach terrace (elevation about 25 m, previously undated), Nestor terrace, San Diego (elevation 23 m, previously dated at 131 to 109 Ky ), Bird Rock terrace, San Diego ( elevation 8 m, previously dated at 81 Ky ). Attached living specimens were collected from the intertidal zone on the modern terrace at Moss Beach.\nConcentrations of ^(232)Th in both living and fossil specimens are much higher than in reef-building corals (12 to 624 pmol/g vs. 0.1 to 1.6 pmol/g, respectively). However, because ^(230)Th/^(232)Th in Balanophyllia elegans are very low (2.22 \u00d7 10^(\u22123) to 4.33 \u00d7 10^(\u22124)), the high ^(232)Th concentrations have negligible effect on the ^(230)Th-^(234)U dates. The high ^(232)Th concentration in the living specimen (33.1 pmol/g) indicates that a significant amount of ^(232)Th is incorporated in the aragonitic skeleton during growth, or attached to clay-sized silicates trapped in the skeletal material. The calculated initial ^(234)U activities in the fossil specimens of Balanophyllia elegans are higher than the ^(234)U activity in modern seawater or in the modern specimen. The higher initial activities could possibly reflect the influx of ^(234)U-enriched continental water into Pleistocene coastal waters, or it could reflect minor diagenetic alteration, a persistent and fundamental problem in dating all corals.\nSamples from a compound specimen from the Cayucos terrace were subjected to different preparation procedures. Samples prepared by a standard acid washing procedure yielded ^(230)Th-^(234)U ages of 125, 123, and 122 Ky, whereas samples prepared by an abbreviated procedure without acid washing yield significantly lower ages of 113 and 112 Ky. Two other specimens from the same bed yielded ^(230)Th-^(234)U ages of 118 and 115 Ky. Also, two specimens from a stratigraphically higher bed yielded ages of 120 and 117 Ky, and three specimens from a lower bed yield ages of 115, 113, and 101 Ky. Nine of the twelve ages of the treated samples from the Cayucos terrace range from 125 to 113 Ky. However, the ages do not follow the stratigraphie order. Two possible interpretations are ( 1 ) the age of the terrace deposit is 125 Ky and all younger ages reflect variable diagenetic alteration or (2) the age of the terrace is 125 to 113 Ky and the ages reflect sediment reworking over a period of 12 Ky.\nThree specimens from a single bed on the Shell Beach terrace yield ages of 126, 122, and 121 Ky, similar to the older ages from Cayucos. The ages of solitary corals from the Cayucos and Shell Beach terraces are similar to ages of reef-building corals from terraces at numerous tropical localities. These are correlated with the last interglacial sea-level highstand, which probably stood 2 to 10 m above present sea level. The youngest ages and present elevations of the Cayucos and Shell Beach terraces yield tectonic uplift rates of 0.01 and 0.15 m/Ky, respectively, assuming the original elevation of each terrace was 7 m.\nFour specimens from the basal gravel on the Nestor terrace yielded ages of 145, 143, 137, and 133 Ky. The three oldest ages, however, are older than that associated with the last interglacial. The possible explanations for these older ages are ( 1 ) diagenic alteration or ( 2 ) the Nestor terrace deposits reflect in some way a poorly documented early phase of the last interglacial sea level high stand.", "doi": "10.1016/0016-7037(91)90069-H", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1991-12", "series_number": "12", "volume": "55", "issue": "12", "pages": "3709-3722" }, { "id": "authors:p3q17-67x70", "collection": "authors", "collection_id": "p3q17-67x70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130717-082526360", "type": "article", "title": "Correlated Si isotope anomalies and large ^(13)C enrichments in a family of exotic SiC grains", "author": [ { "family_name": "Stone", "given_name": "J.", "clpid": "Stone-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Epstein", "given_name": "S.", "clpid": "Epstein-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A suite of morphologically distinctive silicon carbide (SiC) grains from the Orgueil and Murchison carbonaceous chondrite meteorites contains Si and C of highly anomalous isotopic composition. All of the SiC grains in this suite are characterized by a distinctive platy morphology and roughly developed hexagonal crystal forms that allow them to be distinguished from other types of SiC found in the host meteorites. The \u03b4^(29)Si and \u03b4^(30)Si values of individual SiC crystals deviate from those of normal solar material by more than 100\u2030, while the \u03b4^(13)C values range from 150 to 5200\u2030. Isotopically normal C and Si are not found in any of these SiC crystals. The SiC grains belonging to this morphological suite are isotopically distinct from fine-grained SiC aggregates and other morphological types of SiC in unequilibrated meteorites. The ^(29)Si/^(28)Si and ^(30)Si/^(28)Si ratios of these platy grains are well correlated and define a linear array that does not pass through the composition of normal, solar Si. This behavior contrasts sharply with the diverse and poorly correlated Si isotopic compositions shown by the total SiC population. We suggest that the distinctive morphological characteristics and comparatively simple Si isotope systematics identify the platy SiC crystals as a genetically related family, formed around a single, isotopically heterogeneous presolar star or an association of related stars.\nThe enrichments in ^(13)C and the Si isotope systematics of the platy SiC are broadly consistent with theoretical models of nucleosynthesis in low-mass, carbon stars on the asymptotic giant branch. The Si isotope array most plausibly reflects mixing between ^(28)Si-rich material, inherited from a previous generation of stars, and material enriched in ^(29)Si and ^(30)Si, produced in intershell regions by neutron capture during He-burning. ^(13)C is also produced in intershell regions by proton reactions on ^(12)C seed nuclei and is carried withs-process nuclei to the stellar envelope by convection which penetrates down to the He shell. The absence of a correlation between the Si and C isotopic compositions of the SiC suggests either episodic condensation of SiC, extending over several thermal pulses, in the atmosphere of a single star, or derivation of the SiC from several stars characterized by different rates of ^(13)C production. In the multiple star scenario, the linear correlation of the ^(29)Si/^(28)Si and ^(30)Si/^(28)Si ratios among the platy SiC indicates that these stars evolved from a common Si seed composition under similar conditions of neutron-capture nucleosynthesis. The ^(29)Si/^(30)Si ratio of the SiC, inferred by us to be produced by neutron capture in the stellar interior, is distinct from values calculated from models of nucleosynthesis in AGB stars.", "doi": "10.1016/0012-821X(91)90102-N", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1991-12", "series_number": "3-4", "volume": "107", "issue": "3-4", "pages": "570-581" }, { "id": "authors:gnjmx-4zq48", "collection": "authors", "collection_id": "gnjmx-4zq48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-153950591", "type": "article", "title": "Trace element partitioning within Mesosiderite clasts", "author": [ { "family_name": "Kennedy", "given_name": "A. K.", "clpid": "Kennedy-Allen-K" }, { "family_name": "Stewart", "given_name": "B. W.", "clpid": "Stewart-B-W" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Mesosiderites are polymict silicate and metal breccias resulting from\nmagmatic differentiation, brecciation, metal-silicate mixing, and metamorphic\nrecrystallization in early planetary bodies. Petrographic and\ntrace element studies have documented the great diversity of differentiated\nsilicates, with eucritic basalt, gabbroic cumulate and diogenite\nclasts and trace element disequilibrium between phases (1-4).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1991-12", "series_number": "4", "volume": "26", "issue": "4", "pages": "356-356" }, { "id": "authors:5vqfm-n9s17", "collection": "authors", "collection_id": "5vqfm-n9s17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140204-081155616", "type": "article", "title": "An experimental study of Mg self-diffusion in spinel", "author": [ { "family_name": "Sheng", "given_name": "Y. J.", "clpid": "Sheng-Y-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Mg isotope heterogeneity, both between coexisting spinel and silicates\nand among spinels, is a prominent feature of Plagioclase-Olivine Inclusions\n(POIs) (1). The preservation of isotopic heterogeneity and relict\nspinel (Sp) in inclusions with igneous textures indicates that the thermal\nevent which partially melted the precursor material either had too low\na temperature or was too brief to allow Mg isotope homogenization\nbetween Sp and the melt. Since the temperature history required to\nhomogenize Mg isotopes depends on the diffusion rate of Mg in Sp, we\ndesigned experiments using an isotope tracer method to determine this\ncritical rate (2).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1991-12", "series_number": "4", "volume": "26", "issue": "4", "pages": "394-395" }, { "id": "authors:n3pc5-ss341", "collection": "authors", "collection_id": "n3pc5-ss341", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131030-155459799", "type": "article", "title": "Uranium-series evidence on diagenesis and hydrology in Pleistocene carbonates of Barbados, West Indies", "author": [ { "family_name": "Banner", "given_name": "Jay L.", "clpid": "Banner-J-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Chen", "given_name": "James H.", "clpid": "Chen-J-H" }, { "family_name": "Humphrey", "given_name": "John D.", "clpid": "Humphrey-J-D" } ], "abstract": "Uranium-series isotope measurements were made by mass spectrometry on aragonite, dolomite and groundwater samples from Pleistocene coral-reef terraces on Barbados in order to evaluate the behavior of U\u2014Th isotopes during water-rock interaction in carbonate systems. Well-preserved aragonitic corals from the Golden Grove terrace yield precise ^(230)Th ages of 219 \u00b1 3 and 224 \u00b1 6 ky, and have high and variable initial \u03b4^(234)U relative to values for modern seawater. These high \u03b4^(234)U values are common to Pleistocene carbonates from many localities and indicate that the U-series has not followed closed-system behavior since the time of deposition. Pervasively dolomitized samples from the Golden Grove terrace have significantly lower \u03b4^(234)U than the unreplaced aragonite, and (^(230)Th/^(238)U)_(ACT) (activity ratios) in excess of values for secular equilibrium. Groundwaters sampled from 125\u2013460 ky old portions of the Pleistocene carbonate aquifer have \u03b4^(234)U values close to secular equilibrium, and low (^(230)Th/^(238)U)_(ACT) of less than 4 \u00d7 10^(\u22123). The pronounced differences in the U\u2014Th isotope systematics between the aragonitic corals, dolomites and groundwaters reflect the enhanced mobility of U relative to Th during water-rock interaction. These results demonstrate that diagenesis can profoundly affect the U\u2014Th isotopic composition of marine carbonates and therefore the accuracy of high-precision ^(230)Th ages determined on such samples. However, diagenesis involving fluids such as the present-day groundwaters on Barbados or those which formed the dolomites cannot account for the elevated\u03b4234U values of the corals. The mechanism by which apparently well-preserved corals become enriched in ^(234)U remains to be identified. Low \u03b4^(234)U for the dolomites and the groundwaters records the transport of dissolved U from portions of the aquifer that are significantly older (e.g., > 10^6 yrs) than their present host carbonate rocks. The preservation of these distinct U-isotopic compositions during fluid migration through younger carbonates indicates that interaction between groundwaters and these carbonates, with accompanying ^(234)U enrichment in the waters from dissolution or alpha-recoil, has been extremely limited.", "doi": "10.1016/0012-821X(91)90049-N", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1991-10", "series_number": "1", "volume": "107", "issue": "1", "pages": "129-137" }, { "id": "authors:0ya96-jrh33", "collection": "authors", "collection_id": "0ya96-jrh33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120820-161958837", "type": "article", "title": "Diffusion of a multi-species component and its role in oxygen and water transport in silicates", "author": [ { "family_name": "Zhang", "given_name": "Youxue", "orcid": "0000-0002-7439-0086", "clpid": "Zhang-Youxue" }, { "family_name": "Stolper", "given_name": "E. M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "An important but poorly understood factor that affects diffusion rates is the role of speciation during diffusion of a multi-species component. The diffusion of such a component is complicated by the different diffusion coefficient of each species and the interconversion reactions among the species. These complexities can be treated by a diffusion equation that incorporates the diffusive fluxes of all species contributing to the concentration of the component. The effects of speciation on the diffusion of the component can be investigated experimentally in some simple cases by measuring concentration profiles of all species developed during diffusion experiments or by studying some of their other consequences.\n\nExperimental data on water diffusion in rhyolitic glasses indicate that although dissolved water is present as two species. H_2O molecules and OH groups, molecular H_2O is the dominant diffusing species at very low to high water concentrations. This explains the apparently complex behavior of water diffusion. Experimental data on oxygen diffusion in some silicates using ^(18)O tracers in the form of H_(2)^(18)O are consistent with the idea that ^(18)O transport is dominated by diffusion of H_2O molecules even at lower water contents (ppm or less). This explains why oxygen transport depends on the presence of water and generally depends on water fugacity linearly. For this mode of oxygen transport, there is a simple theoretical relationship between the effective total oxygen diffusion coefficient and the total water diffusion coefficient that is a function of only the water concentration of the silicate at low water content. This relationship appears to describe quantitatively the existing data over a wide range in water contents and diffusion coefficients in several phases.", "doi": "10.1016/0012-821X(91)90163-C", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1991-04", "series_number": "1-4", "volume": "103", "issue": "1-4", "pages": "228-240" }, { "id": "authors:99qfs-bkj69", "collection": "authors", "collection_id": "99qfs-bkj69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-132412535", "type": "article", "title": "Origin of plagioclase-olivine inclusions in carbonaceous chondrites", "author": [ { "family_name": "Sheng", "given_name": "Y. J.", "clpid": "Sheng-Y-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Plagioclase-Olivine Inclusions (POIs) are an abundant group of chondrule-like objects with igneous textures found in carbonaceous chondrites. POIs consist of plagioclase, olivine, pyroxene, and spinel, and cover a wide range of compositions between Type C Ca-Al-rich Inclusions (CAIs) and ferromagnesian chondrules. POIs are distinguished from CAIs by the absence of melilite, lack of refractory siderophile-rich opaque assemblages, more sodic plagioclase, and abundance of olivine and aluminousenstatite. Rare accessory minerals including armalcolite, zirconolite, rutile, and sapphirine are found in several POIs. The petrographie and chemical properties of POIs indicate that they are not condensates or evaporative residues but formed by melting or partial melting of pre-existing solids. Seven of fourteen POIs contain isotopically fractionated Mg, and despite their textures these POIs are not isotopically homogeneous. Spinel is the major carrier of fractionated Mg in six POIs. The magnitude of Mg isotopic fractionation (FMg) of spinel ranges from \u22128 to +11%./amu among the POIs but F_(Mg) is always either positive or negative within an individual POL Within a single inclusion, F_(Mg) of coexisting spinel is not constant but varies by up to 7%./amu. Isotopic fractionation of Mg in silicates is less common and always positive (F_(Mg) > 0). Pyroxenes in two POIs and plagioclase in a third contain isotopically heavy Mg. Radiogenic ^(26)Mg\u2217 is rare in POIs as only two inclusions show evidence of excess ^(26)Mg with ^(26)Mg^\u2217/^(27)Al ~ 4 \u00d7 10^(\u22126). The preservation of isotopic heterogeneity in objects whose igneous textures suggest crystallization from a homogeneous melt implies that melting was incomplete, allowing survival of relict phases. A comparison of the essential characteristics of POIs and CAIs suggests that the major processes leading to formation of POIs\u2014including condensation, dust/gas fractionation, aggregation of chemically and isotopically disparate materials, and partial melting\u2014are common to most CAIs and chondrules. We present a scenario for the formation of these objects and conclude that the homogeneity of the final assemblage\u2014CAI, POI, or chondrule\u2014is primarily a reflection of the thermal history rather than the nature of precursor materials.", "doi": "10.1016/0016-7037(91)90014-V", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1991-02", "series_number": "2", "volume": "55", "issue": "2", "pages": "581-599" }, { "id": "authors:k2eem-8aq84", "collection": "authors", "collection_id": "k2eem-8aq84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120821-102906151", "type": "article", "title": "Diffusion of water in rhyolitic glasses", "author": [ { "family_name": "Zhang", "given_name": "Youxue", "orcid": "0000-0002-7439-0086", "clpid": "Zhang-Youxue" }, { "family_name": "Stolper", "given_name": "E. M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Water dehydration experiments on rhyolitic glasses have been carried out at 400\u2013550\u00b0C under a N_2 atmosphere. Concentration profiles of both H_2O molecules and OH groups were measured by Fourier transform infrared spectroscopy. As found in previous studies of water diffusion in rhyolitic melts, the measured total water concentration profiles do not match expectations based on a single constant diffusion coefficient for total water.\nThe diffusion of total water is described by considering the diffusion of both H_2O molecules and OH groups and the reaction between them. The concentration relationship between the two species has been obtained from direct infrared measurement on quenched experimental charges. The quench is inferred to be rapid enough to preserve concentrations of both species at experimental temperature based on experimental results designed to examine reaction kinetics. The measured species concentrations along diffusion profiles show that local equilibrium between H_2O and OH is approximately reached at high temperatures and high water contents. However, at lower water content or lower temperature, local equilibrium is not reached. In treating the diffusion problem, this disequilibrium effect is partially compensated by using empirical relationships between H_2O and OH concentrations based on measurements, instead of using an equilibrium relationship. It is thus possible to obtain diffusion coefficients for both species from their concentration profiles. The diffusion coefficient of OH is found to be negligible compared to that of H_2O at 403\u2013530\u00b0C (D_(OH) < 0.02D_(H2O) and could be much smaller); i.e., H_2O is the dominant diffusing species even at total water concentration as low as 0.2 wt%. The variation of OH concentration along the diffusion profile is inferred to be due to the local interconversion between OH groups and H_2O molecules; the reaction also provides the diffusing H_2O species. D_(H2O) values are found to vary by less than a factor of 2 over a total water concentration range of 0.2 to 1.7 wt%. This simple model, coupled with the assumption of local equilibrium between H_2O and OH, yields a very good fit to the data from diffusion-couple experiments of Lapham et al. (1984) at 850\u00b0C. When our data are combined with D_(H2O) obtained from that fit, D_(H2O) (in m^2/s) is given by In D_(H2O) = (\u221214.59 \u00b1 1.59) \u2212 (103000 \u00b1 5000)/RT 673 K \u2264 T \u2264 1123 K where T is temperature in K and R is the gas constant in J K^(\u22121) mol^(\u22121). This equation also approximates well D_(H2O) values calculated from previous measurements of concentration-dependent bulk water diffusion coefficients of Karsten et al. ( 1982). The diffusion of H_2O is also compared to the diffusion of the noble gas elements. The activation energy for diffusion in rhyolitic glasses is well correlated with neutral species radii of He, Ne, H_2O, and Ar. This supports the contention that the diffusing species for \"water\" is neutral molecular H_2O. The role of speciation may also be important in understanding the diffusion of many other multi-species components, and the effect can be treated in a similar fashion as that during water diffusion.", "doi": "10.1016/0016-7037(91)90003-N", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1991-02", "series_number": "2", "volume": "55", "issue": "2", "pages": "441-456" }, { "id": "authors:hj9a7-mn760", "collection": "authors", "collection_id": "hj9a7-mn760", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-153926024", "type": "article", "title": "Negative thermal ion mass spectrometry of osmium, rhenium, and iridium", "author": [ { "family_name": "Creaser", "given_name": "R. A.", "clpid": "Creaser-R-A" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report on a technique for obtaining intense ion beams of negatively charged oxides of Os, Re and Ir by thermal ionization, in a conventional surface ionization mass spectrometer. It was found that the principal ion species of Os, Re and Ir produced are OsO_3^\u2212, ReO_4^\u2212 and IrO_2^\u2212. The sharp distinction in the masses of the dominant molecular species produced by this technique permits the measurement of isotopic compositions of each element from mixtures of platinum-group elements without significant isobaric interferences. For ^(187)Re-^(187)Os isotope studies, this technique offers the advantage of isotopic analyses without prior chemical separation of Re from Os, as no isobaric interference between the oxides of ^(187)Os and ^(187)Re exists under these conditions. For 4 ng Os, stable ion currents of 3 \u00d7 10^(\u221212) A can be maintained for over one hour, which allows determination of isotopic ratios with a Faraday collector to a precision of better than \u00b12\u2030 (2 \u03c3_m. For 70 pg Os, isotopic ratios can be measured with a precision of better than \u00b15\u2030 using a secondary electron multiplier. The detection limit for Os is estimated to be below 10^(\u221214) g. Osmium isotopic ratios have also been determined by direct loading of natural iridosmine with a precision of \u00b10.5\u2030 or better. We have obtained ionization efficiencies of 2\u20136% for Os and >20% for Re; these are superior to those reported for other techniques available to date and demonstrate that negative thermal ion mass spectrometry will have widespread application to ^(187)Re-^(187)Os chronometry and to studies of the geochemistry and environmental chemistry of the platinum-group elements.", "doi": "10.1016/0016-7037(91)90427-7", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1991-01", "series_number": "1", "volume": "55", "issue": "1", "pages": "397-401" }, { "id": "authors:swy3p-yha24", "collection": "authors", "collection_id": "swy3p-yha24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-154031184", "type": "article", "title": "Precise chronology of the last interglacial period:\n ^(234)U-^(230)Th data from fossil coral reefs in the Bahamas", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Curran", "given_name": "H. A.", "clpid": "Curran-H-A" }, { "family_name": "White", "given_name": "B.", "clpid": "White-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A detailed study of ^(238)U-^(234)U-^(230)Th ages was made for different coral species from two Bahamian reefs to determine the time scale of the sea-level high during the last interglacial period, using recently developed mass spectrometric techniques for the measurement of U and Th isotopes. Thirty-seven coral samples were analyzed in replicate. Typical errors at 125 ky are \u00b11.5 ky (2\u03c3), and 3-ky time intervals appear to be well resolved. This high precision permits detailed chronologic study with time resolution adequate to define stages of the reef's history. These data demonstrate that the time between transgression and regression of the ocean in the last interglacial was about 12 ky, after which sea level fell rapidly at more than \u223c2 m/ky. The high sea-level stand began possibly by 132 ky and certainly by 129 ky ago, when sea level reached \u223c6 m above present mean low sea level. High sea level was sustained until 120 ky and then fell rapidly. This time period covers the Milankovitch insolation peak at 65\u00b0N but is not sharply defined, and the sea-level high lasted from about 4 ky before the insolation peak to 8 ky after it. We find no evidence for a double peak of sea-level rise in the last interglacial episode (that is, high stands at both \u223c125 and 142 ky). There appears to be some discrepancy between this precise chronology for a coral reef on a tectonically stable platform and the chronology assigned to deep-sea sediments. The present results show that the duration of the last interglacial led to a 12-ky period of high sea-level stand which is much longer than the insolation peak.\nThe study area consists of two sizeable bank/barrier coral reefs of Sangamon age that crop out along the coast northwest of Cockburn Town on San Salvador Island and at Devil's Point on Great Inagua Island. The initial stage of reef development is not revealed at either site, but the main parts of both reefs are well preserved. At Cockburn Town, the beginning of the reef was marked by colonization of Acropora palmata on hardground areas and possibly other corals at 132 ky ago. Patch reefs at the southeastern flank of the developing reef were growing by 129 to 126 ky ago. By 126 to 123 ky ago, the crest of the reef was formed by the frame-building coral A. palmata, and associated patch reefs flourished along its flanks. A. palmata coral heads grew upward to a mean low sea level \u223c6 m above the present one. The reef began to decline as sea level dropped at about 123 to 120 ky ago.\nNear two measured profiles at Devil's Point, the top of a rubblestone, dominated by A. cervicornis, and patch-reef corals preserved in growth position have been beveled off and represent an ancient wave-cut surface. ^(230)Th ages on corals below and above this surface indicate that it was cut at about 125 \u00b1 1 ky ago.", "doi": "10.1130/0016-7606(1991)103<0082:PCOTLI>2.3.CO;2", "issn": "0016-7606", "publisher": "Geological Society of America", "publication": "Geological Society of America Bulletin", "publication_date": "1991-01", "series_number": "1", "volume": "103", "issue": "1", "pages": "82-97" }, { "id": "authors:np4ff-fhp93", "collection": "authors", "collection_id": "np4ff-fhp93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-111018862", "type": "article", "title": "^(234)U-^(238)U-^(230)Th-^(232)Th systematics in saline groundwaters from central Missouri", "author": [ { "family_name": "Banner", "given_name": "Jay L.", "clpid": "Banner-J-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Chen", "given_name": "James H.", "clpid": "Chen-J-H" }, { "family_name": "Moore", "given_name": "Clyde H.", "clpid": "Moore-C-H" } ], "abstract": "Saline groundwaters with 4.7 to 26\u2030 total dissolved solids were sampled from springs and artesian wells in Mississippian and Ordovician carbonates and sandstones in central Missouri. U\u2014Th isotopic variations provide a means of evaluating processes of water-rock interaction and fluid mixing and estimating the time scales of element transport. Recently developed mass spectrometric techniques are used to make isotopic measurements on small-volume groundwater samples (0.1\u20134 l) with high precision (e.g., < \u00b15% for ^(234)U/^(238)U activity ratios). The groundwaters have a wide range of ^(238)U concentrations, 50 \u00d7 10^(\u221212) to 200 \u00d7 10^(\u221212) g/g; ^(234)U/^(234)U activity ratios, 2.15\u201316.0; ^(232)Th concentrations, 0.10 \u00d7 10^(\u221212) to 33 \u00d7 10^(\u221212) g/g; and ^(230)Th concentrations, 0.91 \u00d7 10^(\u221217) to 26 \u00d7 10^(\u221217) g/g. Unfiltered and filtered (0.4 \u03bcm, 0.1 \u03bcm) aliquots of a saline sample have the same isotopic composition and concentration of U, indicating that ^(234)U and ^(238)U occur almost entirely as dissolved species. The concentration of ^(232)Th is up to seven times lower in filtered vs. unfiltered aliquots, indicating that ^(232)Th is predominantly associated with particulates in the groundwaters. In contrast, most of the ^(230)Th is in solution.\nPrevious geochemical studies indicate that: (1) the saline waters originated as meteoric recharge and evolved through halite dissolution, reactions with silicates and saline-dilute mixing processes during a long-distance flow history; and (2) interaction with limestone and dolomite aquifer rocks in central Missouri has been limited. A consistent relationship between U/Ca and ^(234)U/^(238)U activity ratio is observed in the groundwaters and provides constraints on the U/Ca ratios and ^(234)U/^(238)U activity ratios of end-member reservoirs and on the processes of isotopic exchange in this water-rock system. Model calculations that simulate (1) saline-dilute groundwater mixing and (2) limited extents of dissolution of carbonate aquifer minerals by the groundwaters can account for the variations in U/Ca, ^(234)U/^(238)U and ^(18)O/^(16)O in the suite of water samples. The model calculations demonstrate that dissolved U isotopic compositions can be a sensitive indicator of water-rock interaction, which in turn limits the usefulness of ^(234)U\u2014^(238)U disequilibria for groundwater age determinations. The concentration of dissolved ^(230)Th in the groundwaters is (1) two to three orders of magnitude below ^(230)Th\u2014^(234)U equilibrium activity levels, and (2) significantly in excess of concentrations estimated for the supply of Th to solution via desorption and dissolution. A model involving the derivation of the excess ^(230)Th from the in situ decay of dissolved ^(234)U in the groundwaters indicates the operation of an adsorption mechanism on the time scale of 10\u201310^3 years. The results reported here may have broader application to the assessment and management of hazardous chemical species in natural environments.", "doi": "10.1016/0012-821X(90)90161-P", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1990-12", "series_number": "2-4", "volume": "101", "issue": "2-4", "pages": "296-312" }, { "id": "authors:ah9fz-fcq44", "collection": "authors", "collection_id": "ah9fz-fcq44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140116-103258781", "type": "article", "title": "Secondary Neutral Mass Spectrometry Using Three-Colour Resonance Ionization: Osmium Detection at the p.p.b. Level and Iron Detection in Silicon at the < 200 p.p.t. Level", "author": [ { "family_name": "Pellin", "given_name": "M. J.", "clpid": "Pellin-M-J" }, { "family_name": "Young", "given_name": "C. E.", "clpid": "Young-C-E" }, { "family_name": "Calaway", "given_name": "W. F.", "clpid": "Calaway-W-F" }, { "family_name": "Whitten", "given_name": "J. E.", "clpid": "Whitten-J-E" }, { "family_name": "Gruen", "given_name": "D. M.", "orcid": "0000-0003-3270-7644", "clpid": "Gruen-Daniel-M" }, { "family_name": "Blum", "given_name": "J. D.", "clpid": "Blum-J-D" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "De Galan", "given_name": "L.", "clpid": "De-Galan-L" }, { "family_name": "Grasserbauer", "given_name": "M.", "clpid": "Grasserbauer-M" }, { "family_name": "Vickerman", "given_name": "J. C.", "clpid": "Vickerman-J-C" }, { "family_name": "Burns", "given_name": "D. T.", "clpid": "Burns-D-T" }, { "family_name": "Mantoura", "given_name": "R. F. C.", "clpid": "Mantoura-R-F-C" } ], "abstract": "Among the many uses of resonantly enhanced multiphoton ionization (REMPI) spectroscopy, secondary neutral mass spectrometry (SNMS) is both one of the most demanding and one of the most important. Recently, we have demonstrated that the selectivity of REMPI, and thus the sensitivity of SNMS, can be greatly enhanced by using resonant excitation schemes involving multiple resonant processes. Of particular interest is the use of autoionizing resonances, resonances with energies in excess of the ionization potential of the atom, in the REMPI process. The use of autoionizing resonances can reduce the laser intensity required to saturate the ionization process by more than an order of magnitude. This reduction can strongly reduce non-resonant ionization of background constituents, enhancing the signal to noise of the SNMS measurement. Although this approach to laser ionization SNMS is generally applicable, the three-colour ionization method has been demonstrated using two widely disparate yet important systems. Iron impurity atoms form deep level traps in Si, changing bulk electrical properties even at concentrations approaching 1 p.p.t. In this case, normal mass spectrometry of impurity atoms is complicated by the isobaric interference of 56Fe and 28Si2 molecule. The required mass resolution of greater than 104 exceeds the capabilities of most mass spectrometers. Even for instruments with sufficient mass resolution, the concomitant reduction in useful yield limits detection sensitivity in the near-surface region to 1 p.p.m. REMPI has now been successfully used to separately ionize the impurity atoms of interest. Three-colour REMPI dramatically reduces the residual non-resonant ionization of the isobarically interfering ion, allowing SNMS measurements at levels below 100 p.p.t. This result is accomplished without significant reduction in the fraction of contaminant atoms ionized and, therefore, in useful yield. Mass spectrometric analysis for Os and Re has long been recognized as an important analytical goal in geochemistry. The concentrations and isotopic compositions of these elements must be determined in order to utilize the radioactive decay of 187Re to 187Os (t1/2 = 4.23 \u00d7 1010 years) as a tracer of geochemical processes. Three problems have limited the analysis of Os and Re. First, the concentrations of Os and Re in naturally occurring samples are extremely low, ranging from 1 p.p.b. to 60 p.p.m. Second, the high-ionization potentials (IP) of Os (8.7 eV) and Re (7.9 eV) have precluded the use of thermal ionization and limited the sensitivity of secondary ion mass spectrometry (SIMS) measurement to parts per million. Finally, the 187Re/187Os mass difference is less than 1 p.p.m., making conventional mass analysis (without complex chemical separation) impossible. We have demonstrated the ability of three-colour resonant SNMS to detect and separate Os and Re in Ni samples at the 4 p.p.b. level. In situ analysis of Os in iron meteorites demonstrates an elemental selectivity of Os over Re of greater than 103 without prior chemical separation. Measurements on a suite of samples with Os concentration varying from 10 per thousand down to 100 p.p.b. show a linear correlation between concentration and signal with a precision of better than \u00b1 13% and a useful yield in excess of 1%. These results demonstrate the potential for three-colour resonant ionization to detect and selectively ionize most high IP elements, including all of the Pt group elements, with good sensitivity, accuracy, and precision.", "doi": "10.1098/rsta.1990.0143", "issn": "1364-503X", "publisher": "Royal Society of London", "publication": "Philosophical Transactions A: Mathematical, Physical and Engineering Sciences", "publication_date": "1990-10-15", "series_number": "1628", "volume": "333", "issue": "1628", "pages": "133-146" }, { "id": "authors:gqh9c-6ta95", "collection": "authors", "collection_id": "gqh9c-6ta95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-104549067", "type": "article", "title": "The role of plumes in mantle helium fluxes", "author": [ { "family_name": "Kellogg", "given_name": "L. H.", "clpid": "Hellogg-L-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We present a simple model of ^3He and ^4He transport in the mantle using the appropriate rates of mass and species transfer and ^4He production. Previous workers have shown the presence of excess ^3He in hotspots such as Hawaii and Iceland and inferred that these hotspots tap a source with a higher ^3He ^4He ratio than the source region of mid-ocean ridge basalts (MORB). Hotspot ocean islands probably originate over upwelling plumes which carry material from the lower mantle to the upper mantle. Melting at hotspots and at mid-ocean ridges degasses the mantle of volatiles such as helium. The upper mantle is outgassed largely of helium due to melting at mid-ocean ridges and hotspots. We postulate that the excess ^3He seen in MORB originates in material that was carried from the lower mantle in plumes but not completely outgassed at hotspots. This helium is incorporated into the depleted upper mantle. Assuming that the upper mantle is in a quasi-steady-state with respect to helium, a simple model balancing ^3He and ^4He fluxes in the upper mantle indicates that the hotspots significantly outgas the lower mantle of ^3He. The concentration of ^4He in the plume source reservoir is 2\u20133 orders of magnitude lower than the concentration in carbonaceous chondrites. The residence time of helium in the upper mantle depends on the outgassing efficiency at hotspots, since the hotspots may outgas some upper mantle material which has been entrained in the plumes. The residence time of He in the upper mantle is about 1.4 \u00d7 10^9 yr. We conclude that the efficiency of outgassing of He from plumes is high and that the plumes dominate the present ^3He loss to the atmosphere. The ^4He in the less depleted layer of the mantle is not trapped \"primordial\" but is predominantly from in situ decay of U and Th in the depleted layer over \u223c 1.4 \u00d7 10^9 yr. The ^4He in the lower mantle is dominantly from in situ decay of U and Th over 4.4 \u00d7 10^9 yr. This model appears to explain the total Ar in the atmosphere as there is about the same amount of K in the depleted mantle as is in the continents.", "doi": "10.1016/0012-821X(90)90116-F", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1990-08", "series_number": "3", "volume": "99", "issue": "3", "pages": "276-289" }, { "id": "authors:3qbag-p4y64", "collection": "authors", "collection_id": "3qbag-p4y64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120821-095022119", "type": "article", "title": "Crystal chemical effects on the partitioning of trace elements between mineral and melt: An experimental study of melilite with applications to refractory inclusions from carbonaceous chondrites", "author": [ { "family_name": "Beckett", "given_name": "John R.", "clpid": "Beckett-J-R" }, { "family_name": "Spivack", "given_name": "Arthur J.", "clpid": "Spivack-A-J" }, { "family_name": "Hutcheon", "given_name": "Ian D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "abstract": "The partitioning behavior of the trace elements Be, Sc, Ba, La, Ce, and Tm between melilite and liquid has been determined using stepwise integration of a Rayleigh fractionation equation for ion microprobe analyses of synthetic zoned melilite crystals. Distribution coefficients between melilite and liquid (D^(Mel/L)_i) were determined over the entire range of melilite + spinel crystallization for one bulk composition corresponding to that of an average Type B inclusion from the Allende C3V carbonaceous chondrite. Beryllium is incompatible in gehlenitic meliliters (e.g.,D^(Mel/L)B_e = 0.5 for X_(ak) = 0.3) but compatible in \u00e5kermanitic melilites (e.g., D^(Mel/L)B_e = 1.9 for X_(Ak) = 0.75). Barium (D^(Mel/L)B_a = 0.04-0.05), Sc (D^(Mel/L)S_c = 0.01-0.02), La (D^(Mel/L)L_\u03b1 \u2264 0.07-0.29), Ce (D^(Mel/L)C_e \u2264 0.05-0.21), and Tm (D^(Mel/L)T_m \u2264 0.03-0.14) are all incompatible in melilites in the range Ak25-Ak75. Variations in D^(Mel/L)i as a function of X_(Ak) are explicable in terms of a simple thermodynamic treatment of trace element partitioning based on crystal chemical considerations.\nCharacteristic trace element zoning patterns are predicted for early crystallizing melilite from meliliterich Type B inclusions. For example, concentrations of the REEs in melilite should continually decrease with increasing degrees of crystallization, opposite the behavior normally expected of an incompatible element. Concentrations of Be should rise with increasing degrees of crystallization even when the element is compatible, again opposite the behavior normally expected of compatible elements. In general, zoning patterns of trace elements in melilite from Type B inclusions are consistent with those predicted for fractional crystallization from a melt in a closed system. Trace element zoning patterns in meteoritic melilite crystals constrain the origin and thermal histories of Ca-, Al-rich inclusions from carbonaceous chondrites.", "doi": "10.1016/0016-7037(90)90406-B", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1990-06", "series_number": "6", "volume": "54", "issue": "6", "pages": "1755-1774" }, { "id": "authors:f4hjy-gpd53", "collection": "authors", "collection_id": "f4hjy-gpd53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-153824115", "type": "article", "title": "The isotopic composition of Ag in meteorites and the presence of ^(107)Pd in protoplanets", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of silver in the metal phase of several types of iron meteorites has been determined. The ratios of ^(107)Ag/^(109)Ag are found to range from the terrestrial value of 1.09 to 9.2. These results show the presence of excess ^(107)Ag (^(107)Ag^\u2217) in almost all iron meteorites studied with a ratio of ^(108)Pd/^(109) Ag greater than ~ 400. ^(107)Ag^\u2217 has been found in iron meteorites of types IVA-IVB, IIIA-IIIB, IIB, and some anomalous types. The typical ratio found is ^(107)Ag^*/^(108)Pd \u2248 2 X 10^(-5) in general agreement with the original report of Kelly and Wasserburg (1978). An intensive study of Gibeon (IVA) shows that the ^(107)Ag/^(109)Ag correlates with ^(108)Pd/^(109)Ag over a wide range for bulk samples of the metal rich phase and yield ^(107)Ag^*/^(108)Pd = (2.40 \u00b1 0.05) X 10^(-5) and an extrapolated initial (^(107)Ag/^(109)Ag)_0 = 1.11 \u00b1 0.01. This is considered to represent an isochron resulting from the in situ decay of ^(107)Pd (T_(\u00bd) = 6.5 X10^6) on the parent planet. The bulk sulfide shows ^(107)Ag^\u2217 uncorrelated with ^(108)Pd and a highly variable isotopic composition of Ag. This phenomena is not well understood. We interpret the sulfide data as partly due to diffusion transport of Ag and segregation into minor phases. Some of this complexity is due to recrystallization after shock melting of FeS and anthropogenic heat treatment. Several other IVA meteorites were analyzed with a wide range in Pd/Ag and all showed the presence of ^(107)Ag^\u2217. A sample of Santa Clara (IVB) metal was analyzed, and it was confirmed that this does not lie on the IVA correlation line. Analysis of metal, schreibersite, and sulfide from the unshocked meteorite Derrick Peak (IIB) shows a correlation of ^(107)Ag^\u2217 with ^(108)Pd and ^(107)Ag^*/^(108)Pd = 1.5 X 10^(-5) and initial(^(107)Ag/^(109)Ag)_0 = 1.092 \u00b1 0.002.\nThese observations demonstrate a correlation of ^(107)Ag^* with ^(108)Pd within samples of the metal phase of a single meteorite and for samples of different meteorites. These results are compatible with the model of decay of ^(107)Pd in the parent planets which initially contained normal Ag. The ^(107)Ag^* in the sulfide is attributed to diffusion, although this is not proven. The cooling rates for the parent bodies must have been much faster than 150\u00b0K/ma thus implying a radius less than ~30 km. The presence of 107Pd in the parent bodies implies that the time scale between production of ^(107)Pd and planet formation, melting, and cooling must be less than ~10^7a. A small but distinct variation in ^(107)Ag^* content exists among different meteorites. If this variation is interpreted to represent an age difference, then the present results indicate a maximum difference in age of ~4 \u00d7 10^7 a. The nuclide ^(107)Pd is inferred to have been widespread throughout the terrestrial-type protoplanets. While the nucleosynthetic origin of ^(107)Pd and ^(26)Al is distinct, their presence in the early solar system appears to fix the time scales for small planet formation relative to the nucleosynthetic sources that produced them. The observations are not consistent with a model in which protosolar material is mixed with ^(107)Ag^\u2217 from the previous decay of extinct ^(107)Pd in old interstellar dust grains. However, the presence of ^(26)Al in protoplanets is not yet established, nor is the heat source for the later melting and planetary differentiation established.", "doi": "10.1016/0016-7037(90)90404-9", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1990-06", "series_number": "6", "volume": "54", "issue": "6", "pages": "1729-1743" }, { "id": "authors:q509e-m8n86", "collection": "authors", "collection_id": "q509e-m8n86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-122031160", "type": "article", "title": "Insitu measurement of osmium concentrations in iron meteorites by resonance ionization of sputtered atoms", "author": [ { "family_name": "Blum", "given_name": "Joel D.", "clpid": "Blum-J-D" }, { "family_name": "Pellin", "given_name": "M. J.", "clpid": "Pellin-M-J" }, { "family_name": "Calaway", "given_name": "W. F.", "clpid": "Calaway-W-F" }, { "family_name": "Young", "given_name": "C. E.", "clpid": "Young-C-E" }, { "family_name": "Gruen", "given_name": "D. M.", "orcid": "0000-0003-3270-7644", "clpid": "Gruen-Daniel-M" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Resonance ionization of sputtered atoms followed by time-of-flight mass spectrometry was used for in situ quantitative measurement of Os with a spatial resolution of \u223c70 \u03bcm. Osmium concentrations in synthetic metals and iron meteorites were measured to demonstrate the analytical capabilities of the technique. A linear correlation between Os+ signal intensity and the known Os concentration was observed over a range of nearly 10^4 in Os concentration with an accuracy of \u223c \u00b110%, a minimum detection limit of 7 parts per billion atomic, and a useful yield of 1%. Resonance ionization of sputtered atoms samples the dominant neutral-fraction of sputtered atoms and utilizes multiphoton resonance ionization to achieve high sensitivity and to eliminate atomic and molecular interferences. Matrix effects should be small compared to secondary ion mass spectrometry because ionization occurs in the gas phase and is largely independent of the physical properties of the matrix material. Resonance ionization of sputtered atoms can be applied to in situ chemical analysis of most high ionization-potential elements (including all of the Pt-group elements) in a wide range of natural and synthetic materials. The high useful yield and elemental selectivity of this method should eventually allow the in situ measurement of Os isotope ratios in some natural samples and in sample extracts enriched in Pt-group elements by fire assay fusion.", "doi": "10.1016/0016-7037(90)90380-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1990-03", "series_number": "3", "volume": "54", "issue": "3", "pages": "875-881" }, { "id": "authors:v5bbc-q5r30", "collection": "authors", "collection_id": "v5bbc-q5r30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-091342721", "type": "article", "title": "Resonance ionization mass spectrometry of sputtered osmium and rhenium atoms", "author": [ { "family_name": "Blum", "given_name": "Joel D.", "clpid": "Blum-J-D" }, { "family_name": "Pellin", "given_name": "M. J.", "clpid": "Pellin-M-J" }, { "family_name": "Calaway", "given_name": "W. F.", "clpid": "Calaway-W-F" }, { "family_name": "Young", "given_name": "C. E.", "clpid": "Young-C-E" }, { "family_name": "Gruen", "given_name": "D. M.", "orcid": "0000-0003-3270-7644", "clpid": "Gruen-Daniel-M" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The mass spectrometric analysis of Os and Re was investigated\nby use of a pulsed primary Ar^+ ion beam to provide\nsputtered atoms for resonance ionization mass spectrometry.\nA useful yield of 10^(-2) and a detection limit of 8 ppb were\ndemonstrated for Os concentration measurement. In situ\nmeasurements of Os concentration are obtainable by this\nmethod at the sub-part-per-million level in conducting and\nsemiconducting materials with a full width at half maximum\nbeam diameter of ~70 \u00b5m. An ionization scheme for Os that\nutilizes three resonant energy levels (including an autoionizing\nenergy level) was investigated and found to have superior\nsensitivity and selectivity compared to nonresonant and one\nand two energy level resonant ionization schemes. An elemental\nselectivity for Os over Re of \u226510^3 was demonstrated.\nIt was found that detuning the ionizing laser from the autoionizing\nenergy level to an arbitrary region in the Ionization\ncontinuum resulted in a 5-fold decrease in signal intensity and\na 10-fold decrease in elemental selectivity.", "doi": "10.1021/ac00201a022", "issn": "0003-2700", "publisher": "American Chemical Society", "publication": "Analytical Chemistry", "publication_date": "1990-01-15", "series_number": "2", "volume": "62", "issue": "2", "pages": "209-214" }, { "id": "authors:yqh1m-ft578", "collection": "authors", "collection_id": "yqh1m-ft578", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140115-140311482", "type": "article", "title": "Seismic recurrence intervals and timing of aseismic subduction inferred from emerged corals and reefs of the Central Vanuatu (New Hebrides) Frontal Arc", "author": [ { "family_name": "Taylor", "given_name": "Frederick W.", "clpid": "Taylor-F-W" }, { "family_name": "Edwards", "given_name": "R. Lawrence", "clpid": "Edwards-R-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Frohlich", "given_name": "Cliff", "clpid": "Frohlich-C" } ], "abstract": "The recognition and dating of corals that have been killed by tectonic uplift allow us to date paleoseismic uplifts in the Vanuatu island arc. We recognize corals that record paleouplifts by their similarity to those known to have died during contemporary sudden uplifts and date them (1) by counting annual coral growth bands (only if part of the coral is alive at the time of collection) or (2) by newly developed techniques for obtaining ^(230)Th ages by mass spectrometry. The mass spectrometric method produces isotopic ages with precisions of \u00b13 to \u00b19 years (2\u03c3) in the 0\u20131000 years B.P. time range. The ^(230)Th ages in this time range appear to be accurate. Samples whose ages are known by counting coral growth bands give ^(230)Th ages that are indistinguishable from their growth band ages. By dividing the average increment of uplift for the latest Holocene uplifts by the mean Holocene uplift rate, we can estimate average seismic uplift recurrence intervals for the past 6000 years. The results for each of four central Vanuatu arc segments are (1) North Santo emerged 1.2 m in 1866 A.D. and 0.6 m 107 years later in 1973 A.D. The average coseismic uplift of 0.9 m and mean Holocene uplift rate of 4.3 mm yr^(\u22121) suggest a longer recurrence interval of 212 years. (2) South Santo emerged 0.29 m in 1946 and 0.26 m 19 years later in 1965, including the related 1971 event. Here the mean Holocene uplift rate is 5.5 mm yr^(\u22121). The uplift data suggest a longer average recurrence interval of about 51 years. (3) North Malekula emerged 1.23 m near 1729 A. D. and 1.05 m 236 years later in 1965. The mean Holocene uplift rate of 2.7 mm yr^(\u22121) and mean coseismic uplift of 1.14 m for dated events suggest a longer recurrence interval of 422 years. (4) Part of southernmost Malekula has uplifted continuously or episodically by about 0.35 m from about 1957 until at least mid-1983 A.D. The maximum uplift of 2.7 mm yr^(\u22121) occurs near a nest of small earthquakes. Both the earthquakes and rapid uplift suggest that interplate slip beneath south Malekula may be continuous, rather than episodic. Episodes of 0.35 m uplift would have to recur every 130 years to maintain the 2.7 mm yr^(\u22121) uplift rate. In contrast, we find no evidence of interseismic vertical movements for the other three blocks. The most reasonable interpretation of these results is that the seismic recurrence intervals and processes for accommodation of slip are quite different on adjacent arc segments. We have used the most widely accepted moment magnitude relationship to evaluate the accumulated seismic slip caused by large earthquakes occurring since 1920. In all four arc segments this analysis suggests that the seismically radiated moments account for less than one-third to one-tenth of the slip associated with plate convergence. The similarity between the paleoseismic record of uplifts and the contemporary record of coseismic uplifts suggests that this analysis can be generalized to times before 1920. For the northern three segments of central Vanuatu, aseismic slip probably occurs in the same years as large earthquakes because the contemporary coral record records uplifts only in years having large historic earthquakes. This suggests that aseismic slip is not continuous and does not occur at rates which vary slowly over the course of the earthquake cycle. The south Santo segment may have the highest proportion of seismic slip because the mean recurrence interval of 51 years is shortest and the mean Holocene uplift rate of at least 5.5 mm yr^(\u22121) is the fastest.", "doi": "10.1029/JB095iB01p00393", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1990-01-10", "series_number": "B1", "volume": "95", "issue": "B1", "pages": "393-408" }, { "id": "authors:30ky5-fny64", "collection": "authors", "collection_id": "30ky5-fny64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140211-134525003", "type": "article", "title": "Neodymium and strontium isotopic characteristics of New Zealand granitoids and related rocks", "author": [ { "family_name": "Pickett", "given_name": "David A.", "clpid": "Pickett-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Initial ^(87)Sr/^(86)Sr and ^(143)Nd/^(144)Nd ratios of Phanerozoic granitoids and related intrusions of the New Zealand block display a mixing-type array indicative of the involvement in their sources of old continental crustal material, most likely of Proterozoic age.\u025b Sr(T) values range from \u22124 to +273 (^(87)Sr/^(86)Sr=0.7041\u20130.7233), while \u025b Nd(T) ranges from +2.7 to \u221211.0. Preexisting metasedimentary rocks have generally higher \u025b_Sr and lower \u025b_Nd (ranging to present-day values of +646 and \u221215.0, respectively), and, particularly for the Mesozoic intrusives, are isotopically appropriate mixing end-members. The widespread, early Paleozoic Greenland Group graywackes, which are derived from Proterozoic sources, are modeled as the source of the crustal end-member mixing with mantle-derived mafic magmas to produce the intrusive rocks. Four different types of models are applied to the isotopic and trace-element (Rb, Sr, Ba, REE) data: simple mixing; mixing with a partial melt of the metasedimentary rock, with or without isotopic equilibrium; and assimilation-fractional crystallization. Based on these models, some constraints may be applied on petrogenesis (e.g., the lack of high Rb concentrations points to the presence of biotite, and HREE depletion points to the presence of garnet); however, the models fail to adequately explain all the data. The New Zealand granitoids show similarities in isotopic character not only to rocks from offshore islands on the New Zealand block, but also to similar-aged granitoids in adjacent regions of Antarctica and Australia. This points to similarities in crustal character between continental blocks formerly proximal in Gondwanaland. We note an overall increase in \u025b_Nd and decrease in \u025b_Sr in felsic magmas from the Paleozoic to the Mesozoic to the Cenozoic in New Zealand, indicative of a decrease over time in the level of influence of recycled continental crust in subduction-related magmatism.", "doi": "10.1007/BF00378499", "issn": "0010-7999", "publisher": "Springer", "publication": "Contributions to Mineralogy and Petrology", "publication_date": "1989-10", "series_number": "2", "volume": "103", "issue": "2", "pages": "131-142" }, { "id": "authors:b0k2k-yyk73", "collection": "authors", "collection_id": "b0k2k-yyk73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-102453585", "type": "article", "title": "The presence of ^(146)Sm in the early solar system and implications for its nucleosynthesis", "author": [ { "family_name": "Prinzhofer", "given_name": "A.", "clpid": "Prinzhofer-A" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The presence of the p-process nucleus ^(146)Sm (mean life, r = 149 x 10^6 yr) in the early solar system and its in situ \u0251-decay into ^(142)Nd is demonstrated by the correlation of ^(142)Nd/^(144)Nd with ^(144)Sm/^(144)Nd in two meteorites which have a large range in ^(144)Sm/^(144)Nd in their constituent mineral phases. Clear excesses of ^(142)Nd/^(144)Nd, relative to the solar system value, are present in high Sm/Nd phases and a clear deficit of ^(142)Nd/^(144)Nd is observed in one sample with low Sm/Nd. The inferred abundance of ^(146)Sm/^(144)Sm is 0.008 at the time of the last equilibration of each meteorite at 4.47 AE ago, which yields ^(146)Sm/^(144)Sm ~0.015 at the time of formation of the solar system, 4.56 AE ago. These results confirm the presence of ^(146)Sm and provide a well defined initial abundance for ^(146)Sm. The abundance of ^(146)Sm is compatible with the p-process production rate estimates but not with the production rate for ^(146)Sm based on a photodisintegration model for the production of p-process nuclides.", "doi": "10.1086/185536", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1989-09-15", "series_number": "2", "volume": "344", "issue": "2", "pages": "L81-L84" }, { "id": "authors:r9kmr-63662", "collection": "authors", "collection_id": "r9kmr-63662", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140416-103522247", "type": "article", "title": "Nd and Sr isotopic evidence for the origin of tektite material from DSDP site 612 off the New Jersey coast", "author": [ { "family_name": "Stecher", "given_name": "O.", "clpid": "Stecher-O" }, { "family_name": "Ngo", "given_name": "H. H.", "clpid": "Ngo-Henry-H-Meteoritics" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Late Eocene tektite material from DSDP site 612 is composed of angular to spherical tektites and microtektites containing abundant vesicles and a few unmelted to partially melted mineral inclusions. The major element compositions of the 612-tektites are generally comparable to those of North American tektites, but the physical features suggest that the DSDP-612 tektites were formed by less severe shock melting. The ^(87)Sr/^(86)Sr and ^(143)Nd/^(144)Nd compositions of 612-tektites: a) show much wider ranges than the tightly constrained group of North American tektites and microtektites, and b) are significantly different from those of other groups of tektites. The existence of large isotopic variations in tektites from DSDP site 612 requires that they were formed from a chemically and isotopically heterogeneous material in a regime that is distinctive from that of other groups of tektites. T^(ND)_(CHUR) and T^(Sr)_(UR) model ages of the 612-tektites indicate that they were formed from a crustal source of late Precambrian mean age (800\u20131000 Ma) which in middle Palaeozoic time (\u2245400 Ma) was further enriched in Rb/Sr during sedimentary processes. These source characteristics suggest that the impact which produced the 612-tektites occurred in rocks of the Appalachian orogeny or sediments derived from this orogenic belt. Potential source materials for both 612-tektites and North American tektites are present on the eastern and southeastern part of the North American continent and its adjacent shelf. The distinct isotopic differences between 612-tektites and North American tektites indicate that the two groups of tektites were either formed by the impact of more than one bolide in the same general area, or by a single impact event that sampled different layers.", "doi": "10.1111/j.1945-5100.1989.tb00949.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1989-06", "series_number": "2", "volume": "24", "issue": "2", "pages": "89-98" }, { "id": "authors:egp64-71s45", "collection": "authors", "collection_id": "egp64-71s45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-121937453", "type": "article", "title": "Isotopic and trace element constraints on the origin and evolution of saline groundwaters from central Missouri", "author": [ { "family_name": "Banner", "given_name": "Jay L.", "clpid": "Banner-J-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Dobson", "given_name": "Patrick F.", "clpid": "Dobson-P-F" }, { "family_name": "Carpenter", "given_name": "Alden B.", "clpid": "Carpenter-A-B" }, { "family_name": "Moore", "given_name": "Clyde H.", "clpid": "Moore-C-H" } ], "abstract": "Na-Ca-Cl groundwaters with salinities of 1 to 30% discharge from natural springs and artesian wells in Mississippian carbonates and Ordovician sandstones and carbonates in central Missouri. Carbonate saturation and quartz supersaturation are maintained throughout the salinity range. Major and trace element and isotopic variations in the waters are used to place constraints on models for rock-water interaction and regional hydrology.\n\nThe groundwaters have \u03b4D values that range from \u2212108 to \u221245\u2030 and \u03b4^(18)O values that range from \u221214.7 to \u22126.5\u2030 (SMOW). These data lie approximately along the meteoric water line, ranging from values similar to local recharge in Missouri, to significantly lower values that are similar to \u03b4^(18)O and \u03b4D for meteoric recharge in high altitude and high latitude regions of North America. The more saline samples have the lowest ^(18)O and D contents, a trend that is opposite to that observed in most other studies of saline waters. The H-O isotopic correlation and the range in salinity and several major and trace element concentrations in central Missouri groundwaters are readily explained by a saline-dilute water mixing model. 87Sr/86Sr ratios for the groundwaters range from 0.7155 to 0.7161. These values are significantly higher than previously published values for: 1) estimates of ^(87)Sr/^(86)Sr in Phanerozoic seawater (0.7068\u20130.7092); and 2) carbonates of the Mississippian Burlington-Keokuk Fm. (0.7075\u20130.7105), through which some of the waters migrate as they pass to the surface. \u03f5Nd(0) values in the groundwaters range from \u221210.9 to \u22128.1, and ^(147)Sm/^(144)Nd ratios range from 0.108 to 0.128. These values are similar to or lower than previously published analyses of carbonates and other authigenic phases from the Burlington-Keokuk Fm. (mean \u03f5Nd(0) = \u22127.8 \u00b1 0.8 (1\u03c3); mean ^(147)Sm/^(144)Nd = 0.141).\n\nThe H, O, Sr and Nd isotopic data and the results of model calculations preclude: 1) models involving the modification of ancient seawater for the origin of the saline waters, and 2) extensive interaction between the groundwaters and their host carbonates. The waters apparently acquired their \u03b4^(18)O and \u03b4D values as meteoric recharge and their 87Sr/86Sr and rare earth element signatures from extraformational crustal sources (high ^(87)Sr/^(86)Sr; low \u03f5Nd(0); low 147Sm/144Nd) and largely preserved these isotopic signatures during subsequent migration through the carbonates. Chemical exchange via rock-water interaction is required for isotopic exchange to occur. Therefore, the present state of chemical equilibrium between the groundwaters and carbonate aquifer minerals may serve to limit rock-water interaction, and hence preserve the extraformational isotopic signatures in the waters.\n\nThe integration of geochemical, isotopic and hydrologic data on a local and regional scale suggests a history for the central Missouri groundwaters involving: 1) meteoric recharge in the Front Range of Colorado; 2) dissolution of Permian halite in the subsurface of Kansas; 3) interaction with predominantly silicate mineral assemblages in Paleozoic strata (and possibly Precambrian basement), with aquisition of crustal Sr and REE signatures; 4) dilution and migration to shallow aquifer levels in central Missouri; and 5) mixing with local meteoric recharge through Mississippian carbonates with no significant change of the isotopic signatures acquired in stage (3).", "doi": "10.1016/0016-7037(89)90390-6", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1989-02", "series_number": "2", "volume": "53", "issue": "2", "pages": "383-398" }, { "id": "authors:34n7y-j2y66", "collection": "authors", "collection_id": "34n7y-j2y66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120821-154919308", "type": "article", "title": "Origin of opaque assemblages in C3V meteorites: Implications for nebular and planetary processes", "author": [ { "family_name": "Blum", "given_name": "Joel D.", "clpid": "Blum-J-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Beckett", "given_name": "J. R.", "clpid": "Beckett-J-R" }, { "family_name": "Stolper", "given_name": "E. M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "abstract": "Mineral phases from opaque assemblages (OAs) in Ca, Al-rich refractory inclusions (CAIs), chondrules and matrix in C3V meteoites were chemically analyzed and compared with experimentally determined phase equilibria and partitioning data in the Ni-Fe-S, Ni-Fe-S and Ni-Fe-O systems to estimate the temperature, sulfur fugacity (f_(S2)) and oxygen (f_(O2)) of OA formation. The kinetics of dissolution and exsolution of metallic phases in the Ni-Fe-Ru system were used to constrain the thermal history of OAss that occur in CAIs. Based on this work, we suggest that OAs formed after the crystallization of host CAIs by exsolution, sulfidation and oxidation of precursor alloys at low temperatures (~ 770 K) and higher than solar gas f_(S2) and f_(S2). Our model contrasts with previous models that call upon the formation of CAI OAs by aggregation of previously formed phases in the solar nebula prior to the crystallization of CAIs. Opaque assemblages in CAIs and chondrules probably originated as homogeneous alloys during melting of the silicate protions of CAIs and chondrules. The compositions of these precursor alloys reflect high-temperature and low-f_(O2) conditions in the early solar nebula. The similarities in the temperature, f_(S2) and f_(O2) of equilibrium for OAs that occur in CAIs, chondrules and matrix suggest that these three components of C3V meteorites share a common, late low-temperature history. The mineral phases in OAs do not preserve an independent history prior to CAI and chondrule melting and crystallization, but instead provide important information on the post-accretionary history of C3V meteorites and allow us to quantify the temperature, f_(S2) and f_(O2) of cooling planetary environments.", "doi": "10.1016/0016-7037(89)90404-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1989-02", "series_number": "2", "volume": "53", "issue": "2", "pages": "543-556" }, { "id": "authors:kaq8s-45h94", "collection": "authors", "collection_id": "kaq8s-45h94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120821-154758315", "type": "article", "title": "Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system", "author": [ { "family_name": "Blum", "given_name": "Joel D.", "clpid": "Blum-J-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Beckett", "given_name": "J. R.", "clpid": "Beckett-J-R" }, { "family_name": "Stolper", "given_name": "E. M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "abstract": "The diffusion coefficient for Ru in Ni (D_(Ni)^(Ru)) was determined by the thin-film diffusion method in the temperature range of 1073 to 1673 K and is given by the expression: D^(Ru)_(Ni)(cm^2 sec^(\u22121))=5.0 (\u00b10.7)\u00b710^(\u22123) exp[\u22122.3(\u00b10.1)\u00b710^(12) erg mole^(\u22121)/RT] where R is the gas constant and T is the temperature in K. Phase boundaries and tie lines in a Ni-Fe-Ru-rich system were determined at 1273, 1073 and 873 K. A wide miscibility gap is present at each temperature, separating a close-packed hexagonal \u03f5Ru-Fe phase from a face-centered cubic \u03b3Ni-Fe phase, The partitioning behavior of Pt and Ir between phases in a Ni-Fe-Ru-rich system and V between phases in a Ni-Fe-O-rich system was determined at 873 K. Pt partitions preferentially into the \u03b3Ni-Fe phase, whereas Ir prefers the \u03f5Ru-Fe phase. V partitions strongly into Fe oxides relative to \u03b3Ni-Fe. The experimental results have applications in the fields of meteoritics, ore-deposit geology and materials science.", "doi": "10.1016/0016-7037(89)90399-2", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1989-02", "series_number": "2", "volume": "53", "issue": "2", "pages": "483-489" }, { "id": "authors:r1am6-7w194", "collection": "authors", "collection_id": "r1am6-7w194", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141105-083239997", "type": "article", "title": "Richard P. Feynman 1918-1988", "author": [ { "family_name": "Reiff", "given_name": "Patricia H.", "clpid": "Reiff-P-H" }, { "family_name": "Feynman", "given_name": "Joan", "clpid": "Feynman-J" }, { "family_name": "Gold", "given_name": "Thomas", "clpid": "Gold-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Sheeley", "given_name": "Neil R., Jr.", "orcid": "0000-0002-6612-3498", "clpid": "Sheeley-N-R-Jr" }, { "family_name": "Akasofu", "given_name": "S.-I.", "clpid": "Akasofu-S-I" } ], "abstract": "Richard Feynman, simply put, was a genius. His quick wit and uncommon grasp of physics meant that any research area he encountered, he quickly mastered. Despite the fact that his own area of research was not geophysics, his life and work influenced almost all of us.\n\nVirtually every physics graduate student who started in the mid 60s or later was exposed to his Lectures on Physics, either by having them as a text for a course or by using them (as I did) to bone up for oral qualifying exams. Feynman diagrams appear in nearly every modern quantum mechanics textbook and are featured in his official Caltech portrait, which illustrates this article.", "doi": "10.1029/88EO01239", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "1988-12-20", "series_number": "51", "volume": "69", "issue": "51", "pages": "1649-1657" }, { "id": "authors:efsbx-pa434", "collection": "authors", "collection_id": "efsbx-pa434", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-122118106", "type": "article", "title": "Neodymium isotopic composition of the Mediterranean outflow\n and the eastern North Atlantic", "author": [ { "family_name": "Spivack", "given_name": "Arthur J.", "clpid": "Spivack-A-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The neodymium concentration and isotopic composition of the Mediterranean outflow in the Strait of Gibraltar has been directly determined. The outflow has a dissolved Nd concentration of ~23 pmoles/kg with \u03f5_Nd(0) = \u22129.4. These results are in clear disagreement with previous values inferred for the Mediterranean. This concentration and \u03f5_Nd(0) do not sharply contrast with North Atlantic Deep Water (NADW) values and can produce isotopic anomalies no larger than 1 \u03f5 unit in the North Atlantic. A new profile in the eastern North Atlantic does not exhibit an \u03f5_Nd(0) anomaly at the depth of the Mediterranean Water core, in accordance with the above inferences, while concentrations and \u03f5Nd(0) at this site indicate that Nd is conservative in the deep eastern North Atlantic. A previously reported \u03f5Nd(0) anomaly in the eastern North Atlantic, originally associated with the Mediterranean outflow, has a different source. The direct contribution of the Mediterranean outflow to the NADW Nd budget is small, ~10% of the high latitude sources. However, the outflow plus entrained water supply ~30% of the total Nd associated with northern latitude deep water sources.\n\nConcentrations of dissolved Nd in the outflow are enriched compared to the Atlantic inflow, which has 16 pmoles/ kg with \u03f5_Nd(0) = \u221211.8. The principal source of the excess dissolved Nd is inferred to be partial dissolution of detrital particles. Simple mass balance calculations suggest that ~0.6% of the Nd associated with detrital river-transported sediments and/or ~3.5% of the Nd associated with eolian particles delivered to the Mediterranean is mobilized during passage into the marine environment. If general, these mobilization efficiencies imply that the dissolution of detrital particles is a significant source of dissolved Nd (and other rare earth elements) in seawater.", "doi": "10.1016/0016-7037(88)90144-5", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1988-12", "series_number": "12", "volume": "52", "issue": "12", "pages": "2767-2773" }, { "id": "authors:dgh14-d7r79", "collection": "authors", "collection_id": "dgh14-d7r79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131025-154223555", "type": "article", "title": "Dating earthquakes with high-precision thorium-230 ages of very young corals", "author": [ { "family_name": "Edwards", "given_name": "R. Lawrence", "clpid": "Edwards-R-L" }, { "family_name": "Taylor", "given_name": "F. W.", "clpid": "Taylor-F-W" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Mass spectrometric techniques have recently yielded significant increases in precision and sensitivity over previous methods for measuring ^(230)Th abundance in corals. To assess the accuracy of ^(230)Th ages, three corals from Vanuatu, whose ages were known from counting annual growth bands, were analyzed. For each sample, the date of growth determined by ^(230)Th analysis (A.D.1969 \u00b1 3, 1932 \u00b1 5,and1806 \u00b1 5; 2\u03c3 uncertainties based on analytical error) was indistinguishable from the date determined by counting bands (A.D. 1971\u20131973, 1935\u20131937, and 1804\u20131810), indicating that the ^(230)Th dates are accurate. ^(230)Th dates were also determined for two adjacent emerged heads from Santo Is., Vanuatu, which were thought to have died when they were raised above sea level during coseismic uplift. The dates (A.D.1864 \u00b1 4, 1866 \u00b1 4) were the same, indicating that the heads died at the same time and consistent with the idea that they were killed by coseismic emergence around A.D. 1865. The difference between this date and the date of the only major historically documented earthquake that caused uplift (A.D. 1973,M_s = 7.5), suggests a seismic recurrence interval of108 \u00b1 4y for Santo. Analogous emerged corals from Malekula Is., Vanuatu yielded ^(230)Th dates that were similar to each other (A.D.1729 \u00b1 3, 1718 \u00b1 5) and are inferred to have died during coseismic emergence around A.D. 1729. In conjunction with the date of the only large historically documented earthquake that caused uplift (A.D. 1965,M_s = 7.5), the recurrence interval for Malekula is236 \u00b1 3y. If similar emerged corals can be found, this appraoch may be extended back in time and to other localities because it appears that such features can now be dated both accurately and precisely.", "doi": "10.1016/0012-821X(88)90136-7", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1988-11-25", "series_number": "4", "volume": "90", "issue": "4", "pages": "371-381" }, { "id": "authors:kmv2b-01m85", "collection": "authors", "collection_id": "kmv2b-01m85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130418-101601905", "type": "article", "title": "Mantle-derived fluids in diamond micro-inclusions", "author": [ { "family_name": "Navon", "given_name": "O.", "clpid": "Navon-O" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Rossman", "given_name": "G. R.", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Micro-inclusions in diamonds from Zaire and Botswana differ in composition from the more common large inclusions of the peridotitic or eclogitic assemblages. These sub-micrometre inclusions resemble potassic magmas in their composition, but are enriched in H_2O, CO^(2\u2212)_3 and K_2O and depleted in MgO. This composition represents a volatile-rich fluid or melt from the upper mantle, which was trapped in the diamonds as they grew.", "doi": "10.1038/335784a0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1988-10-27", "series_number": "6193", "volume": "335", "issue": "6193", "pages": "784-789" }, { "id": "authors:hzvac-48d63", "collection": "authors", "collection_id": "hzvac-48d63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140909-123651045", "type": "article", "title": "Correlated Isotope Fractionation and Formation of Purple FUN Inclusions", "author": [ { "family_name": "Brigham", "given_name": "C. A.", "clpid": "Brigham-C-A" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Allende coarse-grained inclusions characterized by a distinct purple color and high spinel contents (\u2264 50 vol.%) exhibit a higher frequency of FUN isotopic anomalies (\u224820%) than the general CAI population (\u22646%). We used the ion microprobe to measure Mg, Si, Cr and Fe isotopic compositions of three Purple Spinel-rich Inclusions (PSI = \u03c8) which are petrographically similar to Type B CAl to investigate: 1) variations in isotopic fractionation within inclusions, including secondary phases; 2) correlated isotopic fractionation; and 3) excess ^(26)Mg.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1988-09", "volume": "23", "pages": "260-261" }, { "id": "authors:tbrs0-nbe08", "collection": "authors", "collection_id": "tbrs0-nbe08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140204-075447076", "type": "article", "title": "Somewhere Over the Rainbow", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The study of meteorites has produced a wealth of information about\nthese objects. Petrologic and chemical observations of meteorites have\nshown the presence of planetary differentiates and of undifferentiated\naggregates resulting from nebular condensation and the interaction of\nthese aggregates due to metamorphism. Equilibrium chemistry in a solar\ngas and in planetary environments has been an excellent guide to our\nstudies. Studies by several groups have yielded remarkable discoveries\nabout the early stages of planetary evolution and of precursor components\nfrom the solar nebula and from the interstellar medium (ISM).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1988-09", "series_number": "3", "volume": "23", "issue": "3", "pages": "308-309" }, { "id": "authors:k3cq4-3hn61", "collection": "authors", "collection_id": "k3cq4-3hn61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-134157384", "type": "article", "title": "High Precision Mass Spectrometric Determinations of ^(234)U & ^(230)Th: Application to Quaternary Geology", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Conventionally, the U-series dating methods involve\nmeasuring the activity of U and its daughter nuclides. It is well-known that measuring all the nuclides in a sample as compared to counting only the activity can result in a substantial increase in sensitivity (e.g., ^(14)C and ^(10)Be.", "doi": "10.1016/0009-2541(88)90703-6", "issn": "0009-2541", "publisher": "Elsevier", "publication": "Chemical Geology", "publication_date": "1988-08-01", "series_number": "1-2", "volume": "70", "issue": "1-2", "pages": "173-173" }, { "id": "authors:tcq8n-zjw76", "collection": "authors", "collection_id": "tcq8n-zjw76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-103005393", "type": "article", "title": "Endemic silver isotopic anomalies in iron meteorites", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The discovery of excess ^(107)Ag (^(107)Ag*) was made\nin a IVB iron meteorite ten years ago. The ^(107)Ag*\nanomaly is inferred to be due to decay of ^(107)pd\n(t_(1/2)=6.5 10^6 y) and appears to provide a chronometer\nfor the timescale of early planet formation and differentiation.", "doi": "10.1016/0009-2541(88)90247-1", "issn": "0009-2541", "publisher": "Elsevier", "publication": "Chemical Geology", "publication_date": "1988-08-01", "series_number": "1-2", "volume": "70", "issue": "1-2", "pages": "24-24" }, { "id": "authors:6c19y-tqx79", "collection": "authors", "collection_id": "6c19y-tqx79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140909-141501428", "type": "article", "title": "Diffusion of Water in Silicate Melts", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The transport of water in silicate melts is examined from a theoretical point of view, taking into account the presence of both H_2O and OH^- species. It was assumed that only H_2O molecules may diffuse and that a constitutive relationship between the number density nH_2O of H_2O molecules and the total water content (n_\u03a3) exists such that nH_2O = g(n_\u03a3). This is related to dissociation or to chemical reactions such as H_2O molecular (melt) + Oxygen (melt) \u21cc 2 OH (melt). This approach leads to diffusion transport equations that are intrinsically nonlinear. Three regions are naturally defined: (I) high water content with a normal linear diffusion equation an: \u2202n_\u03a3/\u2202t = DV^2n_\u03a3, where D is the intrinsic diffusion coefficient of a H_2O molecule in the silicate; (II) an intermediate or transitional region where the transport equation is \u2202n_\u03a3/\u2202t = DV^2g(n_\u03a3); and (III) a region of low water concentration where the transport equation is an: \u2202n_\u03a3/\u2202t = D^*V^2n^2_\u03a3. In the latter region, the equation is strongly nonlinear. D^* is a constant diffusion coefficient related to D. It follows that the dissociation of water molecules to form OH^- in silicates automatically implies a nonlinear transport behavior due to the storage of dissociated water molecules in immobile sites. This study of the kinetics of\ntransport will aid in our understanding of speciation and structure in silicate melts.", "issn": "0022-1376", "publisher": "University of Chicago Press", "publication": "Journal of Geology", "publication_date": "1988-05", "series_number": "3", "volume": "96", "issue": "3", "pages": "363-367" }, { "id": "authors:7ne51-73m17", "collection": "authors", "collection_id": "7ne51-73m17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140305-135601573", "type": "article", "title": "Tribute to Carleton Moore", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "This issue of Meteoritics presents a new format and a new\neditor. It represents change and growth of the diverse interests\nof The Meteoritical Society, but it is based on the traditions of\nthe Society and the solid foundation which has been established\nby Carleton B. Moore. His footprint (or regmaglypt) first appeared\non the color-coded covers of Meteoritics in 1969-the\nyear of Allende and Apollo. For almost two decades, the editor\nwas Carleton Moore and the focus of the Society was seated at\nthe Center for Meteorite Studies at Arizona State University.\nThe tradition which grew out of the fabulous Nininger collection\nand the careful but good-humored attention to the science and\nto the journal by Carleton have helped us grow to where we are\ntoday. We have remained a small society with excellent meetings\nfull of scientific excitement and a good journal which does not\nweigh a kilogram. Meteoritics is the only journal that does not\nthreaten me with overfilling my bookshelves.", "doi": "10.1111/j.1945-5100.1988.tb00902.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1988-03", "series_number": "1", "volume": "23", "issue": "1", "pages": "97-97" }, { "id": "authors:cyabh-7h097", "collection": "authors", "collection_id": "cyabh-7h097", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120824-093146326", "type": "article", "title": "'Domestic' origin of opaque assemblages in refractory inclusions in meteorites", "author": [ { "family_name": "Blum", "given_name": "Joel D.", "clpid": "Blum-J-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hutcheon", "given_name": "Ian D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Beckett", "given_name": "John R.", "clpid": "Beckett-J-R" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "abstract": "Experimental studies indicate that opaque assemblages rich in refractory siderophile elements were formed within host calcium- and aluminium-rich inclusions (CAIs) by exsolution, oxidation and sulphidization of homogeneous alloys, rather than by aggregation of materials in the solar nebula before the formation of CAIs. These opaque assemblages are thus not the oldest known solid materials, as was once thought, and they do not constrain processes in the early solar nebula before CAI formation. Instead, the assemblages record the changing oxygen fugacity experienced by CAIs during slow cooling in nebular and/or planetary environments.", "doi": "10.1038/331405a0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1988-02-04", "volume": "331", "pages": "405-409" }, { "id": "authors:5wmhg-s3j82", "collection": "authors", "collection_id": "5wmhg-s3j82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130313-091753466", "type": "article", "title": "An Experimental Study of Metallic Diffusion and Phase Equilibria in Fremdlinge", "author": [ { "family_name": "Blum", "given_name": "J. D.", "clpid": "Blum-J-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Hutcheon", "given_name": "I. E.", "clpid": "Hutcheon-I-E" }, { "family_name": "Beckett", "given_name": "J. R.", "clpid": "Beckett-J-R" }, { "family_name": "Stolper", "given_name": "E. M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "abstract": "Fremdlinge are opaque assemblages within CAis that are mainly composed of NiFe metal, V-magnetite and \u00b5m-sized RuOs nuggets. The prevailing scenario for their origin includes condensation, aggregation and equilibration at low T (\u227e 600\u00b0C); they are then thought to be introduced into CAis at high T, followed by rapid cooling, thereby preserving the textures and assemblages from the pre-CAl, low T histories (Armstrong et al., 1985; Armstrong et al., 1987). A constraint on cooling rates of Fremdlinge comes from sharp contacts observed between RuOs nuggets and NiFe\nmetals that enclose them. To determine the length of time that these contacts could have been held at high T, thin-film diffusion experiments were conducted with an\nelectroplated Ru film on Ni. Samples were annealed at 1400, 1200, 1000 and 800\u00b0C for 0.3-137 hours. Measured Ru profiles in Ni were consistent with the following Arrhenius expression: D(cm^2/sec) = 0.0050exp(-2.3 x 10^(12)/RT) (T in K, R in Cgs units). Based on these data, we calculate that cooling rates of \u2273 10^5C/hr are necessary to preserve sharp contacts between RuOs and NiFe metals if they experienced the T of CAl melting (~ 1400\u00b0C) (Stolper and Paque, 1986). We consider this rate unreasonable in light of cooling rates inferred from experimental studies of the silicate portions of CAis (10^(-1) to 10^2\u00b0C/hr) (Stolper and Paque, 1986).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1987-12-31", "series_number": "4", "volume": "22", "issue": "4", "pages": "331-331" }, { "id": "authors:aqbj4-65343", "collection": "authors", "collection_id": "aqbj4-65343", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-100725086", "type": "article", "title": "Isotopic abundances: inferences on solar system and planetary evolution", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Members of the Royal Swedish Academy, ladies and gentlemen.\nIn thinking over why I am here today, I recalled the story of Tom Sawyer, a character of Mark Twain's. On a beautiful, bright Saturday morning, when all of his friends were playing, he appeared by the wall in front of his aunt's house with a bucket of whitewash paint and a long-handled brush. Before him stood about thirty meters of continuous wooden fence, three meters tall. He dipped his brush and passed it over a plank and then repeated it. Then he stopped and compared the insignificant whitewashed streak with the far-reaching continent of unpainted fence and became melancholy. Then he took up the brush again and went to work. A friend came by and teased him for working on Saturday when he could be swimming or playing. Tom said it wasn't so bad, because a boy didn't get the chance to whitewash a fence every day. Tom took a new brush stroke at the fence and stepped back to note the beauty of the effect. His friend got interested and then asked permission to make a stroke or two. He then offered Tom the core of an apple he had just started to nibble on. Tom told him that it was doubtful that his friend could help because this was the front fence and that a very good and sophisticated job had to be done. Possibly only but one child in a thousand, possibly two-thousand, could do it. Well, after this denial, his friend just had to try and offered Tom the whole apple for a chance to paint. Then more young friends came around to attempt this challenging task. By the end of the afternoon, Tom was the wealthiest boy in town. He had twelve marbles, a key that didn't unlock anything, a piece of blue glass to look through, a tin soldier, a dog collar (but no dog) and lots of other valuable things. The fence had been coated three times and if he had not run out of whitewash, Tom would have bankrupted every kid in the village. My presence here is due to an ability to attract young talent to help whitewash the fence. The only difference is that we have just started on the job.", "doi": "10.1016/0012-821X(87)90219-6", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1987-12", "series_number": "2-4", "volume": "86", "issue": "2-4", "pages": "129-173" }, { "id": "authors:gss27-dbg89", "collection": "authors", "collection_id": "gss27-dbg89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-153637025", "type": "article", "title": "Isotopic studies of Mg, Fe, Mo, Ru and W in Fremdlinge from\n Allende refractory inclusions", "author": [ { "family_name": "Hutcheon", "given_name": "Ian D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Armstrong", "given_name": "John T.", "clpid": "Armstrong-J-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic abundances of Mg, Fe, Mo, Ru and W in Fremdlinge and a refractory metal nugget in coarse-grained, Ca-Al-rich inclusions from the Allende meteorite have been determined using the PANURGE ion microprobe. These data represent the first measurement of the isotopic composition of Fremdlinge. No evidence for large, non-mass-dependent deviations (\u22731%) from normal solar isotopic abundances was found for any of the elements measured. The only hint, of a nonlinear isotopic anomaly is for Mo in Fremdling 1 of Allende inclusion 5171; the measured ^(100)Mo/^(98)Mo ratio lies slightly more than two standard deviations above the value measured in standards. Isotopic variations due to mass-dependent fractionation are suggested for Mo in two Fremdlinge, Zelda of Egg 6 and Fremdling 1 of 5171, and for Ru in a refractory metal nugget in the FUN inclusion Cl. Mo is enriched in the lighter isotopes by ~ 4\u2030/amu and ~ 9\u2030/amu, respectively, while Ru is enriched in the heavier isotopes by ~ 4\u2030/amu. Despite their unusual mineralogy and extreme enrichment in refractory siderophile elements, Fremdlinge do not contain an enhanced component from a single nucleosynthetic source, but appear to contain the normal solar system mixture of \u0454-, s-, and r-process material. While the possibility that some Fremdlinge may have formed under presolar conditions cannot be excluded, we believe that the chemical, petrologic and isotopic data are most plausibly interpreted in terms of the origin of Fremdlinge within the solar nebula.", "doi": "10.1016/0016-7037(87)90126-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1987-12", "series_number": "12", "volume": "51", "issue": "12", "pages": "3175-3192" }, { "id": "authors:v595e-cvy80", "collection": "authors", "collection_id": "v595e-cvy80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-153538719", "type": "article", "title": "Zelda and Company: Petrogenesis of sulfide-rich Fremdlinge\n and constraints on solar nebula processes", "author": [ { "family_name": "Armstrong", "given_name": "John T.", "clpid": "Armstrong-J-T" }, { "family_name": "Hutcheon", "given_name": "Ian D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A detailed mineralogic and chemical study of Zelda, a gigantic (1mm diameter) Fremdling from the Allende CAI, Egg 6, was performed in an attempt to understand the mode of formation of sulfide-rich Fremdlinge and their relation to other types of Fremdlinge. Zelda is composed primarily of pentlandite, pyrrhotite and V-Cr-rich magnetite. Minor phases include NiFePt metal, molybdenite, whitiockite and refractory metal nuggets (RMN) of OsRu and PtIr. The refractory siderophile abundances in Zelda are about 20,000 to 70,000 times chondritic.\nNiFe grains are highly embayed and are surrounded by a mixture of pentlandite and PtIr RMN. PtIr RMN are found exclusively at the embayed boundaries of NiFe, while OsRu RMN are found distributed throughout the entire Fremdlinge. The texture and mineral and bulk chemistry of Zelda are consistent with closed system sulfidization of a metal-magnetite precursor, with the metal reacting to form a mixture of pentlandite and PtIr, and the magnetite reacting to form pyrrhotite. The evidence suggests that this sulfidization approached equilibrium at a temperature of 800\u2013900\u00b0C.\nExamination of Egg 6 in the vicinity of Zelda indicates that the Fremdling underwent extensive reaction with its surroundings, losing perhaps 40% of its original mass. The reaction involved partial melting, breakdown of NiFe, magnetite and sulfide, formation of V-magnetite-rich veins, and diffusion of Fe, V and Cr into neighboring spinels. Compositional profiles measured in a large spinel near Zelda suggest a diffusion time of approximately 1 hour at a temperature of about 1150\u00b0C. Examination of other Fremdlinge indicates that the presence of V-fassaite rims around Fremdlinge helps to protect them from undergoing such types of reaction.\nThe most likely formation of Fremdlinge appears to have involved relatively cold accretion of previously formed grains of magnetite, NiFe and RMN, followed by partial sintering and in some cases sulfidization before incorporation into proto-CAIs. Following incorporation, further sulfidization and reaction of some Fremdlinge with their surroundings occurred. The common coexistence of very high concentrations of refractory aderophiles and low-T metal-magnetite-sulfide assemblages, as well as the evidence that Fremdlinge were incorporated into proto-CAI as solid objects, underscore the complexity of early solar nebula processes and require local mixing of phases formed at considerably different T and fO_2. Many of the phase relations observed in Fremdlinge point to CAIs existing for reasonable periods of time at temperatures of about 850\u00b0C and cooler, but only for very short times at temperatures greater than 1000\u00b0C, although some of these phase assemblages may have been created by exsolution during lower temperature reequilibration.", "doi": "10.1016/0016-7037(87)90125-6", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1987-12", "series_number": "12", "volume": "51", "issue": "12", "pages": "3155-3173" }, { "id": "authors:qebkf-c8p40", "collection": "authors", "collection_id": "qebkf-c8p40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130415-151025244", "type": "article", "title": "Rb, Sr, Nd and Sm concentrations in quartz", "author": [ { "family_name": "Rossman", "given_name": "George R.", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Weiss", "given_name": "D.", "clpid": "Weiss-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "contributor": [ { "family_name": "Frey", "given_name": "F. A.", "clpid": "Frey-F-A" } ], "abstract": "The concentrations of Rb, Sr, Nd and Sm in quartz crystals from Crystal Peak, Colorado; Stewart Mine, California; Tomas Gonzaga, Minas Gerais, Brazil; and Coleman Mines, Arkansas, were determined by isotope dilution mass spectrometry. Concentrations ranged from: 1.17 to 177 ppb Rb; 3.26 to 1027 ppb Sr; 0.0159 to 0.48 ppb Sm; 0.127 to 2.81 ppb Nd. In the Brazilian crystal, concentrations of these elements were correlated with the amount of fluid inclusion water measured visually by turbidity and quantitatively with infrared adsorption spectroscopy. The highest Rb content was found for a crystal free of visible inclusions, indicating that small amounts of Rb can also occur in quartz itself. Rb and Sr contents are much lower in synthetic quartz grown commercially from the Arkansas quartz.", "doi": "10.1016/0016-7037(87)90286-9", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1987-09", "series_number": "9", "volume": "51", "issue": "9", "pages": "2325-2329" }, { "id": "authors:h7s6s-66w17", "collection": "authors", "collection_id": "h7s6s-66w17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140416-103915822", "type": "article", "title": "Nd-Sr-Pb systematics and age of the Kings River ophiolite,\n California: implications for depleted mantle evolution", "author": [ { "family_name": "Shaw", "given_name": "H. F.", "clpid": "Shaw-H-F" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Saleeby", "given_name": "J. B.", "clpid": "Saleeby-J-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Sm-Nd whole-rock and mineral data for the Kings River ophiolite define two isochrons of 485\u00b121 Ma and 285\u00b145 Ma age with \u03b5_Nd (483)= +10.7\u00b10.5 and \u03b5_Nd (285)= +9.9\u00b11.1, respectively. The 483 Ma isochron is defined by samples of the main igneous construct. Samples from crosscutting diabase dikes and flaser gabbro sheets within the peridotite unit yield the 285 Ma isochron. The 483 Ma data provide the first evidence of lower Paleozoic oceanic crust in the Sierran ophiolite belt. New U-Pb analyses of zircons from a plagiogranite lying on the 483 Ma Sm-Nd isochron yield upper and lower intercepts with the concordia of 430^(+200)_(\u221260) and 183\u00b115 Ma. Published zircon ages have underestimated the primary age of the ophiolite by 200\u2013300 m.y. due to the effects of polymetamorphism. The 483 Ma samples have initial ^(87)Sr/^(86)Sr=0.7023\u20130.7030, ^(206)Pb/^(204)Pb=17.14\u201317.82, ^(207)Pb/^(204)Pb=15.37\u201315.52, ^(208)Pb/^(204)Pb=36.80\u201337.38. The 285 Ma samples have similar initial 87Sr/86Sr, but more radiogenic Pb. The range in Sr and Pb compositions is probably due to introduction of radiogenic Sr and Pb during multiple post-emplacement metamorphic events. The high \u03b5 Nd, low ^(87)Sr/^(86)Sr, ^(206)Pb/^(204)Pb, ^(207)Pb/^(204)Pb, ^(208)Pb/^(204)Pb of the least disturbed samples are clearly diagnostic of a midocean ridge origin for the 483 Ma portion of the ophiolite. Igneous activity at 285 Ma is thought to have occurred in an arc or back-arc setting, or perhaps along a leaky transform. The initial \u03b5_Nd (483)=+10.7 is indistinguishable from that of the similar age Trinity Peridotite (Jacobsen et al. 1984). This value is the highest yet reported for the Mesozoic or Paleozoic depleted mantle and requires either a mantle source that was depleted \u223c 850 m.y. earlier than average or a source more highly depleted than average. Alternatively, if such values were more typical of the early Paleozoic mantle than is currently thought, then there has been little evolution of the depleted mantle over the last \u223c 500 m.y. This requires that the modern mantle has been refluxed by material with low \u03b5_Nd, such as continental crust.", "doi": "10.1007/BF00371249", "issn": "0010-7999", "publisher": "Springer", "publication": "Contributions to Mineralogy and Petrology", "publication_date": "1987-07", "series_number": "3", "volume": "96", "issue": "3", "pages": "281-290" }, { "id": "authors:1c0bm-5kb68", "collection": "authors", "collection_id": "1c0bm-5kb68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-140842214", "type": "article", "title": "Precise Timing of the Last Interglacial Period from Mass Spectrometric Determination of Thorium-230 in Corals", "author": [ { "family_name": "Edwards", "given_name": "R. Lawrence", "clpid": "Edwards-R-L" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Ku", "given_name": "T.-L.", "clpid": "Ku-T-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The development of mass spectrometric techniques for determination of ^(230)Th abundance has made it possible to reduce analytical errors in ^(238)U-^(234)U-^(230)Th dating of corals even with very small samples. Samples of 6 x 10^8 atoms of ^(230)Th can be measured to an accuracy of \u00b13 percent (2\u03c3) and 3 x 10^(10) atoms of ^(230)Th can be measured to an accuracy of \u00b10.2 percent. The time range over which useful age data on corals can be obtained now ranges from about 50 to about 500,000 years. For young corals, this approach may be preferable to ^(14)C dating. The precision with which the age of a coral can now be determined should make it possible to critically test the Milankovitch hypothesis concerning Pleistocene climate fluctuations. Analyses of a number of corals that grew during the last interglacial period yield ages of 122,000 to 130,000 years. The ages coincide with, or slightly postdate, the summer solar insolation high at 65\u00b0N latitude which occurred 128,000 years ago. This supports the idea that changes in Pleistocene climate can be the result of variations in the distribution of solar insolation caused by changes in the geometry of the earth's orbit and rotation axis.", "doi": "10.1126/science.236.4808.1547", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1987-06-19", "series_number": "4808", "volume": "236", "issue": "4808", "pages": "1547-1553" }, { "id": "authors:21nh0-bpv81", "collection": "authors", "collection_id": "21nh0-bpv81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-153728702", "type": "article", "title": "Rare earth element transport in the western North Atlantic\n inferred from Nd isotopic observations", "author": [ { "family_name": "Piepgras", "given_name": "D. J.", "clpid": "Piepgras-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Nd in the water column from several western North Atlantic sites and formational areas for North Atlantic Deep Water shows extensive vertical structure at all locations. In regions where a thermocline is well-developed, large isotopic shifts (2 to 3 \u03f5 units) are observed across the base of the thermocline. Regions without a thermocline are characterized by much more gradual shifts in isotopic composition with depth. In general, the data reveal an excellent correlation between the Nd isotopic distribution in the western North Atlantic water column and the distribution of water masses identified from temperature and salinity characteristics. NADW, as identified from T-S properties, is also characterized by a well-defined isotopic composition having \u03f5_(Nd)(0) = \u221213.5 \u00b1 0.5. This signature is associated with waters identified as NADW from high latitudes near formational areas in the Labrador Sea down to the equatorial region. The isotopic signature of NADW would appear to be formed by a blend of more negative waters originating in the Labrador Sea (\u03f5_(Nd)(0) < \u221218) and more positive waters originating in the overflows from the Norwegian and Greenland Seas (\u03f5_(Nd)(0) \u2248 \u22128 to \u221210) and is consistent with classical theories on the formation of NADW. The isotopic signature of NADW is propagated southward to the equator where it is gradually being thinned out by mixing from above and below with more radiogenic Nd associated with northward-spreading Antarctic Intermediate and Bottom Waters. The preservation of the isotopic signature of NADW over these large distances indicate that the REE undergo extensive lateral transport. The isotopic composition of Nd is largely conservative over the time scales of mixing within the Atlantic in spite of the intrinsic nonconservative behavior of neodymium. Nd concentration gradients generally show surface waters to be depleted in Nd relative to deep waters, which must require vertical transport processes. However, isotopic differences in the water column preclude the local downward transport of REE from the surface into underlying deep waters as a simple explanation of the concentration gradient. The apparent decoupling of REE in NADW from overlying (local) surface waters and the increasing concentration with depth provide a conflict with simple vertical transport mechanisms that is not yet resolved.", "doi": "10.1016/0016-7037(87)90217-1", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1987-05", "series_number": "5", "volume": "51", "issue": "5", "pages": "1257-1271" }, { "id": "authors:t6ctp-mcz64", "collection": "authors", "collection_id": "t6ctp-mcz64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-151401863", "type": "article", "title": "Rb-Sr and Sm-Nd isotope geochemistry and chronology of cherts from the Onverwacht Group (3.5 AE), South Africa", "author": [ { "family_name": "Weis", "given_name": "D.", "clpid": "Weis-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report Rb-Sr and Sm-Nd isotopic analyses of chert samples from the Geluk Subgroup (previously called the mafic-to-felsic unit (MFU)) of the Onverwacht Group in South Africa.\nThese Archean cherts have the same characteristic Rb and Sr concentrations as Phanerozoic cherts with high Rb/Sr ratios. The dense, massive, essentially low-carbonate cherts from the Onverwacht Group show a very large range of ^(87)Rb/^(86)Sr ratios (from 0.859 to 7.99). One sample of chert leached in acid yielded ^(87)Rb/^(86)Sr = 7.04. The data define a very good correlation line in the ^(87)Rb-^(87)Sr evolution diagram which corresponds to an age of 2119 \u00b1 44 m.y. with an initial ^(87)Rb/^(86)Sr ratio of 0.72246 \u00b1 16. Exchange of Sr in the cherts with the associated carbonate appears very limited. The correlation line is interpreted as reflecting the age of rehomogenization of the Sr in the protolith and the recrystallization of these cherts due to circulating hydrothermal fluids during regional metamorphism about 1.4 AE after deposition of the Onverwacht Group. It may also correspond to the closure of the Rb-Sr system in the cherts when tectonic activity stopped in the region (~2200 m.y.). The initial ^(87)Rb/^(86)Sr ratio obtained for the cherts requires the protolith which provided the Sr to have Rb/Sr ~ 1.\nThe Sm-Nd systematics do not provide any strict chronologic information but appear to reflect an ancient source age ~3.5 AE. The \u03f5_(Nd) at 3.54 AE for the cherts are grouped around zero, i.e. close to the initial value observed for volcanics of the same age, and provide no evidence for the presence of abundant crustal material older than 3.5 AE.", "doi": "10.1016/0016-7037(87)90109-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1987-04", "series_number": "4", "volume": "51", "issue": "4", "pages": "973-984" }, { "id": "authors:jmrdw-s9f25", "collection": "authors", "collection_id": "jmrdw-s9f25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-155121296", "type": "article", "title": "Rb-Sr and Sm-Nd systematics of cherts and other siliceous deposits", "author": [ { "family_name": "Weis", "given_name": "D.", "clpid": "Weis-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have analyzed a suite of marine and lacustrine cherts to determine the concentration of Rb, Sr, Sm and Nd and the isotopic composition of Sr and Nd. The samples ranged from Pliocene to Silurian in age and included nodular cherts in carbonates as well as bedded cherts.\nMassive samples were leached in acid to remove carbonate and both the leach and residue analyzed. The residues contained 0.1 to 17 ppm Rb and 0.5 to 20 ppm Sr. All samples have high Rb/Sr ratios (~0.1 to 0.8) and thus show enrichment of Rb relative to Sr of 6 to 60 times that of seawater. The Rb and Sr in pegmatitic quartz are much lower by factors of 10 to 10^3, although these also may have high Rb/Sr. The site of Rb and Sr in the cherts was not established but appears to be correlated with Al content. The high Rb/Sr ratios permit the use of cherts for dating in favorable circumstances.\nThe Nd contents range from 9 to 1000 ppb with Sm/Nd ~ 0.16 to 0.19, typical of continental sources. The initial ^(87)Sr/^(86)Sr ratio for a Pacific deep sea chert is equal to that of associated carbonates and hence reflects the seawater environment. In shelf and marginal basin environments, the initial ^(87)Sr/^(86)Sr ratios of chert are distinctly more radiogenic than seawater. This is most obvious where a substantial clay component is present, but is observed even in samples with Al_2O_3 contents less than 0.1%. These results show the Rb-Sr system in chert to be rather isolated from the associated carbonate with very little Sr exchange. This separate behavior appears to persist through both early and late recrystallization stages.\nThese data suggest that, in many cases, cherts are formed by \"dissolved\" SiO_2 nucleating on clay-like material which preserves the isotopic characteristics of the detrital source. The detrital component required is less than 1% of the total chert. In some cases, it is possible that the cherts were formed from silica-saturated waters from a nonmarine source, possibly in coastal environments or during uplift. These waters contained radiogenic Sr in solution that was not exchanged with the carbonate matrix. This latter mechanism is also indicated by oxygen isotopic studies (KNAUTH and EPSTEIN, 1976; KOLODNY and EPSTEIN, 1976). The Nd isotopic signature of the deep sea samples reflects the seawater composition in agreement with the initial ^(87)Sr/^(86)Sr data on the same samples. Samples with excesses of ^(87)Sr relative to seawater show low \u03f5_(Nd), both sets of data thus indicating inheritance of an old detrital component. The results demonstrate that the Rb-Sr and Sm-Nd systems may be used in elucidating the origin and evolution of cherts and that the Rb-Sr system may be used for dating, if consideration is given to the initial Sr composition and to diagenetic changes. This opens up numerous possibilities for sedimentological-geochemical studies.", "doi": "10.1016/0016-7037(87)90108-6", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1987-04", "series_number": "4", "volume": "51", "issue": "4", "pages": "959-972" }, { "id": "authors:k9hcf-xvr55", "collection": "authors", "collection_id": "k9hcf-xvr55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-120433463", "type": "article", "title": "^(238)U-^(234)U-^(230)Th-^(232)Th systematics and the precise measurement of time over the past 500,000 years", "author": [ { "family_name": "Edwards", "given_name": "R. Lawrence", "clpid": "Edwards-R-L" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have developed techniques to measure the ^(230)Th abundance in corals by isotope dilution mass spectrometry. This, coupled with our previous development of mass spectrometric techniques for ^(234)U and ^(232)Th measurement, has allowed us to reduce significantly the analytical errors in ^(238)U-^(234)-^(230)Th dating and greatly reduce the sample size. We show that 6 \u00d7 10^8 atoms of ^(230)Th can be measured to \u00b130\u2030 (2\u03c3) and 2 \u00d7 10^(10) atoms of ^(230)Th to \u00b1 2\u2030. The time over which useful age data on corals can be obtained ranges from a few years to \u223c 500 ky. The uncertainty in age, based on analytical errors, is \u00b1 5 y (2\u03c3) for a 180 year old coral (3 g), \u00b1 44 y at 8294 years and \u00b1 1.1 ky at 123.1 ky (250 mg of coral). We also report ^(232)Th concentrations in corals (0.083\u20131.57 pmol/g) that are more than two orders of magnitude lower than previous values. Ages with high analytical precision were determined for several corals that grew during high sea level stands \u223c 120 ky ago. These ages lie specifically within or slightly postdate the Milankovitch insolation high at 128 ky and support the idea that the dominant cause of Pleistocene climate change is Milankovitch forcing.", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1987-01", "series_number": "2-3", "volume": "81", "issue": "2-3", "pages": "175-192" }, { "id": "authors:qqn92-j4105", "collection": "authors", "collection_id": "qqn92-j4105", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150211-140923804", "type": "article", "title": "To: the world from: spelled out re: name game", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "How far will things go in the spellings of my name? I calculate \u223c(26)^N, where N is the number of characters arbitrarily assigned to my name. In the September 30, 1986, issue of Eos in which awards of the Union are announced, my name is misspelled both in the description of the Hess Medal and also as a recipient. AGU is to be congratulated for spelling it correctly on the medall AGU recently asked me to serve on its Nominations Committee, and in the letter of appointment and in the published list of committee members in Eos, my name is also misspelled. Claude Allegre and I have just received the 1986 Crafoord Prize from the Royal Swedish Academy.", "doi": "10.1029/EO067i047p01342-01", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "1986-11-25", "series_number": "47", "volume": "67", "issue": "47", "pages": "1342" }, { "id": "authors:pbnem-jkh69", "collection": "authors", "collection_id": "pbnem-jkh69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-111048720", "type": "article", "title": "^(238)U, ^(234)U and ^(232)Th in seawater", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Edwards", "given_name": "R. Lawrence", "clpid": "Edwards-R-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have developed techniques to determine ^(238)U,^(234)U and ^(232)Th concentrations in seawater by isotope dilution mass spectrometry. U measurements are made using a ^(233)U-^(236)U double spike to correct for instrumental fractionation. Measurements on uranium standards demonstrate that ^(234)U/^(238)U ratios can be measured accurately and reproducibly. ^(234)U/^(238)U can be measured routinely to \u00b1 5\u2030 (2\u03c3) for a sample of 5 \u00d7 10^9 atoms of ^(234)U (3 \u00d7 10^(\u22128) g of total U, 10 ml of seawater). Data acquisition time is \u223c 1 hour. The small sample size, high precision and short data acquisition time are superior to\u03b1-counting techniques. ^(238)U is measured to \u00b1 2\u2030 (2\u03c3) for a sample of 8 \u00d7 10^(12) atoms of ^(238)U (\u223c 3 \u00d7 10^(\u22129) g of U, 1 ml of seawater). ^(232)Th is measured to \u00b1 20\u2030 with 3 \u00d7 10^(11) ^(232)Th atoms (10^(\u221210) g ^(232)Th, 1 1 of seawater). This small sample size will greatly facilitate investigation of the ^(232)Th concentration in the oceans. Using these techniques, we have measured ^(238)U, ^(234)U and ^(232)Th in vertical profiles of unfiltered, acidified seawater from the Atlantic and ^(238)U and ^(234)U in vertical profiles from the Pacific. Determinations of ^(234)U/^(238)U at depths ranging from 0 to 4900 m in the Atlantic (7\u00b044\u2032N, 40\u00b043\u2032W) and the Pacific (14\u00b041\u2032N, 160\u00b001\u2032W) Oceans are the same within experimental error (\u00b1 5\u2030,2\u03c3). The average of these ^(234)U/^(238)U measurements is 144 \u00b1 2\u2030 (2\u03c3) higher than the equilibrium ratio of 5.472 \u00d7 10\u22125. U concentrations, normalized to 35\u2030 salinity, range from 3.162 to 3.281 ng/g, a range of 3.8%. The average concentration of the Pacific samples (31\u00b04\u2032N, 159\u00b01\u2032W) is \u223c 1% higher than that of the Atlantic (7\u00b044\u2032N, 40\u00b043\u2032W and 31\u00b049\u2032N, 64\u00b06\u2032W). ^(232)Th concentrations from an Atlantic profile range from 0.092 to 0.145 pg/g. The observed constancy of the ^(234)U/^(238)U ratio is consistent with the predicted range of ^(234)U/^(238)U using a simple two-box model and the residence time of deep water in the ocean determined from ^(14)C. The variation in salinity-normalized U concentrations suggests that U may be much more reactive in the marine environment than previously thought.", "doi": "10.1016/0012-821X(86)90108-1", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1986-11", "series_number": "3-4", "volume": "80", "issue": "3-4", "pages": "241-251" }, { "id": "authors:rnvmq-gw977", "collection": "authors", "collection_id": "rnvmq-gw977", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-134244496", "type": "article", "title": "The U-Th-Pb systematics in hot springs on the East Pacific\n Rise at 21 \u00b0N and Guaymas Basin", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "von Damm", "given_name": "K. L.", "clpid": "von-Damm-K-L" }, { "family_name": "Edmond", "given_name": "J. M.", "clpid": "Edmond-J-M" } ], "abstract": "We have determined the concentrations and isotopic compositions of U, Th and Pb in hydrothermal fluids from 21\u00b0N, East Pacific Rise and Guaymas Basin, Gulf of California. The purest hydrothermal end members (96%) have 0.06\u20130.18 ppb U, < 0.1\u20134.3 ppt Th and 40\u201367 ppb Pb. Several samples show a ^(234)U enrichment relative to the equilibrium value. This indicates that U was quantitatively removed from seawater and deposited to the crust during the hydrothermal circulation. The 21\u00b0N fluids with intermediate Mg content show that U and Mg are coherently removed from seawater, but Pb is not, during mixing of the hot hydrothermal fluid and cold ambient seawater. Both the end-member and intermediate hydrothermal fluids at 21\u00b0N have similar Pb isotopic compositions and limited ranges in ^(206)Pb/^(204)Pb (18.444\u201318.503), ^(207)Pb/^(204)Pb (15.471\u201315.514), and ^(208)Pb/^(204)Pb (37.832\u201337.966). These ratios are within the range of values of MORB and are distinctly less radiogenic than the ambient seawater. This means that a significant amount of Pb was removed from the basalts by the hot springs. In contrast, Th does not appear to be significantly removed from the basalts. Some of this Pb was incorporated into the metalliferous sediments in a wide area straddling the EPR. The Pb isotopic composition of a hydrothermal sample from the Guaymas Basin is more radiogenic than at 21\u00b0N and resembles that of sediments from the Gulf of California. This is consistent with the uptake of Pb from heated sediments having a substantial component of the volcanogenic detritus.\nUsing the present data and the literature values of the natural river fluxes, the global hydrothermal system removes ~25% U from the total natural U flux to the ocean and contributes < 0.02% Th and ~2% Pb to the ocean. The U/Pb ratio in the hydrothermally altered oceanic crust may be increased by from 40% to a factor of 2, and the Th/U ratio decreased by from 10 to 25%. The ridge crest-hydrothermal system represents only a part of a continuous geochemical process which modifies the U-Th-Pb systematics of the oceanic upper crust or ultimately the source of some oceanic island basalts.", "doi": "10.1016/0016-7037(86)90030-X", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1986-11", "series_number": "11", "volume": "50", "issue": "11", "pages": "2467-2479" }, { "id": "authors:yffky-h8t87", "collection": "authors", "collection_id": "yffky-h8t87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-142330017", "type": "article", "title": "A comparative petrologic study of iron meteorites with ^(107)Ag* anomalies", "author": [ { "family_name": "Teshima", "given_name": "J.", "clpid": "Teshima-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "El Goresy", "given_name": "A.", "clpid": "El-Goresy-A" }, { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" } ], "abstract": "We have made a petrographic study of the iron meteorites: Derrick Peak (IIB), Cape York (IIIA), Grant (IIIB), Gibeon (IVA) and Santa Clara (IVB). Each of these meteorites has been reported to contain excess ^(107)Ag from the decay of now extinct ^(107)Pd. Isotopic data on metal and sulfide phases for groups IIB and IIIAB iron meteorites have been explained using conventional interpretations which show a correlation between ^(107)Ag/^(109)Ag and Pd/Ag while data on sulfide nodules in meteorites from groups IVA and IVB are very complex. We have studied the extent to which shock and thermal events may have caused the redistribution of Ag and disturbed the original relationship between ^(107)Ag\u2217 and Pd, particularly in sulfide-rich regions. The petrography of the iron meteorites studied is consistent with the Pd-Ag isotopic data. The textures observed in the metal and sulfide in groups IIA and IIIAB were found to be indicative of shock but not extensive thermal metamorphism. The contacts between metal and sulfide are sharp and the sulfide and metal have remained discrete homogeneous phases. These meteorites yield isochrons between metal and sulfide and it is concluded that no significant Ag redistribution occurred after their formation. The petrography of group IVA and IVB meteorites reveals a history involving extensive shock and thermal metamorphism. Contacts between metal and sulfide nodules are irregular and the two phases are intimately mixed. In Gibeon, unequilibrated \u03b1_2-martensitic structures in the metal matrix suggest that some reheating affected entire individual fragments of this meteorite. While bulk samples of the metal phases of the IVA and IVB meteorites appear well behaved with regard to Pd-Ag systematics, the sulfide-rich regions show extreme isotopic heterogeneities and do not yield well-defined isochrons. The Pd-Ag data reflect complicated postformation Ag transport. This petrographic study has found that the complexity of Pd-Ag isotopic data is related to the shock and thermal histories of the iron meteorites. However, no self-consistent explanation has been found to explain the Pd-Ag results observed for the nodules. The mineral phase(s) in which Ag resides in both the metal and sulfide phases is as yet undetermined, though late-forming Cu-precipitates and chalcopyrite found in IIIAB irons are possible getters of volatiles (Ag, Au) and may be host to ^(107)Ag\u2217.", "doi": "10.1016/0016-7037(86)90261-9", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1986-09", "series_number": "9", "volume": "50", "issue": "9", "pages": "2073-2087" }, { "id": "authors:7eftc-7pb08", "collection": "authors", "collection_id": "7eftc-7pb08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230530-212112870", "type": "article", "title": "Exploring the Planets: A Strategic But Practical Proposal", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald Jos.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The series of accidents that have grounded all major U.S. rocket systems makes it increasingly clear that the United States will have to choose between competing goals in space. Most of the analyses of U.S. goals have focused only on the troubles in the U.S. space program, but important developments in the Soviet Union's space program and those of other countries could also affect future U.S. choices. The Soviets have dramatically increased planetary exploration and other space science activities in the last decade. Western Europe's space community has become larger, more independent, and more involved in the Soviet space efforts. \n\nGerald Jos. Wasserburg, a professor of geology and geophysics with long experience in space science, argues that these developments call for the United States to reassess its goals in space. 1 A manned mission to Mars is\nnot a realistic goal, Wasserburg says. Instead, he urges the United States to lead a truly international program of unmanned exploration of Mars, Venus, and nearby comets to bring back samples to Earth. Wasserburg recommends that the first stage of this program be a U.S.-Soviet bilateral effort with strong European participation soon after.", "issn": "1938-1557", "publisher": "Arizona State University", "publication": "Issues in Science and Technology", "publication_date": "1986-09", "series_number": "1", "volume": "3", "issue": "1", "pages": "78-86" }, { "id": "authors:0tbwq-jwn33", "collection": "authors", "collection_id": "0tbwq-jwn33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-154907008", "type": "article", "title": "Formation ages and evolution of Shergotty and its parent planet from U-Th-Pb systematics", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of lead was determined in different phases from Shergotty, Zagami and EETA 79001. Using phases with low ^(238)U/^(204)Pb, the initial leads of these meteorites could be well defined and are distinct from each other and have high ^(204)Pb/^(206)Pb (from 0.0652 to 0.0739). These leads evolved in different reservoirs over most of solar system history in a low ^(238)U/^(204)Pb \u2248 5 environment. It follows that the parent planet of the shergottites has a high ^(204)Pb concentration relative to U and must also be high in other volatiles. If the parent planet of the shergottites is Mars, then this planet must be volatile-rich compared to the Earth by a factor of ~ 1.8. This implies that Mars lost its original atmosphere and that the present atmosphere was derived from a previously outgassed Martian upper mantle.\nThe U-Th-Pb isotopic relationships involving phases with high ^(238)U/^(204)Pb are quite regular and give ages for three shergottites which indicate an event of U-Th-Pb fractionation at ~200 m.y. The initial leads at that time were highly evolved relative to the primordial lead. The absence of substantial additions of radiogenic lead (above the initial lead) in high U phases precludes an older age for the U-Th-Pb fractionation. However, details of the data arrays are complex. The young age is in general agreement with some of the ages obtained by other methods, but precise concordance between the different methods is not established. It is suggested that the shock event that produced maskelynite may possibly be associated with the late-stage breakup at ~2.5 m.y. and not necessarily related to the ~ 180 m.y. record. The major event of chronometer resetting is taken to be ~ 180 m.y. This event does not appear to be an endogenic igneous event but an almost complete equilibration during a major impact on more ancient igneous rocks which were contained in the target. Problems of the polymetamorphic history of meteorites appear as complicated as those of polymetamorphic terrestrial terranes.", "doi": "10.1016/0016-7037(86)90376-5", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1986-06", "series_number": "6", "volume": "50", "issue": "6", "pages": "955-968" }, { "id": "authors:xavsf-2nd51", "collection": "authors", "collection_id": "xavsf-2nd51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-105701825", "type": "article", "title": "Trends of Sr and Nd isotopes through time near the Japan Sea\n in northeastern Japan", "author": [ { "family_name": "Nohda", "given_name": "S.", "clpid": "Nohda-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Nd and Sr isotopic analyses were made on selected volcanic rocks of known stratigraphic age from a limited area in the \"Green Tuff\" region, northeastern Japan, and in adjacent areas. Two ultramafic inclusions from Ichinomegata were also analyzed. The volcanic rocks range in age from 27 to 6 Ma, and vary in \u03b5_(Nd) from \u22120.9 to 5.7 and in \u03b5_(Sr) from 14.1 to \u221216.3. The isotopic data plot generally along the region of the \"mantle array\". When plotted against time, the isotopic ratios are found to be a regular function of geologic age. The results indicate that: (1) the volcanic rocks in the area are part of a \"related\" sequence or evolutionary pattern over a time period of 27 Ma; (2) the \"evolutionary\" pattern goes from an initially enriched source to that of a very depleted source. The shift in isotopic composition appears to reflect the ongoing lining of magma conduits or the decreasing extraction of lower crustal contributions with increasing infiltration of oceanic magma types in an environment where the crust is thinning. Based on the geotectonic development of this area due to the back-arc spreading of the Japan Sea, we identify two different stages: the pre-opening stage (> 15 Ma) and the post-opening stage (< 15 Ma). The volcanic rocks of the pre-opening stage are characterized by an enriched isotopic signature, and those of the post-opening era by a depleted signature. The host rocks of the Kuroko ore deposit lie within this evolutionary trend and contain a substantial amount of continentally derived materials processed through an oceanic environment. In general, we infer that the degree of continental crust involvement is high during the pre-opening stages of a back-arc basin when it is associated with a rifted continental mass.", "doi": "10.1016/0012-821X(86)90057-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1986-06", "series_number": "2-3", "volume": "78", "issue": "2-3", "pages": "157-167" }, { "id": "authors:3yqks-08q58", "collection": "authors", "collection_id": "3yqks-08q58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-100240361", "type": "article", "title": "Neodymium isotopic study of Baffin Bay water: sources of REE from very old terranes", "author": [ { "family_name": "Stordal", "given_name": "M. C.", "clpid": "Stordal-M-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Water samples were collected from Baffin Bay and surrounding areas in order to evaluate this region as a potential source of Nd from old continental material to Atlantic water. The isotopic data ranged from \u03b5_(Nd)(0) = \u22129.0 to \u221226 with most of the data around \u03b5_(Nd)(0) = \u221220 compared with values of North Atlantic Deep Water (NADW) with \u03b5_(Nd)(0) = \u221213.5. The concentration of Nd in Baffin Bay waters was as high as 6 \u00d7 10^(\u221212) g/g compared with 2.5 \u00d7 10^(\u221212) g/g for NADW. The combination of low \u03b5_(Nd) and high Nd concentration indicates that Baffin Bay may be a significant source of Nd from very old crustal material. A simple box model was used to evaluate the contribution to the Nd budget of NADW and it was concluded that a substantial fraction of the Nd from ancient crustal sources that is required to maintain the isotopic composition of NADW could be supplied by Baffin Bay outflow.", "doi": "10.1016/0012-821X(86)90138-X", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1986-04", "series_number": "3-4", "volume": "77", "issue": "3-4", "pages": "259-272" }, { "id": "authors:fajvy-71k43", "collection": "authors", "collection_id": "fajvy-71k43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150121-143354004", "type": "article", "title": "1985 Hess Medal to Gerald J. Wasserburg", "author": [ { "family_name": "Kaula", "given_name": "William M.", "clpid": "Kaula-W-M" }, { "family_name": "Wasserburg", "given_name": "Gerald", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "This is the first presentation of the Harry Hess Medal. Harry Hess was long Professor of Geology at Princeton. He is most renowned as a founding father of seafloor spreading but contributed significantly to a variety of advances in geology and petrology. Harry Hess died in 1969 after seeing man land on the moon, an event of interest to him as chair of the Space Science Board.", "doi": "10.1029/EO067i002p00021", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "1986-01-14", "series_number": "2", "volume": "67", "issue": "2", "pages": "21-22" }, { "id": "authors:ypq5c-1zq85", "collection": "authors", "collection_id": "ypq5c-1zq85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140909-114620653", "type": "article", "title": "Nd and Sr isotopes in the Aleutians: multicomponent parenthood of island-arc magmas", "author": [ { "family_name": "von Drach", "given_name": "V.", "clpid": "von-Drach-V" }, { "family_name": "Marsh", "given_name": "B. D.", "clpid": "Marsh-B-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Young volcanic rocks from different sections of the Aleutian Islands-Alaska Peninsula Arc have been measured for ^(87)Sr/^(86)Sr, ^(143)Nd/^(144)Nd and some trace elements. We found the ^(143)Nd/^(144)Nd to be highly restricted in range (\u025b_(Nd)=6 to 7) and low as compared to midocean ridge basalts (MORB). This indicates that the source of the Aleutian Arc magmas is different from MORB and remarkably isotopically homogeneous with respect to Nd. The range reported here for arc rocks is substantially smaller than found by other workers. However, the Sr isotope ratios vary considerably (\u025b_(Sr)=\u221224 to \u221214). Those samples from small volcanic centers north of the main arc (second arc) are characterized by low \u025b_(Sr). Our data in combination with previous studies suggest that there are slight geochemical differences between discrete sections of the arc. The general uniformity of Nd isotope ratios are thought to be the surface expression of an efficient mixing or homogenization process beneath the arc plate, but which still causes a wide dispersion in Sr isotopic composition.\n\nTo relate the arc rocks to the broader tectonic setting and to identify possible sources of arc magmas, measurements were done on volcanic and sedimentary rocks from the North Pacific/Bering Sea area. Alkali basalts from the back-arc islands St. George, Nunivak and St. Lawrence and alkali-rich tholeiites from the fore-arc have \u025b_(Nd)=+4 to +9 and are correlated on the \u025b_(Sr)-\u025b_(Nd)diagram parallel to the mantle array but shifted to lower \u025b_(Sr). These samples are thought to be isotopically representative of the mantle transported to that region. A tholeiitic basalt from the Kamchatka Basin ocean floor (back-arc), however, yielded typical MORB values (\u025b_(Nd)=10, \u025b_(Sr)=\u221224). Composite sediment samples were made from DSDP cores in the Aleutian Abyssal Plain, Gulf of Alaska and the Alka Basin which represent mixtures of continentally and arc-derived materials. These composites have intermediate Nd isotopic (\u025b_(Nd)= \u22122 and +2) and high Sr isotopic values (\u025b_(Sr)=+9 and +37). These data show that possible source materials of the Aleutian Arc volcanics are isotopically different from and much more heterogeneous than the arc rocks themselves.\n\nOn the basis of this study and of literature data, we developed a set of alternative models for volcanic arc magma generation, based on the restricted range in \u025b_(Nd) and the wider range in \u025b_(Sr) for arc rocks. Different isotopic and trace element characteristics found in different arcs or arc sections are explained by varying mixing proportions or concentrations in source materials. The basic observations require rather strict mixing ratios to obtain constant \u025b_(Nd). The preferred model is one where the melting of subducted oceanic crust is controlled by the amount of trapped sediment with the melting restricted to the upper part of the altered basaltic layer. Homogenization within the upper part of the oceanic crust is brought about by hydrothermal circulation attending dewatering of the slab during subduction and possibly some oxygen exchange of the magmas on ascent.", "doi": "10.1007/BF00373960", "issn": "0010-7999", "publisher": "Springer", "publication": "Contributions to Mineralogy and Petrology", "publication_date": "1986-01", "series_number": "1", "volume": "92", "issue": "1", "pages": "13-34" }, { "id": "authors:v4tek-y6k07", "collection": "authors", "collection_id": "v4tek-y6k07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131022-111252758", "type": "article", "title": "Trace element and Sr-Nd isotopic constraints on the compositions of lithospheric primary sources of Serra Geral continental flood basalts, southern Brazil", "author": [ { "family_name": "Hughes", "given_name": "S. S.", "clpid": "Hughes-S-S" }, { "family_name": "Schmitt", "given_name": "R. A.", "clpid": "Schmitt-R-A" }, { "family_name": "Wang", "given_name": "Y. L.", "clpid": "Wang-Y-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Multi-element abundances in twenty-four samples from the Serra Geral continental flood basalt system (Parana Basin) were determined by INAA to assess the trace element signature of primary magmatric sources. Isotopic Sr and Nd data were obtained on a 24-sample composite and three individual samples of the suite to constrain the influences of older enriched material. Twenty basaltic samples have enriched LILE commensurate with most continental tholeiites and, display fractionated REE patterns similar to those in the Columbia River Group and other flood basalt provinces. The mafic units exhibit low-moderate Ti, variable V, Cr and Ni and relatively uniform Co and Sc abundances. Four intermediate to silicic units exhibit higher overall incompatible element abundances, strongly fractionated patterns and depletions of compatible elements consistent with derivation by fractionation of basaltic parents. Isotopic data for two basalts and the composite analysis indicate ^(87)Sr/^(86)Sr = 0.7090 to 0.7105 and \u03b5Nd = -6.6 to -6.9 requiring magma genesis in an evolved LILE-enriched upper mantle or lower crust. A silicic sample has ^(87)Sr/^(86)Sr = 0.7219 and \u03b5Nd = -9.2 reflecting a stronger crustal influence. Chemical comparisons within the basaltic members allow the delineation of ten least-evolved compositions having a regionally characteristic trace element pattern and two additional samples (of one flow) representing a second, less fractionated pattern. Trace element models for both types predict magma segregation from lower lithospheric sources having relatively uniform enrichments of incompatible elements via regional metasomatism. The most viable scenarios for basalt magma production require either enriched mantle partial-melt liquids, some of which comingle with crustal components, or partial melting of ultramafic, LILE-enriched lower crust. Either process requires a zone of primary magma extraction in a region where initially uniform source enrichments act independently of subsequent contamination, probably in the crust/mantle transition zone.", "doi": "10.2343/geochemj.20.173", "issn": "0016-7002", "publisher": "Geochemical Society of Japan", "publication": "Geochemical Journal", "publication_date": "1986", "series_number": "4", "volume": "20", "issue": "4", "pages": "173-189" }, { "id": "authors:2x3vy-cnf66", "collection": "authors", "collection_id": "2x3vy-cnf66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131118-133848294", "type": "article", "title": "A Petrographic and MG Isotopic Study of CAI in BALI (C3V) and Coolidge (C4V)", "author": [ { "family_name": "Teshima", "given_name": "J.", "clpid": "Teshima-J-M" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "One of the least well understood and most controversial aspects of CAI is the degree\nto which their mineralogical, chemical and isotopic composition has been affected by\nalteration and metamorphism. Coolidge is a highly metamorphosed carbonaceous chondrite,\nthe only C4V (Van Schmus, 1969) and we have begun a petrographic and Mg isotopic\nstudy of Coolidge CAI to investigate the extent of chemical and isotopic reequilibration\nduring thermal metamorphism. We also present the first Mg isotopic results from a coarse-grained\nCAI from Bali (C3V).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1985-12-31", "series_number": "4", "volume": "20", "issue": "4", "pages": "771-772" }, { "id": "authors:wj6dc-yg278", "collection": "authors", "collection_id": "wj6dc-yg278", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140204-082034018", "type": "article", "title": "Ti Isotope Abundances in Whole Meteorites", "author": [ { "family_name": "Kastenmayer", "given_name": "P.", "clpid": "Kastenmayer-P" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Previous work has identified the presence of nonlinear isotope effects for Ti in CM\nand CV chondrites (NPW, 1984, 1985; KPW, 1985; Niemeyer and Lugmair, 1984). We\nreport new measurements on CO and CV meteorites, two chondrites (Parnallee, LL3; Parsa,\nE4) and a shergottite. Since our earlier reports (NPW, 1985; KPW, 1985) on the absolute\nTi composition, we have concentrated on the measurement of Ti abundances normalized to\n^(46)Ti/^(48)Ti, in order to establish first the extent of nonlinear effects.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1985-12-31", "series_number": "4", "volume": "20", "issue": "4", "pages": "680-681" }, { "id": "authors:pfvrr-4yn72", "collection": "authors", "collection_id": "pfvrr-4yn72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140911-091644186", "type": "article", "title": "The Cr Isotopic Composition of Phosphates in IIIB Iron Meteorites: A Search for ^(53)Mn", "author": [ { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Teshima", "given_name": "J.", "clpid": "Teshima-J" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The metal phases of iron meteorites contain excess ^(107) Ag most plausibly derived from the in situ decay of ^(107)Pd (T_(1/2) = 6.5 x 10^6y) (Kaiser and Wasserburg, 1983; Chen and Wasserburg, 1983). The Ag isotopic data suggest that diverse types of iron meteorites, including the Type IIIABs, usually associated with fractional crystallization and core formation in planetesimals, formed and cooled to - 600\u00b0C within - 10^7y of ^(107)Pd production.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1985-12", "series_number": "4", "volume": "20", "issue": "4", "pages": "668-669" }, { "id": "authors:tpfcd-n2125", "collection": "authors", "collection_id": "tpfcd-n2125", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140909-111128801", "type": "article", "title": "Cr Isotopic Abundances", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Zyskind", "given_name": "J. L.", "clpid": "Zyskind-J-L" }, { "family_name": "Ngo", "given_name": "H. H.", "clpid": "Ngo-Henry-H-Meteoritics" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have developed techniques for the chemical separation and isotopic analysis of Cr in silicates and spinels. The purpose is to pursue the evidence for correlated isotopic effects in Ca-AI-rich inclusions (CAl) for elements in the vicinity of the Fe-abundance peak. Such a correlation is most striking for Ca and Ti for the FUN inclusions EK-1-4-1 and C-1 (Lee eta/., 1978; Niederer et al., 1980).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1985-12", "volume": "20", "pages": "724-725" }, { "id": "authors:q1mqc-07537", "collection": "authors", "collection_id": "q1mqc-07537", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-101439969", "type": "article", "title": "U-Th-Pb Systematics in Shergottites: Young Ages and Low \u03bc", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report on U-Th-Pb in Shergotty, Zagami and EETA 79001. The Rb-Sr, Sm-Nd and K-Ar ages of these meteorites indicate young ages of metamorphism and of possibly young igneous activity.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1985-12", "series_number": "4", "volume": "20", "issue": "4", "pages": "623-624" }, { "id": "authors:rh2g9-4ex54", "collection": "authors", "collection_id": "rh2g9-4ex54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140911-085141302", "type": "article", "title": "Ni-Pt-Ge-Rich Fremdlinge; indicators of a turbulent early solar nebula", "author": [ { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "One of the oddest aspects of CAis is the presence of Fremdlinge-complex aggregates of refractory metal alloys and volatile oxides and sulfides. In a series of recent studies of Fremdlinge we have provided evidence that (I) they are not isotopically anomalous and presumably formed in the solar nebula, (2) they were formed as solid objects before any of the major phases in CAis, (3) processes involved in their formation , prior to incorporation in CAis. included oxidation and reduction both at high and low temperatures, and (4) their phase assemblages and reaction textures place strict constraints on the maximum temperatures and cooling rates during CAl formation (Armstrong et al., 1984, 1985a, 1985b; Hutcheon et al., 1985).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1985-12", "series_number": "4", "volume": "20", "issue": "4", "pages": "603-604" }, { "id": "authors:w899q-8vx08", "collection": "authors", "collection_id": "w899q-8vx08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131021-131558858", "type": "article", "title": "Anatomy of an Allende coarse-grained inclusion", "author": [ { "family_name": "El Goresy", "given_name": "A.", "clpid": "El-Goresy-A" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Inclusion 5241 is a petrographically complex, coarse-grained CAI from the Allende meteorite, containing a core with two petrographically and chemically distinct units. The core is surrounded by a melilite mantle similar to that described for Allende Type B1 inclusions, which consists of large, millimetersized crystals. The two different units of the core are (1) spinel-free islands consisting of melilite, fassaite, and minor anorthite (2) spinel-rich areas with major fassaite and reversely zoned melilite.\nIn this unit, spinel occurs in fassaite, melilite, and in densely packed belts surrounding the spinel-free islands. Mineral chemistries of melilite and fassaite in the spinel-free islands are different from those in the spinel-rich areas: melilite in the spinel-free islands is unzoned and displays a very narrow chemical variation (<10 mol %) within individual crystals, ranging between \u00c5k_(52) and \u00c5k_(68) in all islands. They also contain considerable amounts of Na-melilite molecule (as much as 2.7 mol %). In contrast, melilite in the spinel-rich areas is reversely zoned and barren of Na-melilite: the composition varies between \u00c5k_(43) and \u00c5k_(62), with the lowest \u00c5k-content within a zone decorated with fassaite and spinel inclusions.\n\nZoning in individual melilite crystals in the mantle is not continuous (as in Allende Type B1 inclusions), but is rhythmic outwards, from \u00c5k_(30) to \u00c5k_(35) near the core/mantle boundary followed by a continuous decrease with the lowest value near the center of the melilite crystals (\u00c5k_(25)). The \u00c5k-content rises again and reaches a value of \u00c5k_(28) at the rim of the inclusion.\n\nFassaite in the spinel-free islands is typically concentrically zoned, with Ti-Al-rich cores and Ti-Al-poor rims. The concentration of Ti^(3+) in some fassaite crystals in the islands appears to be lower than in the spinelrich areas. Zoning of fassaite in the spinel-rich areas is nonsystematic and the Tio_2 variations are considerable (2\u201312wt%).\n\nBulk compositions of the spinel-free islands plot inside the Type B CAI field but considerably below the Fo-An-Ge plane because they are spinel deficient. In contrast, compositions of the spinel-rich areas plot outside the Type B CAI field close to pyroxene-saturated compositions (STOLPER, 1982).\n\nTextural relations and mineral chemistries in the spinel-free islands, spinel-rich areas, and melilite mantle cannot be explained by gas solid condensation, simple stage crystallization from a refractory silicate liquid, or evaporative loss by distillation, but suggest a series of complex events including the capture of solid spinel-free bodies by a refractory liquid; the melilite mantle may have formed by crystallization from a liquid which enveloped the complex core.", "doi": "10.1016/0016-7037(85)90243-1", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1985-11", "series_number": "11", "volume": "49", "issue": "11", "pages": "2433-2444" }, { "id": "authors:n5gef-z2683", "collection": "authors", "collection_id": "n5gef-z2683", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-094207515", "type": "article", "title": "Extinct nuclides - \"Much ado about nothing\"", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A concise review of the status of research on short-lived nuclei is presented. The importance of these nuclei is very great in spite of the fact that they are essentially absent today (except for cosmic ray products). The significance of\nthese nuclei for understanding broader cosmic problems is outlined and it is shown that they are a key to the earliest processes in solar system formation and possibly provide a link with pre solar processes in the interstellar medium or of intense activity of the early sun. A few reminiscences are about some random interactions with Hans Suess are given illustrating different ways of doing and thinking science.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1985-06-30", "series_number": "2", "volume": "20", "issue": "2", "pages": "295-310" }, { "id": "authors:6z2pz-3hf40", "collection": "authors", "collection_id": "6z2pz-3hf40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130924-100743372", "type": "article", "title": "Identification of isobaric interferences. A computer program for ion microprobe mass spectral data", "author": [ { "family_name": "Eugster", "given_name": "O.", "clpid": "Eugster-O-J" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A computer program for generating all possible atom clusters interfering in mass spectrometer analyses is described. Program COMBIN constructs clusters of up to seven atoms and up to three electron charges which might interfere with a user-selected atomic mass. Based on a scan from mass 1 to 250 including the half masses, the upper limit of the intensity of each possible interference is investigated. Interferences whose intensity is calculated to be below a given limit are cancelled from the list of possible interferences. This reduced table of interfering clusters is the basis for identifying the peaks appearing in a high resolution scan of the mass region for the selected atomic species.", "doi": "10.1016/0168-1176(85)80004-5", "issn": "0168-1176", "publisher": "Elsevier", "publication": "International Journal of Mass Spectrometry and Ion Processes", "publication_date": "1985-06-26", "series_number": "3", "volume": "66", "issue": "3", "pages": "291-312" }, { "id": "authors:x14yp-zth73", "collection": "authors", "collection_id": "x14yp-zth73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130924-101654119", "type": "article", "title": "Nd and Sr isotopic compositions of tektite material from Barbados and their relationship to North American tektites", "author": [ { "family_name": "Ngo", "given_name": "Henry H.", "clpid": "Ngo-Henry-H-Meteoritics" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Glass", "given_name": "Billy P.", "clpid": "Glass-B-P" } ], "abstract": "Isotopic analyses of Nd and Sr on individual microtektites and a bulk microtektite sample from Barbados show them to have a very well defined isotopic composition. These data plot on an \u03b5_(Sr)\u03b5_(Nd) diagram precisely within the narrow field determined by North American tektites (\u03b5_(Sr) \u2248 111; \u03b5_(Nd) \u2248 \u22126.2). They yield an Nd model age of 0.6 AE. These results show that the microtektites from the Oceanic beds of late Eocene age are derived from the same target as the North American tektites and should be associated with the same event. Samples of the deep sea sediments in which the Barbados microtektites occur are found to have isotopic signatures which appear to reflect ambient sea water and detrital sediments. They cannot be the source of Sr or Nd in the tektites. Following the arguments of SHAW and WASSERBURG (1982) we conclude that the target area which produced the North American tektite field was composed of sediments (Eocambrian or younger) derived from very late Precambrian crust. Glass beads from Lake Wanapitei Crater are isotopically different from all other tektites (\u03b5_(Sr) \u2248 960; \u03b5_(Nd) \u2248 \u221231.4) and cannot be related to the North American tektites.", "doi": "10.1016/0016-7037(85)90297-2", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1985-06", "series_number": "6", "volume": "49", "issue": "6", "pages": "1479-1485" }, { "id": "authors:9qfch-mjb20", "collection": "authors", "collection_id": "9qfch-mjb20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131021-130808058", "type": "article", "title": "Willy: A prize noble Ur-Fremdling\u2014Its history and implications for the formation of Fremdlinge and CAI", "author": [ { "family_name": "Armstrong", "given_name": "John T.", "clpid": "Armstrong-J-T" }, { "family_name": "El Goresy", "given_name": "A.", "clpid": "El-Goresy-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A detailed mineralogic and chemical study of Willy, a very large (150 \u03bcm diameter) Fremdling from the Allende CAI 5241, was performed and compared to other Fremdlinge from Allende CAI's 5241 and TS-34 in an attempt to understand the nature and mode of formation of these exotic and complex objects. Willy is composed primarily of V-rich magnetite, V-rich fassaite, and Ni-Fe metal containing Co and Pt. Minor phases include an Fe-Ni-sulfide, V-rich spinel, scheelite (the first reported occurrence in a meteorite), and Cl-apatite. Phases found in trace amounts include nuggets of Os-Ru-Re metal, molybdenite, an unidentified Fe-, Mg-molybdate, and diopside. The Fremdling is concentrically zoned and contains a complex porous core of magnetite, metal, sulfide, scheelite, and other minor phases surrounded by a compact mantle of magnetite with minor apatite. The mantle is surrounded by a dense rim composed of fassaite with minor spinel that appears to be a typical occurrence around oxide-containing Fremdlinge. At the boundary between the fassaite-rim and the magnetite-mantle of Willy is a thin zone (<20 \u03bcm wide) of an apparent reaction assemblage consisting of V-rich MgAl_2O_4, FeAl_2O_4, and a third V-rich spinel, possibly FeV_2O_4, in intimate intergrowth.\n\nFrom the observed chemistry and texture, a multistage sequence of formation of Willy, possibly occurring in the solar nebula and involving major changes in T and fO_2, can be deduced. The first phases that may have formed in the interior are magnetite and an Fe or Ca tungstate. Refractory metal nuggets and sulfide were introduced after this stage followed by two stages of Ni-Fe formation during which Pt was dissolved in the metal. This was followed by formation of the magnetite mantle, introduction of apatite and possible alteration of ferberite to scheelite. Finally, the V-rich fassaite rim formed, accompanied or followed by reaction forming the complex Fe-, V-rich spinels. All of these steps preceded introduction of the Fremdling into the CAI precursor which in turn appears to have occurred prior to formation of spinel and the major silicate phases in the CAI.\n\nThe concentric mineral zoning and texture of Willy may indicate that it is one of the few Fremdlinge that was not substantially recrystallized after having been captured in the CAI. It thus may represent the precursor material for many of the other Fremdlinge, since numerous Fremdlinge studied exhibit many of the mineral and chemical features observed in Willy. The co-existence of magnetite, sulfide, and Ni-Fe metal in the interior of Willy and the co-existence of metal, hercynite spinel and magnetite at the rimmantle boundary suggests that the maximum temperature at which Willy could have existed for long periods of time in its present state was about 500\u2013600\u00b0C. Similarly, the existence of highly heterogeneous V-, Ti-rich fassaite rims around Willy and other Fremdlinge implies rapid cooling rates for the CAI's.", "doi": "10.1016/0016-7037(85)90315-1", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1985-04", "series_number": "4", "volume": "49", "issue": "4", "pages": "1001-1022" }, { "id": "authors:d18fj-jqd89", "collection": "authors", "collection_id": "d18fj-jqd89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-101530290", "type": "article", "title": "Self-shielding in O_2\u2014a possible explanation for oxygen isotopic anomalies in meteorites?", "author": [ { "family_name": "Navon", "given_name": "Oded", "clpid": "Navon-O" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "It is known that self-shielding of UV radiation by ^(16)O_2 produces selective isotopic effects upon photodissociation. An analysis of this process and the chemical kinetics of isotopic exchange and trapping of O has been carried out for different gas compositions and temperatures. Calculations of the shift in ^(16)O,^(17)O,^(18)O abundances due to self-shielding were carried out, and it is shown that the specific rates of photodissociation J_i give J_(17)/J_(18) \u223c 1 for column densities of O_2 between \u223c 10^(19) and 10^(22) molecules/cm^2 with a maximum value of J_(17)/J_(16) = 11 at a column density of \u223c 10^(21) molecules/cm^2. The O produced in this manner would have ^(17)O/^(18)O close to the starting material but be depleted in ^(16)O. These large shifts are quenched at temperatures higher than 500 K, or if water is present in higher concentration than O_2. Following dissociation, fast isotopic exchange reactions (e.g. ^(17)O + ^(16)O_2 \u2192 ^(16)O + ^(17)O ^(16)O) may destroy the effect unless the atomic oxygen is efficiently trapped. Competition between trapping and exchange is shown to be of a simple mathematical form which depends on the ratio of the rate of trapping of O to the rate of exchange. Using known rate constants it is shown that trapping of anomalous O by metal atoms, hydrogen, or the O_2 itself is inefficient at pressures lower than 10^(\u22123) atm and normal solar abundances. Trapping on dust grains may be efficient if all oxides are present as sub-micron particles. However, the extinction of radiation by the dust is likely to quench the self-shielding effect itself. Self-shielding of radiation by O_2, may, under special conditions, lead to the production of isotopically anomalous products. However, in the light of the difficulties throughout many stages of the process, it appears to be an unsatisfactory explanation for the oxygen anomalies observed in meteorites.\nThe above considerations are also applied to two experiments where O is trapped by O_2 to form ozone. The isotopic shifts found in experiments by Sander et al. [10] in O_3 are compatible with the criteria developed here. The shifts found by Thiemens and Heidenreich [11,12] using a discharge cannot be explained by self-shielding of UV radiation as the pressure is below the minimum needed for self-shielding to occur. The general nature of the pressure dependence of recent discharge experiments by Thiemens and others is in agreement with the prediction of a simple kinetic model based on the production of isotopically anomalous O during dissociation of O_2, isotopic exchange of O and O_2, and ozone formation. The observed isotopic effects in O_3 produced and trapped during discharge in O_2 thus appear to be understood phenomenologically but the mechanism for selective isotopic dissociation of O_2 is still obscure and remains a fundamental problem.\nOur analysis is directed toward O_2-rich environments and may only have limited applicability in the environment of the solar nebula. However, the general approach presented here is useful and may be applied to CO. It appears that selective isotopic shielding, or the mechanism which operates in the discharge experiments may still provide an explanation for some isotopic effects observed in meteorites but only if rapid trapping and isolation mechanisms (relative to exchange) can be found which apply in a low-pressure regime.", "doi": "10.1016/0012-821X(85)90030-5", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1985-04", "series_number": "1", "volume": "73", "issue": "1", "pages": "1-16" }, { "id": "authors:ebbg9-avd43", "collection": "authors", "collection_id": "ebbg9-avd43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-103534320", "type": "article", "title": "Strontium and neodymium isotopes in hot springs on the East\n Pacific Rise and Guaymas Basin", "author": [ { "family_name": "Piepgras", "given_name": "D. J.", "clpid": "Piepgras-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have determined the concentrations and isotopic compositions of Sr and Nd in hydrothermal fluids from 21\u00b0N, East Pacific Rise and Guaymas Basin, Gulf of California. The purest solutions analyzed from 21\u00b0N exhibit a small range in Sr concentration between individual vents from 5.8 to 8.7 ppm, close to normal seawater Sr concentrations. They exhibit a small range in ^(87)Sr/^(86)Sr from \u03b5_(Sr)(0) = \u221213.4 to \u221217.7, corresponding to \u03b5_(Sr)(0) \u2248 \u221218 \u00b1 2 in the pure hydrothermal end-member. These results indicate extensive but not complete isotopic exchange with Sr in the depleted oceanic crust (\u03b5 _(Sr)(0) = \u221231.8) and suggest that Sr concentrations in these solutions are buffered. In contrast, the concentration and isotopic composition of Nd in solutions show large variations between vents. The concentration of Nd ranges from 20 to 336 pg/g (6\u2013100 times seawater Nd concentrations). The isotopic composition ranges from \u03b5_(Nd)(0) = \u22123.6 (similar to Pacific seawater) to + 7.9. Many samples show substantial contributions from MORB, but all have \u03b5_(Nd)(0) well below MORB at this locality (\u03b5_(Nd)(0) = + 9.7) in spite of very large enrichments in Nd concentrations. While complete isotopic exchange with water/rock\u2248 2 or exchange with anomalous oceanic crust can explain the Sr data, the Nd data require exchange with a reservoir having \u03b5_(Nd)(0) < Pacific seawater. Low-temperature reactions with metalliferous sediments on the ridge flanks may provide such a source. Both Sr and Nd in the Guaymas Basin solution are very different from21\u00b0N. \u03b5_(Sr)(0) = + 11.0 and \u03b5_(Nd)(0) = \u221211.4 and are consistent with the fluid exchanging Sr and Nd with heated sediments having a substantial component of old continental detritus. Some irregularities in the Nd isotopic data reported here indicate that there must be a problem of contamination for some ultra-low-level trace elements during sample collection and processing which requires further attention.\nUsing a simple box model, the estimates for hydrothermal Nd fluxes are compared with fluxes which would be required to maintain the relatively radiogenic value of \u03b5_(Nd)(0) \u2248 \u22123 in the Pacific against the influx of more negative Antarctic waters (\u03b5_(Nd)(0) \u2248 \u22129). It is shown that the hydrothermal flux of Nd from mid-ocean ridges falls far short of that necessary to maintain the isotopic balance. This indicates that weathered material from volcanic terranes (\u03b5_(Nd)(0) \u2248 +7) is the most reasonable major source of radiogenic Nd in the Pacific.", "doi": "10.1016/0012-821X(85)90057-3", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1985-03", "series_number": "4", "volume": "72", "issue": "4", "pages": "341-356" }, { "id": "authors:bw8xj-rpz48", "collection": "authors", "collection_id": "bw8xj-rpz48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131025-133958633", "type": "article", "title": "Absolute isotopic abundances of Ti in meteorites", "author": [ { "family_name": "Niederer", "given_name": "F. R.", "clpid": "Niederer-F-R" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The absolute isotope abundance of Ti has been determined in Ca-Al-rich inclusions from the Allende and Leoville meteorites and in samples of whole meteorites. The absolute Ti isotope abundances differ by a significant mass dependent isotope fractionation transformation from the previously reported abundances, which were normalized for fractionation using ^(46)Ti/^(48)Ti. Therefore, the absolute compositions define distinct nucleosynthetic components from those previously identified or reflect the existence of significant mass dependent isotope fractionation in nature. We provide a general formalism for determining the possible isotope compositions of the exotic Ti from the measured composition, for different values of isotope fractionation in nature and for different mixing ratios of the exotic and normal components. The absolute Ti and Ca isotopic compositions still support the correlation of ^(50)Ti and ^(48)Ca effects in the FUN inclusions and imply contributions from neutron-rich equilibrium or quasi-equilibrium nucleosynthesis. The present identification of endemic effects at ^(46)Ti, for the absolute composition, implies a shortfall of an explosive-oxygen component or reflects significant isotope fractionation. Additional nucleosynthetic components are required by ^(47)Ti and ^(49)Ti effects. Components are also defined in which ^(48)Ti is enhanced.\nBulk samples of carbonaceous meteorites (C2 and C3 types) show distinct excesses at ^(50)Ti but no nonlinear effects at the other Ti isotopes. Other chondrites, including Orgueil (Cl), show no nonlinear effects. Relative to terrestrial Ti, a small isotope fractionation is found for only an enstatite chondrite. The Ti absolute compositions in Ca-Al-rich inclusions show significant isotope fractionation effects corresponding to an enhancement in the heavier isotopes relative to the lighter isotopes as compared to Ti in a TiO_2 standard and in chondrites. The absence of a correlation of Ti isotope fractionation effects with those for Ca and Mg is indicative of multiple processes of condensation, volatilization and recondensation; however, the mechanisms causing the isotope fractionation are not well understood.", "doi": "10.1016/0016-7037(85)90176-0", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1985-03", "series_number": "3", "volume": "49", "issue": "3", "pages": "835-851" }, { "id": "authors:k5yjc-35350", "collection": "authors", "collection_id": "k5yjc-35350", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-083445259", "type": "article", "title": "The age and emplacement of obducted oceanic crust in the Urals from Sm-Nd and Rb-Sr systematics", "author": [ { "family_name": "Edwards", "given_name": "R. Lawrence", "clpid": "Edwards-R-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The Urals contain a 2000 km belt of mafic-ultramafic bodies. The Sm-Nd and Rb-Sr systematics of two of these bodies, the Kempersai Massif in the South Ural Mountains and the Voykar-Syninsky Ophiolite Complex in the Polar Ural Mountains have been examined. These data confirm the hypothesis that these bodies represent fragments of pre-collision oceanic crust and establish constraints on the nature and timing of events in the Uralian Orogeny. Two Kempersai gabbros define Sm-Nd internal isochrons of 397 \u00b1 20 My and 396 \u00b1 33 My with \u03b5_(Nd)(T) = + 8.7 \u2213 0.6 and + 8.4 \u2213 1.3, respectively. Whole rock samples of pillow basalt, diabase, gabbros, troctolite, and a metasediment give Sm-Nd values which lie on this isochron indicating that these rocks are genetically related and have an igneous crystallization age of 397 My. Whole rock samples of Voykar-Syninsky diabase, gabbros, and clinopyroxenite give Sm-Nd values which lie on or within\u223c 1 \u03b5-unit of this isochron indicating an age and \u03b5_(Nd)(T) virtually identical to those of Kempersai. \u03b5_(Nd)(T) for the Kempersai and Voykar-Syninsky mafic samples range from +7.3 to + 9.0 with an average value of + 8.4. This indicates that the Urals ophiolites are derived from an ancient depleted mantle source and are most plausibly pieces of the oceanic crust and lithosphere. The fact that a metasediment has the same \u03b5_(Nd)(397 My) as the other samples indicates derivation from an oceanic source with negligible continental input. \u03b5_(Nd)(T) for the massifs is\u223c 1.5 \u03b5-units lower than the average for modern MORBs. This may be due to the differential evolution of the MORB source over the past 397 My and in conjunction with data for other ophiolites and Mesozoic MORB suggests that over the past 750 My the source for MORB has evolved at a rate less than or equal to its rate of evolution averaged over the age of the earth. Initial ^(87)Sr^(86)Sr ratios are highly variable ranging from \u03b5_(Sr)(T) = \u221225.2 for a gabbro to +70.3 for a highly serpentinized harzburgite. This reflects the effects of seawater alteration which is particularly strong on ultrabasic rocks. We conclude that the long belt of mafic-ultramafic rocks in the Urals, which includes the Kempersai and Voykar-Syninsky Massifs, represents segments of Siluro-Devonian oceanic crust. Our igneous age for Kempersai in conjunction with other age constraints suggest that these segments of oceanic crust formed at least 80 My before the collision that produced the Urals.", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1985-03", "series_number": "4", "volume": "72", "issue": "4", "pages": "389-404" }, { "id": "authors:z1dm9-vq949", "collection": "authors", "collection_id": "z1dm9-vq949", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-140440003", "type": "article", "title": "Sm-Nd in marine carbonates and phosphates: Implications for\n Nd isotopes in seawater and crustal ages", "author": [ { "family_name": "Shaw", "given_name": "H. F.", "clpid": "Shaw-H-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "This study explores the possibility of establishing Nd isotopic variations in seawater over geologic time. Calcite, aragonite and apatite are examined as possible phases recording seawater values of \u03f5_(Nd). Modern, biogenic and inorganically precipitated calcite and aragonite from marine environments were found to have Nd concentrations of from 0.2 to 70 ppb, showing that primary marine CaCO_3 contains little REE and that Nd/Ca is not greatly enhanced relative to seawater during carbonate precipitation. Very young marine limestone and dolomite containing no continental detritus have ~200 ppb Nd. All the carbonates are LREE enriched (-0.16\u2264\u0192^(Sm/Nd) \u2264-0.45). Modern and very young Atlantic and Pacific carbonates have \u03f5_(Nd) in the range of shallow Atlantic and Pacific seawater respectively, implying that they derive their REE from local seawater. The Nd in well preserved carbonate fossils is \u22644 \u00d7 10^4 ppb, much greater than in their modern counterparts but like the high values found for carbonates in other studies. We believe the high REE contents (at the 500 ppb level) in some detritusfree carbonates are due to REE-rich Fe-hydroxide in/on the carbonate. In favorable cases, such material may record seawater \u03f5_(Nd) values, however introduction of extraneous REE may obscure the original isotopic composition of pure CaCO_3 because of its very low intrinsic primary REE abundance.\nModern biogenic apatite is also shown to have very low REE content (<150 ppb Nd) but appears to quickly scavenge REE from seawater. Inorganically precipitated apatite from phosphorites has high concentrations of seawater-derived REE. Young phosphorite apatite from the Atlantic and Pacific oceans has \u03f5_(Nd) in the range of the seawater from these oceans. Older apatite samples of similar age from different localities bordering common oceans record similar values of \u03f5_(Nd)(T). Sedimentary apatite has \u03f5_(Sr)(T) values in good agreement with the curves for ^(87)Sr/^(86)Sr of seawater as a function of time. Individual conodonts from a single formation yield the same \u03f5_(Sr)(T) and \u03f5_(Nd)(T). Other workers have shown that sedimentary apatite preserves seawater REE patterns. These characteristics suggest that sedimentary apatite can be used to determine \u03f5_(Nd)(T) in ancient seawater. The seawater values so inferred range between \u22121.7 and \u22128.9 over the last 700 my and lie in the range of modern seawater, showing no evidence for drastic changes. High values of seawater \u03f5_(Nd)(T) in the Triassic and latest Precambrian may correlate with the breakup of large continental landmasses. The initial \u03f5_(Nd)(T) =\u221215.0 of a 2 AE old phosphorite implies the presence of ~ 1.5 AE old continental crust at 2 AE ago. The approach outlined here can be used to constrain the age of the exposed crust as a function of time.", "doi": "10.1016/0016-7037(85)90042-0", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1985-02", "series_number": "2", "volume": "49", "issue": "2", "pages": "503-518" }, { "id": "authors:sxce3-djh66", "collection": "authors", "collection_id": "sxce3-djh66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140305-095632945", "type": "article", "title": "Excess ^(41)K in Allende CAI: a hint re-examined", "author": [ { "family_name": "Hutcheon", "given_name": "I. E.", "clpid": "Hutcheon-I-E" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The timescale for injection of fresh nucleosynthetic material and for the formation of the first solids in the early solar system is determined by the existence and abundance of short-lived nuclei. The presence of live ^(26)Al with ^(26)AI/^(27)AI ~ 5 x 10^(-5) in numerous CAI from C2 and C3 meteorites places an upper limit to this timescale of ~ 8 x 10^6 y but the lower limit is poorly\nconstrained.", "doi": "10.1111/j.1945-5100.1984.tb00840.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1984-12", "series_number": "4", "volume": "19", "issue": "4", "pages": "243-244" }, { "id": "authors:5ctnk-xhs70", "collection": "authors", "collection_id": "5ctnk-xhs70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140130-094000801", "type": "article", "title": "Fremdlinge in Leoville and Allende CAI \u2013 Clues to Post-Formation Cooling and Alteration", "author": [ { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Fremdlinge are perhaps the most exotic and least understood objects in CAI and their very\nexistence places severe constraints regarding formation and cooling histories of the host CAI.\nFollowing the discovery and description of Willy, which appears to be an \"Ur-Fremdling\" or\nprototype for smaller Fremdlinge in CAI, we have begun a systematic study of CAI of different\npetrographic types to see if the Fremdlinge are consistent with a common mode of formation\nand differing degrees of reprocessing. Fifteen type B I, B2, and compact A CAI from Allende\nand Leoville were selected. The relative abundance of Fremdlinge varies dramatically among\nCAI, however some CAI of each type and from each meteorite contain abundant Fremdlinge.\nThe range of phase assemblages and mineral chemistries of Fremdlinge from Allende and Leoville\nis very similar suggesting that the parent sources for Fremdlinge were quite similar. Chemically\nand texturally, Fremdlinge grade continuously from complex, heterogeneous Willy-like objects\nto altered, homogeneous metal nuggets. Some complex Fremdlinge like Willy were found in B1\nCAI; none were observed in B2 CAI.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1984-12", "series_number": "4", "volume": "19", "issue": "4", "pages": "186-187" }, { "id": "authors:042k0-b6n55", "collection": "authors", "collection_id": "042k0-b6n55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140305-102245028", "type": "article", "title": "Absence of excess ^(26)Mg in anorthite from the Vaca Muerta mesosiderite", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The absence of ^(26)Mg excesses in Al-rich phases (feldspars) from basaltic achondrites, high petrographic grade chondrites and a K-feldspar from an iron meterorite was established by\nprevious work (Schramm et at., 1970).", "doi": "10.1111/j.1945-5100.1984.tb00840.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1984-12", "series_number": "4", "volume": "19", "issue": "4", "pages": "289-290" }, { "id": "authors:q2cd3-nbw94", "collection": "authors", "collection_id": "q2cd3-nbw94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140305-101511796", "type": "article", "title": "Mg Isotopic studies of Leoville \"compact\" type a CAI", "author": [ { "family_name": "Hutcheon", "given_name": "I. E.", "clpid": "Hutcheon-I-E" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "One long-standing problem in the application of Al-Mg isotopic systematics to the chronology of CAI is the enigmatic Mg isotopic record of hibonite. Hibonite (ideally, CaAI_(12)O_(19)) is one of the first major element bearing phases to appear in the condensation sequence [1] and occurs as a major constituent only in CAI whose bulk composition is considerably more refractory\nthan Allende Type Bl CAI.", "doi": "10.1111/j.1945-5100.1984.tb00840.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1984-12", "series_number": "4", "volume": "19", "issue": "4", "pages": "244-245" }, { "id": "authors:r5qgh-8f173", "collection": "authors", "collection_id": "r5qgh-8f173", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140305-092640535", "type": "article", "title": "Mg Isotopic measurements in fine-grained Ca-AI-rich inclusions", "author": [ { "family_name": "Brigham", "given_name": "C. A.", "clpid": "Brigham-C-A" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A study of the Mg isotopic composition and mineralogy of fine-grained, Ca-Al-rich inclusions has been initiated, to search for isotope fractionation and for excess ^(26)Mg^* due to the decay of ^(26)Al. It is important to establish whether there is evidence, in these inclusions, of isotopic\nheterogeneity, whether ^(26)Mg^* is correlated with AI/Mg, and whether there is a correlation of the isotopic effects with mineralogy.", "doi": "10.1111/j.1945-5100.1984.tb00840.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1984-12", "series_number": "4", "volume": "19", "issue": "4", "pages": "198-199" }, { "id": "authors:yb5q0-8kz88", "collection": "authors", "collection_id": "yb5q0-8kz88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-093222394", "type": "article", "title": "Petrography of Cape York and Grant: Irons with Simple Pd-Ag Systematics", "author": [ { "family_name": "Teshima", "given_name": "J. M.", "clpid": "Teshima-J-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "El Goresy", "given_name": "A.", "clpid": "El-Goresy-A" } ], "abstract": "The presence of excess ^(107)Ag from the decay of extinct ^(107)Pd(t_(1/2) = 6.5 my) has been determined in IVB, IV A and two anomalous irons (Kaiser and Wasserburg, 1983). Excesses of ^(107)Ag in groups IIIAB and IIB meteorites, Cape York and Grant, and Derrick Peak, respectively,\nshow the widespread presence of ^(107)Pd in the early solar system (Chen and Wasserburg, 1983).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1984-12", "series_number": "4", "volume": "19", "issue": "4", "pages": "322-322" }, { "id": "authors:zp4kk-h4878", "collection": "authors", "collection_id": "zp4kk-h4878", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140305-094103116", "type": "article", "title": "Anomalous silver in sulfide nodules", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Excesses of ^(107)Ag (^(107)Ag^*) correlated with Pd/Ag have been found in iron meteorites of IVA, IVB and IIIAB groups, and is inferred to be the daughter of extinct ^(107)Pd (\u01ac = 9.4 m. y.) (Kelly and Wasserburg, 1978; Kaiser and Wasserberg, 1983; Chen and Wasserburg, 1983, 1984). However the Pd/Ag systematics involving the coexisting metal and sulfide phases of Santa Clara\n(IVB) and Gibeon (IVA) do not show a good internal isochron.", "doi": "10.1111/j.1945-5100.1984.tb00840.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1984-12", "series_number": "4", "volume": "19", "issue": "4", "pages": "206-207" }, { "id": "authors:1bf5x-a9y71", "collection": "authors", "collection_id": "1bf5x-a9y71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140911-074832546", "type": "article", "title": "Willy: A Prize Noble Ur-Fremdling from the Allende Meteorite", "author": [ { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "El Goresy", "given_name": "A.", "clpid": "El-Goresy-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Among the most exotic and complex objects found in CAI are Fremdlinge (1). The small size of these objects (typically << 50 \u00b5m) has limited their petrologic and chemical investigation, and, to date, no isotopic analyses of individual Fremdlinge have been performed. The Allende CAl 5241 contains numerous Fremdlinge, two of which are of very large size (>100 \u00b5m P) and are contained in a single melilite grain. We report on a detailed petrologic and chemical investigation of \"Willy\", the larger of these Fremdlinge (~150 \u00b5m \u00d8). Willy is compose primarily of a V-rich magnetite (V-mt), Ni-Fe metal, and troilite (FeS). Minor constituents include scheelite (CaW0_4), apatite, an Os-Ru alloy, MoS_2, and an unidentified Mg- Fe- molybdate.\nWilly contains a complex fluffy core of V-mt, metal, FeS, and other minor phases. The core is surrounded by a compact V-rich magnetite mantle. The mantle is surrounded by a rim\ncomposed of V-rich fassaite and V-rich spinels. This type of rimming is typical of oxide-bearing Fremdlinge in 5241 and other CAl from the Allende carbonaceous chondrite (CV3).", "issn": "0015-8186", "publisher": "Deutsche Mineralogische Gesellschaft.", "publication": "Fortschritte der Mineralogie", "publication_date": "1984-08", "series_number": "1", "volume": "62", "issue": "1", "pages": "12-14" }, { "id": "authors:qdfg9-s6w95", "collection": "authors", "collection_id": "qdfg9-s6w95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131022-150302212", "type": "article", "title": "A Nd and Sr isotopic study of the Trinity peridotite; implications for mantle evolution", "author": [ { "family_name": "Jacobsen", "given_name": "S. B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Quick", "given_name": "J. E.", "clpid": "Quick-J-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Field evidence indicates that the Trinity peridotite was partially melted during its rise as a part of the upwelling convecting mantle at a spreading center. A Sm-Nd mineral isochron for a plagioclase lherzolite yields an age,T = 427 \u00b1 32 Ma and initial \u03b5_(Nd) = + 10.4 \u2213 0.4 which is distinctly higher than that expected for typical depleted mantle at this time. This age is interpreted as the time of crystallization of trapped melt in the plagioclase lherzolite P-T field. This time of crystallization probably represents the time when the massif was incorporated as a part of the oceanic lithosphere. The Sm-Nd model age of the plagioclase lherzolite total rock is T_(CHUR)^(Nd) = 3.4 AE. This suggests that the Trinity peridotite was derived from a mantle that was depleted rather early in earth history. The peridotite contains many generations of pyroxenite dikes and some microgabbro dikes. We report data for two dikes that clearly crosscut the main metamorphic fabric of the peridotite. A microgabbro dike yields a Sm-Nd mineral isochron age of T = 435 \u00b1 21 Ma and \u03b5_(Nd) = + 6.7 \u2213 0.3. A pyroxenite dike yields an initial \u03b5_(Nd) = + 7.3 \u00b1 0.4. The initial \u03b5_(Nd) values for the pyroxenite and gabbro dikes are fairly similar to those for the depleted mantle at this time and are distinct from the lherzolite\u2014demonstrating that they are not genetically related. Rb-Sr data do not give any coherent pattern. However, some bounds can be put on initial Sr values of \u03b5_(Sr) \u2a7d \u221221 for the plagioclase lherzolite and \u03b5_(Sr) \u2a7d \u22128.7 for the microgabbro dike. It is plausible that the dikes represent cumulates left behind from island arc magmas that rose through the the oceanic lithosphere within the vicinity of a subduction zone. Major and trace elements and Sm-Nd isotopic data indicate a multiple stage history for the Trinity peridotite; a small melt fraction was extracted from an undepleted source \u223c 3.4 AE or more ago to produce the proto-lherzolite; a large fraction of melt (\u223c 12 to 23%) was extracted from the proto-lherzolite to produce the present rock; the lherzolite was then crosscut by dikes from average depleted mantle \u223c 0.44 AE ago. The data are compatible with the depleted mantle source being formed very early in earth history. Although most available data indicate that the depleted upper mantle has been relatively well stirred through time, the Trinity data suggest that very ancient Nd isotopic values are preserved and thus chemical and physical heteorgeneities are sometimes preserved in the depleted source of mid-ocean ridge basalts as well as the oceanic lithosphere which they intrude.", "doi": "10.1016/0012-821X(84)90122-5", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1984-06", "series_number": "3", "volume": "68", "issue": "3", "pages": "361-378" }, { "id": "authors:s7xjb-dqv62", "collection": "authors", "collection_id": "s7xjb-dqv62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140305-103135141", "type": "article", "title": "Isotopic constraints on the origin of Appalachian mafic complexes", "author": [ { "family_name": "Shaw", "given_name": "H. F.", "clpid": "Shaw-H-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Isotopic analyses of modern oceanic basalts and ophiolites\nhave shown that both modern and ancient oceanic crust have a\ncharacteristic Nd and Sr isotopic signature indicative of derivation from a depleted mantle reservoir. It also appears that the Nd isotopic system is not appreciably disturbed by metamorphism. These isotopic characteristics have been extended to the Pt. Sal, Kings-Kaweah, and Josephine ophiolites of California. We have used these characteristics in an attempt to identify pieces of proto-Atlantic oceanic crust among the mafic and ultramafic rocks of the Appalachians. Sm-Nd mineral isochrons for the Baltimore Mafic Complex, Maryland (BMC) yield an age of 490 \u00b1 20 my which we interpret as the igneous crystallization age. BMC whole rock samples do not define isochrons and have initial isotopic compositions of -6.4 < \u0404_(Nd)(T) <\n- 2.2, +51 < \u0404_(Sr)(T) < + ll5. \u0404_(Nd)(T) and \u0404_(Sr)(T) are anti-correlated. This is not the signature of depleted mantle and oceanic crust hut is similar to old continental crust. We propose that the BMC is a mafic continental intrusion, possibly subduction related, which was contaminated with old continental crust during emplacement. Whole rock samples from the Thetford Mines Complex, Qe (TMC), do not define isochrons and have -1.5 < \u0404_(Nd)(T) < +4.2, + 2.6 < \u0404_(Sr)(T) < + 114. These data do not in any way reflect the signature of normal oceanic crust. These results are in contrast with geologic relationships that show the TMC to have the characteristics of an ophiolite\ncomplex. The TMC is chemically and isotopically similar to a class of other ophiolites that have affinities to modern honinites. The Chunky Gal Amphibolite, North Carolina, Lake Chatuge complex, North Carolina, and Hazen's Notch Amphibolite, Vermont were found to have a depleted mantle signature with +5 < \u0404_(Nd) (T) < +8 and may he fragments\nof oceanic crust. The Webster-Addie body, North Carolina, has \u0404_(Nd)(T)~-1, \u0404_(Sr)(T)~+30 and is not isotopically similar to oceanic crust or the other North Carolina mafic bodies analyzed. From these isotopic results we infer that Appalachian mafic rocks have diverse origins: some are continental intrusives (BMC), others are probably fragments of oceanic crust (Vermont and North Carolina amphiholites). Future models for the development of the Appalachians must\nallow for these various origins. The possibility that some onhiolites are not normal oceanic crust but have an origin in a partially continental setting or as anomalous oceanic crust may require further attention.", "issn": "0002-9599", "publisher": "American Journal of Science", "publication": "American Journal of Science", "publication_date": "1984-05", "series_number": "4-5", "volume": "284", "issue": "4-5", "pages": "319-349" }, { "id": "authors:kt377-zxg73", "collection": "authors", "collection_id": "kt377-zxg73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140115-111648559", "type": "article", "title": "Sm-Nd and Rb-Sr Systematics in Volcanics and Ultramafic Xenoliths From Malaita, Solomon Islands, and the Nature of the Ontong Java Plateau", "author": [ { "family_name": "Bielski-Zyskind", "given_name": "Miriam", "clpid": "Bielski-Zyskind-M" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Nixon", "given_name": "P. H.", "clpid": "Nixon-P-H" } ], "abstract": "A Rb-Sr and Sm-Nd study was carried out on five ultrabasic inclusions, three alnoite host rocks, and one sample of basalt from Malaita in an effort to determine the isotopic stratigraphy of the mantle in this area. The results of this study show the presence of relatively undepleted mantle segments underlying relatively older depleted upper mantle. The alnoite samples, three megacrysts and one Iherzolite inclusion, and the basalt are relatively uniform isotopically and yielded \u03b5_(Nd) (T) \u2248 +3.5 and \u03b5_(Sr) (T) \u2248 \u22126 to +17 (T = 100 m.y. for the basalt and Iherzolite and 34 m.y. for the rest of the samples). It is suggested that a mantle segment of that isotopic composition exists at a depth of more than 100 km. This mantle segment is relatively undepleted. A Iherzolite inclusion with \u03b5_(Nd) (T) = 6.6 is included in the alnoite and indicates the location of a light rare earth element depleted layer overlying a less depleted mantle at a depth of approximately 100 km. The mantle source for the alnoite and basalt cannot be old, depleted oceanic mantle or subducted old continental crust but may come from a relatively young, slightly depleted mantle segment. The isotopic results are compatible with a mixture of about 99% depleted oceanic mantle homogenized with 1% continental crust possibly by metasomatic processes. Such a mixture is only slightly fractionated and has \u0192^(Sm/Nd) \u2248 0.13 and \u0192^(Rb/Sr) \u2248 0. Assuming that the basalt is characteristic of the Ontong Java Plateau, a volume greater than 108 km3 of mantle source with \u03b5_(Nd) \u223c 3.5, \u03b5_(Sr) \u223c 0 was involved. This corresponds to a block of continental crust of \u223c 10^6 km^3 which had to reach a depth greater than 100 km to produce the proposed nearly homogeneous isotopic mixture. Alternatively, the source of the Ontong Java Plateau may be a segment of a type of young continental crust with the appropriate isotopic signature which was subducted below 100 km. This would not require homogenization with a large volume of depleted mantle.", "doi": "10.1029/JB089iB04p02415", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1984-04-10", "series_number": "B4", "volume": "89", "issue": "B4", "pages": "2415-2424" }, { "id": "authors:7867d-wpk40", "collection": "authors", "collection_id": "7867d-wpk40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140115-133554905", "type": "article", "title": "Eruption Age of a ~100,000-Year-Old Basalt From ^(40)Ar-^(39)Ar Analysis of Partially Degassed Xenoliths", "author": [ { "family_name": "Gillespie", "given_name": "A. R.", "clpid": "Gillespie-A-R" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have applied ^(40)Ar-^(39)Ar dating, using stepwise thermal extraction of Ar, to five potassium-rich granitic xenoliths and their host basalt from Sawmill Canyon in the Sierra Nevada, California. Previous K/Ar analyses showed the age of the basalt to be roughly 100,000 years or less. The xenoliths, which had accumulated large amounts of radiogenic ^(40)Ar since their crystallization \u223c100 m.y. ago, were partially degassed upon their inclusion in the basaltic magma. Ar released from the xenoliths in the laboratory at temperatures substantially below the melting temperature of the basalt, was created since the host magma cooled. Isotopic compositions of Ar released from the xenoliths in several extraction steps at temperatures below \u223c900\u00b0C were colinear in ^(36)Ar/^(40)Ar versus ^(39)Ar/^(40)Ar diagrams and defined isochrons giving a mean age of degassing of 119,000\u00b17000 (2\u03c3) years. ^(40)Ar extracted at higher temperatures included ancient radiogenic ^(40)Ar that was never diffused from the xenoliths during immersion in the magma. This ^(40)Ar caused an increase in the apparent age for the high-temperature extractions. The high precision of the eruption age determined by this method is comparable to that obtained elsewhere by conventional K/Ar dating of sanidine. ^(40)Ar-^(39)Ar analysis of granitic xenoliths to date young basaltic lava flows may prove to yield results superior to those found from analysis of the lava itself. Establishing the age of eruption of the basalt flow in Sawmill Canyon establishes age limits for two Sierran glaciations which left moraines stratigraphically above and below the lava. Thus the younger glaciation must be Wisconsin; the older must be pre-Wisconsin in age.", "doi": "10.1029/JB089iB02p01033", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1984-02-10", "series_number": "B2", "volume": "89", "issue": "B2", "pages": "1033-1048" }, { "id": "authors:h77zc-55263", "collection": "authors", "collection_id": "h77zc-55263", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-073748285", "type": "article", "title": "Sm-Nd isotopic evolution of chondrites and achondrites, II", "author": [ { "family_name": "Jacobsen", "given_name": "S. B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The ^(147)Sm-^(143)Nd and ^(146)Sm-^(142)Nd isotope systematics have been investigated in five chondrites and the achondrites Moama and Angra dos Reis (ADOR). The new chondrite data and those we have reported before are all consistent with our previously reported reference values for CHUR (\"chondritic uniform reservoir\") of (^(143)Nd/^(144)Nd)_(CHUR)^0 = 0.511847 and (^(147)Sm/^(144)Nd)_(CHUR)^0 = 0.1967. Most of the bulk chondrites analyzed have ^(143)Nd/^(144)Nd and ^(147)Sm/^(144)Nd within 0.5 \u03b5-units and 0.15% of the CHUR values, respectively. This strongly suggests that the CHUR evolution is now known to within these error limits throughout the history of the solar system. The St. Severin chondrite yields an Sm-Nd internal isochron age of T = 4.55 \u00b1 0.33AE and an initial \u03b5_(Nd) = 0.11 \u2213 0.26. Much larger variations in Sm/Nd ratios were measured in mineral separates of the Moama and ADOR achondrites. Thus, very precise ages of 4.46 \u00b1 0.03 AE and 4.564 \u00b1 0.037 AE were obtained for these meteorites, respectively. The initial \u03b5_(Nd) values obtained for Moama and ADOR are 0.03 \u2213 0.25 and 0.14 \u2213 0.20, respectively. The values obtained on these meteorites are fully consistent with the CHUR evolution curve. Initial \u03b5_(Nd) data on terrestrial igneous and meta-igneous rocks demonstrates that positive initial \u03b5_(Nd) values occur throughout the past 4 AE. This confirms our earlier report that a light rare earth element-depleted layer has existed throughout most of the Earth history and is the source of present-day mid-ocean ridge basalts. The inferred shape of the \u03b5_(Nd) vs. age curve for the depleted mantle suggests profound changes in tectonic regimes with time; in particular, it suggests a much higher rate of recycling of continental materials into the mantle during the Archean as compared to later time periods.\n^(146)Sm-^(142)Nd systematics of ADOR and Moama are supportive of the hypothesis that ^(146)Sm was present in the early solar system and suggests a ^(146)Sm/^(144)Sm ratio of about 0.01 for the solar system \u223c 4.56 AE ago. This inferred high ^(146)Sm abundance cannot be explained as a late injection from a supernova and must be due to galactic nucleo-synthesis.", "doi": "10.1016/0012-821X(84)90109-2", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1984-02", "series_number": "2", "volume": "67", "issue": "2", "pages": "137-150" }, { "id": "authors:rjqqc-jd748", "collection": "authors", "collection_id": "rjqqc-jd748", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-090940921", "type": "article", "title": "The On-Going Search for FUN Inclusions", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report on the Mg and Ca isotopic composition in two inclusions from the Allende meteorite for which there are hints of FUN characteristics. Inclusion EK25-S2-TE is a coarse-grained olivine-rich inclusion discovered and analyzed in detail by El Goresy and co-workers (Dominik et al., 1978).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1983-12", "series_number": "4", "volume": "18", "issue": "4", "pages": "370-371" }, { "id": "authors:rbbzc-34639", "collection": "authors", "collection_id": "rbbzc-34639", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-141828052", "type": "article", "title": "A Search for Primordial Pb in Iron Meteorites", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "This report is on our efforts to identify and measure primordial lead (PAT) in iron meteorites. We previously found variable Pb isotopic composition in several iron meteorites after etching the surface of the meteorites to remove terrestrial contamination (Chen and Wasserburg, 1983).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1983-12", "series_number": "4", "volume": "18", "issue": "4", "pages": "279-280" }, { "id": "authors:p05x4-k3q23", "collection": "authors", "collection_id": "p05x4-k3q23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-090049637", "type": "article", "title": "I-Xe Studies of Allende Inclusions", "author": [ { "family_name": "Hohenberg", "given_name": "C. M.", "clpid": "Hohenberg-C-M" }, { "family_name": "Caffee", "given_name": "M. W.", "clpid": "Caffee-M-W" }, { "family_name": "Swindle", "given_name": "T. D.", "clpid": "Swindle-T-D" }, { "family_name": "Hudson", "given_name": "G. B.", "clpid": "Hudson-G-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "This work reports isotopic studies of xenon extracted in stepwise heating from five neutron-irradiated\ncoarse-grained refractory Allende inclusions (EGGs). Besides trapped xenon, these objects contain xenon derived from I, Ba, Pu and U. The five EGGs display a range of xenon\ncompositions indicating a wide variety of chemical and isotopic structures.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1983-12", "series_number": "4", "volume": "18", "issue": "4", "pages": "313-313" }, { "id": "authors:js4zd-s1w72", "collection": "authors", "collection_id": "js4zd-s1w72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-111444154", "type": "article", "title": "The isotopic composition of silver and lead in two iron meteorites: Cape York and Grant", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Silver in the metal phases of Cape York (IIIA) and Grant (IIIB) has been determined after an extensive surface cleaning process. The ^(107)Ag/^(109)Ag was found to be enriched over that found in terrestrial Ag by ~7%. to 19%., demonstrating the presence of excess ^(107)Ag (^(107)Ag^\u2217) in this class of meteorites. An effort was made to find schreibersite with a distinctive ^(108)Pd/^(109)Ag ratio in order to establish a three-point isochron, but the results are not markedly different from those obtained for the bulk metal. The Ag isotopic ratio of sulfides from the same meteorites were nearly normal in composition. These results demonstrate correlations of ^(107)Ag/^(109)Ag with ^(108)Pd/^(109)Ag between coexisting phases of two iron meteorites that are associated with planetary differentiation processes. The ratios ^(107)Ag^*/^(109)Pd were found to be 1.7 \u00d7 10^(\u22125) and 1.2 \u00d7 10^(\u22125) for Cape York and Grant, respectively. These observations are in support of the widespread presence of ^(107)Pd in the early solar system. The difference in isotopic composition between metal and sulfide phases demonstrates that silver diffusion was small (over 6.5 \u00d7 10^6 y) indicating a cooling rate much greater than 150\u00b0C/my for meteorites which have been attributed to small planetary cores. Uranium determinations were carried out on the metal phases and concentrations of ~ 1 \u00d7 10 ^(12) g U/g and 2 \u00d7 10^(\u221210)g U/g were found for Cape York and Grant, respectively. The Pb in these meteorites was determined using the improved cleaning procedures and chemical separations with low blank levels. The results confirm the presence of variable proportions of radiogenic Pb in both the metal and sulfide phases of iron meteorites. No simple explanation for the presence of radiogenic lead is apparent; while terrestrial contamination may appear to be the obvious explanation, it is possible that this effect could result from relatively recent metamorphism in the meteorite parent body.", "doi": "10.1016/0016-7037(83)90022-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1983-10", "series_number": "10", "volume": "47", "issue": "10", "pages": "1725-1737" }, { "id": "authors:kyzwc-c2b87", "collection": "authors", "collection_id": "kyzwc-c2b87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130904-154603038", "type": "article", "title": "Chemical and isotopic study of extraterrestrial particles from the ocean floor", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Brownlee", "given_name": "D. E.", "clpid": "Brownlee-D-E" } ], "abstract": "We report chemical, mineralogic and Rb-Sr data on deep-sea spherules and on particles from an Antarctic Ocean core in which an excess Ir content has been identified. ^(87)Sr/^(86)Sr compositions in the deep-sea spherules are determined to 1\u20132\u2030 and are in the range 0.730\u20130.757. The ^(87)Sr/^(86)Sr compositions and the Sr concentrations are in the range observed for the majority of chondritic meteorites. ^(84)Sr/^(88)Sr ratios are normal to within 1%. Extreme depletion of Rb relative to the chondritic abundance is found in the deep-sea spherules. These data support the inference based on chemical composition and mineralogy that the deep-sea spherules are produced by the ablation or heating of meteoroids in the Earth's atmosphere with substantial loss of Rb by volatilization. Most terrestrial sources for the deep-sea spherules can be excluded, based on the chemical composition and on the Sr isotopic composition. The results on vesicular, Ir-rich particles from the Antarctic Ocean core give ^(87)Sr/^(86)Sr in the range 0.703\u20130.705 and within the range observed for ocean island basalts but significantly above mid-ocean ridge basalts (MORB). A crystalline basaltic particle from this core shows non-radiogenic ^(87)Sr/^(86)Sr= 0.701 \u00b1 0.001, in the range observed for MORB and basaltic achondrites. The Sr data on the vesicular particles do not provide positive support for an extraterrestrial provenance for these materials. The basaltic particles cannot reasonably be the primary source of the high Ir concentration and some other lithic component remains to be identified.", "doi": "10.1016/0012-821X(83)90095-X", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1983-09", "series_number": "3", "volume": "64", "issue": "3", "pages": "341-355" }, { "id": "authors:72k4r-me765", "collection": "authors", "collection_id": "72k4r-me765", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-114200776", "type": "article", "title": "FUN with PANURGE: High mass resolution ion microprobe\n measurements of Mg in Allende inclusions", "author": [ { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The performance characteristics of PANURGE, a modified CAMECA IMS3F ion microprobe, have been studied at a mass resolving power of 5000 for the purpose of determining isotopic ratios at a precision level approaching that of counting statistics using beam switching. The techniques used for this type of measurement are described. Using this approach, the isotopic composition of Mg and Si and the atomic ratio of Al/Mg in minerals from the Allende inclusion WA and the Allende FUN inclusion Cl have been measured with the ion microprobe at high mass resolving power. Enrichments in ^(26)Mg of up to 260%. have been found. Mg and Al/Mg measurements on cogenetic spinel inclusions and host plagioclase crystals yield Mg-Al isochrons in excellent agreement with precise mineral isochrons determined by thermal emission mass spectrometry. The measurements confirm the presence of substantial excess (^(26)Mg in WA ^(26)Mg^*/^(27)Al = 5 X 10^(-5)) and its near absence in Cl (^(26)Mg^*/^(27)Al < 4 X 10^(-6)). In WA plagioclase, data for which ^(27)Al/^(24)Mg = 300 to 1000 define a linear array with ^(26)Mg^*/^(27)Al = 3 X 10^5 and with initial ^(26)Mg/^(24)Mg composition 30%. greater than in high Mg phases. This suggests a metamorphic reequilibration of Mg in Allende plagioclase at least 0.6 my after WA formation. There were no variations in detected ^(26)Mg^*/^(27)Al in WA plagioclase associated with concentration of ^(26)Mg^\u2217 into isolated clusters. We have confirmed by ion probe measurements that the Mg composition in Allende Cl is highly fractionated and is uniform among pyroxene, melilite, plagioclase, spinel crystals and spinel included in melilite and plagioclase crystals. Likewise, the Si composition is mass fractionated and is the same in pyroxene, melilite and plagioclase.", "doi": "10.1016/0016-7037(83)90190-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1983-09", "series_number": "9", "volume": "47", "issue": "9", "pages": "1635-1650" }, { "id": "authors:g6jy0-dz823", "collection": "authors", "collection_id": "g6jy0-dz823", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131016-091716372", "type": "article", "title": "Influence of the Mediterranean Outflow on the isotopic composition of neodymium in waters of the North Atlantic", "author": [ { "family_name": "Piepgras", "given_name": "D. J.", "clpid": "Piepgras-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of neodymium in the water column of the eastern North Atlantic near the Strait of Gibraltar has been determined for several depths. The data show that the Mediterranean outflow results in a significant shift in \u03b5_(Nd)(0) toward more radiogenic values of ^(143)Nd/^(144)Nd in the water column at a 1000-m depth. This corresponds to a depth in the neighborhood of the salinity maximum associated with the Mediterranean outflow. The core of the Mediterranean outflow gives \u03b5_(Nd)(0) = \u22129.8, as compared to \u03b5_(Nd)(0) \u2248 \u221212 in overlying and underlying waters, demonstrating that the Mediterranean waters are distinct from the Atlantic. From mixing considerations we estimate that pure Mediterranean waters have \u03b5_(Nd)(0) \u2248 \u22126. Possible sources of this relatively radiogenic Nd could be from drainage of young continental terranes or the injection of remobilized Nd from deep-sea sediments that have a young radiogenic volcanic component. New data from a depth profile in the western Atlantic is presented. Comparison of Nd data for the eastern North Atlantic with that for the western North Atlantic shows fundamental differences in the water column structures for \u03b5_(Nd)(0). While both regions show a pronounced maximum in \u03b5_(Nd)(0), the western basin maximum occurs at the near surface rather than at 1000 m. In addition, deep waters of the eastern basin are found to be more radiogenic than the western basin. These differences indicate several sources of isotopically distinct Nd in the North Atlantic. The deep waters of the North Atlantic (>1000 m) have the lowest values of \u03b5_(Nd)(0) measured in the oceans. We believe that the source of these low \u03b5_(Nd)(0) values, which we associate with North Atlantic deep water, is either from freshwater drainage off the Precambrian shields of North America and Asia into the Arctic Ocean or from the injection of 'older,' continentally derived REE from deep-sea sediments. Sm and Nd concentrations are found to increase with depth and \u03b5_(Nd)(0) changes with depth, indicating both vertical and lateral transport processes from different sources. This suggests a surface source of Nd and injection of REE into the water column from deep-sea sediments or large-scale bottom currents with high REE concentrations.", "doi": "10.1029/JC088iC10p05997", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research C", "publication_date": "1983-07-20", "series_number": "C10", "volume": "88", "issue": "C10", "pages": "5997-6006" }, { "id": "authors:skdx2-fr180", "collection": "authors", "collection_id": "skdx2-fr180", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140115-132130945", "type": "article", "title": "Eruption Age of a Pleistocene Basalt From ^(40)Ar-^(39)Ar Analysis of Partially Degassed Xenoliths", "author": [ { "family_name": "Gillespie", "given_name": "A. R.", "clpid": "Gillespie-A-R" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have applied ^(40)Ar\u2212^(39)Ar dating to potassium-rich granitic xenoliths and host basalt from the Pleistocene Big Pine volcanic field, California. These xenoliths had been partially degassed upon their inclusion in the basaltic lava. Argon released from the xenoliths at extraction temperatures below \u223c900\u00b0C yielded plateau ages indistinguishable from the total K-Ar age of the basalt. The best estimate of the age of eruption was 1.18\u00b10.05 (2\u03c3) m.y. ^(40)Ar extracted at higher temperatures included radiogenic argon not degassed from the late Cretaceous xenoliths 1.18 m.y. ago, causing an increase in the apparent age for the high-temperature fractions. The agreement of the low-temperature xenolith plateau ages and the basalt K-Ar ages demonstrates that ^(40)Ar\u2212^(39)Ar analysis of xenoliths may be used to measure the age of eruption of very young lavas. This is significant because in many instances ages cannot be reliably determined by analysis of the lavas themselves.", "doi": "10.1029/JB088iB06p04997", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1983-06-10", "series_number": "B6", "volume": "88", "issue": "B6", "pages": "4997-5008" }, { "id": "authors:we3n3-kty79", "collection": "authors", "collection_id": "we3n3-kty79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130910-134304904", "type": "article", "title": "^(39)Ar recoil losses and presolar ages in Allende inclusions", "author": [ { "family_name": "Villa", "given_name": "I. M.", "clpid": "Villa-I-M" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Ar analyses are reported for five coarse-grained, Ca-Al-rich inclusions from the Allende meteorite. The samples were neutron-irradiated in individual evacuated ampoules, and the Ar gas in the ampoules as well as the samples was analyzed. A large fraction (up to 60%) of the ^(39)Ar from ^(39)K (n, p) reactions was lost out of the inclusions into the ampoules. The ^(39)Ar losses resulted in substantial increases in the apparent ^(40)Ar-^(39)Ar ages of the samples. ^(39)Ar recoil loss during neutron-irradiation is a major effect and must be accounted for in ^(40)Ar-^(39)Ar dating. All of the Allende inclusions studied contained substantial trapped ^(36)Ar. The origin of the trapped ^(36)Ar is unknown, and the possible presence of trapped ^(40)Ar cannot be excluded. Ar measurements on Allende inclusions which have yielded anomalously old ages must be re-examined in the context of ^(39)Ar recoil loss and possible contributions of trapped ^(40)Ar. Allende inclusions appear on both accounts to be poor candidates to search for relicts of presolar materials with well-defined K/Ar ages.", "doi": "10.1016/0012-821X(83)90017-1", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1983-04", "series_number": "1", "volume": "63", "issue": "1", "pages": "1-12" }, { "id": "authors:gbwwz-0ee71", "collection": "authors", "collection_id": "gbwwz-0ee71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131021-153014750", "type": "article", "title": "Replacement textures in CAI and implications regarding planetary metamorphism", "author": [ { "family_name": "Meeker", "given_name": "G. P.", "clpid": "Meeker-G-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" } ], "abstract": "Textural and chemical features of five coarse-grained, calcium-aluminum-rich inclusions from the Allende meteorite indicate that some of the melilite in these inclusions was formed by a secondary metamorphic event and not by primary crystallization from a melt or by a sequential nebular condensation process. These inclusions contain embayed pyroxene surrounded by melilite. Physically separated pyroxene crystals are often in optical continuity indicating that they were once part of larger single crystals that have been partly replaced by melilite. Other evidences of metamorphism include reaction textures between melilite and spinel, and metamorphic textures such as kink-band-like features, lobate sutured grain boundaries, and 120\u00b0 triple-points. This type of metamorphic process requires the addition of Ca which we propose came from calcite or by introduction of a fluid phase. We believe that the most likely environment for this metamorphic process is on a small planetary body, and not in the solar nebula. The results of this study are compatible with oxygen isotopic heterogeneities within CAI, and provide a mechanism for producing lower temperature alteration phases and the rim phases found in these inclusions. We conclude that planetary processes must thus be considered in the formation history of CAI, and that it is necessary to reconsider the classification system of these objects in light of the replacement process proposed here.", "doi": "10.1016/0016-7037(83)90105-9", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1983-04", "series_number": "4", "volume": "47", "issue": "4", "pages": "707-721" }, { "id": "authors:mvy92-5xf04", "collection": "authors", "collection_id": "mvy92-5xf04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-073927201", "type": "article", "title": "The isotopic composition and concentration of Ag in iron\n meteorites and the origin of exotic silver", "author": [ { "family_name": "Kaiser", "given_name": "T.", "clpid": "Kaiser-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Ag and the concentration of Ag and Pd have been determined in Canyon Diablo (IA), Grant (IIIB), Hoba, Santa Clara, Tlacotepec and Warburton Range (IVB), Pi\u00f1on and Deep Springs (anom.). Troilite from Grant and Santa Clara have also been analyzed. All of these meteorites, with the exception of Canyon Diablo, give ^(107)Ag/^(109)Ag in the metal phase that is greater than the terrestrial value with the enrichments of ^(107)Ag ranging from ~2% to 212%. These data show that Ag of anomalous isotopic composition is common to all IVB and anomalous meteorites. The results on Grant suggest that the anomalies may be widespread including more common meteorite groups. There is a general correlation of ^(107)Ag/^(109)Ag with Pd/Ag except for the data from FeS of Santa Clara. It is concluded that the excess ^(107)Ag is the result of decay of ^(107)Pd, a nuclide that is extinct at present with an abundance of ^(107)Pd/^(108)Pd of about 3 \u00d7 10^(\u22125). The troilite in Grant exhibits normal ^(107)Ag/^(109)Ag to within errors, a high Ag concentration and a low ratio of ^(108Pd/^(109)Ag ~0.17. Grant metal has ^(107)Ag/^(109)Ag that is ~2% greater than normal and a high ratio of ^(108)Pd/^(109)Ag ~ 10^3. The data from Grant appear to represent a ^(107)Pd-^(107)Ag isochron and indicate that the cooling rate at elevated temperatures was sufficiently rapid to preserve substantial isotopic differences between metal and troilite. Troilite in Santa Clara was found to contain Ag with a very high ^(107)Ag/^(109)Ag ratio (108% above normal), an Ag concentration only a factor of three above the metal and a high value of ^(108Pd)/^(109)Ag ~1.3 \u00d7 10^4. The troilite has a higher ^(107)Ag/^(109)Ag than the metal. These data are not compatible with a simple model of in situ decay and subsequent local Ag redistribution between metal and troilite during cooling. These data suggest that Ag in Santa Clara and possibly other IVB meteorites is made up of almost pure ^(107)Ag produced from ^(107)Pd decay and ^(109)Ag produced by nuclear reactions with only a small amount of \"normal\" Ag. This indicates an intense energetic particle bombardment history in the early solar system (~10^(20) p/m^2) which occurred after the formation of small planetary bodies. We infer that a T-Tauri activity by the early sun contributed to some late stage \"nucleosynthesis\" and the heating of a dust cloud. In addition, implications on the early thermal evolution of iron meteorites are presented based on ^(107)Pd decay and models of the cooling history.", "doi": "10.1016/0016-7037(83)90089-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1983-01", "series_number": "1", "volume": "47", "issue": "1", "pages": "43-58" }, { "id": "authors:k9aa8-72663", "collection": "authors", "collection_id": "k9aa8-72663", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-092000702", "type": "article", "title": "An ^(107)Ag^*-^(108)Pd internal isochron for Gibeon (IVA)", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Chen", "given_name": "J.", "clpid": "Chen-J" } ], "abstract": "Previous studies (Kelly and Wasserburg, 1979; Kaiser and Wasserburg, 1983) have established the presence of ratios of ^(107)Ag/^(109)Ag which are far above the value for normal Ag. These effects were observed in IVB iron meteorites and some anomalous meteorites highly depleted in\nvolatiles. A correlation of ^(107)Ag/^(109)Ag with ^(108)Pd/^(109)Ag was found, indicating that the excess of\n^(107)Ag(^(107)Ag^*) was correlated with Pd, implying the presence of ^(107)Pd in the meteorites.", "issn": "1086-9379", "publisher": "Meteoritical Society", "publication": "Meteoritics and Planetary Science", "publication_date": "1983", "series_number": "4", "volume": "18", "issue": "4", "pages": "417-418" }, { "id": "authors:1vr83-6wr96", "collection": "authors", "collection_id": "1vr83-6wr96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140115-130828974", "type": "article", "title": "An Assessment of ^(40)Ar-^(39)Ar Dating of Incompletely Degassed Xenoliths", "author": [ { "family_name": "Gillespie", "given_name": "A. R.", "clpid": "Gillespie-A-R" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The possibility of measuring the age of eruption of Pleistocene lavas by ^(40)Ar-^(39)Ar analysis of entrapped ancient potassic xenoliths is demonstrated by a study of model systems. Upon inclusion in the hot magma such xenoliths are commonly only partially degassed of radiogenic ^(40)Ar which has accumulated in them since their original crystallization. The residual ^(40)Ar will increase the apparent K/Ar age of the xenolith. However, if a xenolith is of Cretaceous age or younger, then a plateau in its ^(40)Ar-^(39)Ar age spectrum giving the age of eruption is expected to extend over 25\u201350% of the total 39Ar released if degassing of the xenolith in the magma exceeded 90% and if the phases in the xenolith are characterized by sufficiently different diffusion dimensions or activation energies. If diffusion was from a bimodal population of spheres, then the radii must differ by a factor of 10 or more (or the diffusion coefficients by a factor of 100 or more); or if the spheres were equal in size (and in diffusion coefficients), then the activation energies must differ by a factor of at least 1.5. That such requirements may be realized in real xenoliths containing K-feldspars is expected from published activation energies for microcline and from data determined on a granitic xenolith which was degassed in an early Pleistocene basalt flow. The experimental results appear to establish that old xenoliths may contain Ar in distinctive phases which degas at sufficiently different temperatures as to permit determination of the age of degassing or eruption.", "doi": "10.1029/JB087iB11p09247", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1982-11-10", "series_number": "B11", "volume": "87", "issue": "B11", "pages": "9247-9257" }, { "id": "authors:pjskt-0kr07", "collection": "authors", "collection_id": "pjskt-0kr07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-072624273", "type": "article", "title": "Age and provenance of the target materials for tektites and\n possible impactites as inferred from Sm-Nd and Rb-Sr systematics", "author": [ { "family_name": "Shaw", "given_name": "H. F.", "clpid": "Shaw-H-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Sm-Nd and Rb-Sr analyses of tektites and other impactites can be used to place constraints on the age and provenance of target materials which were impact melted to form these objects. Tektites have large negative \u03b5^(Nd)(0) values and are uniform within each tektite group while the \u03b5^(Sr)(0) are large positive values and show considerable variation within each group. Chemical, trace element, and isotopic compositions of tektites are consistent with production by melting of sediments derived from old terrestrial continental crust. Each tektite group is characterized by a uniform Nd model age, T_(CHUR)^(Nd), interpreted as the time of formation of the crustal segment which weathered to form the parent sediment for the tektites: (1) \u223c1.15 AE for Australasian tektites; (2) \u223c1.91 AE for Ivory Coast tektites; (3) \u223c0.9 AE for moldavites; (4) \u223c0.65 AE for North American tektites, and (5) \u223c0.9 AE for high-Si irghizites. Sr model ages, T_(UR)^(Sr), are variable within each group reflecting Rb-Sr fractionation and in the favorable limit of very high Rb/Sr ratios, approach the time of sedimentation of the parent material which melted to form the tektites. Australasian tektites are derived from \u223c0.25 AE sediments, moldavites from \u223c0.0 AE sediments, Ivory Coast tektites from \u223c0.95 AE sediments. Possible parent sediments of other tektite groups have poorly constrained ages. Our data on moldavites and Ivory Coast tektites are consistent with derivation from the Ries and Bosumtwi craters, respectively. Irghizites are isotopically distinct from Australasian tektites and are probably not related. Sanidine spherules from a Cretaceous-Tertiary boundary clay have initial \u03b5^(Nd) \u223c +2; \u03b5^(Sr) \u223c +5 and are not derived from old continental crust or meteoritic feldspar. They may represent a mixture of basaltic oceanic crust and sediments, implying an oceanic impact. These isotopic results are also consistent with a volcanic origin for the spherules.", "doi": "10.1016/0012-821X(82)90001-2", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1982-09", "series_number": "2", "volume": "60", "issue": "2", "pages": "155-177" }, { "id": "authors:avb4g-xsy58", "collection": "authors", "collection_id": "avb4g-xsy58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150116-132456584", "type": "article", "title": "Chemical composition of HAL, an isotopically-unusual Allende inclusion", "author": [ { "family_name": "Davis", "given_name": "Andrew M.", "clpid": "Davis-A-M" }, { "family_name": "Tanaka", "given_name": "Tsuyoshi", "clpid": "Tanaka-Tsuyoshi" }, { "family_name": "Grossman", "given_name": "Lawrence", "clpid": "Grossman-L" }, { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Thirty-seven major, minor and trace elements were determined by INAA and RNAA in samples of hibonite, black rim and portions of friable rim from an unusual Allende inclusion, HAL. The peculiar isotopic, mineralogical and textural properties of HAL are accompanied by very unusual trace element abundances. The most striking feature of the chemistry is the virtual absence of Ce from an inclusion otherwise highly enriched in REE compared to Cl chondrites. HAL is also depleted in Sr, Ba, U, V, Ru, Os and Ir, relative to other refractory elements. Of the lithophile elements determined which are normally considered to be refractory in a gas of solar composition, Sr, Ba, Ce, U and V are the most volatile in oxidizing gases. The distribution of REE between hibonite and rims seems to have been established when hibonite and other refractory minerals were removed at slightly different temperatures from a hot, oxidizing gas in which they previously coexisted as separate grains. On the basis of HAL's chemical and isotopic composition, possible locations for the chemical and mass dependent isotopic fractionation are in ejecta from the low temperature helium-burning zone of a supernova and in the locally oxidizing environment generated by evaporation of interstellar grains of near-chondritic chemical composition.", "doi": "10.1016/0016-7037(82)90319-2", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1982-09", "series_number": "9", "volume": "46", "issue": "9", "pages": "1627-1651" }, { "id": "authors:hxf79-xte23", "collection": "authors", "collection_id": "hxf79-xte23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130910-133017082", "type": "article", "title": "Isotopic Composition of Neodymium in Waters from the Drake Passage", "author": [ { "family_name": "Piepgras", "given_name": "Donald J.", "clpid": "Piepgras-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of neodymium has been determined in seawaters from the Drake Passage. The Antarctic Circumpolar Current, which controls interocean mixing, flows through this passage. The parameter \u03b5_(Nd)(0) which is a function of the ratio of neodymium-143 to neodymium-144, is found to be uniform with depth at two stations with a value which is intermediate between the values for the Atlantic and the Pacific and indicates that the Antarctic Circumpolar current consists of about 70 percent Atlantic water. Cold bottom water from a site in the south central Pacific has the neodymium isotopic signature of the waters in the Drake Passage. By using a box model to describe the exchange of water between the Southern Ocean and the ocean basins to the north together with the isotopic results, an upper limit of approximately 33 million cubic meters per second is calculated for the rate of exchange between the Pacific and the Southern Ocean. Concentrations of samarium and neodymium were also determined and found to increase approximately linearly with depth. These results suggest that neodymium may be a valuable tracer in oceanography and may be useful in paleo-oceanographic studies.", "doi": "10.1126/science.217.4556.207", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1982-07-16", "series_number": "4556", "volume": "217", "issue": "4556", "pages": "207-214" }, { "id": "authors:83e25-5st05", "collection": "authors", "collection_id": "83e25-5st05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130924-090528876", "type": "article", "title": "The Blue Angel: I. The mineralogy and petrogenesis of a hibonite inclusion from the Murchison meteorite", "author": [ { "family_name": "Armstrong", "given_name": "John T.", "clpid": "Armstrong-J-T" }, { "family_name": "Meeker", "given_name": "G. P.", "clpid": "Meeker-G-P" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A detailed mineralogie, chemical, and petrologic study of the Blue Angel, a relatively large (~1.5 mm) hibonite-containing inclusion from the Murchison meteorite, was performed in an attempt to understand the mechanisms of formation and modification of hibonite-rich inclusions. The Blue Angel inclusion is composed of roughly equal amounts of hibonite and calcite, with minor amounts of spinel, perovskite, diopside, and an Fe-rich silicate. The inclusion can be divided into three roughly concentric zones\u2014a hibonite-rich core, a calcite-rich mantle, and a spinel-rich layered rim. The mineral chemistry and petrography of the Blue Angel are consistent with a three-stage formation history: (1) an early stage of nebular condensation which produced the hibonite, perovskite, and spinel; (2) a moderate temperature stage of aqueous alteration and metamorphism occurring on a small planetary body containing CO_2 and H_2O during which calcite was formed in the inclusion; and (3) the final emplacement of the Blue Angel into its present position in Murchison. The study of the Blue Angel indicates that extensive alteration of Ca-Al-rich inclusions (CAI) may have occurred by aqueous alteration and thermal metamorphism followed by explosive mixing processes on a parent body. Such metamorphic reactions may involve formation and destruction of phases, such as melilite and diopside, which have been previously thought to be primary condensates. The mechanisms proposed for the formation and modification of the Blue Angel help to explain the secondary phases and oxygen isotope anomalies found in many CAI and eliminate the need for invoking kinetically-complicated back-reactions at very low pressures with a cool part of the solar nebula. The contribution of planetary metamorphism in the formation and alteration of CAI must be considered along with nebular processes in order to understand the formation of carbonaceous chondrites.", "doi": "10.1016/0016-7037(82)90160-0", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1982-04", "series_number": "4", "volume": "46", "issue": "4", "pages": "575-595" }, { "id": "authors:v4gqc-96e11", "collection": "authors", "collection_id": "v4gqc-96e11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130828-144929479", "type": "article", "title": "Spalogenic rare gases in iron meteorites with anomalous silver", "author": [ { "family_name": "Villa", "given_name": "I. M.", "clpid": "Villa-I-M" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "He, Ne, and Ar have been measured in seven iron meteorites for which anomalous Ag isotopic compositions were reported, in order to determine if ^(107)Ag excesses could be related to galactic cosmic-ray bombardment of these meteorites. Our results show that no correlation exists between ^(107)Ag excess and either the fluence or the energy spectrum of the particles producing spallogenic rare gases. Cosmic-ray-produced ^(107)Ag estimated from ^(38)Ar concentrations can account for only about 1% of the observed excess. Elimination of cosmic-ray bombardment as a production mechanism for ^(107)Ag excess strengthens the conclusion that the excess ^(107)Ag is the decay product of short-lived ^(107)Pd (\u03c4_(1/2)=6.5Myr). The iron meteorite Pi\u00f1on is shown to contain trapped rare gases with ^4He/^(20)Ne\u223c600.", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1981-12", "volume": "56", "pages": "9-18" }, { "id": "authors:fyrfw-87h94", "collection": "authors", "collection_id": "fyrfw-87h94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-082256930", "type": "article", "title": "Correlated Isotope Anomalies on the Wing of the Iron Abundance Peak", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Niederer", "given_name": "F. R.", "clpid": "Niederer-F-R" } ], "abstract": "The measurement of isotope anomalies for many elements in the same samples has shown the presence of significant correlations which have permitted the identification of contributions from specific nucleosynthetic processes (e.g., enhancements in the \"r\" -process isotopes at the higher Z region of Ba, Nd, Sm).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1981-12", "series_number": "4", "volume": "16", "issue": "4", "pages": "375-375" }, { "id": "authors:bna25-ghp12", "collection": "authors", "collection_id": "bna25-ghp12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-155623774", "type": "article", "title": "Precise determination of Sm/Nd ratios, Sm and Nd isotopic\n abundances in standard solutions", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Jacobsen", "given_name": "S. B.", "clpid": "Jacobsen-S-B" }, { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "McCulloch", "given_name": "M. T.", "clpid": "McCulloch-M-T" }, { "family_name": "Wen", "given_name": "T.", "clpid": "Wen-T" } ], "abstract": "The methods used for precise calibrations of Sm/Nd ratios and the average isotopic abundances obtained for normal Sm and Nd are given. A mixed Sm-Nd normal solution with a precisely known ^(147)Sm/^(144)Nd ratio close to the nominal average chondritic value is described and the calibration discussed. Aliquots of this standard solution are available on request and may be useful for precise interlaboratory calibration of Sm and Nd.", "doi": "10.1016/0016-7037(81)90085-5", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1981-12", "series_number": "12", "volume": "45", "issue": "12", "pages": "2311-2323" }, { "id": "authors:n2wvs-xy449", "collection": "authors", "collection_id": "n2wvs-xy449", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-083330040", "type": "article", "title": "Cm/U, Th/U, and ^(235)U/^(238)U in Meteorites", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The relative abundances of the actinides, ^(247)Cm, ^(244)Pu, ^(235)U, ^(238)U, and ^(232)Th are important\nfor the estimation of the duration of galactic nucleosynthesis and the time interval between the\ntermination of the last contributing \"r\" process nucleosynthetic event and formation of the solar system. ^(247)Cm is particularly important because of its half life (1.56 x 10^7y). As ^(247)Cm is an extinct nuclide, the basic evidence for its presence must come from observed shifts in the ^(235)U/^(238)U ratio and anomalies in ^(207)Pb/^(206)Pb and U-Pb ages in early solar system samples.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1981-12", "series_number": "4", "volume": "16", "issue": "4", "pages": "301-301" }, { "id": "authors:6pf73-r7377", "collection": "authors", "collection_id": "6pf73-r7377", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230105-601436600.1", "type": "article", "title": "Isotopic determination of uranium in picomole and subpicomole quantities", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A procedure for the separation of U and measurement of U isotopes in meteoritic, lunar, and terrestrial samples Is described. Accurate \u00b2\u00b3\u2078U/\u00b2\u00b3\u2075U ratios and U concentration measurements can be done on a routine basis at the level of ~10\u207b\u00b9\u00b3 mol of U by isotope dilution using a double tracer composed of \u00b2\u00b3\u00b3U and \u00b2\u00b3\u2076U. Precise determination of the number of U atoms in a sample can be done at the level of 10\u2078-10\u2079 atoms. The technique Involves careful control of the chemical procedures to eliminate laboratory contamination and precise calibration of the mass spectrometer in order to obtain high reproducibility. The \u00b2\u00b3\u2078U/\u00b2\u00b3\u2075U ratios were measured on a wide variety of samples which include (1) bulk meterorites, (2) lunar samples, (3) coarse-grained Ca-Al-Tl-rich inclusions and (4) fine-grained AI-Mg-Na-rich Inclusions from the Allende meteorite, and (5) phosphates from three meteorites. The results show the same Isotopic values within limits of errors as that measured on normal terrestrial U to within 4\u2030. All of the analyzed meteorite samples are very ancient and several of them show large fractionations of U relative to Th and Nd. These data Imply that \u00b2\u2074\u2077Cm was not abundant in the early solar system (\u00b2\u2074\u2077Cm/\u00b2\u00b3\u2075U \u00ab 4 X 10\u207b\u00b3) and that the last major \"r\" process terminated at ~10\u2078 years prior to the formation of the solar system.", "doi": "10.1021/ac00236a027", "issn": "0003-2700", "publisher": "American Chemical Society", "publication": "Analytical Chemistry", "publication_date": "1981-11-01", "series_number": "13", "volume": "53", "issue": "13", "pages": "2060-2067" }, { "id": "authors:g99zb-nwv56", "collection": "authors", "collection_id": "g99zb-nwv56", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131219-105317755", "type": "article", "title": "Isotopic Determination of Uranium in Picomole and\n Subpicomole Quantities", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A procedure for the separation of U and measurement of U\nIsotopes in meteoritic, lunar, and terrestrial samples Is described. Accurate ^(238)U/^(235)U ratios and U concentration measurements can be done on a routine basis at the level of ~ 10^(-13) mol of U by Isotope dilution using a double tracer composed of ^(233)U and ^(238)U. Precise determination of the number of U atoms In a sample can be done at the level of 10^8-10^9 atoms. The technique Involves careful control of the chemical procedures to eliminate laboratory contamination and precise calibration of the mass spectrometer In order to obtain high reproducibility. The ^(238)U/^(235)U ratios were measured\non a wide variety of samples which Include bulk\nmeterorltes, lunar samples, coarse-grained Ca-AITI-\nrlch Inclusions and fine-grained AI-Mg-Na-rich Inclusions from the Allende meteorite, and phosphates from three meteorites. The results show the same Isotopic values within limits of errors as that measured on normal terrestrial U to within 4\u2030. All of the analyzed meteorite samples are very ancient and several of them show large fractionations of U relative to Th and Nd. These data Imply that ^(247)Cm was not abundant In the early solar system (^(247)Cm/^(235)U \u00ab 4 X 10^(-3)) and that the last major \"r\" process terminated at ~ 10^8 years prior to the formation of the solar system.", "doi": "10.1021/ac00236a027", "issn": "0003-2700", "publisher": "American Chemical Society", "publication": "Analytical Chemistry", "publication_date": "1981-11", "series_number": "13", "volume": "53", "issue": "13", "pages": "2060-2067" }, { "id": "authors:sbvhq-r7k98", "collection": "authors", "collection_id": "sbvhq-r7k98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-155800072", "type": "article", "title": "The isotopic composition of titanium in the Allende and\n Leoville meteorites", "author": [ { "family_name": "Niederer", "given_name": "F. R.", "clpid": "Niederer-F-R" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We describe the analytical techniques developed for the precise measurement of the titanium isotope abundances using a TiO^+ ion beam. Terrestrial, lunar, and bulk meteorite samples yield identical results. Using a normalization to ^(46)Ti/^(48)Ti for mass dependent isotope fractionation, we obtain the normal Ti composition: ^(46)Ti/^(48)Ti = 0.108548; ^(47)Ti/^(48)Ti = 0.099315 \u00b1 0.000005; ^(49)Ti/^(48)Ti = 0.074463 \u00b1 0.000004; ^(50)Ti/^(48)Ti = 0.072418 \u00b1 0.000004 (2\u03c3 grand mean), taking ^(18)O/^(16)O = 0.00037. Measurements on thirteen coarse-grained and fine-grained Ca-Al-Ti-rich inclusions from the Allende and Leoville meteorites show the presence of widespread, significant, nonlinear isotope anomalies in the Ti isotopes which were not used for normalization. The data require the addition of at least three exotic components. The distinct correlation of non-linear effects for the most neutron-rich isotopes of Ca and Ti and the absence of substantial effects at ^(46)Ca in the FUN samples EK-1-4-1 and C-1 indicate that the effects reflect neutron-rich equilibrium or quasi-equilibrium nucleosynthetic processes in the outer layers of a supernova core. The results on Ca and Ti in conjunction with the isotopic effects on other elements (Mg, Sr, Ba, Nd, Sm) show that the samples represent mixtures of different nucleosynthetic components from distinctive processes ('e', 'r', 'p') which do not appear to be related to processes in the same stellar sites.", "doi": "10.1016/0016-7037(81)90128-9", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1981-07", "series_number": "7", "volume": "45", "issue": "7", "pages": "1017-1031" }, { "id": "authors:b1v5a-gzd23", "collection": "authors", "collection_id": "b1v5a-gzd23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130904-155554144", "type": "article", "title": "Transport models for crust and mantle evolution", "author": [ { "family_name": "Jacobsen", "given_name": "S. B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The exact solutions for the isotopic compositions and the concentrations of two models for mantle\u2014crust evolution are given for arbitrary rates of crustal growth and of backflow to the mantle. In Model I, continents are derived by melt extraction over the history of the earth from undepleted mantle. In Model II, new additions to the continents are derived from a mantle reservoir which becomes increasingly depleted through time by repeated extraction of melts. The key parameters are the chemical fractionation factors for crustal growth and refluxing and the integrated fractional mass removal rates from the crust and the mantle. The relationships between the mean age of the mass of the continents and the isotopic parameters are given. The models suggest that the pre-Archean era (prior to 3.8 AE) was dominated by rapid refluxing of crust to the mantle which during the early Archean gave way to a regime where transport from the mantle to the crust substantially dominated over refluxing of crust to the mantle. The mean age of the mass of the continents appears to be ~1.8 AE. Even for small amounts (~10%) of refluxing Model II shows that highly incompatible elements have very short residence times in the mantle. Mass balance considerations implies that the continents were derived from only a small fraction (~30%) of the mantle.", "doi": "10.1016/0040-1951(81)90214-6", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "1981-05-10", "series_number": "1-2", "volume": "75", "issue": "1-2", "pages": "163-179" }, { "id": "authors:nz7ej-nqb19", "collection": "authors", "collection_id": "nz7ej-nqb19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-091952043", "type": "article", "title": "^(40)Ar-^(39)Ar and Rb-Sr age determinations on Quaternary\n volcanic rocks", "author": [ { "family_name": "di Brozolo", "given_name": "F. Radicati", "clpid": "di-Brozolo-F-R" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "^(40)Ar-^(39)Ar and Rb-Sr ages have been measured on separated minerals from the potassic volcanics of the Roman Comagmatic Region to test the ability of these methods to accurately data Quaternary geological events. The very high K and Rb contents of the Roman magmas present particularly favorable situations in which the very high concentrations of the radioactive nuclides ^(40)K and ^(87)Rb result in well resolved in situ enrichments of the daughter isotopes despite the very young ages. Six leucite separates contained Ar with very high bulk 40/36 ratios (above 1000) and in which the ^(40)Ar and the ^(39)Ar were very well correlated, yielding well-defined ages averaging 3.38\u00b10.08\u00d710^5 years. Two leucites contained Ar with lower bulk 40/36 ratios (\u223c400), and in at least two release steps from these leucites the ^(40)Ar/^(36)Ar ratio was significantly lower than atmospheric. Despite the uncertainty in the composition of the trapped component, these two leucites have ages that do not differ significantly from the ages of the other leucites. For the biotites, it was not possible to obtain through stepwise degassing a good separation of in situ radiogenic ^(40)Ar from trapped ^(40)Ar and therefore the calculated ages are not as precise as those of the leucites. In three cases the biotite age agrees with the age of the cogenetic leucite, but in the remaining two cases discordant ages are obtained, suggesting caution when using biotites as Quaternary age indicators.\nRb-Sr measurements on leucite, biotite, and pyroxene separates hand-picked from each of three tuff samples yielded a dispersion in ^(87)Sr/^(86)Sr as large as 16 parts in 10^4 and ^(87)Rb/^(86)Sr as high as 218 for leucites, and permitted the determination of internal isochron ages. The ages obtained range from 3.8 \u00b1 0.2 \u00d7 10^5 to 3.3 \u00b1 0.2 \u00d7 10^5 years and are in good agreement with the ^(40)Ar-^(39)Ar ages on the leucites. The data for each tuff sample yield a well-defined uniform initial ^(87)Sr/^(86)Sr. However, different tuffs show small differences in initial ^(87)Sr/^(86)Sr pointing to distinct sources or to assimilation of different materials during the extrusion of the tuffs. These measurements demonstrate the possibility of dating Quaternary materials by both the ^(40)Ar-^(39)Ar method and the Rb-Sr method. The observation of concordant ages with a precision of a few percent represents a powerful tool in Quaternary stratigraphy.", "doi": "10.1016/0012-821X(81)90049-2", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1981-05", "series_number": "3", "volume": "53", "issue": "3", "pages": "445-456" }, { "id": "authors:22h32-b7093", "collection": "authors", "collection_id": "22h32-b7093", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131016-094434603", "type": "article", "title": "Sm-Nd, Rb-Sr, and ^(18)O/^(16)O isotopic systematics in an oceanic crustal section: Evidence from the Samail Ophiolite", "author": [ { "family_name": "McCulloch", "given_name": "Malcolm T.", "clpid": "McCulloch-M-T" }, { "family_name": "Gregory", "given_name": "Robert T.", "clpid": "Gregory-R-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Taylor", "given_name": "Hugh P., Jr.", "clpid": "Taylor-H-P-Jr" } ], "abstract": "The Sm-Nd, Rb-Sr, and ^(18)O/^(16)O isotopic systems have been used to distinguish between the effects of seafloor hydrothermal alteration and primary magmatic isotopic variations. The Sm-Nd isotopic system is essentially unaffected by seawater alteration, while the Rb-Sr and ^(18)O/^(16)O systems are sensitive to hydrothermal interactions with seawater. Sm-Nd mineral isochrons from the cumulate gabbros of the Samail ophiolite have an initial ^(143)Nd/^(144)Nd ratio of \u03b5_(Nd) = 7.8 \u00b1 0.3, which clearly substantiates the oceanic affinity of this complex. The initial ^(143)Nd/^(144)Nd ratios for the harzburgite, plagiogranite, sheeted diabase dikes, and basalt units have a limited range in \u03b5_(Nd) of from 7.5 to 8.6, indicating that all the lithologies have distinctive oceanic affinities, although there is also some evidence for small isotopic heterogeneities in the magma reservoirs. The Sm-Nd mineral isochrons give crystallization ages of 128 \u00b1 20 m.y. and 150 \u00b1 40 m.y. from Ibra and 100 \u00b1 20 m.y. from Wadi Fizh, which is approximately 300 km NW of Ibra. These crystallization ages are interpreted as the time of formation of the oceanic crust. The ^(87)Sr/^(86)Sr initial ratios on the same rocks have an extremely large range of from 0.7030 to 0.7065 and the \u03b4^(18)O values vary from 2.6 to 12.7. These large variations clearly demonstrate hydrothermal interaction of oceanic crust with seawater.", "doi": "10.1029/JB086iB04p02721", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1981-04-10", "series_number": "B4", "volume": "86", "issue": "B4", "pages": "2721-2735" }, { "id": "authors:q4gxv-8dx26", "collection": "authors", "collection_id": "q4gxv-8dx26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-094017563", "type": "article", "title": "A search for evidence of a fissionable nuclide in iron meteorites and implications on heat sources in planetary cores", "author": [ { "family_name": "Kaiser", "given_name": "T.", "clpid": "Kaiser-T" }, { "family_name": "Piepgras", "given_name": "D.", "clpid": "Piepgras-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "It is shown that nuclear fission could not have significantly contributed as a heat source to drive an early lunar core dynamo. Furthermore, contributions of any fissionable nuclide to the energetics of the earth's core today are very unlikely in comparison to other sources of energy. These conclusions are inferred from searches for records of fission events in the metal phase of IA and IVB meteorites. We obtain strict upper limits for the concentration level of Nd and Sm in the Canyon Diablo (IA), Pi\u00f1on (anom.), and Santa Clara (IVB) meteorites which are not distinguishable from the levels of the procedural blank and exhibit a normal isotopic composition. No contribution from fission to the unshielded isotopes could be detected. Upper limits for contributions by fission are 10^8 atoms g^(\u22121) per isobar. Assuming a low fission yield of 10^(\u22124), we obtain 10^(12) fission events g^(\u22121). It is reasonable to assume no losses of REE fission products due to late stage recrystallization or outgassing. This limit would correspond to a maximum deposition of 30 J g^(\u22121) in the earth's core due to fission. From earlier experiments on Kr and Xe in other IA iron meteorites, upper limits for contributions by fission of 3 \u00d7 10^5 and 2 \u00d7 10^6 fission events g^(\u22121) per isobar can also be estimated for the unshielded isotopes. Recent studies on nuclear tracks in silicate inclusions of IA iron meteorites set upper limits of 10^9\u201310^(10) fission events g^(\u22121), the detected tracks being most plausibly explained by spontaneous fission of ^(244)Pu. We can find no evidence in support of a fissionable, siderophile superheavy element and all limits for fission events are too low to support fission as a heat source in planetary cores. Furthermore, by Nd and Sm studies on two IVB iron meteorites, we demonstrate that Ag anomalies found earlier in meteorites of this class cannot have been produced by in situ fission of any known nuclide. This further supports the interpretation that extinct ^(107)Pd is the source of the ^(107)Ag anomalies.", "doi": "10.1016/0012-821X(81)90178-3", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1981-02", "series_number": "2", "volume": "52", "issue": "2", "pages": "239-250" }, { "id": "authors:gt46r-nnc18", "collection": "authors", "collection_id": "gt46r-nnc18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-095500035", "type": "article", "title": "Nd and Sr isotopic study of volcanic rocks from Japan", "author": [ { "family_name": "Nohda", "given_name": "Susumu", "clpid": "Nohda-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Two older granitic rocks and some selected Quaternary volcanic rocks from the Japanese Islands were analyzed in a reconnaissance study for the purpose of examining the relationships between Nd and Sr isotopic abundances and the megatectonic structure around the Japanese Islands. Model ages of \u223c0.9 AE were determined by the Nd and Sr methods on a Paleozoic gneiss which confirms that a relatively ancient acidic basement exists in the Japanese Islands. The Nd and Sr isotopic data show that the Cretaceous granodiorite is the result of partial melting of older crust.\nThe Nd of tholeiitic rocks from the Izu arc gives \u03b5_(Nd) ranging from 8.3 to 9.3 and with the corresponding \u03b5_(Sr) from \u221214.5 to \u221218.5. These results are identical to those found for the Mariana arc. These values are distinctly lower than typical MORB by around 1\u223c2 \u03b5u. This difference in \u03b5_(Nd) between arcs and MORB is attributed to the contribution of oceanic sediments to the partial melts produced during subduction of oceanic crust. The Hakone volcano is clearly confirmed as belonging to an oceanic source by Nd isotopic results.\n\u03b5_(Sr)-\u03b5_(Nd) values of the volcanics from a section along the Fossa Magna show a clear indication that they are a blend of oceanic mantle material and continental crustal material. The crustal component clearly increases in going from south to north. Volcanics across the Northeast Japan arc also show a distinct correlation of \u03b5_(Sr)-\u03b5_(Nd) related to the position relative to the active subduction zone but with the opposite trend. These relationships of the present isotopic pattern and the zonal arrangement relative to the subduction zone suggest the former existence of a local spreading center in the Japan Sea.\nIn general there appear to be regular isotopic relationships between the Izu-Mariana oceanic island arc and the continental island arc of Japan which indicates that partially melted or assimilated older continental basement is admixed with young rising oceanic arc magmas.", "doi": "10.1016/0012-821X(81)90181-3", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1981-02", "series_number": "2", "volume": "52", "issue": "2", "pages": "264-276" }, { "id": "authors:xw73w-mcg96", "collection": "authors", "collection_id": "xw73w-mcg96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-114857404", "type": "article", "title": "The isotopic composition of uranium and lead in Allende inclusions and meteoritic phosphates", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We measured the isotopic compositions of U and Pb in eight Ca-Al-rich inclusions from the Allende chondrite, in whitlockite from the St. S\u00e9verin chondrite, and in a whitlockite and a whole rock sample from the Angra dos Reis achondrite (ADOR). The total range in ^(235)U/^(238)U in the acid-soluble phases of the Allende inclusions and meteoritic whitlockites is from 1/137.6 to 1/138.3, and to within the error limits (3\u201320\u2030) indistinguishable from normal terrestrial U. The ^(235)U/^(238)U ratios for whitlockites from St. S\u00e9verin and ADOR are the same as that in the bulk meteorites and are normal. The Pb isotopic compositions of the acid-soluble phases of the Allende coarse-grained inclusions (except C-1) give a mean ^(207)Pb/^(206)Pb model age of4.559 \u00b1 0.015AE which is consistent with the observation of normal U isotopic composition. The Pb isotopic compositions of coarse-grained (FUN) inclusion, C-1, and of two fine-grained inclusions from Allende indicate that the U-Pb systems of these samples have evolved differently from the rest of the meteorite. The ^(207)Pb/^(206)Pb model ages for the whitlockites and for bulk ADOR are the same as those for St. S\u00e9verin whitlockite,4.551 \u00b1 0.004AE. The Pb results from St. S\u00e9verin indirectly constrain the value of the U isotopic abundance to be within 7.4\u2030 of normal. Both the directly measured235U/238U and the Pb data on St. S\u00e9verin are in complete disagreement with claims of large ^(235)U excess reported by other workers on the same meteorite. The Th/U ratios of some acid-soluble phases of Allende inclusions and of meteoritic whitlockite show varying degrees of enrichment of Th relative to U by factors of 2 to 25 relative to the bulk meteorites. Previous studies have shown that ^(244)Pu/^(238)U ratios in whitlockite are also fractionated relative to the bulk meteorites. The observation of no isotopic effects in U reported here does not support the claims of either fractionation of ^(247)Cm/^(238)U or of a large amount of live ^(247)Cm at the early stage of formation of the solar system. Using the present data we obtain a limit of ^(247)Cm/^(235) U\u2264 4 \u00d7 10^(\u22123) at the time of meteorite formation or differentiation. This implies that the last major \"r\" process contribution to the material in the protosolar nebula was \u223c10^8 years prior to ^(26)Al formation and injection.", "doi": "10.1016/0012-821X(81)90202-8", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1981", "series_number": "1", "volume": "52", "issue": "1", "pages": "1-15" }, { "id": "authors:xhqse-s6z44", "collection": "authors", "collection_id": "xhqse-s6z44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140116-105556785", "type": "article", "title": "U and Pb Isotopes in Allende Inclusions and Meteoritic Whitlockite", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We measured the isotopic composition of U and Pb in five Ca-Al rich inclusions from the Allende and in phosphates from the St. S\u00e9v\u00e9rin chondrite and the Angra dos Reis achondrite. The purpose of this study is to test claims of large isotopic anomalies in U from meteoritic materials made by other workers.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1980-12", "series_number": "4", "volume": "15", "issue": "4", "pages": "271-272" }, { "id": "authors:j95t0-9gp86", "collection": "authors", "collection_id": "j95t0-9gp86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131106-154816965", "type": "article", "title": "Sm-Nd Isotopic Systematics of Chondrites and Achondrites", "author": [ { "family_name": "Jacobsen", "given_name": "S. B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The ^(143)Nd/^(144)Nd and ^(147)Sm/^(144)Nd ratios have been measured in five chondrites and the Juvinas achondrite. The range in ^(143)Nd/^(144)Nd for the analyzed meteorite samples is 5.3 \u03b5-units (0.511673 to 0.511944) normalized to ^(150)Nd/^(142)Nd = 0.2096. This is correlated with the variation of 4.2% in ^(147)Sm/^(144)Nd (0.1920 to 0.2000).", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1980-12", "series_number": "4", "volume": "15", "issue": "4", "pages": "307-307" }, { "id": "authors:2dns8-bsw54", "collection": "authors", "collection_id": "2dns8-bsw54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-073554984", "type": "article", "title": "Titanium Isotope Anomalies in Allende Inclusions", "author": [ { "family_name": "Niederer", "given_name": "F. R.", "clpid": "Niederer-F-R" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report on Ti isotope abundances in Ca-Al-rich inclusions from Allende. Data are obtained using a TiO^+ beam. The data on oxides of isotopes 46-49 are insensitive to the correction for isobaric interferences among the TiO^+ species.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1980-12", "series_number": "4", "volume": "15", "issue": "4", "pages": "339-340" }, { "id": "authors:g5cdy-grp22", "collection": "authors", "collection_id": "g5cdy-grp22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-071848603", "type": "article", "title": "Spallogenic Rare Gases in Iron Meteorites with Isotopically Anomalous Ag", "author": [ { "family_name": "Villa", "given_name": "I. M.", "clpid": "Villa-I-M" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Cosmic-ray produced rare gases have been measured in four meteorites with excess ^(107)Ag^* (Kelly and Wasserburg, 1978; Kaiser et al., 1980a, 1980b) to determine if ^(107)Ag^* is related to cosmic ray exposure. Kaiser et al. (1980a) considered the possibility that ^(107)Ag^* could derive from energetic particle reactions on Pd if the cross section times multiplicity for all reactions were ~ 10^2 b.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1980-12", "series_number": "4", "volume": "15", "issue": "4", "pages": "382-382" }, { "id": "authors:3bbx2-e0w94", "collection": "authors", "collection_id": "3bbx2-e0w94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140115-142824413", "type": "article", "title": "Hoba and Tlacotepec: Two new meteorites with isotopically anomalous Ag", "author": [ { "family_name": "Kaiser", "given_name": "T.", "clpid": "Kaiser-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Kelly", "given_name": "W. R.", "clpid": "Kelly-W-R" } ], "contributor": [ { "family_name": "Criswell", "given_name": "Paula", "clpid": "Criswell-P" } ], "abstract": "Excesses of ^(107)Ag/^(109)Ag(^(107)Ag^*) of up to 4% relative to terrestrial silver were discovered by Kelly and Wasserburg (1978) in the Santa Clara iron meteorite. Subsequent investigations by Kaiser et al. (1980) (hereafter KKW) revealed much larger ratios of ^(107)Ag/^(109)Ag and showed that the true ^(109)Ag concentration was at a very low level for both the Pi\u00f1on and Santa Clara iron meteorites. Experiments on other iron meteorites were indicated in order to further clarify the role of extinct ^(107)Pd as the source of the ^(107)Ag excesses compared to other possible sources.", "doi": "10.1111/j.1945-5100.1980.tb00533.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1980-12", "series_number": "4", "volume": "15", "issue": "4", "pages": "310-311" }, { "id": "authors:ydp92-4d117", "collection": "authors", "collection_id": "ydp92-4d117", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-072830291", "type": "article", "title": "The Murchison Blue Angel Inclusion: Its Mineralogy and Petrology", "author": [ { "family_name": "Armstrong", "given_name": "J. T.", "clpid": "Armstrong-J-T" }, { "family_name": "Meeker", "given_name": "G. P.", "clpid": "Meeker-G-P" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Hibonite-bearing inclusions found in CV and CM chondrites are thought to contain some of the earliest phases condensed from the solar nebula. A well preserved inclusion of this type, found by R. Becker, has been isolated from the Murchison CM chondrite for extensive analysis.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1980-12", "series_number": "4", "volume": "15", "issue": "4", "pages": "259-260" }, { "id": "authors:p7z65-faz03", "collection": "authors", "collection_id": "p7z65-faz03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-070750178", "type": "article", "title": "Evidence of ^(26)Mg Excess in Hibonite from Murchison", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report Mg isotopic analyses on a hibonite inclusion from Murchison (CM), named the Blue Angel for its distinct color, and discovered by R.H. Becker. Petrographic, mineralogic, and chemical information is provided in a companion abstract (Armstrong et al., 1980). Hibonite is\nimportant as it has the highest estimated condensation temperature for major element oxides (Blander and Fuchs, 1975), may have a high Al/Mg ratio, and may be chemically resistant to alteration.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1980-12", "series_number": "4", "volume": "15", "issue": "4", "pages": "348-348" }, { "id": "authors:gh9mw-4f874", "collection": "authors", "collection_id": "gh9mw-4f874", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:JACpnas80", "type": "article", "title": "A two-reservoir recycling model for mantle-crust evolution", "author": [ { "family_name": "Jacobsen", "given_name": "S. B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The exact solutions for the isotopic compositions and the concentrations of the two-reservoir model for mantle-crust evolution are given for arbitrary rates of crustal growth and of back flow to the mantle. The critical parameters are the chemical fractionation factors for crustal growth and refluxing and the integrated fractional mass-removal rates from the crust and the mantle. For the case where refluxing is proportional to crustal growth, all the solutions reduce to simple analytic expressions. The expression for the mean age of the mass of the crust with refluxing is given. If refluxing is significant, the model shows that highly incompatible elements have short residence times in the mantle. With plausible concentration values, material balance implies that the continents were derived from only a small fraction of the mantle.", "doi": "10.1073/pnas.77.11.6298", "pmcid": "PMC350270", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1980-11", "series_number": "11", "volume": "77", "issue": "11", "pages": "6298-6302" }, { "id": "authors:ptq2m-zg440", "collection": "authors", "collection_id": "ptq2m-zg440", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-084240231", "type": "article", "title": "Neodymium isotopic variations in seawater", "author": [ { "family_name": "Piepgras", "given_name": "Donald J.", "clpid": "Piepgras-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "New data for the direct measurement of the isotopic composition of neodymium in Atlantic Ocean seawater are compared with previous measurements of Pacific Ocean seawater and ferromanganese sediments from major ocean basins. Data for Atlantic seawater are in excellent agreement with Nd isotopic measurements made on Atlantic ferromanganese sediments and are distinctly different from the observed compositions of Pacific samples. These results clearly demonstrate the existence of distinctive differences in the isotopic composition of Nd in the waters of the major ocean basins and are characteristic of the ocean basin sampled. The average \u03b5_(Nd)(0) values for the major oceans as determined by data from seawater and ferromanganese sediments are as follows: Atlantic Ocean,\u03b5_(Nd)(0) \u2245 \u221212 \u00b1 2; Indian Ocean,\u03b5_(Nd)(0) \u2245 \u22128 \u00b1 2; Pacific Ocean,\u03b5_(Nd)(0) \u2245 \u22123 \u00b1 2. These values are considerably less than \u03b5_(Nd)(0) value sources with oceanic mantle affinities indicating that the REE in the oceans are dominated by continental sources. The difference in the absolute abundance of ^(143)Nd between the Pacific and Atlantic Oceans corresponds to \u223c106 atoms ^(143)Nd per gram of seawater. The correspondence between the ^(143)Nd/^(144)Nd in seawater and in the associated sediments suggests the possible application of this approach to paleo-oceanography.\nDistinctive differences in \u03b5_(Nd)(0) values are observed in the Atlantic Ocean between deep-ocean water associated with North Atlantic Deep Water and near-surface water. This suggests that North Atlantic Deep Water may be relatively well mixed with respect to Nd isotopic composition whereas near-surface water may be quite heterogeneous, reflecting different sources for surface waters relative to deep water. This suggests that it may be possible to distinguish the sources of water masses within an ocean basin on the basis of Nd isotopic composition.\nThe Nd isotopic variations in seawater are used to relate the residence time of Nd and mixing rates between the oceans.", "doi": "10.1016/0012-821X(80)90124-7", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1980-10", "series_number": "1", "volume": "50", "issue": "1", "pages": "128-138" }, { "id": "authors:brh7p-vae81", "collection": "authors", "collection_id": "brh7p-vae81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-085945740", "type": "article", "title": "Sm-Nd isotopic evolution of chondrites", "author": [ { "family_name": "Jacobsen", "given_name": "Stein B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The ^(143)Nd/^(144)Nd and ^(147)Sm/^(144)Nd ratios have been measured in five chondrites and the Juvinas achondrite. The range in ^(143)Nd/^(144)Nd for the analyzed meteorite samples is 5.3 \u03b5-units (0.511673\u20130.511944) normalized to ^(150)Nd/^(142)Nd= 0.2096. This is correlated with the variation of 4.2% in ^(147)Sm/^(144)Nd (0.1920\u20130.2000). Much of this spread is due to small-scale heterogeneities in the chondrites and does not appear to reflect the large-scale volumetric averages. It is shown that none of the samples deviate more than 0.5 \u03b5-units from a 4.6-AE reference isochron and define an initial ^(143)Nd/^(144)Nd ratio at 4.6 AE of 0.505828 \u00b1 9. Insofar as there is a range of values of ^(147)Sm/^(144)Nd there is no unique way of picking solar or average chondritic values. From these data we have selected a new set of self-consistent present-day reference values for CHUR (\"chondritic uniform reservoir\") of (^(143)Nd/^(144)Nd)_(CHUR)^0 = 0.511836 and (^(147)Sm/^(144)Nd)_(CHUR)^0 = 0.1967. The new ^(147)Sm/^(144)Nd value is 1.6% higher than the previous value assigned to CHUR using the Juvinas data of Lugmair. This will cause a small but significant change in the CHUR evolution curve. Some terrestrial samples of Archean age show clear deviations from the new CHUR curve. If the CHUR curve is representative of undifferentiated mantle then it demonstrates that depleted sources were also tapped early in the Archean. Such a depleted layer may represent the early evolution of the source of present-day mid-ocean ridge basalts. There exists a variety of discrepancies with most earlier meteorite data which includes determination of all Nd isotopes and Sm/Nd ratios. These discrepancies require clarification in order to permit reliable interlaboratory comparisons. The new CHUR curve implies substantial changes in model ages for lunar rocks and thus also in the interpretation of early lunar chronology.", "doi": "10.1016/0012-821X(80)90125-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1980-10", "series_number": "1", "volume": "50", "issue": "1", "pages": "139-155" }, { "id": "authors:mfjmc-pwx23", "collection": "authors", "collection_id": "mfjmc-pwx23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-154522497", "type": "article", "title": "Endemic isotopic anomalies in titanium", "author": [ { "family_name": "Niederer", "given_name": "F. R.", "clpid": "Niederer-F-R" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Abundances of the titanium isotopes were determined using a new high-precision technique that shows terrestrial, lunar, and bulk meteorite samples to be indistinguishable. Ca-Al-Ti-rich inclusions in the Allende meteorite are found to contain Ti of widely varying isotopic composition reflecting the presence of at least three nucleosynthetic components. The anomalies in Ti appear to be relatively widespread and, when correlated with Ca data, provide a clue to nucleosynthesis in the neighborhood of the iron peak and to the late-stage nucleosynthetic processes which immediately preceded formation of the solar nebula.", "doi": "10.1086/183326", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1980-08-15", "volume": "240", "pages": "L73-L77" }, { "id": "authors:dbmff-69008", "collection": "authors", "collection_id": "dbmff-69008", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150121-152101655", "type": "article", "title": "James B. Macelwane Award: Citation and Acceptance of Lawrence Grossman", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "It is a pleasure to present Lawrence Grossman for the Macelwane Award. This occasion is particularly auspicious since the AGU meeting is held here in Toronto, Canada, where Larry was born and raised. As a young man he worked in a mining company plant in northern Manitoba, fixing railroad ties and then doing copper analyses of drill cores in their assay office. On careful investigation I found that he also had some criminal connections with the nearby offices of the Ontario Provincial Police, which was located a short distance from here along the waterfront. Fortunately, this turned out to be on the legal side and not the seamy side. It appears that Larry had directed his natural investigative skills toward doing mineral and chemical analyses of soils scraped from the shoes of suspected criminals. Larry Grossman has not changed directions\u2014just subjects. His investigative skills are now directed toward rocks and soils scraped from the sole of the early solar system. The solar nebula is a place for which scientific proofs are often circumstantial, there being few witnesses to the crimes of creation.", "doi": "10.1029/EO061i030p00547", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "1980-07-22", "series_number": "30", "volume": "61", "issue": "30", "pages": "547-548" }, { "id": "authors:nj05n-z2p11", "collection": "authors", "collection_id": "nj05n-z2p11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150116-131325523", "type": "article", "title": "Mineralogy and petrography of HAL, an isotopically-unusual Allende inclusion", "author": [ { "family_name": "Allen", "given_name": "John M.", "clpid": "Allen-J-M" }, { "family_name": "Grossman", "given_name": "Lawrence", "clpid": "Grossman-L" }, { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A detailed mineralogical study of HAL was initiated to elucidate the origin of this inclusion because LEE et al. (1979) had found large mass fractionation effects and small nuclear effects in its Ca isotopic composition, but no ^(26)Mg excesses in samples of it with very high ^(27)Al/^(24)Mg ratios. HAL's 1.0 mm radius interior consists almost entirely of three hibonite crystals and is surrounded by a 2.0 mm thick, multi-layered rim. The first layer, called the black rim, is black and compact, resembles a devitrified glass and contains an anisotropic Al-Fe-oxide similar to hercynite in composition. This is followed by a friable rim sequence, layer I of which is predominantly feldspathoids with minor anorthite, Ti-Fe-oxide and Al-Fe-oxide. Layer II contains abundant perovskite, plus grossular, andradite and pyroxene in addition to the minerals of layer I. Layer III is mostly Ca-phosphate, possibly hydroxy-apatite and perovskite. Layer IV is rich in hibonite, Al-Fe-oxide, perovskite, nepheline and the two garnets, lacks Ca-phosphate but contains traces of a Ti-Sc-Zr-oxide. Layer V is rich in Al-Fe-oxide, pyroxene, nepheline, the two garnets and olivine whose crystals display peculiar rectangular cross-sections. The black rim does not completely surround the hibonite core. Sectors of the friable rim exist where layer I is missing and where the mineralogy of adjacent layers is no different from that of the same layers in other sectors. Pentlandite, nickel-iron and barrel-shaped olivine crystals, minerals typical of the matrix of Allende and found nowhere else in HAL, are found in layer V and increase in abundance toward its exterior, as if grains of these phases accreted together with the other minerals of layer V. This layer also contains alternating olivine-rich and garnet-, pyroxene-rich bands, resembling rhythmic layering. For these reasons, we conclude that each of the layers of the friable rim formed by the accretion of an assemblage of condensate grains rather than by complete reaction of a precursor to HAL with a nebular gas. Thus, the unusual isotopic characteristics of HAL are thought to have been inherited from a nebular reservoir which was isotopically distinct from that which gave rise to the bulk of the material in Allende. HAL's mineralogical peculiarities indicate that its formation reservoir was also chemically distinct from the latter one.", "doi": "10.1016/0016-7037(80)90158-1", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1980-05", "series_number": "5", "volume": "44", "issue": "5", "pages": "685-699" }, { "id": "authors:1c695-s4k28", "collection": "authors", "collection_id": "1c695-s4k28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-085152103", "type": "article", "title": "Isotopically anomalous silver in the Santa Clara and Pi\u00f1on iron meteorites", "author": [ { "family_name": "Kaiser", "given_name": "T.", "clpid": "Kaiser-T" }, { "family_name": "Kelly", "given_name": "W. R.", "clpid": "Kelly-W-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition and concentration of Ag and the concentration of Pd have been determined in the Santa Clara and Pi\u00f1on iron meteorites. It is shown that these meteorites contain isotopically anomalous Ag with an excess of ^(107)Ag relative to normal Ag, confirming earlier findings. Using an improved procedure for cleaning the sample surface from terrestrial Ag, a new concentration of 1-4\u00d710^(11) atoms of ^(109)Ag/g meteorite is established which is an order of magnitude below the levels found earlier. As a result ratios of ^(107)Ag/^(109)Ag were found which are enriched in ^(107)Ag by 60% to 160%. The existence of an excess ^(107)Ag in these two meteorites, which have high ^(108)Pd/^(109)Ag ratios of \u223c 7\u00d710^4, is established. These findings are consistent with the in situ decay of extinct ^(107)Pd (\u03c4_\u00bd = 6.5\u00d710^6y) produced by a late nucleosynthetic event shortly before solar system formation; however, production of Ag isotopes by reaction of cosmic ray secondaries with the Pd isotopes in the meteorites cannot be excluded.", "doi": "10.1029/GL007i004p00271", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1980-04", "series_number": "4", "volume": "7", "issue": "4", "pages": "271-274" }, { "id": "authors:wyjax-mad60", "collection": "authors", "collection_id": "wyjax-mad60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131113-151445203", "type": "article", "title": "A search for isotopic anomalies in uranium", "author": [ { "family_name": "Chen", "given_name": "J. H.", "clpid": "Chen-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The ^(238)U/^(235)U ratios for nine bulk chondritic meteorites and a terrestrial basalt were measured. The total range in ^(238)U/^(235)U determined for both total meteorites and for acid leaches was from 137.2 to 138.3 and to within the error limits indistinguishable from normal terrestrial U. The typical errors in a single determination are \u00b16\u2030 (2\u03c3_M) for a 2 ng U sample from a chondrite. Taking the extreme values of \u03b4^(235)U for each measurement the maximum amount of excess ^(235)U that can be allowed to be present ranges from 2 \u00d7 10^8 to 2 \u00d7 10^9 atoms per gram of bulk meteorite. These results do not support the claims of variations in ^(238)U/^(235)U at the percentage levels or number of excess ^(235)U atoms in some of the same meteorites as reported by several other previous workers.", "doi": "10.1029/GL007i004p00275", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1980-04", "series_number": "4", "volume": "7", "issue": "4", "pages": "275-278" }, { "id": "authors:dtqvv-aak15", "collection": "authors", "collection_id": "dtqvv-aak15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-071026022", "type": "article", "title": "A neodymium, strontium, and oxygen isotopic study of the Cretaceous Samail ophiolite and implications for the petrogenesis and seawater-hydrothermal alteration of oceanic crust", "author": [ { "family_name": "McCulloch", "given_name": "Malcolm T.", "clpid": "McCulloch-M-T" }, { "family_name": "Gregory", "given_name": "Robert T.", "clpid": "Gregory-R-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Taylor", "given_name": "Hugh P., Jr.", "clpid": "Taylor-H-P-Jr" } ], "abstract": "In the Samail ophiolite, ^(147)Sm-^(143)Nd,^(87)Rb-^(87)Sr, and ^(18)O/^(16)O isotopic systems have been used to distinguish between sea-floor hydrothermal alteration and primary magmatic isotopic variations. The Rb-Sr and ^(18)O/^(16)O isotopic systems clearly exhibit sensitivity to hydrothermal interactions with seawater while the Sm-Nd system appears essentially undisturbed. Internal isochrons have been determined by the ^(147)Sm-^(143)Nd method using coexisting plagioclase and pyroxene and give crystallization ages of 130 \u00b1 12m.y. from Ibra and 100 \u00b1 20 m.y. from Wadi Fizh. These ages are interpreted as the time of formation of the Samail oceanic crust and are older than the inferred emplacement age of 65\u201385 m.y. The initial ^(143)Nd/^(144)Nd ratios for a tectonized harzburgite, cumulate gabbros, plagiogranite, sheeted dikes and a basalt have a limited range in \u03b5_(Nd) of from 7.5 to 8.6 for all lithologies, demonstrating a clear oceanic affinity and supporting earlier interpretations based on geologic observations and geochemistry. The ^(87)Sr/^(86)Sr initial ratios on the same rocks have an extremely large range of from 0.70296 to 0.70650 (\u03b5_(Sr) = \u221219.7 to +30.5) and the \u03b4^(18)O values vary from 2.6 to 12.7. These large variations are clearly consistent with hydrothermal interaction of seawater with the oceanic crust. A model is presented for the closed system exchange of Sr and O, that in principle illustrates how the Sr isotopic data may be utilized to estimate the water/rock ratio and subsequently used to evaluate the temperature of equilibration between the water and silicates from the ^(18)O/^(16)O water-rock fractionation.", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1980-01", "series_number": "2", "volume": "46", "issue": "2", "pages": "201-211" }, { "id": "authors:g3ere-4kx21", "collection": "authors", "collection_id": "g3ere-4kx21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131121-105115358", "type": "article", "title": "Nd and Sr Isotopic Study of the Bay of Islands Ophiolite Complex and the Evolution of the Source of Midocean Ridge Basalts", "author": [ { "family_name": "Jacobsen", "given_name": "Stein B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Two Sm-Nd internal isochrons for pyroxene gabbros of the Bay of Islands Ophiolite Complex give well-defined ages of 508 \u00b1 6 m.y. and 501 \u00b1 13 m.y. with initial ^(143)Nd/^(144)Nd of \u03b5_(Nd) = +7.7 \u2213 0.1 and \u03b5_(Nd) = +7.5 \u2213 0.2, respectively. Total rock samples from pillow basalts, sheeted dikes, trondhjemites, hornblende gabbros, pyroxene gabbros, and an orthopyroxenite layer from the harzburgite give initial \u03b5_(Nd) in the range from +6.5 to +8.1 with an average value of +7.6. The initial ^(87)Sr/^(86)Sr obtained on a pyroxenegabbro is \u03b5_(Sr) = \u221219.3 \u00b1 0.3, which is typical of oceanic samples. However, the initial ^(87)Sr/^(86)Sr within the different phases of the complex is found to be highly variable (\u223c52 \u03b5 units) and shows the effect of sea water alteration. The \u03b5_(Nd) values demonstrate a clear oceanic affinity for the Bay of Islands complex and support earlier interpretations made on the basis of structure and geochemistry. The magnitudes of the initial \u03b5_(Nd) values (+7.6) are somewhat smaller than for typical present-day midocean ridge basalts (MORB) (+10). This is most likely due to differential evolution over the past 0.5 aeon of the oceanic mantle relative to the bulk earth. The observed shift is quantitatively what should be expected for a simple single-stage evolution. For a model with a single differentiation event at time T_D to produce the depleted mantle, both Sm-Nd and Rb-Sr data for MORB and the Bay of Islands Complex give T_D \u2248 1.8 aeons. This age is, however, interpreted as the mean age of the MORB source and does not refer to a unique event. The total time for producing this source by a uniform process would be of the order of 3.6 aeons. The Nd isotopic signature of oceanic crust is clearly present in this Paleozoic ophiolite and suggests that typical high-\u03b5_(Nd) reservoirs are sources of oceanic crust through the Phanerozoic. This implies relatively rapid turnover between oceanic crust and mantle sources and a good mixing of oceanic mantle for the past 1.0 aeon, including contributions from recycled continental materials. These data indicate that the major distinction between oceanic basalts and continental basalts observed in recent rocks is also preserved through the Phanerozoic. These isotopic differences clearly imply a long time distinction between the magma sources of these basalt types. It should be possible to apply the distinctive \u03b5_(Nd) values of oceanic crust and mantle to identify old obducted oceanic segments on continental blocks.", "doi": "10.1029/JB084iB13p07429", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1979-12-10", "series_number": "B13", "volume": "84", "issue": "B13", "pages": "7429-7445" }, { "id": "authors:q2201-qr709", "collection": "authors", "collection_id": "q2201-qr709", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131120-153025570", "type": "article", "title": "The Mean Age of Mantle and Crustal Reservoirs", "author": [ { "family_name": "Jacobsen", "given_name": "Stein B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Mantle and crust evolution is discussed in terms of two simple transport models. In model I, continents (j = 3) are derived by melt extraction over the history of the earth from undepleted mantle (j = 1), and the residue forms a depleted mantle (j = 2), which today is the source of mid-ocean ridge basalts. In model II, new additions to continents are derived from a mantle reservoir 2, which becomes more depleted through time by repeated extraction of melts. Transport equations were solved for stable s, radioactive r, and daughter d isotopes for arbitrary mass growth curves M_j(\u03c4). For both models the isotopic composition and concentrations of trace elements are shown to reduce to simple mathematical expressions which readily permit calculations of basic evolutionary parameters from the data. For longlived isotopes (\u03bb^(\u22121) \u226b 4.5 aeons) for model I the deviations in parts in 10^4 of the ratio of a daughter isotope to a stable reference isotope of the same element in reservoirs j = 2, 3 from that of 1 is given by E_(dj)^*=Q_d^*t_(Mj)\u0192_j^(r/s). Here t_(Mj) is the mean age of the mass of j,\u0192_j^(r/s) is the enrichment factor of the ratio of a radioactive isotope to a stable isotope relative to that in 1, and Q_d^* \u2243 const. Thus for long-lived isotopes such as ^(147)Sm and ^(87)Rb the only time information that can be obtained from model I from measurement of the relative chemical enrichment factors and isotopic ratios at a single time is the mean age of the mass of the continental crust and the complementary depleted mantle reservoir. This mean age is independent of the long-lived parent-daughter system. An analogous result is obtained for model II, where E_(d.2)^*= Q_d^*(\u0192_2^(r/s))t. Here (\u0192_2^(r/s)) is the weighted time average of the enrichment factor, and \u03c4 is the time measured from the origin of the earth. The mean age of the mass of the crust (t_(M.3)) and the time parameter t_(r/s)=t(\u0192_2^(r/s))/\u0192_2^(r/s) for the crust in model II will for long-lived parent-daughter systems be different depending on the element fractionation during partial melting. Decay systems with small parent-daughter fractionations during partial melting may, however, be used to estimate the mean age of the continental crust. Sm-Nd and Rb-Sr isotopic data for continental crust, depleted and undepleted mantle, have been used to evaluate both models and yield young mean ages for the mass of the continental crust of 1.8 and 1.5 aeons for model I and model II, respectively. Both models also suggest that the rate of growth of the continents for the last 0.5 aeon is much less than the average growth rate. The young mean age of the continents implies either rapid refluxing of crustal materials to the mantle in the period from 4.5 to 3.6 aeons or that very little early crust ever formed. Mass balance calculations for both models show that the continents were only formed from \u223c30% of the total mantle, leaving 70% of the mantle as undepleted. The major difference in the two models lies in the difference in the compositions of newly derived crust. For model I the trace element concentrations in new additions to the crust is constant, and the isotopic values are those of the undepleted mantle reservoir, in agreement with recent Nd isotopic studies. The correlation line between \u03b5_(Nd) and \u03b5_(Sr) for young basalts can be explained with model I by mixing depleted and undepleted mantle, but it cannot in any simple way be explained by model II. Model II implies that new additions to the continents have the isotopic characteristics of depleted mantle and that the concentration of Rb, U, Ba, and other highly incompatible trace elements in newly added material have changed by a factor of \u223c10 through time, for which there is no evidence. For both models the simple analytical expressions derived herein permit calculations of earth models with great facility without requiring a computer calculation.", "doi": "10.1029/JB084iB13p07411", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1979-12-10", "series_number": "B13", "volume": "84", "issue": "B13", "pages": "7411-7427" }, { "id": "authors:n61sw-ed853", "collection": "authors", "collection_id": "n61sw-ed853", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131121-100326695", "type": "article", "title": "Isotopic Constraints for the Early Evolution of the Moon", "author": [ { "family_name": "Oberli", "given_name": "F.", "clpid": "Oberli-F" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "McCulloch", "given_name": "M. T.", "clpid": "McCulloch-M-T" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A synthesis of the early evolution of the moon and of the lunar highland crust is made on the basis of U-Th-Pb, Rb-Sr, K-Ar and Sm-Nd isotopic data from lunar highland breccias.", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1979-12", "series_number": "4", "volume": "14", "issue": "4", "pages": "502-503" }, { "id": "authors:3j8fx-29b90", "collection": "authors", "collection_id": "3j8fx-29b90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131022-152821831", "type": "article", "title": "The isotopic composition of Nd in different ocean masses", "author": [ { "family_name": "Piepgras", "given_name": "D. J.", "clpid": "Piepgras-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Dasch", "given_name": "E. J.", "clpid": "Dasch-E-J" } ], "abstract": "Sm-Nd data for authigenic ferromanganese sediments from the oceans indicate that the Atlantic, Pacific, and Indian Oceans each have a distinct range in Nd isotopic composition which are characteristic of each ocean basin and reflect the dissolved load of Nd in the water mass. Within each basin, Nd isotopic compositions show some variability but are relatively well defined. Isotopic compositions of Nd measured in these samples are all far less than the ^(143)Nd/^(144)Nd ratios of source rocks with oceanic affinities. Direct measurements of the Nd isotopic composition of seawater presented here support the view that REE in ferromanganese sediments are derived by the direct precipitation of these elements out of seawater. Nd isotopic variations in ferromanganese sediments cannot be explained by contributions from continental detritus. It is therefore believed that the Nd isotopic variations found for ferromanganese sediments represent true variations in the isotopic composition of Nd dissolved in seawater in various ocean masses. These variations reflect primarily the age and ^(147)Sm/^(144)Nd of the continental masses being sampled, which is believed to be the major source of REE in seawater. These variations indicate that the residence time of Nd in seawater must be very short relative to the mixing rates between ocean masses. Nd isotopic studies, both in seawater and sediments should, therefore, be useful as a monitor of ocean currents and interocean mixing over the past several million years.", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1979-11", "series_number": "2", "volume": "45", "issue": "2", "pages": "223-236" }, { "id": "authors:ps1hy-bnv58", "collection": "authors", "collection_id": "ps1hy-bnv58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131210-151341716", "type": "article", "title": "Magnesium Isotopic Composition of Interplanetary Dust Particles", "author": [ { "family_name": "Esat", "given_name": "Tezer M.", "clpid": "Esat-T-M" }, { "family_name": "Brownlee", "given_name": "D. E.", "clpid": "Brownlee-D-E" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The magnesium isotopic composition of some extraterrestrial dust particles has been measured. The particles are believed to be samples of interplanetary dust, a significant fraction of which originated from the disaggregation of comets and may contain preserved isotopic anomalies. Improvements in mass spectrometric and sample preparation techniques have made it possible to measure the magnesium isotopic composition of the dust particles, which are typically 10 micrometers in size and contain on the order of 10^(\u201310) gram of magnesium. Of the 13 samples analyzed, nine have the terrestrial magnesium isotopic composition within 2 parts per thousand, and one shows isotopic mass fractionation of 1.1 percent per mass unit. A subset of the particles, described as chondritic aggregates, are very close to normal isotopic composition, but their normalized isotopic ratios appear to show nonlinear effects of 3 to 4 parts per thousand, which is near the present limit of detection for samples of this size. The isotopic composition of calcium was also determined in one particle and found to be normal within 2 percent. It is clear that the isotopic composition of interplanetary dust particles can be determined with good precision. Collection of dust particles during the earth's passage through a comet tail or an intense meteor stream may permit laboratory analysis of material from a known comet.", "doi": "10.1126/science.206.4415.190", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1979-10-12", "series_number": "4415", "volume": "206", "issue": "4415", "pages": "190-197" }, { "id": "authors:71n1c-yee75", "collection": "authors", "collection_id": "71n1c-yee75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WASpnas79", "type": "article", "title": "Models of earth structure inferred from neodymium and strontium isotopic abundances", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" } ], "abstract": "A simplified model of earth structure based on the Nd and Sr isotopic characteristics of oceanic and continental tholeiitic flood basalts is presented, taking into account the motion of crustal plates and a chemical balance for trace elements. The resulting structure that is inferred consists of a lower mantle that is still essentially undifferentiated, overlain by an upper mantle that is the residue of the original source from which the continents were derived.", "doi": "10.1073/pnas.76.8.3594", "pmcid": "PMC383878", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1979-08", "series_number": "8", "volume": "76", "issue": "8", "pages": "3594-3598" }, { "id": "authors:pa18j-hwr04", "collection": "authors", "collection_id": "pa18j-hwr04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-145504198", "type": "article", "title": "Sm-Nd age of the Stillwater complex and the mantle evolution curve for neodymium", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "An internal isochron determined for a gabbro from the Stillwater complex by the Sm-Nd method yields a precise age of 2701 \u00b1 8 Myr and initial ^(143)Nd/^(144)Nd = 0.508248 \u00b1 12. The initial is close to the CHUR evolution curve but clearly displaced below it by \u03f5_(Nd) = \u22122.8 \u00b1 0.2. A spectrum of total rocks in the Stillwater complex ranging from anorthosite to pyroxenite were found to lie on the same isochron to within experimental error indicating the same age and initial. These data demonstrate that some ancient mantle-derived rocks have initial ^(143)Nd/^(144)Nd which deviate substantially from the CHUR evolution curve at the time of their formation. This implies that there was early layering in the mantle with substantial REE fractionation (~6\u201312% Nd/Sm enrichment) or that the Stillwater complex was highly contaminated with REE from much older continental crust during emplacement. The results show the necessity of high-precision ages and initial ^(143)Nd/^(144)Nd values in order to properly describe REE fractionation in the mantle. While the Sm-Nd age results show no indication of any irregularities, we have confirmed that the Rb-Sr data for the Stillwater are highly disturbed. This comparison indicates that the Sm-Nd parent-daughter system may be much less susceptible to element redistribution during metamorphism, therefore permitting wide application of this technique to rocks of complex histories.", "doi": "10.1016/0016-7037(79)90089-9", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1979-07", "series_number": "7", "volume": "43", "issue": "7", "pages": "999-1008" }, { "id": "authors:wqe0m-98n45", "collection": "authors", "collection_id": "wqe0m-98n45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:DEPpnas79", "type": "article", "title": "Neodymium isotopes in flood basalts from the Siberian Platform and inferences about their mantle sources", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The initial isotopic compositions of Nd and Sr in basalts from the Central Siberian Plateau and other major continental flood basalts are reported. The continental flood basalts appear to be the product of partial melting of mantle sources that consist of relatively primitive undifferentiated material and are clearly distinct from midocean ridge basalts, which sample mantle reservoirs that have been modified by extraction of continental crust earlier in earth history. These observations provide fundamental constraints on models of mantle structure and dynamics. Isotopic effects of crustal contamination are clearly recognizable in some continental flood basalts, but these effects can be distinguished from isotopic patterns inherited from the mantle magma sources.", "doi": "10.1073/pnas.76.7.3056", "pmcid": "PMC383761", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1979-07", "series_number": "7", "volume": "76", "issue": "7", "pages": "3056-3060" }, { "id": "authors:4txba-sce09", "collection": "authors", "collection_id": "4txba-sce09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-094108190", "type": "article", "title": "Argon 40-argon 39 chronology of lithic clasts from the Kapoeta howardite", "author": [ { "family_name": "Rajan", "given_name": "R. S.", "clpid": "Rajan-R-S" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Smith", "given_name": "S. P.", "clpid": "Smith-S-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "^(40)Ar-^(39)Ar age spectra have been measured on plagioclase separates from three basaltic clasts (A, B, C), a pyroxene separate from clast B, and a total sample of a fourth basaltic clast (\u03c1) from the Kapoeta achondritic meteorite. The Ar data show that three of the four clasts crystallized \u22654.5 AE ago. Xe measurements indicate all four formed within a 0.1 AE period (Huneke, et al., 1977, Lunar Science VIII, pp. 484\u2013486). Three clasts have suffered various degrees of ^(40)Ar loss since that time. The times of ^(40)Ar degassing do not cluster about a single time analogous to the lunar cataclysm. The survival of \u22654.5 AE ages contrasts with the general absence of ages \u22654.0 AE on the moon.\nThe Ar retention age of clast B of \u22654.57 AE is atypically older than the Rb-Sr age of 3.6 AE (Papanastassiou et al., 1974, Lunar Science V, p. 583). The 3.5 AE Ar age of clast A is distinctly younger than the Rb-Sr age of 3.9 AE (Papanastassiou et al., 1974). The K-Ar and Rb-Sr systems are clearly not equivalent dating techniques in these instances.\nThe combined evidence of Ar, Xe and Rb-Sr studies suggests the period of volcanism on the Kapoeta parent planet was restricted to the first ~0.2 AE of solar system history. The subsequent thermal metamorphic histories recorded in each of the four clasts after formation are distinctly different. The clasts must have existed as independent fragments at least as recently as 3.5 AE ago. The cosmic ray exposure ages of all the four clasts are similar (~ 3 Myr), and are not significantly different from that of the bulk meteorite. The clasts spent essentially all of the time prior to the formation of Kapoeta at depths greater than a few meters.", "doi": "10.1016/0016-7037(79)90086-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1979-07", "series_number": "7", "volume": "43", "issue": "7", "pages": "957-971" }, { "id": "authors:rmzdm-g0s88", "collection": "authors", "collection_id": "rmzdm-g0s88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-155250156", "type": "article", "title": "Petrogenetic mixing models and Nd-Sr isotopic patterns", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The possible Nd and Sr isotopic variations which would result from assimilation of continental crust by mantle-derived magmas can be systematized by considering the chemical and isotopic compositions of the magmas and models for layering within the continental crust. These systematics may provide a valuable framework for studying crustal contamination, the formation of magmas within the crust, and the chemical and age structure of continental segments. The isotopic patterns arise from (1) the overall contrast in Nd and Sr isotopic composition between old continental crust and mantle magma sources, (2) regularities in the variations of ^(143)Nd/^(144)Nd and ^(87)Sr/^(86)Sr in crustal rocks which are related to age and the contrasting geochemical behavior of Sm and Nd relative to Rb and Sr.\nConsideration of two-component mixing models suggests that the correlation of initial Nd and Sr isotopes in selected young basalts could represent a mixing line, possibly between mantle reservoirs of distinct chemistry and age. However, the possibility that the trend results from mixing of old low - Sm/Nd, high - Rb/Sr crustal material with complementary high - Sm/Nd, low - Rb/Sr mantle reservoirs cannot be eliminated. Such recycling of crust into the mantle could occur in subduction zones. One problem with a recycling model to explain the correlation is that it requires the crustal endmember to have chemical and isotopic properties which do not appear to be common in crustal rocks.", "doi": "10.1016/0016-7037(79)90169-8", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1979-04", "series_number": "4", "volume": "43", "issue": "4", "pages": "615-627" }, { "id": "authors:zxpm1-dcc20", "collection": "authors", "collection_id": "zxpm1-dcc20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-154419570", "type": "article", "title": "Calcium isotopic anomalies and the lack of aluminum-26 in an unusual Allende inclusion", "author": [ { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Russell", "given_name": "William A.", "clpid": "Russell-W-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have studied the Mg and Ca isotopic compositions of an unusual Allende inclusion dominated by hibonite, which is the most refractory and possibly the most primitive major oxide mineral. No ^(26)Mg excess was found in spite of the high ^(27)Al/^(24)Mg (1 \u2273 10^3) of some samples, indicating an initial (^(26)Al/^(27)Al)_0 < 2 X 10^(-7), a factor of 250 less than found in some other Allende inclusions.\nThe upper limit for Mg isotopic fractionation is 20%o per amu. Anomalous but uniform Ca isotopic compositions were found for bulk samples of coexisting phases and microscopic grains. The Ca anomaly is a superposition of a large mass-dependent fractionation effect of 7.5\u2030 per amu favoring\nthe heavy isotopes and small (1\u2030-2\u2030) \"nonlinear\" effects of presumably nuclear origin. If the lack of ^(26)Al is due to a time delay of 6 X 10^6 yr for the formation of the hibonite inclusion, then condensation models require modification. The Ca effects suggest the alternative that ^(26)Al was not uniformly distributed in the solar system. These results accentuate the curious and unexplained\nassociation between large mass fractionation and nuclear effects. They also reinforce the scenario which envisages an early solar system consisting of isotopically and chemically distinct reservoirs resulting from the incomplete mixing of several nucleosynthetic components. It is not evident whether these components originated within the solar system or from another star.", "doi": "10.1086/182911", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1979-03-01", "volume": "228", "pages": "L93-L98" }, { "id": "authors:sd252-mcr52", "collection": "authors", "collection_id": "sd252-mcr52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221204-224152982", "type": "article", "title": "Acceptance Speech for the V. M. Goldschmidt Medal", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Mr. President. Colleagues and Friends: It is a privilege to receive the V. M. Goldschmidt Award of the Geochemical Society. I am much honored to be put in the company of the previous recipients who have been my teachers. my colleagues and my friends for over the past 30 years. I thank the society and the committee for their generosity in this selection. It is most gratifying that my scientific works should be so recognized. Over the years it has been my good fortune to have close associates and students with a profound dedication to scientific studies and with whom a great deal of any credit must be shared. I consider this day particularly auspicious because of the presence of an old friend, Sam Epstein, who has introduced me today, and preceded me in this award. and the recognition of a young friend, Don DePaolo, who is the most recent recipient of the Clarke Medal. Sharing honors with a young scientist who is pioneering a new area of knowledge is particularly gratifying.", "doi": "10.1016/0016-7037(79)90211-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1979-03", "series_number": "3", "volume": "43", "issue": "3", "pages": "440-442" }, { "id": "authors:4n01k-yta18", "collection": "authors", "collection_id": "4n01k-yta18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130821-130858313", "type": "article", "title": "Presentation of the Arthur L. Day Medal to Samuel Epstein", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "I am charged with the most delightful task of introducing Sam Epstein. I have\nknown him for 30 years. The opportunity to present someone with so many character flaws\nis particularly appealing to me. I have consulted with many individuals about the\ndarkest details of Sam Epstein's past and am simultaneously encouraged by these\nsources to tell the most revealing stories about him, but I am also admonished never\never to overdo it, because Sam is really a \"nice guy.\"", "doi": "10.1130/GSAB-P2-90-608", "issn": "0016-7606", "publisher": "Geological Society of America", "publication": "Geological Society of America Bulletin", "publication_date": "1979-03", "series_number": "3", "volume": "90", "issue": "3", "pages": "612-621" }, { "id": "authors:zecxe-sye53", "collection": "authors", "collection_id": "zecxe-sye53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-083240256", "type": "article", "title": "Evidence for the existence of ^(107)Pd in the early solar system", "author": [ { "family_name": "Kelly", "given_name": "William R.", "clpid": "Kelly-W-R" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The concentration and isotopic composition of Ag and Pd were measured in the Santa Clara iron meteorite. This meteorite has Pd/Ag of about 10^4. The isotopic composition of Pd is identical to terrestrial Pd within 0.1%. The ^(107)Ag/^(109)Ag ratio was 4% greater than the terrestrial value and suggests the in situ decay of ^(107)Pd(\u03c4_\u00bd = 6.5 \u00d7 10^6y) in this meteorite or its parent body. From the observed ^(107)Ag^*/^(110)Pd ratio (^* \u2261 excess) we infer an initial (^(107)Pd/^(110)Pd)_\u2299 \u2a7e2 \u00d7 10^(\u22125). These data are incompatible with an interval of \u223c 10^8y between the end of nucleosynthesis and the formation of planetary objects but are compatible with a last-minute injection of material. The inferred existence of ^(107)Pd and ^(26)Al indicates that the late injection included freshly synthesized material of both intermediate and low atomic weight on a similar time scale. We estimate the fraction of freshly synthesized material to be between 10^(\u22125) to 10^(\u22124) in the region of Z \u223c 50. The ^(244)Pu and some of the ^(129)I present in the early solar system may be due to earlier contributions. The highly granular nature of stellar nucleosynthesis is made apparent by these considerations. The ^(107)Pd-^(107)Ag chronometer is of particular importance as it can measure the time interval between the last injection of freshly synthesized material and the formation of differentiated planetary-size objects. Our data suggest that the time scale for the differentiation of some planets into large scale metallic and silicate segregations is as short as \u223c10^6y.", "doi": "10.1029/GL005i012p01079", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1978-12", "series_number": "12", "volume": "5", "issue": "12", "pages": "1079-1082" }, { "id": "authors:157ds-p3d07", "collection": "authors", "collection_id": "157ds-p3d07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131028-082625003", "type": "article", "title": "Interpretation of Nd, Sr and Pb isotope data from Archean migmatites in Lofoten-Vester\u00e5len, Norway", "author": [ { "family_name": "Jacobsen", "given_name": "Stein B.", "clpid": "Jacobsen-S-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Sm-Nd data for the Archean granulite and amphibolite facies migmatites of Lang\u00f8y and Hinn\u00f8y in Vester\u00e5len are presented which indicate that their protoliths formed \u223c2.6 AE ago. Rubidium and U loss during a granulite facies metamorphism at \u223c1.8 AE caused serious disturbance of total-rock U-Pb and Rb-Sr systems. Therefore these systems do not provide any precise age information for the granulite facies migmatites. For the amphibolite facies migmatites of Vester\u00e5len both Sm-Nd, Rb-Sr and Pb-Pb total-rock systems give model ages of \u223c2.6 AE. The results on both granulite and amphibolite facies rocks are thus in agreement. Previous interpretations based on Pb-Pb data, which indicated an age of 3.41 AE for the Archean terrane of Vester\u00e5len, are not valid.\nOne Sm-Nd model age from the granulite facies migmatites at Moskenes\u00f8y in Lofoten indicates that the protoliths of these migmatites formed \u223c2.0 AE ago and are thus not related to the Vester\u00e5len migmatites.", "doi": "10.1016/0012-821X(78)90181-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1978-11", "series_number": "3", "volume": "41", "issue": "3", "pages": "245-253" }, { "id": "authors:5hxye-e1t20", "collection": "authors", "collection_id": "5hxye-e1t20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-082110041", "type": "article", "title": "Search for ^(26)Al effects in the Allende Fun Inclusion C1", "author": [ { "family_name": "Esat", "given_name": "Tezer M.", "clpid": "Esat-T-M" }, { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The Mg isotopic composition in plagioclase from the Allende inclusion C1 has been measured to correlate excess ^(26)Mg^* with isotopic anomalies for elements of higher atomic number. No large ^(26)Mg^* excesses were observed in samples with ^(27)Al/^(24)Mg up to 165. The inferred initial ^(26)Al/^(27)Al is 5 \u00d7 10^(\u22126) which is a factor of ten less than previously observed in other Allende inclusions. The low ^(26)Al abundance may be the result of late formation of C1 (by 2.5 m.y.) or due to the non-uniform addition of ^(26)Al to the solar system. The major mineral phases in C1 which are Mg rich and the bulk alteration products all have a uniform Mg isotopic composition with 30\u2030 per mass unit fractionation and \u03b4^(26)Mg\u2248 \u22121.6\u2030. The plagioclase data show variable Mg isotopic fractionation which ranges from 0 to 30\u2030 per mass unit. Isotopic homogeneity was demonstrated for the major mineral phases rich in Mg both in macroscopic samples and in microscopic individual crystals. The detailed correlation of ^(26)Al with the more general isotopic anomalies and its use as a chronometer marking the production and introduction of isotopically anomalous material into the solar system remains an open question.", "doi": "10.1029/GL005i009p00807", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1978-09", "series_number": "9", "volume": "5", "issue": "9", "pages": "807-810" }, { "id": "authors:cb8d7-nbr14", "collection": "authors", "collection_id": "cb8d7-nbr14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131025-131247188", "type": "article", "title": "Isotopic Determination of Silver in Picomole Quantities by Surface Ionization Mass Spectrometry", "author": [ { "family_name": "Kelly", "given_name": "William R.", "clpid": "Kelly-W-R" }, { "family_name": "Tera", "given_name": "Fouad", "clpid": "Tera-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A microanalytical procedure is described for the quantitative\nseparation of Ag from natural samples by anion exchange and\nanalysis by surface ionization mass spectrometry using silica\ngel as an emitter. The isotopic composition of 50 pmol of Ag\ncan be measured on a Faraday detector with a precision of\n0.1%. Isotopic measurements have been made on as little\nas 0.15 pmol with a precision of 1% using an electron multiplier\ndetector. The total procedural blank for the anion exchange\nSeparation is 0.15 pmol. Using stable isotope dilution 0.5 pmol\nof Ag, which Is 3 X 10^(11) atoms, can be measured with a\nprecision of better than 1% with only a 30% blank correction.\nThis allows the accurate determination of Ag in natural samples\ndown to concentration levels of 1 pmol per gram. The ionization\nefficiency for Ag is about 1-2% and the detection limit\nis 1 fmol. This procedure has been applied to several meteorites, and a standard terrestrial rock.", "doi": "10.1021/ac50031a023", "issn": "0003-2700", "publisher": "American Chemical Society", "publication": "Analytical Chemistry", "publication_date": "1978-08", "series_number": "9", "volume": "50", "issue": "9", "pages": "1279-1286" }, { "id": "authors:rtpa6-83m52", "collection": "authors", "collection_id": "rtpa6-83m52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151106-114913238", "type": "article", "title": "Scientific Drilling", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "I was very pleased to read the support given to a new program of future scientific drilling on the President's Page of April 1978 EOS. There was, however, a matter which deeply concerned me and which was omitted in the discussion. Experience has shown that it is imperative to identify the science function as an intrinsic part of an enterprise such as this. Unless there is proper support for the scientific studies both on board ship and in the land laboratories, there will not be an adequate scientific return. It is very easy to place large efforts in the exploration and technical aspects without sufficient regard to the 'post mission' scientific work that must be done. This matter is particularly serious when the status of most research groups is severely limited by lack of funds for the construction and purchase of equipment and the lack of support for research and operating staff on a prolonged time basis. There is also some concern on my part for the long-time curation of the materials which are returned from deep-sea exploration. I am certain that Mr. Maxwell is sensitive to the importance of supporting and carrying out vigorous scientific researches as an inherent part of a new generation JOIDES project. \n\nMy personal enthusiasm for this enterprise is only limited by the extent to which these\nmatters are given a proper part in the intrinsic definition of the project.", "doi": "10.1029/EO059i008p00771", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "1978-08", "series_number": "8", "volume": "59", "issue": "8", "pages": "771" }, { "id": "authors:ec07t-w8b66", "collection": "authors", "collection_id": "ec07t-w8b66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130828-142328961", "type": "article", "title": "More anomalies from the Allende Meteorite: Samarium", "author": [ { "family_name": "McCulloch", "given_name": "M. T.", "clpid": "McCulloch-M-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Sm has been measured in the Allende inclusions Cl and EK1-4-1. These inclusions were previously shown to have isotopic anomalies for the elements O, Mg, Ca, Ba and Nd. Sample Cl has a normal Sm isotopic composition except for the \"p-process\" isotope ^(144)Sm, which has an excess of 15\u00b15 parts in 10^4. Sample EK1-4-1 was found to have Sm with a highly aberrant composition, indicating excess at all unshielded isotopes and an excess at ^(144)Sm. These data confirm the previous evidence for an addition of \"r-process\" isotopes to this material and also indicate an addition to the \"p-process\" isotope ^(144)Sm. From the observations on Cl it is inferred that the \"p-process\" addition is decoupled from the \"r-process\" addition.", "doi": "10.1029/GL005i007p00599", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1978-07", "series_number": "7", "volume": "5", "issue": "7", "pages": "599-602" }, { "id": "authors:8rb7k-1g358", "collection": "authors", "collection_id": "8rb7k-1g358", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-075130913", "type": "article", "title": "Strontium isotopic anomalies in the Allende Meteorite", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report Sr isotope anomalies in two Ca-Al-rich inclusions (EK1-4-1 and Cl) of the Allende meteorite which also contain anomalies in O, Mg, Ca, Ba, Nd and Sm. The Sr effects correspond to ^(84)Sr or ^(88)Sr deficits of 3.2\u2030 and 0.8\u2030 or to ^(86)Sr excesses of 1.6\u2030 and 0.4\u2030. Although it cannot be ascertained in which isotope the anomalies reside, arguments based on the ^(87)Sr abundance indicate that the anomalies may reside in ^(84)Sr and ^(86)Sr. The data indicate deficits in the p-process component (^(84)Sr) up to 3.2\u2030 or in the r-process component in Sr (^(88)Sr) of up to 32\u2030 and are not easily reconcilable with effects in Ba and Nd, which indicate excess r, and in Sm, which indicate excess r and p components. The existence of positive and negative anomalies for many elements requires an isotopically heterogeneous solar system at the time of formation of these inclusions. The use of ^(87)Sr/^(86)Sr as a chronometer in the early solar system requires reevaluation, although the anomalies found in Sr thus far do not show the presence of any obvious artifacts in ^(87)Sr/^(86)Sr.", "doi": "10.1029/GL005i007p00595", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1978-07", "series_number": "7", "volume": "5", "issue": "7", "pages": "595-598" }, { "id": "authors:3mhrd-5wc02", "collection": "authors", "collection_id": "3mhrd-5wc02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131107-143832294", "type": "article", "title": "Sm-Nd and Rb-Sr Chronology of Continental Crust Formation", "author": [ { "family_name": "McCulloch", "given_name": "M. T.", "clpid": "McCulloch-M-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Samarium-neodymium and rubidium-strontium isotopic systematics together with plausible assumptions regarding the geochemical evolution of continental crust material, have been used to ascertain the times at which segments of continental crust were formed. Analyses of composites from the Canadian Shield representing portions of the Superior, Slave, and Churchill structural provinces indicate that these provinces were all formed within the period 2.5 to 2.7 aeons. It has been possible to determine the mean age of sediment provenances, as studies of sedimentary rocks suggest that the samarium-neodymium isotopic system is not substantially disturbed during sedimentation or diagenesis.", "doi": "10.1126/science.200.4345.1003", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1978-06-02", "series_number": "4345", "volume": "200", "issue": "4345", "pages": "1003-1011" }, { "id": "authors:wdzg1-1fw38", "collection": "authors", "collection_id": "wdzg1-1fw38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130904-151817720", "type": "article", "title": "Neon in gas-rich samples of the carbonaceous chondrites Mokoia, Murchison, and Cold Bokkeveld", "author": [ { "family_name": "Smith", "given_name": "S. P.", "clpid": "Smith-S-P" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "High-resolution stepwise-release patterns of neon extracted from gas-rich whole-rock samples of the carbonaceous chondrite meteorites Murchison, Cold Bokkeveld, and Mokoia are characterized by multiple release peaks and complex isotopic variations. Mokoia contains abundant ancient solar wind neon with ^(20)Ne/^(22)Ne = 13.7, identical in composition to the modern solar wind. For Murchison and Cold Bokkeveld, ^(20)Ne/^(22)Ne ratios of low-temperature release fractions are about 11 and 12.4, respectively. In higher-temperature fractions ^(20)Ne/^(22)Ne of trapped neon migrates toward neon-E, reaching a minimum of 6.9 for Murchison. Features in the Murchison thermal release and isotopic variation patterns can be associated with the release of neon from the gas-rich trace phases chromite/carbon and \"Q\". The characteristic high-temperature release of neon-E is closely related to the release of neon from \"Q\" in Murchison.\nFor simplicity, in this paper we consider a model in which neon in the early solar system consisted originally of two components, one component in the gas phase and the second trapped in dust grains. Neon present in solar system reservoirs today is then described as a mixture of galactic cosmic ray spallation neon and two primary trapped components, neon with (^(20)Ne/^(22)Ne)_t = 13.7 and neon-E. The composition of neon in the gas phase is determined from the composition of neon in the sun. Intermediate neon compositions observed in condensed materials such as the earth and meteorites require mechanisms such as gravitational collection, ion implantation or adsorption to combine gas-phase neon with dust-phase neon. The present detailed release patterns show no clear evidence of preferred intermediate compositions such as neon-A. The apparently uniform composition of neon in gas-rich chromite/carbon residues may represent a special mixture of gas-phase and dust-phase neon, but requires detailed investigation. The composition of neon in \"Q\" is variable and different from the composition in chromite/carbon. It is suggested that the total neon composition in a solar system object will be determined by the relative proportions of various gas-rich trace phases accreted, plus the amounts incorporated of galactic cosmic ray spallation neon and pure gas-phase neon such as the solar wind.", "doi": "10.1016/0012-821X(78)90136-X", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1978-03", "series_number": "1", "volume": "39", "issue": "1", "pages": "1-13" }, { "id": "authors:55f54-gtv53", "collection": "authors", "collection_id": "55f54-gtv53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-154259693", "type": "article", "title": "Calcium Isotopic anomalies in the Allende meteorite", "author": [ { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report isotopic anomalies in Ca which were found in two Ca-Al-rich inclusions of the Allende meteorite. These inclusions previously had been shown to contain special anomalies for Mg and O which were attributed to fractionation and unknown nuclear effects. The Ca data, when corrected for mass fractionation by using ^(40)Ca/^(44)Ca as a standard show nonlinear isotopic effects in ^(48)Ca of + 13.5 per mil and in ^(42)Ca of +1.7 per mil for one sample. The second sample shows a ^(48)Ca depletion of - 2.9 per mil, but all other Isotopes are normal. Samples with large excesses in ^(26)Mg show no Ca\nanomalies. The effects demonstrate that isotopic anomalies exist for higher-atomic-number refractory elements in solar-system materials and do not appear to be readily explainable by a simple model. The correlation of O, Mg, and Ca results on the same inclusions requires the addition and preservation in the solar system of components from diverse nucleosynthetic sources. Observed anomalous\nMg. and Ca compositions for coexisting mineral phases are uniform within each inclusion, and require initial isotopic homogeneity within an inclusion but the preservation of wide variations between inclusions. Assumming formation of these inclusions by condensation from a gaseous part of the solar nebula, this Implies Isotopic heterogeneity on a scale of 10-10^2 km within the nebula.", "doi": "10.1086/182629", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1978-02-15", "volume": "220", "pages": "L21-L25" }, { "id": "authors:arqa8-msv93", "collection": "authors", "collection_id": "arqa8-msv93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131029-154126991", "type": "article", "title": "Barium and neodymium isotopic anomalies in the Allende meteorite", "author": [ { "family_name": "McCulloch", "given_name": "M. T.", "clpid": "McCulloch-M-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Isotopic anomalies have been found for Ba and N d in two inclusions from the Allende meteorite. These inclusions are typical Ca-Al-rich objects associated with early condensates from the solar nebula but have distinctive 0 and Mg isotopic anomalies of the FUN type. Sample C1 shows a\ndepletion only in ^(135)Ba of 2 parts in 10^4 and normal Nd. Sample EK1-4-1 shows large positive excesses\nin the unshielded isotopes ^(135)Ba and ^(137)Ba of 13.4 and 12.3 parts in 10^4, respectively. The Nd isotopic\ncomposition in EK1-4-1 is highly aberrant in at least five isotopes. Both the Ba and Nd anomalies can be explained by a model of r-process addition. These anomalies are found to be uniform between coexisting mineral phases. These observations show the existence of substantial isotopic anomalies in refractory elements in the neighborhood of Xe and extend the range of elements showing isotopic effects to 0, Ne, Mg, Ca, Kr, Xe, Ba, and Nd. The observations, in conjunction with the presence of ^(26)Al (r_(1/2) = 7 X 10^5 years), are interpreted as the result of a nearby supernova explosion which produced elements over a wide mass range and injected them into the early solar nebula shortly before condensation.", "doi": "10.1086/182628", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "1978-02-15", "series_number": "2", "volume": "220", "issue": "2", "pages": "L15-L19" }, { "id": "authors:ryaf3-7aw59", "collection": "authors", "collection_id": "ryaf3-7aw59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140115-113455649", "type": "article", "title": "Ion Microprobe Evidence for the Presence of Excess ^(26)Mg in an Allende Anorthite Crystal", "author": [ { "family_name": "Bradley", "given_name": "J. G.", "clpid": "Bradley-J-G" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "An ion microprobe has been used to observe ^(26)Mg/^(24)Mg in excess of normal values in anorthite crystals from Allende refractory inclusions. In one crystal, ^(26)Mg excesses up to 40% above normal, correlated with Al/Mg, were observed, These excesses are many times larger than those observed by other techniques. The correlation with Al/Mg indicated that the excess ^(26)Mg in the Allende anorthite is uniformly distributed in the anorthite crystal. Analytical procedures and conditions were carefully controlled. Nevertheless, small but significant apparent ^(26)Mg/^(24)Mg anomalies in isotopically normal samples were observed in analyses by one ion microprobe. A repetition of the isotopic analyses using another ion probe produced normal ratios in the normal samples and confirmed large ^(26)Mg excesses in the Allende anorthite.", "doi": "10.1029/JB083iB01p00244", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "1978-01-10", "series_number": "B1", "volume": "83", "issue": "B1", "pages": "244-254" }, { "id": "authors:mj17k-wtf80", "collection": "authors", "collection_id": "mj17k-wtf80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-073814237", "type": "article", "title": "The sources of island arcs as indicated by Nd and Sr isotopic studies", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Island arc lavas from New Britain and the Marianas have ^(143)Nd/^(144)Nd similar to other oceanic basalts and distinctly different from continental flood basalts and thus appear to be derived from a high Sm/Nd, light-REE-depleted reservoir. Consideration of both Nd and Sr isotopes suggests seawater involvement in the generation of some island arc lavas and thus indicates that they may be derived from altered subducted oceanic crust. Other island arc lavas show no evidence of seawater involvement and may be derived from mantle reservoirs with affinities to the sources of ocean island basalts. Andesite and rhyolite from an Andean volcano reflect assimilation of old continental crust. Nd and Sr in basaltic and ultrapotassic continental rocks indicate that some mafic magmas in continental regions may be derived from old low-Sm/Nd reservoirs or are heavily contaminated with old continental crustal material. Fish debris from the ocean floor provides an estimate of ^(143)Nd/^(144)Nd in seawater and indicates that light-REE in the marine environment are derived mainly from continents. Basalts erupted above sea level in oceanic and continental areas are isotopically distinct from those erupted on the ocean floor, suggesting a relationship between parental reservoirs and hydrostatic head.", "doi": "10.1029/GL004i010p00465", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1977-10", "series_number": "10", "volume": "4", "issue": "10", "pages": "465-468" }, { "id": "authors:1ctrk-2m068", "collection": "authors", "collection_id": "1ctrk-2m068", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130910-134926527", "type": "article", "title": "Mg and Ca isotopic study of individual microscopic crystals from the Allende meteorite by the direct loading technique", "author": [ { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have developed a direct loading technique for determining the isotopic composition of Mg in chemically unseparated samples. This technique has a sensitivity and precision comparable with those of the conventional technique of analyzing pure Mg salt and eliminates contamination introduced during the chemical separation of Mg. This results in a significant reduction in sample size required for an analysis. This technique was combined with other characterization techniques of microscopic samples (e.g. optical microscopy, SEM, EPMA), and was applied to four single crystals of pure phases from an Allende inclusion ranging in size from 25 to 150 \u03bcm. Using a total sample of 4 \u03bcg, we found an anorthite crystal showing an enrichment in ^(26)Mg of 10% and were able to construct an ^(26)Al-^(26)Mg isochron which confirms our previous results obtained on macroscopic samples of the same inclusion. The isotopic composition of Ca was also measured along with Mg, on a directly loaded anorthite crystal from this inclusion, during the same mass spectrometer run and was shown to be essentially normal. Thus, the direct loading technique is applicable to Ca and will be useful in a correlative study of isotopic effects of different elements on individual microscopic samples. The extension of this technique to other elements appears feasible but will require extensive testing to control possible interferences.", "doi": "10.1016/0016-7037(77)90252-6", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1977-10", "series_number": "10", "volume": "41", "issue": "10", "pages": "1473-1485" }, { "id": "authors:808m1-61y13", "collection": "authors", "collection_id": "808m1-61y13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131023-140546018", "type": "article", "title": "Initial Pb of the Am\u00eetsoq gneiss, West Greenland, and implications for the age of the Earth", "author": [ { "family_name": "Gancarz", "given_name": "A. J.", "clpid": "Gancarz-A-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Pb isotopic abundances and U-Th-Pb concentrations are reported for feldspar megacrysts from the 3.59 AE old Am\u00eetsoq gneisses, Godthaab District, West Greenland. The distinctive Pb in the feldspars is the most primitive terrestrial Pb so far observed. It is observed in feldspars which are from different geographic localities and which exhibit varying degrees of deformation and recrystallization. This appear to be either the initial Pb in the Am\u00eetsoq gneiss or the initial Pb only slightly modified by subsequent metamorphism in a low ^(238)U/^(204)Pb environment. ^(238)U/^(204)Pb in the feldspars is low and the corrections for in situ produced Pb are only 0.4% for ^(207)Pb/^(206)Pb and 0.6% for ^(204)Pb/^(206)Pb. The mean corrected isotopic abundances are ^(204)Pb/^(206)Pb = 0.08720, ^(207)Pb/^(206)Pb = 1.1513, and ^(208)Pb/^(206)Pb = 2.7350. The feldspars contain a very small amount of easily leachable radiogenic Pb which is correlated with U and which indicates the formation of U-rich phases at about 2.7 AE. The matrix surrounding the feldspar megacrysts contains Pb which is much evolved relative to the megacrysts and this matrix does not appear to have behaved as a simple closed system. Element redistribution and open system behavior at about 2.7 AE is also suggested by Pb in feldspar from a dike cutting across the gneiss. Assuming that the Am\u00eetsoq gneiss feldspar Pb corrected for in situ U decay was the initial Pb in the gneiss at 3.59 AE (Baadsgaard, 1973), a single-stage \"age of the earth\" is determined as 4.47 \u00b1 0.05 AE and \u03bc is 8.5. This is indistinguishable from the single-stage age for modern rocks and is distinctly younger than the 4.55 AE age of some meteorites. If the feldspar Pb was modified by metamorphism at 2.7 AE the model age of the earth is calculated as 4.53 AE which is similar to the 4.55 AE age of some meteorites. Two-stage models using the nominal 3.59 AE initial Pb indicate that if the earth is ~4.55 AE old then \u03bc values were low in the early Earth's history and differentiation occurred within a few hundred million years after the planet formed.", "doi": "10.1016/0016-7037(77)90073-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1977-09", "series_number": "9", "volume": "41", "issue": "9", "pages": "1283-1301" }, { "id": "authors:4m40t-btd17", "collection": "authors", "collection_id": "4m40t-btd17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130906-105900561", "type": "article", "title": "Correlated O and Mg Isotopic Anomalies in Allende Inclusions: II. Magnetism", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Lee", "given_name": "T.", "clpid": "Lee-T" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" } ], "abstract": "Mg in two Allende Ca-Al rich inclusions shows large isotopic, mass-dependent fractionation which\nenriched the heavier isotopes. After normalization, Mg in these inclusions shows negative \u03b4^(26)Mg which appears to require the presence of nuclear effects in Mg distinct from ^(26)Al decay.", "doi": "10.1029/EO058i008p00681", "issn": "0002-8606", "publisher": "American Geophysical Union", "publication": "Transactions - American Geophysical Union", "publication_date": "1977-08", "series_number": "8", "volume": "58", "issue": "8", "pages": "828-828" }, { "id": "authors:005cf-2dc84", "collection": "authors", "collection_id": "005cf-2dc84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131217-070811934", "type": "article", "title": "Correlated O and Mg isotopic anomalies in Allende Inclusions: II. Magnesium", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" } ], "abstract": "Mg in two Allende Ca-Al rich inclusions shows large isotopic, mass-dependent fractionation which enriched the heavier isotopes. After normalization, Mg in these inclusions shows negative \u03b4^(26)Mg which appears to require the presence of nuclear effects in Mg distinct from ^(26)Al decay. The Mg mass fractionation is correlated with distinct but smaller fractionation effects for O reported by Clayton and Mayeda for the same inclusions (see companion paper). The observation of distinctive but uniform Mg isotopic composition in different phases within single Allende inclusions indicates that nuclear effects in O and Mg are not due to the entrapment of interstellar carrier grains as discrete entities, which are preserved as remnants, but are instead due to a homogenized mixture of components of extraordinary isotopic composition mixed with a component of ordinary solar system material and subjected to isotopic fractionation. The distinct O isotopic composition of different phases within a single inclusion is believed to be due to incomplete back-reaction of the higher temperature condensates with a cooler solar nebula of \"normal\" composition. The processes responsible for the O and Mg nuclear effects and the astrophysical site of their occurrence remain undefined.", "doi": "10.1029/GL004i007p00299", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1977-07", "series_number": "7", "volume": "4", "issue": "7", "pages": "299-302" }, { "id": "authors:w08j9-2sh09", "collection": "authors", "collection_id": "w08j9-2sh09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130906-111009918", "type": "article", "title": "Nd in Island Arc and Continental Volcanic Rocks", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" } ], "abstract": "Measurements of initial ^(143)Nd/^(144)Nd (expressed as \u03b5_I ^(CHUR)) and ^(87)Sr/^(86)Sr were made on an andesite\n(BMR-1) and two dacites (BMR-3,5) from the New\nBritain volcanic arc to compare them with oceanic\nbasalts and continental volcanics, and to evaluate\nmodels of the genesis of island arc magmas\nand their role in the growth of continental crust.\nIn addition, continental ultrapotassic volcanics\nhave been measured to determine if they are\nderived from a special magma source.", "doi": "10.1029/EO058i006p00366", "issn": "0002-8606", "publisher": "American Geophysical Union", "publication": "Transactions - American Geophysical Union", "publication_date": "1977-06", "series_number": "6", "volume": "58", "issue": "6", "pages": "533-533" }, { "id": "authors:ed1n4-8fd28", "collection": "authors", "collection_id": "ed1n4-8fd28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131025-154612468", "type": "article", "title": "Isotopic and chemical investigations on Angra dos Reis", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Tera", "given_name": "Fouad", "clpid": "Tera-F" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" } ], "abstract": "We report on extensive isotopic studies of Pb, Sr and Xe and on chemical abundance measurements of K, Rb, Sr, Ba, Nd, Sm, U and Th for total meteorite and mineral separates of the Angra dos Reis achondrite. U-Pb, Th-Pb and Pb-Pb ages are concordant at 4.54 AE for the total meteorite and for high-purity whitlockite in Angra dos Reis. This establishes Angra dos Reis as an early planetary differentiate which has not been disturbed for these systems since 4.54 AE ago. Measured ^(87)Sr/^(86)Sr in pyroxene and whitlockite for Angra dos Reis (ADOR) are distinctly below BABI by two parts in 10^4 and only one part in 10^4 above the lowest ^(87)Sr/^(86)Sr (ALL) measured in an Allende inclusion. The difference in ADOR-ALL corresponds to an interval of condensation in the solar nebula of \u223c3 m.y. If ^(26)Al was the heat source for the magmatism on the parent planets of Angra dos Reis and the basaltic achondrites (BABI) then the relatively large difference in ^(87)Sr/^(86)Sr, BABI - ALL, must be the result of planetary evolution rather than condensation over \u223c10 m.y. Xe isotopic measurements confirm the presence of large amounts of ^(244)Pu-produced fission Xe and show that ^(244)Pu was enriched in the whitlockite relative to the pyroxene by a factor of \u223c18. We present chemical element enrichment factors between the whitlockite and the fassaitic pyroxene in Angra dos Reis. The enrichment factors demonstrate close analogy between the rare earth elements and their actinide analogs. The enrichment factor for Pu is intermediate to the enrichment factors of Nd and Sm.", "doi": "10.1016/0012-821X(77)90133-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1977-06", "series_number": "2", "volume": "35", "issue": "2", "pages": "294-316" }, { "id": "authors:yex11-rp120", "collection": "authors", "collection_id": "yex11-rp120", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131016-075846994", "type": "article", "title": "Neon and argon in the Allende meteorite", "author": [ { "family_name": "Smith", "given_name": "S. P.", "clpid": "Smith-S-P" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Rajan", "given_name": "R. S.", "clpid": "Rajan-R-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Trapped and cosmogenic Ne and Ar were measured in Ca,Al-rich aggregates and chondrules, mafic chondrules, and bulk and matrix samples from the Allende C3V chondritic meteorite to investigate the possible occurrence of anomalous isotopic compositions of noble gases that would correlate with oxygen or magnesium isotopic anomalies previously found in this meteorite.\nLarge enrichments of both ^(22)Ne and ^(36)Ar were observed in low-temperature release fractions from several Ca,Al-rich inclusions, but the enrichments are consistent with galactic cosmic-ray production of 22Ne by spallation from sodium and ^(36)Ar by neutron capture on chlorine. Trapped neon in matrix samples is comprised of two distinctive compositions, with (^(20)Ne/^(22)Ne)_t equal to 8.7 \u00b1 0.1 and 10.4 \u00b1 1.0, that appear to correlate with the two gas-rich trace phases chromite/carbon and 'Q' described by Lewis et al. (1975). Several Ca,Al-rich aggregates which have high contents of the volatile elements Na, Cl, K, and Rb also contain trapped neon. However, no neon-E has been identified in any of the samples studied, including samples of several inclusions known to contain isotopically anomalous oxygen and magnesium.", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1977-05", "series_number": "5", "volume": "41", "issue": "5", "pages": "627-647" }, { "id": "authors:ph95n-znh37", "collection": "authors", "collection_id": "ph95n-znh37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131016-090218351", "type": "article", "title": "I. The Accumulation and Bulk Composition of the Moon - Outline of a Lunar Chronology", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-F" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" } ], "abstract": "We present here an outline of lunar chronology and evolution based on analyses of the isotopic parent-daughter systems ^(87)Rb-^(87)Sr,U -Th-^(206)Pb-^(207)Pb-^(208)Pb and ^(40)K-^(40)Ar. An overview of the chronology will first be given, followed by an outline of the observational basis. A more complete discussion of ^(40)K-^(40)Ar results and their interpretation is presented in the paper by G. Turner in this volume. While the body of data on lunar materials is limited, the chronology for lunar evolution appears to be rather well defined. The samples which have been investigated represent mare basalts [returned by the Apollo missions (11, 12, 15 and 17) and by the Soviet Luna 16 mission] and terra rocks, which include non-mare basalts, anorthosites, troctolites and norites but are predominantly comprised of complex breccias [returned by Apollo 12, 14, 16 and 17 and Luna 20]. The mare basalts are associated with the late stage lava flows which covered the mare basins. These flood basalts have been broken up by impact processes but for the most part are associated with the local areas and have not been subject to major transport or metamorphism by impact. The highland rocks predate the mare lava flows but are not clearly associated with a particular magmatic or impact process. They may have been excavated from considerable depths and transported over wide distances. Impact meta-morphism is certainly one of the critical stages in their development. The techniques which permit the precise dating of lunar rocks are the result of a rapid development over the past nine years in mass spectrometric techniques, in refined chemical separation methods and mineral separation procedures, and in mineral identification and analysis. These methods have been applied most extensively to lunar problems, but in the future they will undoubtedly be utilized in a new generation of studies of meteorites and of terrestrial samples.", "doi": "10.1098/rsta.1977.0039", "issn": "1364-503X", "publisher": "Royal Society of London", "publication": "Philosophical Transactions A: Mathematical, Physical and Engineering Sciences", "publication_date": "1977-03-31", "series_number": "1327", "volume": "285", "issue": "1327", "pages": "7-22" }, { "id": "authors:kerdw-92g33", "collection": "authors", "collection_id": "kerdw-92g33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230105-146138400.1", "type": "article", "title": "Aluminum-26 in the early solar system: Fossil or fuel?", "author": [ { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-Typhoon" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Mg was measured in different phases of a Ca-Al-rich inclusion in the Allende meteorite. Large excesses of \u00b2\u2076Mg of up to 10% were found. These excesses correlate strictly with the \u00b2\u2077Al/\u00b2\u2074Mg ratio for four coexisting phases with distinctive chemical compositions. Models of in situ decay of \u00b2\u2076Al within the solar system and of mixing of interstellar dust grains containing fossil \u00b2\u2076Al with normal solar system material are presented. The observed correlation provides definitive evidence for the presence of \u00b2\u2076Al in the early solar system. This requires either injection of freshly synthesized nucleosynthetic material into the solar system immediately before condensation and planet formation, or local production within the solar system by intense activity of the early sun. Planets promptly produced from material with the inferred \u00b2\u2076Al/\u00b2\u2077Al would melt within ~3 x 10\u2075 yr.", "doi": "10.1086/182351", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1977-01-15", "volume": "211", "pages": "L107-L110" }, { "id": "authors:hewys-hyf04", "collection": "authors", "collection_id": "hewys-hyf04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130906-103629481", "type": "article", "title": "The Sources of Island Arcs as Indicated by Nd and Sr Isotopic Studies", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Island arc lavas from New Britain and the Marianas have ^(143)Nd/^(144)Nd similar to other oceanic basalts and distinctly different from continental flood basalts and thus appear to be derived from a high Sm/Nd, light-REE-depleted reservoir. Consideration of both Nd and Sr isotopes suggests seawater involvement in the generation of some island arc lavas and thus indicates that they may be derived from altered subducted oceanic crust.", "issn": "0002-8606", "publisher": "American Geophysical Union", "publication": "Transactions - American Geophysical Union", "publication_date": "1977", "series_number": "12", "volume": "58", "issue": "12", "pages": "1260-1260" }, { "id": "authors:p7hx8-nt550", "collection": "authors", "collection_id": "p7hx8-nt550", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131216-141125720", "type": "article", "title": "Inferences about magma sources and mantle structure from variations of ^(143)Nd/^(144)Nd", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Continental flood basalts and mid-ocean ridge (MOR) tholeiitic basalts have distinctly different ^(143)Nd/^(144)Nd which may permit a priori distinction between \"continental\" and \"oceanic\" igneous rocks. Initial ^(143)Nd/^(144)Nd of continental igneous rocks through time fall on a Sm/Nd evolution curve with chondritic REE abundance ratio. These observations indicate that many continental igneous rocks are derived from a reservoir with chondritic REE pattern which may represent primary material remaining since the formation of the earth. Oceanic igneous rocks are derived from a different ancient reservoir which has Sm/Nd higher than chondritic. Initial ^(143)Nd/^(144)Nd and ^(87)Sr/^(86)Sr in young basalts from both oceans and continents show a strong correlation suggesting that Sm-Nd and Rb-Sr fractionation events in the mantle may be correlative and caused by the same process. From this correlation Rb/Sr for the earth is inferred to be 0.029.", "doi": "10.1029/GL003i012p00743", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1976-12", "series_number": "12", "volume": "3", "issue": "12", "pages": "743-746" }, { "id": "authors:6m023-ccn36", "collection": "authors", "collection_id": "6m023-ccn36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131121-093757361", "type": "article", "title": "Variation of ^(143)Nd/^(144)Nd in continental and oceanic igneous rocks and chemical zonation of the mantle", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Measurements of ^(143)Nd/^(144)Nd in igneous rocks have been continued as a means of studying the parental regions from which the magmas are derived. To test the model of a uniform source for crustal rocks through geologic time and distinct oceanic magma sources (DePaolo and Wasserburg GRL 3, 109, 1976) we have extended coverage of young samples to include basalts from ocean islands, mid-ocean ridges and continents, as well as carbonatites and a rhyolite. Initial ratios of two more dated ancient rocks have also been determined.", "issn": "0016-7592", "publisher": "Geological Society of America", "publication": "Abstracts with Programs - Geological Society of America", "publication_date": "1976-09", "series_number": "6", "volume": "8", "issue": "6", "pages": "835" }, { "id": "authors:4wfh1-fbd76", "collection": "authors", "collection_id": "4wfh1-fbd76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221122-637456100.1", "type": "article", "title": "Citation on the Award of the Leonard Medal of The Meteoritical Society", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Marvin", "given_name": "Ursula B.", "clpid": "Marvin-Ursula-B" } ], "abstract": "In recent years The Meteoritical Society has attracted so many new members, including large numbers from Europe and Asia as well as North America, that on these occasions one sometimes hears the query, \"Who was Leonard?\" Indeed, that question was raised this evening by one of our vice presidents. It seems appropriate, therefore, to recall that it was Frederick C. Leonard who conceived the idea of forming the world's first international society devoted to the study of meteorites.", "doi": "10.1111/j.1945-5100.1976.tb00325.x", "issn": "0026-1114", "publisher": "Meteoritical Society", "publication": "Meteoritics", "publication_date": "1976-09", "series_number": "3", "volume": "11", "issue": "3", "pages": "239-241" }, { "id": "authors:cg5fm-86788", "collection": "authors", "collection_id": "cg5fm-86788", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131021-154533262", "type": "article", "title": "Petrography of isotopically-dated clasts in the Kapoeta howardite and petrologic constraints on the evolution of its parent body", "author": [ { "family_name": "Dymek", "given_name": "R. F.", "clpid": "Dymek-R-F" }, { "family_name": "Albee", "given_name": "A. L.", "clpid": "Albee-A-L" }, { "family_name": "Chodos", "given_name": "A. A.", "clpid": "Chodos-A-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Detailed mineralogic and petrographic data are presented for four isotopically-dated basaltic rock fragments separated from the howardite Kapoeta. Clasts C and \u03c1 have been dated at ~4.55 AE and ~ 4.60 AE respectively, and Clast \u03c1 contains ^(244)Pu and ^(129)I decay products. These are both igneous rocks that preserve all the features of their original crystallization from a melt. They thus provide good evidence that the Kapoeta parent body produced basaltic magmas shortly after its formation (< 100 m.y.). Clast A has yielded a Rb-Sr age of ~ 3.89 AE and a similar ^(40)Ar/^(39)Ar\nage. This sample is extensively recrystallized, and we interpret the ages as a time of recrystallization, and not the time of original crystallization from a melt. Clast B has yielded a Rb-Sr age of ~ 3.63 AE, and an ^(40)Ar/^(39)Ar age of \u2a86 4.50 AE. This sample is moderately recrystallized, and the Rb-Sr age probably indicates a time of recrystallization, whereas the ^(40)Ar/^(39)Ar age more closely approaches the time of crystallization from a melt. Thus, there is no clearcut evidence for 'young' magmatism on the Kapoeta parent body.\n\nKapoeta is a 'regolith' meteorite, and mineral-chemical and petrographic data were obtained for numerous other rock and mineral fragments in order to characterize the surface and near-surface materials on its parent body. Rock clasts can be grouped into two broad lithologic types on the basis of modal mineralogy\u2014basaltic (pyroxene- and plagioclase-bearing) and pyroxenitic (pyroxenebearing). Variations in the compositions of pyroxenes in rock and mineral clasts are similar to those in terrestrial mafic plutons such as the Skaergaard, and indicate the existence of a continuous range in rock compositions from Mg-rich orthopyroxenites to very iron-rich basalts. The FeO and MnO contents of all pyroxenes in Kapoeta fall near a line with FeO/MnO ~ 35, suggesting that the source rocks are fundamentally related. We interpret these observations to indicate that the Kapoeta meteorite represents the comminuted remains of differentiated igneous complexes together with 'primary' undifferentiated basaltic rocks. The presently available isotopic data are compatible with the interpretation that this magmatism is related to primary differentiation of the Kapoeta parent body. In addition, our observations preclude the interpretation that the Kapoeta meteorite is a simple mixture of eucrites and diogenites.\n\nThe FeO/MnO value in lunar pyroxenes (~60) is distinct from that of the pyroxenes in Kapoeta. Anorthositic rocks were not observed in Kapoeta, suggesting that plagioclase was not important in the evolution of the Kapoeta parent body, in contrast to the Moon. Both objects appear to have originated in chemically-distinct portions of the solar system, and to have undergone differentiation on different time scales involving differing materials.", "doi": "10.1016/0016-7037(76)90053-3", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1976-09", "series_number": "9", "volume": "40", "issue": "9", "pages": "1115-1130" }, { "id": "authors:a6q86-9kd32", "collection": "authors", "collection_id": "a6q86-9kd32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131016-084246170", "type": "article", "title": "Nd isotopic variations and petrogenetic models", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The decay of ^(147)Sm to ^(143)Nd allows ^(143)Nd/^(144)Nd to be used to trace Sm/Nd fractionation in long time-scale geologic processes. ^(143)Nd/^Nd(144) has been measured in terrestrial rock samples of different ages to establish the characteristics of Nd isotopic evolution in the crust and mantle. The evolution of ^(143)Nd/^(144)Nd in the mantle indicates Sm/Nd essentially equal to that of chondrites, and implies a chondritic REE distribution for the earth. Variations in ^(143)Nd/^(144)Nd do exist in the mantle, however, indicating Sm/Nd heterogeneity and the existence of distinct mantle reservoirs with characteristic ^(143)Nd/^(144)Nd. ^(143)Nd/^(144)Nd in average crustal rocks today is much lower than found in recent mantle samples and reflects their age and low Sm/Nd. Oceanic tholeiites and alkali basalt are derived from sources with Sm/Nd which has been 5-10% greater than chondritic over the age of the earth. Alkali basalt can not be derived from mantle reservoirs which have been light REE-enriched for long times.", "doi": "10.1029/GL003i005p00249", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1976-05", "series_number": "5", "volume": "3", "issue": "5", "pages": "249-252" }, { "id": "authors:fg77q-w5w14", "collection": "authors", "collection_id": "fg77q-w5w14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230105-221316311", "type": "article", "title": "Souvenirs from Russia", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "One the central tenets of the search for scientific \ntruth is that knowledge is to be shared - a fairly \ncomplicated process when moon rocks and international boundaries are involved. Take transmitting samples from the Soviet Luna missions to the moon to \nCaltech's surgically clean laboratory known as the Lunatic Asylum, for example.", "issn": "0013-7812", "publisher": "California Institute of Technology", "publication": "Engineering and Science", "publication_date": "1976-05", "series_number": "4", "volume": "39", "issue": "4", "pages": "18-19" }, { "id": "authors:rys7j-38e45", "collection": "authors", "collection_id": "rys7j-38e45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221128-212653609", "type": "article", "title": "Introduction of Harold Clayton Urey for the V.M. Goldschmidt Medal", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "This presentation of the V. M. Goldschmidt Medal is to Harold Clayton Urey. The previous recipients of this award were Paul W. Gast and H. E. Suess. The range in age of the recipients is very great and covers a wide range of achievements which are all fundamental to the science of geochemistry. The award to a younger man such as the late Paul W. Gast can be associated with particular accomplishments over his short career. The award to H. E. Suess recognizes a highly imaginative career with many accomplishments, one of which was done jointly with Urey. The present award to Harold C. Urey reflects a distinguished and lengthy career that covers the whole development of modern geochemistry. It is sometimes not clear whether an award is to honor the recipient or the society making the award. In this case it does not matter. It is simply unreasonable to have an award in geochemistry in this era which is not associated in some way with Urey.", "doi": "10.1016/0016-7037(76)90227-1", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1976-05", "series_number": "5", "volume": "40", "issue": "5", "pages": "569-570" }, { "id": "authors:3rfjz-nkr74", "collection": "authors", "collection_id": "3rfjz-nkr74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130905-101114694", "type": "article", "title": "Internal Isochrons of Allende Inclusions by the ^(26)Al-^(26)Mg Method", "author": [ { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Large Mg isotopic shifts were discovered in two Ca-Al rich inclusions of the Allende meteorite.", "doi": "10.1029/EO057i004p00231", "issn": "0002-8606", "publisher": "American Geophysical Union", "publication": "Transactions - American Geophysical Union", "publication_date": "1976-04", "series_number": "4", "volume": "57", "issue": "4", "pages": "278-278" }, { "id": "authors:emsxn-9vx55", "collection": "authors", "collection_id": "emsxn-9vx55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131218-094610021", "type": "article", "title": "Model Ages", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" } ], "abstract": "Hutchison et al. have reported U-Pb analyses on samples of the meteorite Nakhla which confirm that this meteorite is younger than 3.68 Gyr.", "doi": "10.1038/259159a0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1976-01-15", "series_number": "5539", "volume": "259", "issue": "5539", "pages": "159-160" }, { "id": "authors:hvza8-gk507", "collection": "authors", "collection_id": "hvza8-gk507", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131216-134234606", "type": "article", "title": "Demonstration of ^(26)Mg excess in Allende and evidence for ^(26)Al", "author": [ { "family_name": "Lee", "given_name": "Typhoon", "clpid": "Lee-T" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We report the discovery of a large anomaly in the isotopic composition of Mg in a Ca-Al rich chondrule from the Allende meteorite. This anomaly is manifest independently of instrumental fractionation and is due to an enrichment of about 1.3 percent in ^(26)Mg while the abundances of ^(25)Mg and ^(24)Mg are terrestrial in value. There is a strong correlation in this chondrule between the ^(26)Mg excess and the Al/Mg ratio so that the most plausible cause of the anomaly is the in situ decay of now extinct ^(26)Al (\u03c4_\u00bd = 0.72 \u00d7 10^6 yr). Mineral phases extracted from a Ca-Al-rich aggregate have distinct Al/Mg but show identical, small Mg anomalies which are apparent after correction for fractionation (\u03b4^(26)Mg = 0.3%). These data indicate that this aggregate was isotopically homogenized in a high Al/Mg environment after the decay of ^(26)Al had occurred or that some of the Mg anomalies are due to effects other than in situ decay of ^(26)Al.", "doi": "10.1029/GL003i001p00041", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1976-01", "series_number": "1", "volume": "3", "issue": "1", "pages": "41-44" }, { "id": "authors:rchz2-zt469", "collection": "authors", "collection_id": "rchz2-zt469", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130515-150336487", "type": "article", "title": "Nd Isotopic variations and petrogenetic models", "author": [ { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-D-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "^(147)Sm \u0251-decays to ^(143)Nd so that ^(143)Nd/^(144)Nd reflects the\ntime-integrated Sm/Nd environment of a sample. The increase\nin 143/144 in a reservoir with chondritic Sm/Nd is\n1.2% in 4.5AE. There exists sufficient variation of Sm/Nd to\ncause sizeable effects in 143/144. Young samples were\nmeasured to elucidate the nature of their source regions. An\noceanic high Fe, Ti basalt (113152) and alk. basalt (113031), a continental alk. besalt (BCR-l), an apatite (Khibiny massif) and two reagent \"normals\", NN1 and NN2, were analyzed. Isotopic ratios of NN2 and BCR-1, normalized to 148/144=0.241572 are tabulated. Following the pioneering\nwork of Lugmair, et al. (EPSL 27, 79) our 143/144 data are\npresented relative to the total rock value for Juvinas\n(0.51278). the present value of a chondritic reservoir. Data\nare given as deviations from this value in parts in 10^4 (\u0454)\nand show a wide range. Nd in the source regions of the rock\nsamples evolved in an environment of approximately chondritic Sm/Nd (\u00b15%) over the history of the earth. Small\nvariations exist, reflecting long time scale differences of\nSm/Nd in the source regions. The low Sm/Nd observed in\nalkali basalts cannot reflect an ancient source region with\nlow Sm/Nd as \u0454 is near zero. REE patterns of alkali basalts\nmust thus reflect relatively recent fractionation from a\nsource with essentially chondritic relative abundances.\nStudy of initial ^(143)Nd/^(144)Nd in conjunction with REE patterns promises to contribute important petrogenetic information.", "issn": "0002-8606", "publisher": "American Geophysical Union", "publication": "Transactions - American Geophysical Union", "publication_date": "1976", "series_number": "4", "volume": "57", "issue": "4", "pages": "351" }, { "id": "authors:ak58t-z6932", "collection": "authors", "collection_id": "ak58t-z6932", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130828-133645299", "type": "article", "title": "Cratering and cosmogenic nuclides", "author": [ { "family_name": "Blake", "given_name": "Michael L.", "clpid": "Blake-M-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A simple probabilistic model was constructed for the average value of a cosmogenic nuclide as a function of depth in a regolith. An arbitrary function was chosen for the size distribution of craters. The resulting integro-differential equation was found to reduce in limiting cases to: 1) the marching equation with a characteristic residence time, and 2) to the diffusion equation. The regolith diffusion constant is shown to be a simple integral of the cratering rate weighted by geometrical terms. This formal treatment provides a direct and general connection between cosmogenic nuclides and cratering rates and crater population in a simple analytical form. The validity of this model remains to be tested.", "doi": "10.1029/GL002i011p00477", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1975-11", "series_number": "11", "volume": "2", "issue": "11", "pages": "477-479" }, { "id": "authors:r7fzh-cj564", "collection": "authors", "collection_id": "r7fzh-cj564", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130910-130902014", "type": "article", "title": "Precise isotopic analysis of lead in picomole and subpicomole quantities", "author": [ { "family_name": "Tera", "given_name": "Fouad", "clpid": "Tera-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A microanalytical procedure for the separation of Pb and U and their determination by isotope dilution-mass spectrometry\nis described. It is shown that high precision isotopic analysis of as little as 8 X 10^(11) Pb atoms is readily achievable.\nThe level of Pb contamination is reduced to as little as 4 X 10^(10) atoms and the blank fluctuation is controllable. In\nthe special case where the chemical separation could be omitted, 4 X 10^(10) Pb atoms were isotopically analyzed with\na blank correction of 6 X 10^9 Pb atoms. This procedure was applied to a 0.2-mg lunar sample containing 2.5 ppm Pb and\n1 ppm U and the U-Pb isotopic measurements obtained are Fully compatible with measurements on large samples. In\naddition, Pb on the surface of individual lunar glass balls of 150-300 \u00b5m diameter was measured. Extension of this approach\nto other heavy metals may be possible.", "doi": "10.1021/ac60363a036", "issn": "0003-2700", "publisher": "American Chemical Society", "publication": "Analytical Chemistry", "publication_date": "1975-11", "series_number": "13", "volume": "47", "issue": "13", "pages": "2214-2220" }, { "id": "authors:e27ag-j1b80", "collection": "authors", "collection_id": "e27ag-j1b80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130904-150755335", "type": "article", "title": "^(40)Ar-^(39)Ar chronology of isolated phases from Bununu and Malvern howardites", "author": [ { "family_name": "Rajan", "given_name": "R. S.", "clpid": "Rajan-R-S" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Smith", "given_name": "S. P.", "clpid": "Smith-S-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "High resolution ^(40)Ar-^(39)Ar age spectra have been measured on plagioclase and glass from two howardites. Both the plagioclase and glass from the gas-rich Bununu howardite show well-defined age plateaux, yielding distinct ages of 4.42 \u00b1 0.04 and 4.24 \u00b1 0.05 AE, respectively. These age patterns are rather well behaved and are interpreted as representing the distinct times of formation of plagioclase from igneous processes and of glass fragments produced by impact on the meteorite body. The release pattern for the glass from the heavily shocked Malvern howardite is undulating at low and intermediate temperatures but does have a high-temperature plateau. Its age spectrum indicates little apparent diffusion loss, but rather an extensive redistribution of either ^(40)Ar during the shock event or of ^(39)Ar during the neutron irradiation or both. The total K-Ar age of Malvern glass is 3.64 \u00b1 0.04 AE and the high-temperature plateau is 3.73 \u00b1 0.05 AE. The age spectrum of the Malvern plagioclase has an intermediate temperature \"plateau\" at 3.80 AE that represents 20% of the total40Ar content and increases towards a high-temperature plateau at 4.29 \u00b1 0.04 AE containing 26% of the total gas release. It seems likely that the event which formed the Malvern glass also reset part of the plagioclase. The distinct histories observed for the different phases of these howardites are consistent with their formation from a regolith. The present results along with similar young ages for igneous clasts from Kapoeta clearly show that the regoliths were extant on the parent bodies of howardites and that they were subjected to violent impact events at least as recently as 3.7 AE ago.", "doi": "10.1016/0012-821X(75)90028-X", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1975-09", "series_number": "2", "volume": "27", "issue": "2", "pages": "181-190" }, { "id": "authors:qq3wj-d2939", "collection": "authors", "collection_id": "qq3wj-d2939", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141006-132842511", "type": "article", "title": "Apollo 17 neutron stratigraphy \u2014 Sedimentation and mixing in the lunar regolith", "author": [ { "family_name": "Curtis", "given_name": "David B.", "clpid": "Curtis-D-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have measured shifts in the isotopic a bundances of Gd and Sm in soils from the Apollo 17 deep drill stem and calculated the neutron fluence from these measurements. The measurements show two well defined regions of nearly constant fluence: (1) a thick deep section with a very large neutron fluence, and (2) a thinner shallow region with a small fluence. This depth dependence is most plausibly described by a model of rapid accumulation in the last 100\u2013200 m.y., the layered structure reflecting accumulations of isotopically homogeneous source material. This interpretation is compatible with a variety of other characteristics of the soils, including the spallation produced126Xe normalized to target element abundances.\nAn alternative model of deposition, followed by irradiation without mixing, followed by shallow mixing will quantitatively describe the data. The model yields an age of 1.25 AE for the bottom of the drill stem. This model was rejected because of the implausible requirement that the soils from the drill stem be accumulated from a source of unirradiated material.\nThe uniformity of various properties of soils provides criteria for defining major stratigraphic intervals in the drill stem which differ from those identified by the Preliminary Examination Team.\nNeutron fluences measured on shallow and deep soils from all lunar landing sites have been normalized to irradiation in an arbitrary standard chemical environment. We infer from histograms of the normalized fluences that there is a distinct difference in neutron fluence between shallow and deep samples which implies a general vertical stratification of neutron fluence in the lunar regolith.\nThe regolith can be divided into three vertical regions: (1) a well mixed surface layer, \u223c100 g cm^(\u22122) thick, with an average fluence of 2.3 \u00d7 10^(16) n cm^(\u22122), (2) a poorly mixed zone extending from 100 g cm^(\u22122) to at least 500 g cm^(\u22122) with an average fluence of 3.5 \u00d7 10^(16) n cm^(\u22122), and (3) a deep layer of lightly irradiated materials (<10^(16) n cm^(\u22122)). Analysis of this stratification, using a vertical mixing model, indicates that the probability of mixing to several hundred g cm^(\u22122) is comparable to the probability of mixing to several kg cm^(\u22122). This is in contrast to the depth-cratering rate models which have been inferred from crater size frequency distributions using a power law. Alternatively, this discrepancy can be resolved if the true ^(157)Gd capture rate is 1/3 of the value calculated by Lingenfelteret al. (1972). The most plausible interpretation is that vertical mixing models are not an adequate description of relatively rare deep cratering events which result in significant lateral heterogeneity and addition of unirradiated material to the lunar surface.", "doi": "10.1007/BF00567515", "issn": "0027-0903", "publisher": "Springer", "publication": "The Moon", "publication_date": "1975-05", "series_number": "1-3", "volume": "13", "issue": "1-3", "pages": "185-227" }, { "id": "authors:xeqe7-ema80", "collection": "authors", "collection_id": "xeqe7-ema80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151106-131614965", "type": "article", "title": "The President's Page: Apollo Belvedere [Guest Editorial]", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "It is five years since the first human beings landed on another planet and then returned to earth. It is almost two years since the last Apollo mission returned to earth from the moon. The excitement of Apollo 11 which reached a large proportion of the population of planet earth is now a quiet, majestic fact in history. The excitement and interest in scientific aspects of all the Apollo missions is active and has grown into an evolving study of our sister planet.", "doi": "10.1029/EO055i009p00819", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "1974-09", "series_number": "9", "volume": "55", "issue": "9", "pages": "819-862" }, { "id": "authors:64wzj-dkr69", "collection": "authors", "collection_id": "64wzj-dkr69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130821-101612294", "type": "article", "title": "Response on Receiving the Kemp Medal", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Recently Columbia University awarded Kemp medals for 'distinguished\npublic service by a geologist' to Gerald J. Wasserburg, professor of geology\nand geophysics at the California Institute of Technology, and the late Paul\nWerner Cast, who was professor of geology at Columbia and chief of the\nDivision of Planetary and Earth Sciences in NASA's Johnson Space Center in\nHouston. Professor Wasserburg's response at the presentation constitutes an\nappropriate tribute to the memory of Paul Cast, who at the time of his death\nwas president of AGU's Section of Volcanology, Geochemistry, and Petrology.\n(Ed.)", "doi": "10.1029/EO055i006p00600", "issn": "0096-3941", "publisher": "American Geophysical Union", "publication": "Eos", "publication_date": "1974-06", "series_number": "6", "volume": "55", "issue": "6", "pages": "600-603" }, { "id": "authors:5xhy9-2mg95", "collection": "authors", "collection_id": "5xhy9-2mg95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141111-143331808", "type": "article", "title": "Evidence for late formation and young metamorphism in the Achondrite Nakhla", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have determined an age T=1.37 AE for Nakhla and an initial ^(87)Sr/^(86)Sr, I = 0.7023. A rather thorough Sr equilibration took place at this time between all the phases of this meteorite, but there is clear evidence of somewhat incomplete isotopic equilibrium during the 1.37 AE event, which is not consistent with the derivation of Nakhla from a magma at this time. Nakhla has a young model age of 3.6-2.9 AE which requires that gross differentiation processes for its parent body occur between 3.6 and 1.37 AE, significantly later than 4.6 AE. The most reasonable model is that Nakhla formed as an igneous rock at \u223c3 AE and was metamorphosed at 1.37 AE. Several similarities exist between the Nakhla parent planet and the Earth and indicate the existence of other objects with close terrestrial chemical affinities.", "doi": "10.1029/GL001i001p00023", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "1974-05", "series_number": "1", "volume": "1", "issue": "1", "pages": "23-26" }, { "id": "authors:dw5kb-89b15", "collection": "authors", "collection_id": "dw5kb-89b15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221128-234667400.5", "type": "article", "title": "Isotopic evidence for a terminal lunar cataclysm", "author": [ { "family_name": "Tera", "given_name": "Fouad", "clpid": "Tera-Fouad" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Most highland total rock samples define a single U-Pb isochron which corresponds to a metamorphism age of \u223c 3.9AE. This age is also obtained for internal U-Pb isochrons for some of these samples. The data on 18 rock samples range from concordant samples with \u00b2\u00b3\u2078U/\u00b2\u2070\u2076Pb\u223c 1.2 to discordant ones with \u00b2\u00b3\u2078U/\u00b2\u2070\u2076Pb\u223c 0.02. This feature coupled with a correlated pattern of \u00b2\u00b3\u2078U/\u00b2\u2070\u2074Pb ratios, indicates that Pb was extensively mobilized at \u223c 3.9AE. The observed Pb-U fractionation is essentially due to Pb volatilization during the metamorphic events. Volatile Pb transport is not accompanied by similar effects in Rb and must therefore be attributed to a specific process. Rb-Sr internal isochrons for the same rocks determine distinct metamorphic events in the interval 3.85\u20134.00 AE. We conclude that highland samples from widely separated areas bear the imprint of an event or series of events in a narrow time interval which can be identified with a cataclysmic impacting rate of the moon at \u223c 3.9AE, although differentiation by internal magma generation cannot be excluded. This cataclysm is associated with the Imbrium impact and very possibly the formation of Crisium and Orientale and possibly several other major basins in a narrow time interval (\u223c2 \u00d7 10\u2078yr or less). The U-Pb data indicate formation of the lunar crust at \u223c 4.4AE, which is distinctly younger than 4.6 AE, the time generally associated with planetary formation. If the lunar crust started being formed at \u223c 4.6AE, then this process must have continued until times significantly younger than 4.4 AE. Rb-Sr data also indicate formation of the lunar crust around 4.5 AE with only minor additions of high Rb/Sr materials to the crust at times younger than 4.3 AE. Using the U-Pb systematics, K/U and the average U concentration of the moon as obtained from heat-flow measurements, we estimate the lunar concentrations: primordial Pb= 35ppb;Rb= 0.5ppm with Rb/Sr= 0.006.", "doi": "10.1016/0012-821x(74)90059-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1974-04", "series_number": "1", "volume": "22", "issue": "1", "pages": "1-21" }, { "id": "authors:zq43y-ax298", "collection": "authors", "collection_id": "zq43y-ax298", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221129-218507500.3", "type": "article", "title": "Evidence for a \u223c 4.5 aeon age of plagioclase clasts in a lunar highland breccia", "author": [ { "family_name": "Jessberger", "given_name": "E. K.", "clpid": "Jessberger-E-K" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Argon from neutron-irradiated mineral separates and whole rock samples of a metamorphosed breccia (65015) from Apollo 16 has been analysed with a large number of gas extraction steps in order to obtain a high resolution in the apparent ages and to identify the gas released from different sources. The results on plagioclase show a \u2074\u2070Ar\u2013\u00b3\u2079Ar plateau age of 3.98 \u00d7 10\u2079 yr, which we attribute to the time of metamorphism, and an age of \u223c 4.5 \u00d7 10\u2079 yr in the high temperature fraction. Correlation of the release pattern with \u00b3\u2077Ar instead of \u00b3\u2079Ar permits the association of the \u223c4.5 \u00d7 10\u2079 yr age with relict plagioclasts which were demonstrated in previous petrographic and Rb-Sr studies as being unequilibrated. This result suggests that it is possible to identify lithic components which represent the early lunar crust.", "doi": "10.1038/248199a0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1974-03-15", "series_number": "5445", "volume": "248", "issue": "5445", "pages": "199-202" }, { "id": "authors:33b1k-9md79", "collection": "authors", "collection_id": "33b1k-9md79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221122-175096100.2", "type": "article", "title": "The identification of early condensates from the solar nebula", "author": [ { "family_name": "Gray", "given_name": "C. M.", "clpid": "Gray-C-M" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Calcium-aluminum-rich chondrules which are highly deficient in alkalis were extracted from the carbonaceous chondrite Allende and yield a range of compositions with the lowest measured isotopic composition of (\u2078\u2077Sr/\u2078\u2076Sr)_(ALL) = 0.69877 \u00b1 0.00002 and identify this material as the earliest known condensate from the solar nebula. Other chondrules suggest the possible presence of even more primitive Sr in this meteorite. This result also shows that some chondritic material formed very near the earliest part of the condensation sequence. Using alkali-deficient planetary objects (Moon, basaltic achondrites, Angra dos Reis, Allende), the Sr data indicate a time interval for condensation of 10 m.y. (from ALL to BABI) if condensation occurred in a solar Rb/Sr environment. A variety of alkali-rich olivine chondrules and Ca-Al-rich aggregates from Allende fail to determine an isochron and indicate that the element distribution in this meteorite was disturbed later than 3.6ae, possibly recently, in a cometary nucleus. This disturbance requires that the determination of initial \u2078\u2077Sr/\u2078\u2076Sr be done on essentially Rb-free phases. Strontium data from equilibrated chondrites and from an iron meteorite establish an interval for metamorphism or differentiation in protoplanetary objects which followed the condensation process by \u224880 mm.y. The chronology for condensation and early planetary evolution obtained for Sr is in disagreement with the \u00b9\u00b2\u2079I chronology but can be brought into agreement, if it is assumed that the high temperature iodine containing phases have not been affected by the metamorphic events determined by Sr.", "doi": "10.1016/0019-1035(73)90052-3", "issn": "0019-1035", "publisher": "Elsevier", "publication": "Icarus", "publication_date": "1973-10", "series_number": "2", "volume": "20", "issue": "2", "pages": "213-239" }, { "id": "authors:nav55-c4a16", "collection": "authors", "collection_id": "nav55-c4a16", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221128-234667400.3", "type": "article", "title": "A response to a comment on U-Pb systematics in lunar basalts", "author": [ { "family_name": "Tera", "given_name": "Fouad", "clpid": "Tera-Fouad" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "In a recent paper [1] we presented U, Th and Pb data for both mineral separates and total rocks for two crystalline rocks from the Apollo 14 mission. In that study we established for the first time the following major points: \n(1) U-Pb internal isochrons for two rocks. \n(2) Demonstration of the presence of initial radiogenie Pb. \n(3) Explicit demonstration of the cause of the apparent disagreement between the different methods of age determination and a possible means of experimentally reconciling this discrepancy in general. \n(4) The most direct estimate yet made of the \"age\" of the moon (or lunar crust). \n(5) A new diagram for representing U-Pb data which explicitly emphasizes initial Pb and which is analogous to the Rb-Sr evolution diagram.", "doi": "10.1016/0012-821x(73)90117-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1973-06", "series_number": "2", "volume": "19", "issue": "2", "pages": "213-217" }, { "id": "authors:mahtg-2tk08", "collection": "authors", "collection_id": "mahtg-2tk08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-185559865", "type": "article", "title": "Introduction of Dimitri A. Papanastassiou for the F. W. Clarke Medal", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "There are, to me, three truly exciting personal experiences in science. The first\nof these is the experience of oneself, privately, observing and understanding something\nthat is new and that is important. The second excitement is the act of precipitating\nunderstanding of some natural phenomenon in someone else. The third is\nto be honored to participate in the formal bestowal of professional recognition of a\nrespected colleague, a student and a friend. I am greatly privileged to stand before\ntwo colleagues and friends of different scientific generations that are being recognized\nby this society today.", "doi": "10.1016/0016-7037(73)90095-1", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1973-06", "series_number": "6", "volume": "37", "issue": "6", "pages": "1629-1632" }, { "id": "authors:w9mz9-ga798", "collection": "authors", "collection_id": "w9mz9-ga798", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180315-083426044", "type": "article", "title": "The age and petrography of two Luna 20 fragments and inferences for widespread lunar metamorphism", "author": [ { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-F-A" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Gancarz", "given_name": "A. J.", "clpid": "Gancarz-A-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Ages were determined by the ^(40)Ar-^(39)Ar method on two metaclastic rocks returned from the lunar highlands north of Mare Fecunditatis by the Luna 20 probe. Both samples gave very well-defined argon retention ages of 3.90 \u00b1 0.04 AE which are indistinguishable from each other within a resolution of 0.02 AE. Both fragments, 22006 and 22007, are highly recrystallized polymict breccias; there is no evidence for loss of radiogenic ^(40)Ar, and the age almost surely dates the time of recrystallization. The cosmic ray exposure ages of these fragments are similar and high: 900 million years for 22006, 1300 million years for 22007. 22007 also contains substantial trapped argon with a high ^(40)Ar^(36)Ar ratio.\nThe Luna 20 results greatly extend the area of the Moon's surface exhibiting a well-defined record of metamorphism at 3.9 AE. So far, lunar history in the interval 4.6\u22123.9 AE is not preserved in the ages of surface rocks. This obliteration suggests lunar-wide metamorphic conditions occurring or terminating at this time as a result of major impacts.", "doi": "10.1016/0016-7037(73)90186-5", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1973-04", "series_number": "4", "volume": "37", "issue": "4", "pages": "887-904" }, { "id": "authors:3spj0-8yj90", "collection": "authors", "collection_id": "3spj0-8yj90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221128-234667400.4", "type": "article", "title": "Rb-Sr ages and initial strontium in basalts from Apollo 15", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Internal isochrons have been determined for six basalts returned by the Apollo 15 mission. The rocks represent each of the major sampling stops during Apollo 15. The ranges in age and I are 3.28 \u00b1 0.04 to 3.44 \u00b1 0.07AE and 0.69923 \u00b1 6 to 0.69937 \u00b1 4. The range in I is very narrow and appears to represent a rather uniform magma source. A detailed study of the initial \u2078\u2077Sr/\u2078\u2076Sr was made on geometrically distinct pieces of 15555. The I value was demonstrated to be well defined to within 3 \u00d7 10\u207b\u2075 and therefore reports of variations in I for this rock are in error. The close similarity in the ages of basalts from both the Apollo 12 and 15 sites indicates that widespread extrusion of basaltic lavas took place at 3.2\u20133.3 AE. From all of the evidence currently available, the last major episode of mare flows took place at 3.16 \u00b1 0.09AE. No clear demonstration of major extrusions subsequent to this time has yet been found. The onset of mare flooding must have begun prior to 3.7 AE.\nAll the results to date show that subsequent to the formation of the Moon the lunar basalts evolved in a magma reservoir with Rb/Sr \u223c 10\u207b\u00b2 and cannot be derived from a mantle which has a chondritic Rb/Sr.", "doi": "10.1016/0012-821x(73)90197-0", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1973-01", "series_number": "2", "volume": "17", "issue": "2", "pages": "324-337" }, { "id": "authors:aa7qs-8a876", "collection": "authors", "collection_id": "aa7qs-8a876", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221122-23467700.4", "type": "article", "title": "Rb-Sr systematics of Luna 20 and Apollo 16 samples", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Lunar soils from all missions indicate that an early lunar differentiation process occurred in the interval 4.3\u20134.6 AE and resulted in the formation of a crust rich in K, Rb, U and Th. An attempt has been made to identify rocks which were formed during this early differentiation event.", "doi": "10.1016/0012-821x(72)90258-0", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-12", "series_number": "1", "volume": "17", "issue": "1", "pages": "52-63" }, { "id": "authors:m8cz6-yct19", "collection": "authors", "collection_id": "m8cz6-yct19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221128-234667400.6", "type": "article", "title": "U-Th-Pb systematics in lunar highland samples from the Luna 20 and Apollo 16 missions", "author": [ { "family_name": "Tera", "given_name": "Fouad", "clpid": "Tera-Fouad" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Luna 20 and Apollo 16 soils which represent two highland sites contain Pb which has \u00b2\u2070\u2076Pb/\u00b2\u2070\u2074Pb of from 53 to 277 and radiogenic \u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb of from 0.78 to 0.83. The soils yield very discordant ages which range from 4.91 up to 6.08 AE. A few of the results on soils can be discussed in terms of a simple two-stage model in which the lunar crust is generated by the addition of magmatic material enriched in Pb relative to both U and Th (without U-Th fractionation). The fractionation factor (Pb/U)_(magma)/(Pb/U)_(source) is commonly \u223c 2.5 or more. In no way can the soil model ages give a direct determination of the age of the Moon. The highland anorthosite 60025 gave a Pb concentration of 6.9 ppb and appears distinctly radiogenic with \u00b2\u2070\u2076Pb/\u00b2\u2070\u2074Pb= 25.4. The \u00b2\u2070\u2077Pb-\u00b2\u2070\u2076Pb age is 6.64 AE but the U concentration of 0.79 ppb is sufficient to account for the radiogenic Pb. This result is distinctly different from ancient and highly radiogenic initial Pb in 14310, 14053 and 15415. The extent to which various rock types of different ages and undetermined exotic materials contribute unsupported initial Pb to lunar soil is not yet established. The complexity of the Pb-U-Th data on the soils is remarkable in comparison with the simple behavior of the Rb-Sr results.", "doi": "10.1016/0012-821x(72)90257-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-12", "series_number": "1", "volume": "17", "issue": "1", "pages": "36-51" }, { "id": "authors:xp7v1-esb91", "collection": "authors", "collection_id": "xp7v1-esb91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221122-23467700.3", "type": "article", "title": "The Rb-Sr age of a crystalline rock from Apollo 16", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A precise internal isochron was determined for 68415, a plagioclase rich basalt or anorthosite returned by the Apollo 16 mission. The age and initial \u2078\u2077Sr/\u2078\u2076Sr are T = 3.84 \u00b1 0.01AE, andI = 0.69920 \u2213 3. This rock appears to have crystallized almost contemporaneously with the younger basalts found at the Apollo 14 site. If we associate the dates of the Apollo 14 rocks with the Imbrium event, then 68415 was formed by an event which followed closely after or during that episode of basin formation. If this rock represents lunar magmatic activity from internal heat sources, then it is likely that the lunar highlands and possibly older mare basins were intruded and flooded by leucocratic basalt flows or by plagioclase rich differentiates just before the major basaltic mare flows preserved in the Sea of Tranquility. If the parent magma for this rock was produced by impact melting, presumably of an anorthositic basement, then this datum suggests an extremely intense period of bombardment at that time. There is as yet no direct evidence of lunar rocks crystallizing in the interval 4.0 to 4.6 AE, or of the location of the ancient radioactive lunar crust (or crustal layers) hypothesized by us. The initial \u2078\u2077Sr/\u2078\u2076Sr of lunar basalts and anorthosites are typically very primitive and show that these rocks are not related to chondrites or to lunar materials with high Rb/Sr such as 12013. The time of formation of the lunar highlands remains undetermined. The possibility exists that the moon underwent a major cataclysmic differentiation at \u223c 4.0 AE during which the highlands were formed.", "doi": "10.1016/0012-821x(72)90205-1", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-10", "series_number": "2", "volume": "16", "issue": "2", "pages": "289-298" }, { "id": "authors:ak59c-8cf62", "collection": "authors", "collection_id": "ak59c-8cf62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-967794900.4", "type": "article", "title": "Lunar neutron stratigraphy", "author": [ { "family_name": "Russ", "given_name": "G. Price, III", "clpid": "Russ-G-Price-III" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Variations in the isotopic ratios \u00b9\u2075\u2078Gd/\u00b9\u2075\u2077Gd and \u00b9\u2075\u2070Sm/\u00b9\u2079\u2074Sm in the Apollo 15 deep drill stem show that the neutron fluence is a smoothly varying function of depth with a relatively symmetric peak at a depth of 190 g/cm\u00b2. The peak fluence is about 60% greater than the surface value. The observed peak is at a depth comparable to the theoretically calculated peak in the neutron flux. These data may be quantitatively explained by a model in which a blanket of pre-irradiated material was deposited rapidly 450 \u00d7 10\u2076 yr ago which has remained essentially undisturbed since, i.e., the material was deposited during terrestrial Cambro-Ordovician time. The upper several cm of the drill stem represents soil which has been mixed and transported to the drill site by shallow impacts. \n\nOther models quantitatively compatible with the data are those for a regolith continuously accreting for a time as long as 400 \u00d7 10\u2076 yr and subsequently irradiated for \u223c 500 \u00d7 10\u2076 yr as an unmixed section. This would allow the base of the drill stem to be as old as 900 \u00d7 10\u2076 yr. \n\nThese results show that at this site the turnover time to 2.5 m depth is significantly greater than about 500 my. No positive evidence of ray material from Aristillus or Autolycus was observed in the fluence data. \n\nStudies of a variety of cosmic-ray nuclei from deep cores from several sites should permit the determination of detailed depositional histories. If deeper core samples could be obtained, it should be possible to study over a billion years of lunar stratigraphy. However, the determination of absolute stratigraphic ages will require that neutron capture rates be determined in situ by accurate methods.", "doi": "10.1016/0012-821x(72)90058-1", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-06", "series_number": "2", "volume": "15", "issue": "2", "pages": "172-186" }, { "id": "authors:75nj8-qrm89", "collection": "authors", "collection_id": "75nj8-qrm89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221128-233541000.1", "type": "article", "title": "U-Th-Pb systematics in three Apollo 14 basalts and the problem of initial Pb in lunar rocks", "author": [ { "family_name": "Tera", "given_name": "Fouad", "clpid": "Tera-Fouad" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Pb and the elemental concentration of U, Th and Pb were measured on 'total' rock samples 14053, 14073 and 14310 and on mineral separates of 14310 and 14053. Sample #73 appears to be quite similar to #310. Sample #310 yields total rock model ages of T(\u00b2\u2070\u2076Pb/\u00b2\u00b3\u2078U) = 4.24AE, T(\u00b2\u2070\u2077Pb/\u00b2\u00b3\u2075U) = 4.27AE, and T(\u00b2\u2070\u2078Pb/\u00b2\u00b3\u00b2Th) = 4.13AE. These are nearly concordant and distinct from the Rb-Sr and K-Ar crystallization ages of 3.88 AE. Mineral separates from 14310 show a wide spread in \u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb ranging from 0.483 to 0.995. The data points define a reasonable linear array on the coupled Pb-U evolution diagram. Similar analyses of 14053 give high, discordant total rock model ages of T(\u00b2\u2070\u2076Pb/\u00b2\u00b3\u2078U) = 5.60AE,T(\u00b2\u2070\u2077Pb/\u00b2\u00b3\u2075U) = 5.18AE, and T(\u00b2\u2070\u2078Pb/\u00b2\u00b3\u00b2Th) = 5.48AE. Mineral separates show a range of \u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb from 0.716 to 1.209. These data also define a reasonable linear array on the coupled Pb-U evolution diagram. \n\nThese are the first Pb-U isochrons obtained for lunar basalts and indicate a reasonable solution to the previous discrepancy between the different methods of 'absolute' age determination. The resulting U-Pb isochron ages are compatible with the Rb-Sr and K-Ar ages on the same rocks. However, it is not possible to establish a precise time of 'crystallization' from the Pb-U data because of the small angle of intersection between the linear arrays and the concordia curve. These data show that total rock model ages do not in general yield crystallization ages. \n\nThe data on #310 and #053 show that these rocks were formed containing a highly radiogenic initial lead (\u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb)I0 \u2248 1.46 which accounts for the excessively high total rock model ages by the U-Th-Pb method. The only significant discrepancy in the data is the apparent variability of (\u00b2\u2070\u2078Pb/\u00b2\u2070\u2076Pb)I0 in #053 which remains to be resolved.\nThe (\u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb)I0 in these rocks corresponds to the radiogenic lead evolved between 4.51 and 3.88 AE in a U-rich environment. Such data from initial Pb may provide a new chronometer for early lunar evolution. \n\nThe high \u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb ages in some total lunar soils as well as in treated fractions may be partly explained as a consequence of the contribution of lunar basalts with radiogenic initial Pb. The data prove that at the time of extrusion of some basalts, unsupported lead with extremely high \u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb ratios was added to the lunar surface.", "doi": "10.1016/0012-821x(72)90128-8", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-04", "series_number": "3", "volume": "14", "issue": "3", "pages": "281-304" }, { "id": "authors:hn5y6-wvk36", "collection": "authors", "collection_id": "hn5y6-wvk36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221122-170513400.1", "type": "article", "title": "Rare gas studies of the galactic cosmic ray irradiation history of lunar rocks", "author": [ { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-F-A" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Eight analyses of all five noble gases in whole rock samples and mineral separates from lunar rocks 10017, 10044 and 10069, in conjunction with available literature data, permit qualitative conclusions concerning average irradiation depths and enable internally consistent exposure ages for Tranquillity Base rocks to be calculated. Correlated variations in He\u00b3Ne\u00b2\u00b9 and Ar\u00b3\u2078Ne\u00b2\u00b9 reflect shielding differences. Diffusion losses cannot explain this correlation, even though evidence for gas loss is obtained from mineral separate data. A qualitative shielding sequence can be constructed which agrees reasonably well with the sequence based on Gd isotopic data. There are no systematic differences between meteoritic and lunar He, Ne and Ar spallation spectra, with the possible exception of Ar\u00b3\u2078Ne\u00b2\u00b9. Observed variations in meteoritic and lunar Xe spallation spectra, except at mass 131, are due primarily to differences in chemical composition. The relative Xe\u00b9\u00b2\u2076 production rates from Ba and rare earths can be derived. Resonance neutron capture on Ba\u00b9\u00b3\u2070 is a plausible source for the anomalous Xe\u00b9\u00b3\u00b9 observed in lunar rocks; however, the required fluxes are quite large. Surface production rates from measurements of radioactive spallation products in lunar samples give more concordant exposure ages than those obtained from meteoritic production rates. This concordance implies that the average irradiation depths for these rocks were small (\u2272150 g/cm\u00b2). Surface production rates for Xe\u00b9\u00b2\u2076 and Ne\u00b2\u00b9 yielded exposure ages for fourteen Tranquillity Base rocks which are in reasonable agreement for most rocks. Five low-K rocks have exposure ages around 100 m.y. in what may be a significant grouping. At least four major impacts are required to produce the fourteen rocks.", "doi": "10.1016/0016-7037(72)90024-5", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1972-03", "series_number": "3", "volume": "36", "issue": "3", "pages": "269-301" }, { "id": "authors:rs9fg-5xp59", "collection": "authors", "collection_id": "rs9fg-5xp59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141013-111058583", "type": "article", "title": "Absolute dating techniques", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-F-A" }, { "family_name": "Husain", "given_name": "Liaquat", "clpid": "Husain-L" }, { "family_name": "Schaeffer", "given_name": "O. A.", "clpid": "Schaeffer-O-A" }, { "family_name": "Sutter", "given_name": "J. F.", "clpid": "Sutter-J-F" } ], "abstract": "In their report on the ages of crystalline rocks from the Apollo 14 mission, Husain, Sutter, and Schaeffer\npresent some important results using the ^(40)Ar-^(39)Ar method. This technique, which has been used by several other workers, depends critically on the use of mineral or rock standards of precisely known ^(40)Ar/K ratio. The \"age\"\nof the standard is not directly relevant. What is required is the 40Ar/K in the standard. These standards should be\nadequately documented somewhere in the literature. Often the point is missed that the ^(40)Ar-^(39)Ar age is not absolute, but is relative to ^(40)Ar/K of the standard sample. The uncertainty of absolute ages determined by this method must include any uncertainty in the ^(40)Ar/K ratio of the comparison sample. At the present stage of development of argon-potassium dating in particular, and geochronology in general, it is rather surprising to find that workers continue to determine ages on lunar samples, using \"standards\" (terrestrial or otherwise) which are themselves uncertain to several percent. In the work by Husain et al. it would appear that the actual uncertainty in age due to both analytical error and the error in the hornblende monitor is 3.77 \u00b1 0.15 \u00b1 0.15 eons, or 3.77 \u00b1 ~0.30 eons. Analytical techniques which have been available for some years easily permit more definitive measurements to be made, particularly on valuable lunar materials. Since the time interval over which lunar igneous activity is presently observed to occur is rather restricted (4.00 to 3.20 eons from current data), the necessity for adequately precise data is apparent.", "doi": "10.1126/science.175.4023.795", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1972-02-18", "series_number": "4023", "volume": "175", "issue": "4023", "pages": "795-795" }, { "id": "authors:p8v85-q8a64", "collection": "authors", "collection_id": "p8v85-q8a64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141105-165451918", "type": "article", "title": "Dynamics of submergence and uplift of a sedimentary basin underlain by a phase-change boundary", "author": [ { "family_name": "O'Connell", "given_name": "Richard J.", "clpid": "O'Connell-R-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A procedure is given for calculating the evolution of a sedimentary basin underlain by a phase-change boundary that is in isostatic equilibrium. The equation of motion of the water depth w(t) as a function of the water depth and as a function of the sedimentation rate ds/dt is Q_w(w) dw/dt + Q_s ds/dt + (1 - \u03c1_1/\u03c1_2) dl/dt = 0 where l(t) is the lag of the phase boundary behind the transient equilibrium position. Numerically precise integrals of this equation are given for different time regimes by use of certain approximations for the temperature field that determine dl/dt. Solutions are demonstrated that are attenuated, explosive, or near periodic, depending on the physical parameters used. The results clearly show the possibility of depositing very thick sedimentary sections and the existence of self-sustained oscillations (above and below sea level) for a sedimentary basin of this type.", "doi": "10.1029/RG010i001p00335", "issn": "8755-1209", "publisher": "American Geophysical Union", "publication": "Reviews of Geophysics", "publication_date": "1972-02", "series_number": "1", "volume": "10", "issue": "1", "pages": "335-368" }, { "id": "authors:qr6qy-1cc22", "collection": "authors", "collection_id": "qr6qy-1cc22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200505-084618384", "type": "article", "title": "Gas-Retention and Cosmic-Ray Exposure Ages of Lunar Rock 15555", "author": [ { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-F-A" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The last lava flow in the Hadley Rille area of Mare Imbrium, as inferred from an argon-40-argon-39 experiment on a plagioclase separate from the lunar basalt 15555, occurred 3.31\u00b10.03x10\u2079 years ago. An argon-40-argon-39 experiment on a whole rock sample shows significant loss of radiogenic argon-40 and yields a well-defined, high-temperature plateau indicating a lower age of 3.22\u00b10.03x10\u2079 years. A cosmic-ray exposure age of 90\u00b110x10\u2076 years is determined from the ratio of spallogenic argon-38 to calcium.", "doi": "10.1126/science.175.4020.423", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1972-01-28", "series_number": "4020", "volume": "175", "issue": "4020", "pages": "423-425" }, { "id": "authors:d3pyc-n1h25", "collection": "authors", "collection_id": "d3pyc-n1h25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221122-23467700.5", "type": "article", "title": "Gas retention and cosmic-ray exposure ages of a basalt fragment from Mare Fecunditatis", "author": [ { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-Frank-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "An \u2074\u2070Ar-\u00b3\u2079Ar gas retention age and an \u00b3\u2078Ar-\u00b3\u2077Ar cosmic ray exposure age have been determined on a total rock sample of the basalt fragment B-1 returned from Mare Fecunditatis by the Luna 16 mission. This sample shows large low-temperature loss of radiogenic \u2074\u2070Ar but defines a reasonably good high-temperature plateau at 3.45 \u00b1 0.04 AE. This is presumed to date a period of igneous activity in Mare Fecunditatis. This activity is later than that at Mare Tranquillitatis but earlier than at Oceanus Procellarum and Mare Imbrium. The cosmic ray exposure age is 475 m.y.", "doi": "10.1016/0012-821x(72)90112-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-01", "series_number": "2", "volume": "13", "issue": "2", "pages": "375-383" }, { "id": "authors:a5nz6-19z64", "collection": "authors", "collection_id": "a5nz6-19z64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221122-18984900.1", "type": "article", "title": "U-Th-Pb analyses of soil from the Sea of Fertility", "author": [ { "family_name": "Tera", "given_name": "Fouad", "clpid": "Tera-Fouad" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of lead was determined on soil samples from two levels of the Luna 16 core. The lead was distinctly radiogenic and yielded \u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb model ages of 4.8 AE. This is interpreted as reflecting early lunar differentiation processes. The most reliable value of \u00b2\u2070\u2078Pb/\u00b2\u2070\u2074Pb = 111 shows that the Luna 16 soils are significantly less radiogenic than found for other lunar soils. The elemental concentrations are Pb \u223c 0.9 ppm, U \u223c 0.3 ppm and Th \u223c 1.2 ppm with a Th/U ratio of 3.8. The U concentration is the lowest so far found for lunar soils. These data indicate that only a very small amount of magic component kreeputh into the Luna 16 soil.", "doi": "10.1016/0012-821x(72)90126-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-01", "series_number": "2", "volume": "13", "issue": "2", "pages": "457-466" }, { "id": "authors:pwa0y-hwm50", "collection": "authors", "collection_id": "pwa0y-hwm50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180228-105651836", "type": "article", "title": "Mineralogy, petrology, and chemistry of a Luna 16 basaltic fragment, sample B-1", "author": [ { "family_name": "Albee", "given_name": "A. L.", "clpid": "Albee-A-L" }, { "family_name": "Chodos", "given_name": "A. A.", "clpid": "Chodos-A-A" }, { "family_name": "Gancarz", "given_name": "A. J.", "clpid": "Gancarz-A-J" }, { "family_name": "Haines", "given_name": "E. L.", "clpid": "Haines-E-L" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Ray", "given_name": "L.", "clpid": "Ray-L" }, { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Wen", "given_name": "T.", "clpid": "Wen-T" } ], "abstract": "Luna 16 sample B-1 was the largest fragment (62 mg) obtained in the sample exchange with the USSR. Petrologic, mineralogic, and chemical investigations have been made on this fragment in conjunction with Rb-Sr and ^(40)Ar/^(39)Ar investigations by our colleagues. Sample B-1 is a fine-grained ophitic basalt but is distinguished from the Apollo samples by containing a single pyroxene, predominantly pigeonitic, an ilmenite content (7%) intermediate to that of the Apollo 11 and 12 samples, and subequal amounts of pyroxene (50%) and plagioclase (40%). Chemically it is distinguished by a high Sr content (437 ppm) and a high K/U value (4700). The K-content (1396 ppm) is higher than that of Luna 16 soil sample A-2.", "doi": "10.1016/0012-821X(72)90110-0", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-01", "series_number": "2", "volume": "13", "issue": "2", "pages": "353-367" }, { "id": "authors:s4jfb-k5c81", "collection": "authors", "collection_id": "s4jfb-k5c81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-967794900.5", "type": "article", "title": "Rb\u2010Sr age of a Luna 16 basalt and the model age of lunar soils", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A Rb-Sr internal isochron on a 62 mg basaltic boulder from the Luna 16 mission yields an age of 3.42 \u00b1 0.18 AE and a low initial \u2078\u2077Sr/\u2078\u2076Sr 0.69906 \u2213 4 (1\u03c3 errors). The total range in measured \u2078\u2077Sr/\u2078\u2076Sr for mineral separates of this sample was 1.3 per mil. The ages of basalts from four mare sites determine a narrow time interval of 0.55 AE for the flooding of the maria. Initial \u2078\u2077Sr/\u2078\u2076Sr for these basalts are restricted to extremely low values, indicating that they all originated in low Rb/Sr regions. \n\nLuna 16 soils have low Rb/Sr (\u2248 0.007) and yield model ages T_(BABI) = 4.2 \u00b1 0.3AE and T_(BABI) = 4.1 \u00b1 0.3AE. Lunar soils from Apollo 11, 12, 14, 15 and Luna 16 all lie very close to a 4.6 AE isochron which passes through BABI. This appears to be a universal characteristic of lunar soils and must correspond to lunar differentiation processes closely following the time of formation of the moon.", "doi": "10.1016/0012-821x(72)90111-2", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1972-01", "series_number": "2", "volume": "13", "issue": "2", "pages": "368-374" }, { "id": "authors:cxb6e-21924", "collection": "authors", "collection_id": "cxb6e-21924", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130822-133746015", "type": "article", "title": "Presentation of the Arthur L. Day Medal to\n Gerald J. Wasserburg", "author": [ { "family_name": "Bader", "given_name": "Henri", "clpid": "Bader-H" }, { "family_name": "Wasserburg", "given_name": "Gerald", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The first course I taught at an American university was a semester of crystallography,\ninflicted on three Rutgers students, one of whom was Gerald J. Wasserburg. This\nmay be why, ever since, Jerry has been busy converting crystals into the most\ntenuous plasma possible.\nIn those days, more than twenty years ago, Jerry was recently out of the Army\nwhere, as the only linguist in his company advancing into Germany, he was the\nlogical choice for stepping forward, challenging the enemy to surrender, and\npromptly getting shot at. So when I first knew him, Wasserburg was still mad at\nthe world. He often came to our house, invited or not, where he liked to sit on the\nfloor, and voice disagreement with our opinions on any subject whatsoever. Jerry\nhas mellowed over the years, but not much.", "issn": "0016-7606", "publisher": "Geological Society of America", "publication": "Geological Society of America Bulletin", "publication_date": "1972", "volume": "83", "pages": "xvii-xxii" }, { "id": "authors:bydr5-tnf58", "collection": "authors", "collection_id": "bydr5-tnf58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-280779900.3", "type": "article", "title": "Neutron capture on \u00b9\u2074\u2079Sm in lunar samples", "author": [ { "family_name": "Russ", "given_name": "G. P., III", "clpid": "Russ-G-P-III" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Lingenfelter", "given_name": "R. E.", "clpid": "Lingenfelter-R-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "High precision isotopic composition measurements of Sm have been carried out for two terrestrial and seven lunar samples from three Apollo sites. The lunar samples, selected to show a wide variation in cosmic ray exposure ages, have a wide range of enrichments in \u00b9\u2075\u2070Sm/\u00b9\u2075\u2074Sm (up to 0.8%) and depletions in \u00b9\u2074\u2079Sm/\u00b9\u2075\u2074Sm which are due to neutron capture. The ratio of the number of neutrons captured per atom by \u00b9\u2074\u2079Sm to \u00b9\u2075\u2077Gd is 0.9 and reflects a hardened lunar neutron spectrum. This ratio is in reasonable but not exact agreement with that obtained from the theoretical lunar neutron energy spectrum of Lingenfelter, Canfield and Hampel. The average composition for terrestrial samarium is \u00b9\u2074\u2074Sm : \u00b9\u2074\u2077Sm : \u00b9\u2074\u2078Sm : \u00b9\u2074\u2079Sm : \u00b9\u2075\u2070Sm : \u00b9\u2075\u00b2Sm : \u00b9\u2075\u2074Sm = 3.074 : 14.995 : 11.243 : 13.820 : 7.380 : 26.739 : 22.749%.", "doi": "10.1016/0012-821x(71)90104-x", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1971-12-02", "series_number": "1", "volume": "13", "issue": "1", "pages": "53-60" }, { "id": "authors:04jva-hgy43", "collection": "authors", "collection_id": "04jva-hgy43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-967794900.2", "type": "article", "title": "Age of an Apollo 15 mare basalt; Lunar crust and mantle evolution", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" } ], "abstract": "An internal Rb-Sr isochron for the large basalt boulder 15555 returned from the edge of Hadley rille by the Apollo 15 mission yields an age 3.32 \u00b1 0.06 AE and an initial \u2078\u2078Sr/\u2078\u2076Sr, I = 0.69934 \u00b1 5. This age andI value fall well within the range obtained for the Apollo 12 basalts from the Ocean of Storms and may indicate that extensive lava flows occurred at \u223c 3.3 AE over widespread areas of the moon. The Sr composition of the anorthosite 15415 is as low as that of plagioclase extracted from the Apollo 11 low K rocks. The initial Sr composition of 15415 for an assumed age of 3.3 to 4.6 AE is extremely primitive and provides further evidence for an extremely short formation interval (3 to 1 \u00d7 10\u2076 yr) of a nonchondritic moon with respect to an origin in time defined by BABI. The initial \u2078\u2077Sr/\u2078\u2076Sr for crystalline rocks returned from all lunar missions is correlated with the concentration of Rb and correspondingly K, U and Th. This correlation places distinctive constraints on the evolution of lunar magmas and the internal structure of the moon.", "doi": "10.1016/0012-821x(71)90110-5", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1971-12", "series_number": "1", "volume": "13", "issue": "1", "pages": "97-104" }, { "id": "authors:arj04-3ke98", "collection": "authors", "collection_id": "arj04-3ke98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221213-626467500.2", "type": "article", "title": "Xe and Kr analyses of silicate inclusions from iron meteorites", "author": [ { "family_name": "Bogard", "given_name": "D. D.", "clpid": "Bogard-D-D" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The Xe and Kr contents of silicate inclusions from the iron meteorites Copiapo, Four Corners, Linwood, Pine River, Weekeroo Station and Woodbine (Xe\u00b9\u00b3\u00b2= 3\u201340, Kr\u2078\u2074= 5\u2013100 \u00d7 10\u2079 atoms/g;Kr\u2078\u2074Xe\u00b9\u00b3\u00b2 = 2) are comparable to chondritic values. The isotopic compositions show trapped gas of both chondritic composition (dominant in Pine River) and atmospheric composition (dominant in Linwood). Large spallation effects (Kr_(sp) \u2078\u2074 = 4 \u00d7 10\u2079, Xe_(sp) \u00b9\u00b2\u2076 = 2 \u00d7 10\u2078 atoms/g) occur in Weekeroo Station and Four Corners. The spallation Xe and Kr spectra in Weekeroo differ from those reported for stone meteorites. A re-analysis of literature data shows that systematic variations also exist among stone meteorite spallation spectra which can be qualitatively understood in terms of target element abundance and shielding variations. Very large neutron capture effects on Br and I occur in several meteorites (Kr\u2078\u2070/Kr\u2078\u00b3/Kr\u2078\u2076 = 100/2/3 \u00d7 10\u00b9\u2070 atoms/g in Linwood). The (Kr\u2078\u2070Kr\u2078\u00b2)n\u2245 2\u00b78 ratios from neutron capture on Br for Linwood and Copiapo are distinct from that found in stone meteorites. All samples have pronounced Xe\u00b9\u00b2\u2079 excesses (3\u201350 \u00d7 10\u2079 atoms/g) which apparently indicate differences in formation times from chondrites of less than about 10\u2078 yr; however, the presence of trapped Xe\u00b9\u00b3\u00b2 in silicates which were enclosed in molten Fe-Ni and cooled slowly prove that they were not entirely outgassed; thus, some of the Xe\u00b9\u00b2\u2079 excess may also be trapped. No discernable fission Xe was observed.", "doi": "10.1016/0016-7037(71)90113-x", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1971-12", "series_number": "12", "volume": "35", "issue": "12", "pages": "1231-1254" }, { "id": "authors:j50bk-51y29", "collection": "authors", "collection_id": "j50bk-51y29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141107-081249997", "type": "article", "title": "Heat flow near major strike-slip faults in California", "author": [ { "family_name": "Henyey", "given_name": "T. L.", "clpid": "Henyey-T-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Seventeen heat-flow measurements were made in crystalline rock near the San Andreas, San Jacinto, and Garlock faults, California, in regions representative of several levels of seismic activity. Data from these measurements, together with other heat-flow determinations in California and offshore along the continental borderland, do not clearly demonstrate the existence of a heat-flow anomaly in the vicinity of these major faults, although regularities in the data are present. The mean value of the seventeen determinations is 1.65 \u03bccal/cm^2/sec, \u00b10.28 s.d. It is concluded that any or all of the following are the case: (a) the amount of energy converted to heat near a fault is no larger than that appearing as seismic waves; (b) the presently inferred rates of slip on the faults studied have been going on for only the last few million years or less; (c) the high density of fault systems in central and southern California contributes to a regionally high heat flow but prevents the resolution of energy from any single member; (d) the frictional heat generation varies from place to place along the faults. In the region between Lake Hughes and San Bernardino, now seismically inactive, but in the zone of rupture from the \u223c8-magnitude Fort Tejon earthquake, six measurements show no correlation with distance from the San Andreas fault. Near the San Jacinto fault in the Peninsular Ranges, a region characterized by frequent intermediate- and low-magnitude earthquakes, determinations at 1 and 4 km from the fault are the same; they are 20% higher than a measurement 13 km to the west but are not appreciably different from a probable regional average 25 km to the east in the Imperial Valley. Near Hollister, where the San Andreas fault is creeping at a rate of several centimeters per year, a measurement 3 km west of the fault gives a value similar to those found elsewhere along the fault, yet significantly higher than values to the east on the western flank of the Sierra Nevada. Finally, measurements across the historically inactive Garlock fault exhibit high fluxes near the fault in comparison with a determination 8 km to the north, but these measurements are only slightly higher than values characteristic of the Mojave block to the south.", "doi": "10.1029/JB076i032p07924", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1971-11-10", "series_number": "32", "volume": "76", "issue": "32", "pages": "7924-7946" }, { "id": "authors:5d23v-h0257", "collection": "authors", "collection_id": "5d23v-h0257", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-962044600.1", "type": "article", "title": "Uranium-bearing minerals of lunar rock 12013", "author": [ { "family_name": "Haines", "given_name": "E. L.", "clpid": "Haines-Eldon-L" }, { "family_name": "Albee", "given_name": "A. L.", "clpid": "Albee-A-L" }, { "family_name": "Chodos", "given_name": "A. A.", "clpid": "Chodos-A-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The U distribution in rock 12013 was studied by fission track and elemental mapping techniques. Major U-bearing phases are whitlockite, apatite, zircon, and phase \u03b2, which is a Zr-Ti mineral rich in Fe, Nb, Y, REE and containing up to 3.6% UO\u2082, 4.7% ThO\u2082, and 4.2% PbO. Calculated microprobe ages for phase \u03b2 average 4.0 AE and are in reasonable agreement with Rb-Sr and K-Ar ages. Phase \u03b2 plays a significant role in the U-Th-Pb systematics of rock 12013 and may play a similar role in the model ages of lunar soil.", "doi": "10.1016/0012-821x(71)90070-7", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1971-10", "series_number": "2", "volume": "12", "issue": "2", "pages": "145-154" }, { "id": "authors:6cerc-a9z32", "collection": "authors", "collection_id": "6cerc-a9z32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-280779900.7", "type": "article", "title": "\u2074\u2070Ar-\u00b3\u2079Ar ages and cosmic ray exposure ages of Apollo 14 samples", "author": [ { "family_name": "Turner", "given_name": "G.", "clpid": "Turner-G" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-Frank-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "We have used the \u2074\u2070Ar-\u00b3\u2079Ar dating technique on eight samples of Apollo 14 rocks (14053, 14310), breccia fragments (14321), and soil fragments (14001, 14167). \n\nThe large basalt fragments give reasonable \u2074\u2070Ar/\u00b3\u2079Ar release patterns and yield well defined crystallization ages between 3.89\u20133.95 aeons. Correlation of the \u2074\u2070Ar/39Ar release patterns with \u00b3\u2079Ar/\u00b3\u2077Ar patterns showed that the low temperature fractions with high radiogenic argon loss came from K-rich phases. A highly shocked sample and fragments included in the breccia yield complex release patterns with a low temperature peak. The total argon age of these fragments is 3.95 AE. \n\nCosmic ray exposure ages on these samples are obtained from the ratio of spallogenic \u00b3\u2078Ar to reactor induced37Ar and show a distinct grouping of low exposure ages of \u223c 26 my correlated with Cone crater. Other samples have exposure ages of more than 260 my and identify material with a more complex integrated cosmic age exposure history.", "doi": "10.1016/0012-821x(71)90051-3", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1971-09", "series_number": "1", "volume": "12", "issue": "1", "pages": "19-35" }, { "id": "authors:cqnrs-hwm64", "collection": "authors", "collection_id": "cqnrs-hwm64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-280779900.2", "type": "article", "title": "Rb-Sr ages of igneous rocks from the Apollo 14 mission and the age of the Fra Mauro formation", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Internal Rb-Sr isochrons were determined on four basaltic rocks and on a basaltic clast from a breccia from the Fra Mauro landing site. Rocks 14310, 14073 and 14001,7,3 yield essentially identical ages T = 3.88 \u00b1 0.04 AE and identical high initial \u2078\u2077Sr/\u2078\u2076Sr, I = 0.70035 \u00b1 4. Rock 14053 and the clast from breccia 14321 both yield a higher age T = 3.95 \u00b1 0.04 AE and a distinctly lower I = 0.69945 \u00b1 4. Model ages relative to BABI for these rocks range from 4.3 to 4.6 AE. Model ages were determined for soil samples 14141, 14149, 14163, 14259 yielding T_(BABI) of 4.4, 4.5, 4.5 and 4.7 AE respectively.\nAn internal isochron was determined for 12004 and yielded (3.29 \u00b1 0.07 AE, 0.69948 \u00b1 5) in agreement with our previous results for basaltic rocks from the Apollo 12 site.\nThe crystallization ages for Apollo 14 basalts are only 0.2 to 0.3 AE older than were found for mare basalts from the Sea of Tranquillity. Assuming these leucocratic igneous rocks to be representative of the Fra Mauro site, it follows that there were major igneous processes active in these regions, and presumably throughout the highlands, at times only slightly preceding the periods at which the maria were last flooded. If the breccias represent the Fra Mauro formation and if this is the result of excavation of the Imbrium Basin, we must conclude that a major bombardment of the earth-moon system continued to take place at least as late as 3.9 AE or about 0.7 AE after the formation of the solar system. Such a late major bombardment could remove the need for internal heat sources to explain some mare lava flows. Some of the lunar differentiation processes could possibly represent the result of collisional melting of a thin outer layer. This late bombardment requires that planetary objects \u223c 100 km in size must be stored in unstable orbits with lifetimes of 10\u2078 yr or more.", "doi": "10.1016/0012-821x(71)90052-5", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1971-09", "series_number": "1", "volume": "12", "issue": "1", "pages": "36-48" }, { "id": "authors:2b90z-b4b59", "collection": "authors", "collection_id": "2b90z-b4b59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-967794900.3", "type": "article", "title": "Lunar chronology and evolution from Rb-Sr studies of Apollo 11 and 12 samples", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Rb-Sr internal isochrons for a total of eight Apollo 12 crystalline rocks yield ages of 3.36 to 3.16 AE. The initial Sr compositions (I) are relatively primitive and range from 0.69918 to 0.69957 as compared to BABI= 0.69898 \u00b1 3. No clear groupings inI are observed, however, the wide range indicates that at least four different rock bodies were sampled. An Apollo 11 basalt (10024) yielded an age of 3.61 \u00b1 0.07AE and I = 0.69935 \u2213 8 in agreement with previous results on other Apollo 11 high K rocks. Several Apollo 12 soil samples yield model ages which range from 4.4 to 4.6 AE and indicate that the special nature and older \"age\" of the lunar soil determined at the Apollo 11 site is a widespread phenomenon. \n\nInitial Sr compositions from Apollo 11 and Apollo 12 support our previous conclusions that the moon as a whole has a Rb/Sr much lower (Rb/Sr \u2248 0.008) than found in chondrites. We summarize the current status of Rb-Sr lunar chronology and some implications regarding the melting and differentiation history of the moon.", "doi": "10.1016/0012-821x(71)90139-7", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1971-05", "series_number": "1-5", "volume": "11", "issue": "1-5", "pages": "37-62" }, { "id": "authors:drwpy-de749", "collection": "authors", "collection_id": "drwpy-de749", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-280779900.5", "type": "article", "title": "Isotopic composition of xenon and krypton in the lunar soil and in the solar wind", "author": [ { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-Frank-A" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Xe and Kr analyses of three lunar samples, the Murray meteorite and Xe from the terrestrial atmosphere are presented. The isotopic compositions of surface-correlated (solar wind?) and lunar soil spallation xenon and krypton are derived from the lunar soil data alone. The lunar soil spallation Xe is similar to that in lunar rocks and meteorites, but the lunar soil spallation Kr has higher (\u2078\u2074Kr/\u2078\u00b3Kr) and \u2078\u00b2Kr/\u2078\u00b3Kr). We have no adequate explanation for this Kr spectrum, although independent evidence for such a component comes from stepwise heating data. The surface-correlated Xe (SUCOR) is distinct from both AVCC and terrestrial Xe. However, SUCOR Xe cannot be directly identified with the solar wind, but may contain an admixture of gases from the lunar atmosphere implanted on the grain surfaces by ion pumping processes. The general fractionation trend in SUCOR Xe relative to the atmosphere presumably reflects the solar wind composition. SUCOR Kr appears to be totally ascribable to the solar wind. Solar wind and terrestrial Kr are related by fractionation, but opposite to that of Xe.", "doi": "10.1016/0012-821x(71)90008-2", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1971-01", "series_number": "2", "volume": "10", "issue": "2", "pages": "199-216" }, { "id": "authors:5asm4-5rv61", "collection": "authors", "collection_id": "5asm4-5rv61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221111-678968900.2", "type": "article", "title": "The isotopic abundance of \u00b2\u2076Mg and limits on \u00b2\u2076Al in the early solar system", "author": [ { "family_name": "Schramm", "given_name": "David N.", "clpid": "Schramm-David-N" }, { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Mg is investigated in meteoritic, lunar and terrestrial feldspar samples and standard reagents using a mass spectrometer with on-line data processing. Isotopically enriched standards were run demonstrating a resolution of better than five parts in 10\u2074 for the \u00b2\u2076Mg/\u00b2\u2074Mg ratio. No \u00b2\u2076Mg/\u00b2\u2074Mg anomalies are found in any samples analyzed to within experimental errors. (These analyses include some samples run by Clarke, de Laeter, Schwarcz and Shane [1] and found by them to have \u00b2\u2076Mg/\u00b2\u2074Mg anomalies of 4\u20136 parts in 10\u00b3 relative to terrestrial values.) There is at the present time no positive evidence indicating the existence of \u00b2\u2076Al in the early solar system.\nFrom these results, limits are placed on the amount of \u00b2\u2076Al (\u03c4\u00bd = 7.4 \u00d7 10\u2075 yr) and the resulting heating effects in the solar system at the time of crystallization of the meteorites. It is clear that when the meteorites solidified, \u00b2\u2076Al was not an important heat source; however, this would not rule out the possibility that a few million years prior to solidification \u00b2\u2076Al was a major heat source.", "doi": "10.1016/0012-821x(70)90063-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1970-12", "series_number": "1", "volume": "10", "issue": "1", "pages": "44-59" }, { "id": "authors:g1n78-rp876", "collection": "authors", "collection_id": "g1n78-rp876", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221115-798018900.2", "type": "article", "title": "A precise \u2078\u2077Rb\u2078\u2077Sr age and initial \u2078\u2077Sr\u2078\u2076Sr for the Colomera iron meteorite", "author": [ { "family_name": "Sanz", "given_name": "H. G.", "clpid": "Sanz-H-G" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Rb-Sr analyses of silicates from the Colomera iron meteorite show a wide range in Rb/Sr and give \u2078\u2077Sr\u2078\u2076Sr values ranging from 0.699 to 8.45. These analyses define a precise linear array on the Rb-Sr evolution diagram yielding an age of 4.61 \u00b1 0.04 \u00d7 10\u2079yr. A highprecision analysis of a whitlockite separate having very low Rb/Sr yields an initial (\u2078\u2077Sr\u2078\u2076Sr)_I = 0.69940 \u00b1 0.00004. An upper limit of 48 \u00b1 7 million years can be set for the time interval between dispersion of the silicate in the metal phase and final Sr isotopic equilibration, if we assume that Colomera silicate formed from a parent material which had the same initial \u2078\u2077Sr\u2078\u2076Sr as Ca-rich achondrites. The data are consistent with a simple evolutionary history in which Colomera differentiated from a parent material of chondritie RbSr ratio at a time 39 million years after the parent material had the initial \u2078\u2077Sr\u2078\u2076Sr of Ca-rich achondrites and 35 million years before the final Sr equilibration in the Guare\u00f1a chondrite.", "doi": "10.1016/0016-7037(70)90059-1", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1970-11", "series_number": "11", "volume": "34", "issue": "11", "pages": "1227-1239" }, { "id": "authors:n4scb-r4m83", "collection": "authors", "collection_id": "n4scb-r4m83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220727-260650800", "type": "article", "title": "U-Th-Pb and Rb-Sr systematics in 2700 \u00d7 10\u2076-year old plutons from the southern Wind River Range, Wyoming", "author": [ { "family_name": "Naylor", "given_name": "R. S.", "clpid": "Naylor-R-S" }, { "family_name": "Steiger", "given_name": "R. H.", "clpid": "Steiger-Rudolf-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "To distinguish between episodic and continuous-diffusion loss mechanisms, and to compare the response of different parent-daughter systems to metamorphism, we have studied a series of well-exposed plutons, all about 2700 \u00d7 10\u2076 yr old and showing different degrees of metamorphism. The Louis Lake granodiorite pluton in the southern Wind River Range, Wyoming was selected to represent granitic rocks only slightly affected by later disturbances (intrusion of Precambrian diabase dikes and gentle Laramide uparching). Rb-Sr data on total-rock samples form a linear array on the Sr-evolution diagram, indicating that the pluton was emplaeed 2630 \u00b1 20 \u00d7 10\u2076 yr ago (\u03bb^(Rb\u2078\u2077) = 1.39 \u00d7 10\u207b\u00b9\u00b9yr\u207b\u00b9) with an initial Sr\u2078\u2077Sr\u2078\u2076 ratio of 0.702 \u00b1 0.001. Data on cogenetic zircon fractions form a linear array on a coupled Pb-U evolution diagram with a primary intercept of 2687 \u00b1 15 \u00d7 10\u2076 yr. The secondary intercept of 130 \u00b1100 \u00d7 10\u2076 yr is distinctly lower than the 480 to 660 \u00d7 10\u2076 yr intercepts predicted by single-phase continuous-diffusion models. If the zircons reflect Laramide disturbance, this is not detected by the Rb-Sr data on mineral separates. Disturbance of these data is readily apparent only in rocks with high RbSr ratios and has yielded no apparent secondary ages younger than 2000 \u00d7 10\u2076 yr.", "doi": "10.1016/0016-7037(70)90055-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1970-11", "series_number": "11", "volume": "34", "issue": "11", "pages": "1133-1159" }, { "id": "authors:drk1j-mya53", "collection": "authors", "collection_id": "drk1j-mya53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221114-173707310", "type": "article", "title": "Nucleochronologies and the Mean Age of the Elements", "author": [ { "family_name": "Schramm", "given_name": "David N.", "clpid": "Schramm-David-N" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The equations for a nucleosynthetic chronology are shown to be separable with the equations for extremely long-lived and stable nuclei yielding the mean age of the elements. This result is independent of the time-dependent production model used. This mean age is a lower bound on the age of the elements. The age of the elements is critically model-dependent. The short-lived isotopes are shown to yield the formation interval for the solar system which also is essentially model-independent. The short-lived and intermediate-lived isotopes taken relative to stable isotopes are shown to yield information on the rate of r-process nucleosynthesis with time and thus may provide the distribution of supernovae in time within the Galaxy.", "issn": "0004-637X", "publisher": "IOP Publishing", "publication": "Astrophysical Journal", "publication_date": "1970-10", "volume": "162", "pages": "57-69" }, { "id": "authors:v37c1-0p109", "collection": "authors", "collection_id": "v37c1-0p109", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220621-862339900", "type": "article", "title": "Mineralogic and isotopic investigations on lunar rock 12013", "author": [ { "family_name": "Albee", "given_name": "A. L.", "clpid": "Albee-A-L" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Chodos", "given_name": "A. A.", "clpid": "Chodos-A-A" }, { "family_name": "Haines", "given_name": "Eldon L.", "clpid": "Haines-Eldon-L" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-F-A" }, { "family_name": "Russ", "given_name": "G. Price, III", "clpid": "Russ-G-Price-III" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Sample 12013, 10 was a sawn slab, 50 X 22 X 4 mm,\ncut from a position about 6 mm from an exterior surface\nof lunar sample 12013 returned from the Apollo\n12 mission. Because of its extreme heterogeneity it was\ndelivered to our clean-lab for division and distribution\nto the various principal investigators. Prior to division\nit was carefully examined and photographed and preliminary\nRb/Sr and microprobe results were obtained\non loose fragments found in the sample container.\nThin section 12013, 4 (Apollo 12 sample catalog)\nfrom an unknown part of the sample also provided\nsome guidance in the distribution.", "doi": "10.1016/0012-821x(70)90046-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1970-09-01", "series_number": "2", "volume": "9", "issue": "2", "pages": "137-163" }, { "id": "authors:frpsa-gc321", "collection": "authors", "collection_id": "frpsa-gc321", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141107-102841930", "type": "article", "title": "Isotopic composition of gadolinium and neutron-capture effects in some meteorites", "author": [ { "family_name": "Eugster", "given_name": "O.", "clpid": "Eugster-O-J" }, { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-F" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Gd in one chondrite, two achondrites, and the silicate inclusions of two iron meteorites has been determined. When corrected for mass discrimination, Gd in all samples except the Norton County achondrite shows the same relative isotopic abundances as terrestrial Gd. These results set an upper limit of 3\u00d710^(15) neutrons per cm^2 on a differential integrated thermal neutron irradiation of the earth and these meteorites. Neutron-capture effects are present in Gd extracted from the Norton County achondrite. These most probably have been produced by secondary neutrons during the exceptionally long cosmic ray exposure of this large stone meteorite. The isotopic anomalies correspond to an integrated thermal neutron flux of (6.3\u00b10.9)\u00d710^(15) neutrons per cm^2. The percent abundances of terrestrial Gd found in our work for Gd^(160), Gd^(158), Gd^(157), Gd^(156), Gd^(155), Gd^(154), and Gd^(152) are 21.863, 24.835, 15.652, 20.466, 14.800, 2.1809, and 0.2029, respectively. Because of the higher precision, these abundances should replace the currently accepted values.", "doi": "10.1029/JB075i014p02753", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1970-05-10", "series_number": "14", "volume": "75", "issue": "14", "pages": "2753-2768" }, { "id": "authors:10eax-f6632", "collection": "authors", "collection_id": "10eax-f6632", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220713-235975900", "type": "article", "title": "Rb-Sr ages from the ocean of storms", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Rb-Sr internal isochrons for two texturally and mineralogically distinct crystalline rocks returned by Apollo 12 yield similar ages of 3.36 \u00b1 0.10 and 3.26 \u00b1 0.10 \u00d7 10\u2079 years. The initial Sr compositions determined are relatively primitive but distinct so that these samples represent two different rock bodies. These ages are slightly but distinctly younger than the Mare Tranquillitatis Rb Sr ages and indicate that the flooding of the maria may have occurred only during a short interval of\u223c 300 \u00d7 10\u2076 years duration 3.6 \u00d7 10\u2079 years ago. The soil at the Ocean of Storms yields a well determined model age of 4.44 \u00d7 10\u2079 years and therefore the special nature and older age of the lunar soil determined at the Apollo 11 site is found to be a widespread phenomenon.\nInitial Sr compositions from Apollo 12 support our previous conclusion based on Apollo 11 measurements that the moon as a whole has a Rb/Sr ratio much lower than that in chondrites.", "doi": "10.1016/0012-821x(70)90111-1", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1970-05", "series_number": "4", "volume": "8", "issue": "4", "pages": "269-278" }, { "id": "authors:4y290-40j94", "collection": "authors", "collection_id": "4y290-40j94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220718-449423900", "type": "article", "title": "The isotopic composition of Gd and the neutron capture effects in samples from Apollo 11", "author": [ { "family_name": "Eugster", "given_name": "O.", "clpid": "Eugster-O-J" }, { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-Fouad" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Gd in six rocks, one breccia, two core samples, and soil has been determined. Isotopic variations due to capture of low energy neutrons produced by cosmic ray interactions have been found in all samples except for two rocks. Using cosmic ray exposure ages, the effective thermal neutron fluxes were calculated using a nominal value of \u00b9\u2075\u2077\u03c3 = 2.62 \u00d7 10\u2075 barns. They vary from less than 0.27 n/cm\u00b2 sec to 1.1 n/cm\u00b2 inidicating variable shielding for the samples studied. The neutron dosage of the top and the bottom of core #2 is the same. This means that the soil has been mixed to 13 cm at least once in the last 100 my. A mixing depth of 23 to 47 m can be calculated based on the integrated effective thermal neutron dosage of 9 \u00d7 10\u00b9\u2075 n/cm\u00b2 for the soil and an assumed surface flux of 0.2 n/cm\u00b2 sec. For rock #17 the barium isotopic composition was determined and found to be the same as terrestrial to within 0.1% for the five abundant isotopes.", "doi": "10.1016/0012-821x(70)90094-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1970-03", "series_number": "1", "volume": "8", "issue": "1", "pages": "20-30" }, { "id": "authors:3e6x7-8g236", "collection": "authors", "collection_id": "3e6x7-8g236", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221111-192237400.2", "type": "article", "title": "Rb-Sr ages of lunar rocks from the sea of tranquillity", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "abstract": "\u2078\u2077Rb-\u2078\u2077Sr internal isochrons have been determined for six crystalline rocks from the Sea of Tranquillity, and all yield ages within the narrow range 3.65 \u00b1 0.06 \u00d7 10\u2079yr. Differences in initial (\u2078\u2077Sr/\u2078\u2076Sr)_I define at least two main rock groups which coincide with the two groups indicated by alkali content of the rocks. This demonstrates that at least two magnetic reservoirs were involved in the 3.65 \u00d7 10\u2079 yr event on the moon. The soil yields a model Rb-Sr age of 4.6 \u00d7 10\u2079 yr which suggests that it consists of an average over a variety of rock systems of different ages which represent a closed total system 4.6 \u00d7 10\u2079 yr old or the widespread existence of rocks of 4.6 \u00d7 10\u2079 yr age. A single peculiar rock fragment from the soil gives a model age of 4.4 \u00d7 10\u2079 yr.\nInitial Sr compositions for the lunar rocks and for soil fragments define a narrow range (0.6990\u20130.6994) whose lower limit is equal to the basaltic achondrite initial Sr. The moon, earth and basaltic achondrites represent planets with Rb/Sr much lower than in the sun. The moon and the basaltic achondrites must have separated from the solar nebula within a time interval of less than 4 \u00d7 10\u2076 yr. From consideration of Sr-Rb relations, if the moon formed by fission from the earth, it must have occurred prior to 4.4 \u00d7 10\u2079 yr ago.", "doi": "10.1016/0012-821x(70)90093-2", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1970-03", "series_number": "1", "volume": "8", "issue": "1", "pages": "1-19" }, { "id": "authors:a5x8p-x9a21", "collection": "authors", "collection_id": "a5x8p-x9a21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220715-505869300", "type": "article", "title": "Neutron capture effects in Gd from the Norton County meteorite", "author": [ { "family_name": "Eugster", "given_name": "O.", "clpid": "Eugster-O-J" }, { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-F" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of Gd in one chondrite, two achondrites and the silicate inclusions of two meteorites have been determined. When corrected for mass discrimination, Gd in all samples except the Norton County achondrite shows the same relative isotopic abundances as terrestrial Gd. These results set an upper limit of 3 \u00d7 10\u00b9\u2075 neutrons per cm\u00b2 on a differential integrated thermal neutron irradiation of the earth and these meteorites. Neutron capture effects are present in Gd extracted from the Norton County achondrite. These most probably have been produced by secondary neutrons during the exceptionally long cosmic ray exposure of this large stone meteorite. The isotopic anomalies correspond to an integrated thermal neutron flux of (6.3 \u00b1 0.9) \u00d7 10\u00b9\u2075 neutrons per cm\u00b2.", "doi": "10.1016/0012-821x(70)90087-7", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1970-02", "series_number": "5", "volume": "7", "issue": "5", "pages": "436-440" }, { "id": "authors:f71hs-wyj76", "collection": "authors", "collection_id": "f71hs-wyj76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130220-113109469", "type": "article", "title": "Ages, Irradiation History, and Chemical Composition of Lunar Rocks from the Sea of Tranquillity", "author": [ { "family_name": "Albee", "given_name": "A. L.", "clpid": "Albee-A-L" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Chodos", "given_name": "A. A.", "clpid": "Chodos-A-A" }, { "family_name": "Eugster", "given_name": "O. J.", "clpid": "Eugster-O-J" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-F-A" }, { "family_name": "Russ", "given_name": "G. Price, II", "clpid": "Russ-G-P-II" }, { "family_name": "Sanz", "given_name": "H. G.", "clpid": "Sanz-H-G" }, { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The ^(87)Rb-^(87)Sr internal isochrons for five rocks yield an age of 3.65\u00b10.05 \u00d7 10^9 years which presumably dates the formation of the Sea of Tranquillity. Potassium-argon ages are consistent with this result. The soil has a model age of 4.5 \u00d7 10^9 years, which is best regarded as the time of initial differentiation of the lunar crust. A peculiar rock fragment from the soil gave a model age of 4.44 \u00d7 10^9 years. Relative abundances of alkalis do not suggest differential volatilization. The irradiation history of lunar rocks is inferred from isotopic measurements of gadolinium, vanadium, and cosmogenic rare gases. Spallation xenon spectra exhibit a high and variable 1^(31)Xe/^(126)Xe ratio. No evidence for ^(129)I was found. The isotopic composition of solar-wind xenon is distinct from that of the atmosphere and of the average for carbonaceous chondrites, but the krypton composition appears similar to average carbonaceous chondrite krypton.", "doi": "10.1126/science.167.3918.463", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1970-01-30", "series_number": "3918", "volume": "167", "issue": "3918", "pages": "463-466" }, { "id": "authors:ssgnm-wn066", "collection": "authors", "collection_id": "ssgnm-wn066", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221111-473983800.1", "type": "article", "title": "Summary of Apollo 11 Lunar Science Conference", "author": [ { "family_name": "Arnold", "given_name": "J.", "clpid": "Arnold-J" }, { "family_name": "Arrhenius", "given_name": "G.", "clpid": "Arrhenius-G" }, { "family_name": "Eglinton", "given_name": "G.", "clpid": "Eglinton-G" }, { "family_name": "Frondel", "given_name": "C.", "clpid": "Frondel-C" }, { "family_name": "Gast", "given_name": "P.", "clpid": "Gast-P-W" }, { "family_name": "MacGregor", "given_name": "I.", "clpid": "MacGregor-I" }, { "family_name": "Pepin", "given_name": "R.", "clpid": "Pepin-R-O" }, { "family_name": "Strangway", "given_name": "D.", "clpid": "Strangway-D" }, { "family_name": "Walker", "given_name": "R.", "clpid": "Walker-R" }, { "family_name": "Wasserburg", "given_name": "G.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Zill", "given_name": "P.", "clpid": "Zill-P" }, { "literal": "Lunar Sample Analysis Planning Team" } ], "abstract": "On 24 July 1969 the first samples from our sister planet, the moon, were returned to earth for direct scientific investigation. Prior to this, our understanding of the extraterrestrial universe derived from study of electromagnetic radiation from stars and planets, from study of cosmic rays, and from analysis of meteorites. Meteorites were, until the return of Apollo 11, the only extraterrestrial objects we could actually hold in our hands and scrutinize in the laboratory. Unlike meteorites, the lunar samples come from a good sized planetary object whose location is well known.", "doi": "10.1126/science.167.3918.449", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1970-01-30", "series_number": "3918", "volume": "167", "issue": "3918", "pages": "449-451" }, { "id": "authors:j2vtf-4bf25", "collection": "authors", "collection_id": "j2vtf-4bf25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220616-446264100", "type": "article", "title": "Comparative U-Th-Pb systematics in 2.7 \u00d7 10\u2079yr plutons of different geologic histories", "author": [ { "family_name": "Steiger", "given_name": "R. H.", "clpid": "Steiger-R-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A comparative study was made of the Pb-U-Th systematics on cogenetic zircons from three plutons with different geological histories but the same age (2.69 \u00d7 10\u2079 yr). The first of these is in the Superior Province, Canada and is believed to be a virginal body. Assuming an episodic model, a secondary age of 455 \u00b1\u00b3\u2070\u2075\u2081\u2080\u2085m.y. is inferred. The second body is from the Grenville front and is known to have suffered an episode at 920 m.y. However, a secondary age of 350 \u00b1 50 m.y. is inferred. A third body in the Wind River Mountains, Wyoming, has no known metamorphic history, but was uparched in Laramide time. After Naylor et al. (1968) a secondary age of 130 \u00b1\u2078\u2070\u2081\u2080\u2080m.y. is inferred,\nWe conclude that unless independently documented, the secondary ages inferred by the episodic model are in general invalid. The zircon systematics appear to be dominated by the occurrence of highly discordant and almost concordant phases. The discordant phase responding to diffusion loss which may be in the \"non linear\" region.", "doi": "10.1016/0016-7037(69)90043-x", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1969-10", "series_number": "10", "volume": "33", "issue": "10", "pages": "1213-1232" }, { "id": "authors:mxqe2-1n844", "collection": "authors", "collection_id": "mxqe2-1n844", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220617-310969500", "type": "article", "title": "Initial strontium for a chondrite and the determination of a metamorphism or formation interval", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Sanz", "given_name": "H. G.", "clpid": "Sanz-H-G" } ], "abstract": "A precise Rb-Sr internal isochron was determined for Guarena, an H6 chondrite, yielding an age of 4.56 \u00b1 0.08 \u00d7 10\u2079 years. Rb-poor, Sr-rich phosphate phases (whitlockite and apatite) were obtained resulting in a precise measurement of the initial Sr isotopic composition (\u2078\u2077Sr/\u2078\u2076Sr)_I = 0.69995 \u2213 0.00015. It is shown that from precise age and initial (\u2078\u2077Sr/\u2078\u2076Sr)_I measurements we can obtain information on the differential evolution of Rb-Sr systems involving either simple metamorphism of closed systems or multi-stage processes. The high initial ratio obtained for Guarena with respect to the value for the basaltic achondrites is the first clear demonstration of differential Sr evolution of a chondrite and affords the simple explanation of Guarena having been metamorphosed 74 million years after its formation. This approach may yield a \"time\" evolution index for the classification of meteorites.", "doi": "10.1016/0012-821x(69)90008-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1969-10", "series_number": "1", "volume": "7", "issue": "1", "pages": "33-43" }, { "id": "authors:fa1h0-2av72", "collection": "authors", "collection_id": "fa1h0-2av72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141107-122112454", "type": "article", "title": "Correlation between fission tracks and fission type xenon in meteoritic Whitlockite", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "abstract": "Whitlockite from the St. Severin chondrite, previously shown to contain excess fission tracks, is here shown to have a large concentration of excess neutron-rich xenon isotopes. The concentration of excess heavy Xe in the whitlockite is about twenty-five times that calculated from the track density. An isotopic spectrum is deduced that is identical to the spectrum calculated previously for excess heavy xenon in the Pasamonte achondrite. These results uniquely associate this xenon spectrum with in situ fission in meteorites. Chemical arguments support the correlation of this with Pu^(244). Identification of the fissioning nucleus as Pu^(244) gives Pu^(244)/U^(238) \u2248 1/30. Neither 'sudden' nor 'uniform' nucleosynthetic models give consistent solutions for Pu^(244)/U^(238) and U^(235)/U^(238).", "doi": "10.1029/JB074i017p04221", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1969-08-15", "series_number": "17", "volume": "74", "issue": "17", "pages": "4221-4232" }, { "id": "authors:6ap83-90714", "collection": "authors", "collection_id": "6ap83-90714", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220621-183942200", "type": "article", "title": "The isotopic composition of lead in potassium feldspars from some 1.0-b.y. old North American igneous rocks", "author": [ { "family_name": "Zartman", "given_name": "Robert E.", "clpid": "Zartman-Robert-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The isotopic composition of lead and the uranium, thorium and lead concentrations in potassium feldspars are determined for more than 30 1.0-b.y. old North American igneous rocks. Samples representing a broad spectrum in petrographic type and mode of occurrence were chosen; an effort was made to include only rocks having well-documented ages from 950 to 1140 m.y. and showing minimal evidence of subsequent metamorphism.\nMost samples, including those from extensive terranes of contemporaneous age, have limited lead isotope variations (Pb\u00b2\u2070\u2076Pb\u00b2\u2070\u2074= 16.74\u201317.38; Pb\u00b2\u2070\u2077Pb\u00b2\u2070\u2074= 15.39\u201315.59; Pb\u00b2\u2070\u2078Pb\u00b2\u2070\u2074= 36.38\u201337.10), which yield model ages close to the radiometric ages. Granite, pegmatite, and rhyolite from within the Grenville province of Canada and age-equivalent rocks of New York, Virginia, Texas, and Colorado and granophyric units associated with the Duluth Gabbro Complex of Minnesota are among the materials yielding this main isotopic spectrum.\nSeveral samples were encountered which had isotopic compositions very different from the above group. Lead showing a marked deficiency in radiogenic isotopes was found in two granitic bodies associated with older Labrador Trough rocks from Quebec, in a rapakivi granite from southern Nevada, and in a small granite stock from Mellen, Wisconsin. These occurrences all involve small intrusions of granite which lie near considerably older areas of basement rock. Model ages calculated from the Pb\u00b2\u2070\u2076Pb\u00b2\u2070\u2074 ratio are older than the age of the intrusions and approach the age of the host basement rock.\nSeveral possible interpretations are offered to explain the isotopic behavior encountered in this study. In particular, a \"vertically differentiated crust\" model is proposed which will account for both the main spectrum and the anomalous lead. The significance of lead isotopic studies in understanding crustal structure in continental regions is discussed.", "doi": "10.1016/0016-7037(69)90104-5", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1969-08", "series_number": "8", "volume": "33", "issue": "8", "pages": "901-942" }, { "id": "authors:e39yr-87z79", "collection": "authors", "collection_id": "e39yr-87z79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220617-181605156", "type": "article", "title": "Nuclear Chronologies for the Galaxy", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Schramm", "given_name": "David N.", "clpid": "Schramm-David-N" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" } ], "abstract": "The ratios U\u00b2\u00b3\u2075/U\u00b2\u00b3\u2078, Th\u00b2\u00b3\u00b2/U\u00b2\u00b3\u2078, Pu\u00b2\u2074\u2074/U\u00b2\u00b3\u2078, and I\u00b9\u00b2\u2079/I\u00b9\u00b2\u2077 have been used to obtain self-consistent\nsolutions for the time evolution of r-process nuclei. Using Pu\u00b2\u2074\u2074/U\u00b2\u00b3\u2078 = 1/30, the solutions all have a large\namount of initial production, with a duration of from 0 to 10\u00b9\u2070 years, followed by a relatively quiescent\nperiod (~3 X 10\u2079 years) terminated by a nucleosynthetic event that possibly initiated the separation\nof the solar system. For values of Pu\u00b2\u2074\u2074 less than 1/60 models of uniform synthesis terminated by a sharp\nnucleosynthetic event are possible.", "doi": "10.1086/180393", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1969-08", "volume": "157", "pages": "L91-L96" }, { "id": "authors:9fa8v-7ha10", "collection": "authors", "collection_id": "9fa8v-7ha10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141107-122849606", "type": "article", "title": "Isotopic analyses of barium in meteorites and in terrestrial samples", "author": [ { "family_name": "Eugster", "given_name": "O.", "clpid": "Eugster-O-J" }, { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-F" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Isotopic composition and concentration of barium in six stone meteorites and the silicate inclusions of two iron meteorites and three terrestrial samples were measured by use of a 'double spike' isotopic dilution technique in order to correct for laboratory fractionation. Any differences between the abundances of the isotopes in meteoritic and terrestrial Ba were found to be less than 0.1% for all isotopes. The per cent abundances of Ba found in our work for Ba^(138), Ba^(137), Ba^(136), Ba^(135), Ba^(134), Ba^(132), and Ba^(130) are 71.699, 11.232, 7.853, 6.592, 2.417, 0.1012, and 0.1058, respectively. Because of the higher precision, these abundances should replace the currently accepted values. These results show the variations in the Ba isotopes reported by S. Umemoto (1962) to be unsubstantiated.", "doi": "10.1029/JB074i015p03897", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1969-07-15", "series_number": "15", "volume": "74", "issue": "15", "pages": "3897-3908" }, { "id": "authors:dgdb7-y0f19", "collection": "authors", "collection_id": "dgdb7-y0f19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WASprl69", "type": "article", "title": "Correlation Between Fission Tracks and Fission-Type Xenon from an Extinct Radioactivity", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "abstract": "Meteoritic whitlockite containing excess fission tracks has a large concentration of excess neutron-rich xenon isotopes which is 25 times that calculated from the track density. The isotopic spectrum is identical to that calculated previously for the Pasamonte achondrite. These results uniquely associate this spectrum with in situ fission. Identification of the fissioning nucleus as Pu244 gives Pu244/U238 \u2245 1/30 at the time of xenon retention. Neither \"sudden\" nor \"uniform\" nucleosynthetic models give consistent solutions for Pu244/U238 and U235/U238.", "doi": "10.1103/PhysRevLett.22.1198", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "1969-06-02", "series_number": "22", "volume": "22", "issue": "22", "pages": "1198-1201" }, { "id": "authors:gzd8y-srd90", "collection": "authors", "collection_id": "gzd8y-srd90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220610-163337949", "type": "article", "title": "The Time Scales of Nucleosynthesis", "author": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The nuclei of the atoms of elements heavier than hydrogen are generally believed to have been synthesized in a variety of stars, more or less continuously, throughout the history of the galaxy. The matter ejected from these stars at various stages in their evolution is mixed into the interstellar gas and, in turn, portions of this gas become isolated from the remainder of the galaxy and form later-generation stars such as the sun. The times required for the various stages in the evolution of the matter of our solar system are of interest, both from an astrophysical and a philosophical point of view. We will discuss how relatively definitive information can be obtained on the times for at least the latter stages in this evolution through the measurement of the isotopic composition of those elements in meteorites which contain the daughter products of radioactive decay.", "issn": "0013-7812", "publisher": "California Institute of Technology", "publication": "Engineering and Science", "publication_date": "1969-06", "series_number": "9", "volume": "32", "issue": "9", "pages": "41-44" }, { "id": "authors:gsp4y-yb414", "collection": "authors", "collection_id": "gsp4y-yb414", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WASrsi69", "type": "article", "title": "A Programmable Magnetic Field Mass Spectrometer with On-Line Data Processing", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Nenow", "given_name": "E. V.", "clpid": "Nenow-E-V" }, { "family_name": "Bauman", "given_name": "C. A.", "clpid": "Bauman-C-A" } ], "abstract": "A single focusing, 30.48 cm radius, 60\u00b0 sector magnet mass spectrometer was constructed with symmetric conjugate foci calculated from fringe field data and corresponding to a beam deflection of 68\u00b0. Experimental and calculated optical characteristics agree well. A rotating coil probe and a rate coil are employed as field sensors for a nulling device and for field scanning. The magnetic field can be set to 27 values corresponding to the center of spectral lines and zero lines on both sides of each peak. The automatic scanning consists of: (1) rapid field change between adjacent field values (~500 G/sec); (2) locking in at the preset field values (~0.3 sec); (3) remaining in a channel for a preset time during which the ion beam current is integrated and the data digitized. Repeated arbitrary excursions between channels do not cause effective field variations of more than |DeltaB/B| = 2\u00d710^\u20135. For 0.2 mm source and 0.64 mm collector slit settings, a typical peak at mass 88 is flat for 2.7 G to 0.01% at a 14 kV accelerating potential. Data consist of channel intensity, scale factors, and internally provided clock time; data signals drive a typewriter and tape punch. A cyclic scan of five isotopes including background requires 35 sec. A segment of data (~10 cycles) is processed by the computer and the results returned to the operator.", "doi": "10.1063/1.1683921", "issn": "0034-6748", "publisher": "Review of Scientific Instruments", "publication": "Review of Scientific Instruments", "publication_date": "1969-02", "series_number": "2", "volume": "40", "issue": "2", "pages": "288-295" }, { "id": "authors:e1mb3-g9872", "collection": "authors", "collection_id": "e1mb3-g9872", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220610-525536500", "type": "article", "title": "Determination of an internal \u2078\u2077Rb-\u2078\u2077Sr isochron for the Olivenza chondrite", "author": [ { "family_name": "Sanz", "given_name": "H. G.", "clpid": "Sanz-H-G" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Rb-Sr isotopic determinations were made on five single chondrules, ranging from 4 to 27 milligrams, extracted from Olivenza, an olivine-hypersthene chondrite. Several density fractions with a particle size smaller than 37\u03bc were separated and Rb-Sr analyses made. These data form a well defined linear array on the Sr-Rb evolution diagram and yield an age of 4.63 \u00d7 10\u2079 years and an initial \u2078\u2077Sr\u2078\u2076Sr = 0.6994. The typical strontium and rubidium blanks were 8 \u00d7 10\u207b\u00b9\u2070 and 4 \u00d7 10\u207b\u00b9\u00b9 g, respectively.\nAn acid wash experiment shows that preferential leaching takes place and that the resulting data from such a procedure are of doubtful reliability.\nConstructing an error envelope of the data points, a graphical representation of the initial \u2078\u2077Sr\u2078\u2076Sr versus the age is presented which demonstrates the constraints on these two anticorrelated parameters. This is a useful means of testing whether two data arrays may have the same age and (\u2078\u2077Sr\u2078\u2076Sr)_I.", "doi": "10.1016/0012-821x(69)90182-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1969", "series_number": "5", "volume": "6", "issue": "5", "pages": "335-345" }, { "id": "authors:baj2c-w2313", "collection": "authors", "collection_id": "baj2c-w2313", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131121-075702149", "type": "article", "title": "Potassium-Feldspar Phenocrysts in the Surface of Colomera, and Iron Meteorite", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Sanz", "given_name": "H. G.", "clpid": "Sanz-H-G" }, { "family_name": "Bence", "given_name": "A. E.", "clpid": "Bence-A-E" } ], "abstract": "Silicate aggregates, including large single crystals of potassium feldspar as long as 11 centimeters and sodium feldspar, are embeded in the surface of the medium octahedrite Colomera. Silicate nodules in the interior appear to be much smaller (about 0.3 centimeter). Glass nodules are abundant both on the external surface and in the interior. These observations are evidence that some iron meteorites formed as segregations within a silicate matrix and did not originate in a metallic planetary core.", "doi": "10.1126/science.161.3842.684", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1968-08-16", "series_number": "3842", "volume": "161", "issue": "3842", "pages": "684-687" }, { "id": "authors:h575j-t3e38", "collection": "authors", "collection_id": "h575j-t3e38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220610-227701800", "type": "article", "title": "Cosmogenic rare gases and the \u2074\u2070K-\u2074\u2070Ar age of the kodaikanal iron meteorite", "author": [ { "family_name": "Bogard", "given_name": "D. D.", "clpid": "Bogard-D-D" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Measurements have been made of the cosmogenic He, Ne, and Ar in the metal phase and of the K-Ar ages of two glass inclusions in the Kodaikanal iron meteorite. The small amounts of cosmogenic rare gas are best interpreted as due to a low cosmic ray exposure age. From empirical production rates, ages of 12, 15 and 15 m.y. were obtained from the \u00b3He, \u00b2\u00b9Ne and \u00b3\u2078Ar concentrations, respectively. The \u00b3He/\u00b2\u00b9Ne, \u00b3He/\u2074He and \u2074He/\u00b3\u2078Ar ratios are all consistent with low shielding during the exposure. The feldspar and glass have approximately equal K-Ar ages of 3.5 \u00b1 0.1 and 3.3 \u00b1 0.1 \u00d7 10\u2079 yr, respectively. These results place constraints on possible origins for the glass and feldspar.", "doi": "10.1016/s0012-821x(68)80052-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1968", "volume": "5", "pages": "273-281" }, { "id": "authors:90gvc-dgr43", "collection": "authors", "collection_id": "90gvc-dgr43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220610-395899300", "type": "article", "title": "Initial strontium isotopic abundances and the resolution of small time differences in the formation of planetary objects", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "It is shown that differences in the \u2078\u2077Sr/\u2078\u2076Sr ratio corresponding to about 10\u207b\u00b2 % are clearly resolvable using improved instrumental techniques. Several basaltic achondrites having a total spread of 0.2% in \u2078\u2077Sr/\u2078\u2076Sr were studied and appear to define an identical initial \u2078\u2077Sr/\u2078\u2076Sr abundance corresponding to 0.698976 \u00b1 0.000055 (maximum uncertainties). These samples are found to lie on a well defined isochron with a slope of 0.0629 \u2213 0.0037 and an age 4.39 \u2213 0.26 \u00d7 10\u2079 yr. for \u03bb = 1.39 \u00d7 10\u207b\u00b9\u00b9 yr\u207b\u00b9. The maximum deviation of a data point from the best fit line is 6 \u00d7 10\u207b\u00b3 %. This shows that if the samples were derived from material with chondritic or solar Rb/Sr abundance ratios, they were formed within a time period of 4 m.y. or 1.6 m.y. respectively. The application of such measurements to establish a refined early solar system chronology is discussed.", "doi": "10.1016/s0012-821x(68)80066-4", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1968", "volume": "5", "pages": "361-376" }, { "id": "authors:g2ybj-fhm73", "collection": "authors", "collection_id": "g2ybj-fhm73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130220-104628650", "type": "article", "title": "^(87)Rb-^(87)Sr isochron and ^(40)K-^(40)Ar ages of the norton county achondrite", "author": [ { "family_name": "Bogard", "given_name": "D. D.", "clpid": "Bogard-D-D" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Eberhardt", "given_name": "P.", "clpid": "Eberhardt-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Analysis of seven different portions of Norton County yielded Rb/Sr ratios ranging from 0.15 to 2.3 and permitted the determination of an isochron with high precision. The Rb and Sr concentrations were found to be as low as \u223c0.16 ppm. All of the data lie to within their experimental errors on a line in the Sr evolution diagram of slope 0.0654 \u00b1 0.0014, and intercept 0.700 \u00b1 0.002. This determines an age of 4.7 \u00b1 0.1 \u00d7 10^9 yr for \u03bb = 1.39 \u00d7 10^(\u221211) yr^(\u22121). ^(40)K^(40)Ar ages on samples containing 42, 53 and 107 ppm K gave ages of 4.2 \u2013 4.5 \u00d7 10^9 yr which are compatible with the Rb-Sr age. The K appears to be concentrated in alkali feldspar grains of about 5\u201350 microns. The ^(87)Rb^(87)Sr age and primary ^(87)Sr/^(86)Sr value is of sufficient precision to permit the age resolution of meteoritic objects which were formed 0.3 \u00d7 10^9 yr apart. No evidence of element redistribution was found for Norton Country as indicated by the consistency of our Rb-Sr and K-Ar results.", "doi": "10.1016/0012-821X(67)90033-7", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1967-11", "volume": "3", "pages": "179-189" }, { "id": "authors:cbhrg-6gx60", "collection": "authors", "collection_id": "cbhrg-6gx60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141105-164724209", "type": "article", "title": "Dynamics of the motion of a phase change boundary to changes in pressure", "author": [ { "family_name": "O'Connell", "given_name": "Richard J.", "clpid": "O'Connell-R-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Because of the significance of both shallow and deep phase changes to geophysical problems, the dynamical response of a phase change to pressure loading was investigated. It was found that the characteristic behavior of the system may be analyzed in terms of simple parameters of the system by using analytic expressions that apply for the initial part and the final part of the motion of the phase boundary. These expressions are obtained from approximations based on generalizations of Neumann's solution for melting at a constant temperature or from simple physical approximations based on the over-all geometry of the model. The range of applicability of the approximations can be obtained from the approximations themselves. The analytic results compare very favorably with exact numerical solutions. The distribution of heat sources and convective heat transport are shown to be generally of minor importance on the motion of the phase boundary; the effect of convective heat transport can be estimated from the analytic approximation. The important parameters are the latent heat of the phase change and the difference in slope between the Clapeyron curve and the temperature distribution in the earth. In addition, the long-term motion depends primarily on the over-all geometry of the model and the boundary condition at depth. The analytic results indicate the time at which thermal blanketing by sediments becomes important and the effect of the rate of sedimentation on the response of the system; they also define slow and fast sedimentation and secular equilibrium. The effect of isostasy in conjunction with a shallow phase change is shown to be of major importance, and for certain cases the sediment thickness that can accumulate in a sedimentary basin may depend only on the sedimentation rate and not the initial depth of the basin. The analytic results permit a more physical discussion of the problem, since the functional dependence of the solution on the parameters may be seen. In addition, important results for a variety of models can be obtained by relatively simple calculations, without resorting to separate numerical solutions for each model considered.", "doi": "10.1029/RG005i004p00329", "issn": "0096-1043", "publisher": "American Geophysical Union", "publication": "Reviews of Geophysics", "publication_date": "1967-11", "series_number": "4", "volume": "5", "issue": "4", "pages": "329-410" }, { "id": "authors:mzedv-4rr47", "collection": "authors", "collection_id": "mzedv-4rr47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130220-074211638", "type": "article", "title": "^(87)Rb-^(87)Sr ages of silicate inclusions in iron meteorites", "author": [ { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Rb-Sr measurements were made on silicate inclusions extracted from the iron meteorites Toluca, Odessa, Four Corners, Linwood, Pine River, Colomera and Weekeroo Station. Strontium isotopic analyses were made on samples as small as 24 ng. The typical Sr and Rb blanks were 2 \u00d7 10^(\u22129) g and 2 \u00d7 10^(\u221210) g, respectively. In certain cases it was possible to obtain relatively precise isochrons.\nWith the exception of Colomera, all of these samples gave ages compatible with 4.4 to 4.8 \u00d7 10^9 y. The Colomera data scatter widely and do not meet the requirements for defining a reliable age. None of the samples are compatible with an age of 6 \u00d7 10^9 y. The primary strontium observed or estimated for Toluca and Pine River agrees with that obtained from achondrites.\nIt is evident that extensive Rb-Sr isotopic studies may be made on a large number of rather typical iron meteorites.", "doi": "10.1016/0012-821X(67)90180-X", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1967-08", "series_number": "5", "volume": "2", "issue": "5", "pages": "397-408" }, { "id": "authors:f205s-w9b05", "collection": "authors", "collection_id": "f205s-w9b05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130212-075050629", "type": "article", "title": "Evidence for the formation of an iron meteorite at 3.8 \u00d7 10^9 years", "author": [ { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Rb Sr isotopic analyses were made on silicate inclusions from Kodaikanal, a brecciated fine octahedrite. Twelve analyses of different mineral fractions and separate inclusions were made. The silicates in this iron meteorite are highly enriched in alkalis and show ^(87)Sr/^(86)Sr ratios ranging up to 8.8. The samples lie on a well defined isochron on the Sr-Rb evolution diagram and indicate an age of 3.8 \u00b1 0.1 \u00d7 10^9 y and an initial ^(87)Sr/^(86)Sr ratio between 0.69 and 0.73. These data provide unambiguous evidence for the 'formation' of younger solid objects in the solar system in a process which demands extensive chemical differentiation. This is evidence for an intermediate history for some meteoritic objects of a different sort than has been previously observed.", "doi": "10.1016/0012-821X(67)90117-3", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1967-05", "series_number": "3", "volume": "2", "issue": "3", "pages": "137-147" }, { "id": "authors:kwrcm-z4q82", "collection": "authors", "collection_id": "kwrcm-z4q82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-280779900.4", "type": "article", "title": "\u2074\u2070Ar-\u2074\u2070K ages of silicate inclusions in iron meteorites", "author": [ { "family_name": "Bogard", "given_name": "D.", "clpid": "Bogard-D-D" }, { "family_name": "Burnett", "given_name": "D.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Eberhardt", "given_name": "P.", "clpid": "Eberhardt-P" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Analyses of the argon and potassium in silicate inclusions were made on Weekerro Station, Toluca, Four Corners and Kodaikanal. The \u2074\u2070Ar-\u2074\u2070K ratios of all samples except Kodaikanal are compatible with an age of 4.5 \u00b1 0.15 \u00d7 10\u2079 yr. These results are in agreement with the Sr-Rb results obtained previously but not with the so-called \u2074\u2070Ar-\u2074\u2070K ages determined on iron meteorites by other workers. The \u2074\u2070Ar-\u2074\u2070K age of 3.5 \u00b1 0.1 \u00d7 10\u2079 yr on Kodaikanal is consistent with the \u2078\u2077Sr-\u2078\u2077Rb age of 3.8 \u00b1 0.1 \u00d7 10\u2079 yr. Estimates of the U + Th content of the silicate inclusions were made based on the \u2074He contents. \n\nKodaikanal was found to have a very young exposure age for an iron meteorite (\u2a8540 m.y) based on upper limits to the cosmogenic He, Ne and Ar in the metal phase.", "doi": "10.1016/0012-821x(67)90048-9", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "1967-01", "volume": "3", "pages": "275-283" }, { "id": "authors:76x3h-f8291", "collection": "authors", "collection_id": "76x3h-f8291", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141110-095505555", "type": "article", "title": "Systematics in the Pb^(208)-Th^(232), Pb^(207)-U^(235), and Pb^(206)-U^(238) Systems", "author": [ { "family_name": "Steiger", "given_name": "Rudolf H.", "clpid": "Steiger-R-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "In a study of cogenetic zircons it was found that the measured Pb^(208)/Th^(232) and Pb^(207)/U^(235) ratios formed a linear array in the corresponding coupled Pb-U-Th evolution diagram, which has an upper intersection on the concordia curve at the same time point as that determined by the Pb^(206)/U^(238), Pb^(207)/U^(235) array. Although the U-Pb data lie in the accessible region for nonfractionating daughter loss, the Th-Pb results lie outside the corresponding region. The zircon concentrates analyzed were shown to be multiphase assemblages with variable U and Th contents and variable Th/U ratios, even within single crystals. The zircons contain local domains of high radioactivity which appear to be highly discordant. A relationship between discordance and the average concentration of U and Th in a sample is given. The degree of discordance increases with the concentration of U and Th and with the increasing Th/U ratio, causing preferential loss of Pb^(208) and the departure from the region accessible to a single phase without fractionation. The theoretical aspects of the (equation image) diagram from the viewpoint of single-phase and multiphase assemblages are discussed, and it is shown that the variability of the Th/U ratio is of fundamental importance in understanding the evolution of the Th-U-Pb system. The existence of these systematics in nature may provide an additional independent dating system and a further means of studying transport from natural systems.", "doi": "10.1029/JZ071i024p06065", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1966-12-15", "series_number": "24", "volume": "71", "issue": "24", "pages": "6065-6090" }, { "id": "authors:pg95e-jva48", "collection": "authors", "collection_id": "pg95e-jva48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200505-085716506", "type": "article", "title": "ACE Report: Quality Ratings in the Academic Marketplace", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "In Wolfle's editorial (27 May, p. 1189) about the report, \"An Assessment of Quality in Graduate Education,\" published by the American Council on Education, the conclusion is reached that \"the ratings are highly dependable statements of the quality of graduate departments, as judged by informed peers.\" It is further concluded that \"the tabulated ratings can be used as the quality equivalent of a social register.\" In his article (News and Comment, p. 1226), John Walsh refers to this report \"as a new Consumer's Guide to the academic marketplace.\" As a member of an institution which has come out relatively unscathed by the report, I feel that I can comment without personal bitterness on the inequities of the original study, some of its failures and pernicious effects, and on the further failure of your editorial and article to evaluate the meaning of such a report.", "doi": "10.1126/science.153.3736.575", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1966-08-05", "series_number": "3736", "volume": "153", "issue": "3736", "pages": "575" }, { "id": "authors:2b76y-55b82", "collection": "authors", "collection_id": "2b76y-55b82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-915035900.2", "type": "article", "title": "Rubidium-Strontium-Messungen an Gl\u00e4sern vom Bosumtwi-Krater und an Elfenbeink\u00fcsten-Tektiten", "author": [ { "family_name": "Lippolt", "given_name": "Hans J.", "clpid": "Lippolt-Hans-J" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A Rb-Sr isotopic study of 5 glasses from the Bosumtwi crater in Ghana and of three Ivory Coast tektites was made. The Sr\u2078\u2077/Sr\u2078\u2076 ratios for the glasses lie between 0.716 and 0.734 and those for the tektites between 0.721 and 0.726. The ratios of Rb/Sr are between 0.196 and 0.328 for the crater glasses and between 0.197 and 0.287 for the tektites. The Ivory Coast tektites lie in a region of the Sr evolution diagram which is distinctly lower than for the other tektite groups. The Bosumtwi glasses define an approximately linear array on the Sr evolution diagram which contains the Ivory Coast tektite points. These results show that the IC tektites are distinctive from other tektite occurences and suggest that the glasses and the tektites may represent fusion products of similar material.", "doi": "10.1515/zna-1966-0306", "issn": "1865-7109", "publisher": "de Gruyter", "publication": "Zeitschrift f\u00fcr Naturforschung A", "publication_date": "1966-03", "series_number": "3", "volume": "21", "issue": "3", "pages": "226-231" }, { "id": "authors:5mt9y-19c96", "collection": "authors", "collection_id": "5mt9y-19c96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141107-164204989", "type": "article", "title": "The relative isotopic abundance of K^(40) in terrestrial and meteoritic samples", "author": [ { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Lippolt", "given_name": "H. J.", "clpid": "Lippolt-H-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Fowler, Greenstein, and Hoyle have proposed that the inner solar system was heavily irradiated during its formation. A consequence of this proposal is that sizable differences in meteoritic and terrestrial K^(41)/K^(40) ratios are possible if the fraction of material which was irradiated was different in the two cases. The isotopic composition of potassium was measured by mass spectrometry for nine stone meteorites, silicate from the Vaca Muerta mesosiderite and the Weekeroo Station iron meteorite, and four terrestrial samples. The measured K^(41)/K^(40) ratios were corrected by normalizing the measured K^(39)/K^(41) ratio to the Nier value of 13.47. This normalization procedure approximately cancels out any variations in the isotopic abundance except those due to nuclear processes. Measurements on enriched standards showed that any variations greater than 1% would certainly have been detected, and variations greater than \u00bd% would probably have been detected with replicate analyses. Within these limits, no variations in the K^(40) abundance between the terrestrial and meteoritic samples could be found which could be ascribed to particle irradiation in the early history of the solar system. Small K^(40) enrichments were observed in Norton County, Weekeroo Station, and Vaca Muerta; however, these appear to have been produced during cosmic-ray irradiation by the Ca^(40)(n, p) reaction. The present results set relatively strong limitations on possible mechanisms for the formation of the earth and the meteorites if the idea of a large-scale irradiation in the early history of the solar system is to be retained. Independent of the model of Fowler et al., limits have been placed on any differential uniform irradiation. The implications of the present work on the K-Ar ages of stone and iron meteorites are discussed. The possibility that iron meteorites are considerably older than the solar system as a whole appears unlikely.", "doi": "10.1029/JZ071i004p01249", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1966-02-15", "series_number": "4", "volume": "71", "issue": "4", "pages": "1249-1269" }, { "id": "authors:kthgf-rw735", "collection": "authors", "collection_id": "kthgf-rw735", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151208-104231231", "type": "article", "title": "Strontium-Rubidium Age of an Iron Meteorite", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Frondel", "given_name": "C.", "clpid": "Frondel-C" } ], "abstract": "The isotopic compositions and concentrations of rubidium and strontium were determined in silicate nodules contained in Weekeroo Station meteorite, a brecciated coarse octahedrite. The strontium had a Sr^(87):Sr^(86) range from 0.729 to 0.768, showing considerable enrichment in Sr^(87) in comparison with achondrites. Data for six samples of nodules lie on a straight line on the Sr-Rb evolution diagram, with an initial Sr^(87):Sr^(86) ratio of 0.696 to 0.702; the slope is 0.0674, corresponding to an age of 4.7 x 10^9 years for \u03bb = 1.39 x 10^(-11) year^(-1). These data agree with the previously assigned ages for the formation of stony meteorites and the earth; they support the conclusion that the major period of chemical and physical differentiation in the solar system occurred in a narrow interval at about this time. This result disagrees with the Ar^(40)-K^(40) ages of 5 to 13 x 10^9 years determined from other iron meteorites. A wide variety of isotopic-age investigations now seem experimentally feasible on iron meteorites that contain silicates.", "doi": "10.1126/science.150.3705.1814", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1965-12-31", "series_number": "3705", "volume": "150", "issue": "3705", "pages": "1814-1818" }, { "id": "authors:hf98v-fey73", "collection": "authors", "collection_id": "hf98v-fey73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221122-327698300.1", "type": "article", "title": "Age Determinations in the Precambrian of Arizona and Nevada", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Lanphere", "given_name": "M. A.", "clpid": "Lanphere-M-A" } ], "abstract": "Sr\u2078\u2077-Rb\u2078\u2077 and Ar\u2074\u2070-K\u2074\u2070 ages were determined from samples of Precambrian rocks from western Arizona, southern Nevada, and southwestern Utah. These and similar ages measured by other workers from rocks of a geographically contiguous region of California, Nevada, and Arizona and from widely distributed localities in Utah, Arizona, and Sonora, Mexico, indicate that the older Precambrian basement throughout the far southwestern United States was involved in an episode of metamorphism and plutonism 1600\u20131800 m.y. ago. Well-documented ages of 1350\u20131450 m.y. are not as extensive as previously thought. An isolated pluton that has an age of 1060 m.y. intruded the older metamorphic terrane in southern Nevada, which indicates that some of the plutonism in the far southwestern United States is later Precambrian.", "doi": "10.1130/0016-7606(1965)76[735:aditpo]2.0.co;2", "issn": "0016-7606", "publisher": "Geological Society of America", "publication": "Geological Society of America Bulletin", "publication_date": "1965-07-01", "series_number": "7", "volume": "76", "issue": "7", "pages": "735-758" }, { "id": "authors:dm8wd-dqh54", "collection": "authors", "collection_id": "dm8wd-dqh54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230105-10568700.4", "type": "article", "title": "Helium, neon, argon, krypton and xenon in gas emanations from Yellowstone and Lassen volcanic National Parks", "author": [ { "family_name": "Mazor", "given_name": "E.", "clpid": "Mazor-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The abundance of helium, neon, argon, krypton and xenon were measured in gas emanations from thermal springs in Yellowstone National Park, Wyoming and Lassen National Park, California. The determinations were made using an isotope dilution procedure. The isotopic composition of argon and the relative abundances of argon, neon, krypton and xenon indicate that these gases originated from the atmosphere through dissolution in ground water. Helium was found to be in marked excess, which is attributed to the contribution of juvenile helium from radioactive decay.", "doi": "10.1016/0016-7037(65)90038-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1965-05", "series_number": "5", "volume": "29", "issue": "5", "pages": "443-454" }, { "id": "authors:w8s41-ntr18", "collection": "authors", "collection_id": "w8s41-ntr18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-565493200.1", "type": "article", "title": "Rare gases in Pacific Ocean water", "author": [ { "family_name": "Mazor", "given_name": "E.", "clpid": "Mazor-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Craig", "given_name": "H.", "clpid": "Craig-Harmon" } ], "abstract": "Concentrations of helium, neon, argon, krypton, and xenon have been measured in some S. Pacific waters. For the latter four gases the observed concentrations are generally consistent to about \u00b110% with concentrations expected for solubility equilibrium with the atmosphere at the observed water temperatures.", "doi": "10.1016/0011-7471(64)90343-2", "issn": "0011-7471", "publisher": "Elsevier", "publication": "Deep Sea Research and Oceanographic Abstracts", "publication_date": "1964-12", "series_number": "6", "volume": "11", "issue": "6", "pages": "929-932" }, { "id": "authors:qc158-qvr29", "collection": "authors", "collection_id": "qc158-qvr29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141110-110243393", "type": "article", "title": "Migration of radiogenic strontium during metamorphism", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Albee", "given_name": "A. L.", "clpid": "Albee-A-L" }, { "family_name": "Lanphere", "given_name": "M. A.", "clpid": "Lanphere-M-A" } ], "abstract": "Study of the concentration and isotopic composition of strontium and rubidium in hornblende diorite dikes and sills of Precambrian age from the Panamint Mountains of California showed that these rock systems were enriched in radiogenic Sr during a late Mesozoic metamorphism. Enrichments in radiogenic Sr were observed for total-rock samples which yielded apparent ages of up to 34,000 m.y., although there is no obvious petrographic evidence for such metasomatic changes. These results indicate that some caution is necessary in interpreting the Sr isotopic composition of rocks in terms of their original source or in assuming that 'total rocks' form closed systems. In general, the initial isotopic Sr composition should be determined, not assumed.", "doi": "10.1029/JZ069i020p04395", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1964-10-15", "series_number": "20", "volume": "69", "issue": "20", "pages": "4395-4401" }, { "id": "authors:7mjxb-12503", "collection": "authors", "collection_id": "7mjxb-12503", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141008-102348997", "type": "article", "title": "Strontium Contamination in Mineral Analyses", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Wen", "given_name": "T.", "clpid": "Wen-T" }, { "family_name": "Aronson", "given_name": "J.", "clpid": "Aronson-J" } ], "abstract": "Significant amounts of strontium contamination occur in analyses of minerals by standard procedures using laboratory glassware. The contamination is much higher than that obtained in blank runs and is associated with the presence of some mineral samples. The contamination can be eliminated by using only teflon and platinum ware during chemical treatment.", "doi": "10.1016/0016-7037(64)90114-0", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1964-04", "series_number": "4", "volume": "28", "issue": "4", "pages": "407-410" }, { "id": "authors:85hvd-0pw26", "collection": "authors", "collection_id": "85hvd-0pw26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151209-100330788", "type": "article", "title": "Relative Contributions of Uranium, Thorium, and Potassium to Heat Production in the Earth", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "MacDonald", "given_name": "Gordon J. F.", "clpid": "MacDonald-G-J-F" }, { "family_name": "Hoyle", "given_name": "F.", "clpid": "Hoyle-Fred" }, { "family_name": "Fowler", "given_name": "William A.", "clpid": "Fowler-W-A" } ], "abstract": "Data from a wide variety of igneous rock types show that the ratio of potassium to uranium is approximately 1 X 10^4. This suggests that the value of K/U \u22481 X 10^4 is characteristic of terrestrial materials and is distinct from the value of 8 X 10^4 found in chondrites. In a model earth with K/U \u2248 10^4, uranium and thorium are the dominant sources of radioactive heat at the present time. This will permit the average terrestrial concentrations of uranium and thorium to be 2 to 4.7 times higher than that observed in chondrites. The resulting models of the terrestrial heat production will be considerably different from those for chondritic heat production because of the longer half-life of U^(238) and Th^(238) compared with K^(40).", "doi": "10.1126/science.143.3605.465", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1964-01-31", "series_number": "3605", "volume": "143", "issue": "3605", "pages": "465-467" }, { "id": "authors:rvfqt-9bx91", "collection": "authors", "collection_id": "rvfqt-9bx91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130903-080825727", "type": "article", "title": "Pb-U-Th evolution models for homogeneous systems with transport", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Various\nauthors have discussed the evolution of lead for\ndifferent models of crust mantle differentiation.\nThe equations which have been used have an implicit\nassumption which can cause them to be in\nserious error, particularly in the case of significant\ntransport of lead from systems with different isotopic\ncomposition.", "issn": "0002-8606", "publisher": "American Geophysical Union", "publication": "Transactions - American Geophysical Union", "publication_date": "1964", "series_number": "1", "volume": "45", "issue": "1", "pages": "111-111" }, { "id": "authors:jq588-xvf31", "collection": "authors", "collection_id": "jq588-xvf31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130821-153248373", "type": "article", "title": "Origin of rare gases in natural gases", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Studies have been made by several laboratories on\nthe isotopic and chemical abundances of He, Ne, Ar,\nKr, and Xe in natural gases from both gas wells and\ngeothermal areas. This work has shown that the rare\ngases consist of a mixture of two distinct components--atmospheric\nand radiogenic. These investigations give\ninformation on the evolution of natural gas accumulations from considering the dissolved atmospheric components\nand the production of He^4, A^(40) and Xe from\nnuclear processes. The importance of solubility phenomena\nin fractionation of these elements may be approached\nby using a simple model. Measurements of\nthe radiogenic gases permit estimates of the rate of\nevolution of the atmosphere.", "issn": "0883-9247", "publisher": "American Association of Petroleum Geologists", "publication": "Bulletin of the American Association of Petroleum Geologists", "publication_date": "1963-12", "series_number": "12", "volume": "47", "issue": "12", "pages": "2076-2077" }, { "id": "authors:wh1p7-avm02", "collection": "authors", "collection_id": "wh1p7-avm02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-211625596", "type": "article", "title": "Age and Composition of a Bounty Islands Granite and Age of a Seychelles Islands Granite", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Craig", "given_name": "H.", "clpid": "Craig-Harmon" }, { "family_name": "Menard", "given_name": "H. W.", "clpid": "Menard-Henry-W-Jr" }, { "family_name": "Engel", "given_name": "A. E. J.", "clpid": "Engel-A-E-J" }, { "family_name": "Engel", "given_name": "Celeste G.", "clpid": "Engel-Celeste-G" } ], "abstract": "Concordant Ar\u2074\u2070-K\u2074\u2070 + Sr\u2078\u2077-Rb\u2078\u2077 ages of 189 m.y. were obtained on biotite from a Bounty Islands granite. Sr\u2078\u2077Rb\u2078\u2077 ages of 638 m.y. and 681 m.y., respectively, were determined on a microcline and a whole rock sample of granite from Mahe Island in the Seychelles Archipelago.", "issn": "0022-1376", "publisher": "University of Chicago Press", "publication": "Journal of Geology", "publication_date": "1963-11", "series_number": "6", "volume": "71", "issue": "6", "pages": "785-789" }, { "id": "authors:mw7j3-ajn81", "collection": "authors", "collection_id": "mw7j3-ajn81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141107-141522887", "type": "article", "title": "Diffusion processes in lead-uranium systems", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The ratio r_\u03bb of radiogenic daughter to residual parent (with decay constant \u03bb) was investigated for a continuous diffusion model for a diffusion coefficient that is an arbitrary function of time. A solution for simultaneous diffusion of both parent and daughter is given in closed form. A theory is also developed that describes the trajectories r\u03bb, r\u03bb\u2032, for paired decay schemes (with decay constants \u03bb and \u03bb\u2032) in the neighborhood of concordia. A wide class of systems is shown to be linear in the r_\u03bb, r_(\u03bb\u2032), diagram when \u222b_0^\u03c4 D(\u03b7) d\u03b7/a^2\u226a1. A radiation damage model is proposed foi the diffusion coefficient that relates D(\u03c4) to the integrated irradiation damage and to the uranium (and thorium) contents. The functional relationship between r_\u03bb and the uranium content is found for three important cases. The model D(\u03c4) = D_(1\u03c4) yields a r_\u03bb, r_(\u03bb\u2032), curve that is very similar to that obtained by Tilton for D = D_0. The slope is somewhat greater and the linear region more extended. The theoretical curves are found to be in reasonable agreement with the existing experimental data, and they fit the existing data at least as well as the constant D model.", "doi": "10.1029/JZ068i016p04823", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1963-08-15", "series_number": "16", "volume": "68", "issue": "16", "pages": "4823-4846" }, { "id": "authors:236sa-gtv62", "collection": "authors", "collection_id": "236sa-gtv62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141110-111959754", "type": "article", "title": "Isotopic variations in terrestrial xenon", "author": [ { "family_name": "Butler", "given_name": "W. A.", "clpid": "Butler-W-A" }, { "family_name": "Jeffrey", "given_name": "P. M.", "clpid": "Jeffrey-P-M" }, { "family_name": "Reynolds", "given_name": "J. H.", "clpid": "Reynolds-J-H" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Isotopic composition and amounts of xenon extracted from eclogite, from old granite, and from CO_2-well gases have been measured. The Xe content of Bavarian eclogite is close to that of the earth (assumed to be outgassed), and this Xe exhibits no isotope anomalies. Xenon from several old granite samples from the central Transvaal contains substantial amounts of fissionogenic Xe from spontaneous fission of U^(238). Isotopic composition of this Xe is in agreement with values reported by Wetherill. The amount of fission Xe in samples from three related granites was very uniform, suggesting that U-Xe dating would be a valuable adjunct to K-Ar dating for old samples. Rough calculations of the U-Xe ages of these granites are in agreement with Rb-Sr ages obtained by Allsopp. Xenon from the CO_2-well gases contained a component from spontaneous fission. The He^4/Xe^(136)_F ratio for this gas is very close to that expected for gas evolved from rocks with a Th/U ratio of 3. In addition, there was a small component of excess Xe^(129), i.e., Xe^(129*)/Xe^(136)_F = 0.92 \u00b1 0.42. Arguments are given to show that this residual Xe^(129) is not due to fast or slow neutron absorption in Te^(126). The excess Xe^(129), if real appears to be due to decay, soon after formation of the earth, of now extinct 17-m.y. I^(129). The effect has far-reaching implications: (1) it implies that the outgassing of the interior of the earth is not complete and that even the decay products of some short-lived activities have not been homogenized; (2) calculations based on an extremely simple model (but one for which results are fairly representative) give a rough indication of the time interval by which the earth postdates the meteorites. It is clear that further experiments with well gases should be made to see whether the effect is reproducible.", "doi": "10.1029/JZ068i010p03283", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1963-05-15", "series_number": "10", "volume": "68", "issue": "10", "pages": "3283-3291" }, { "id": "authors:twrer-rmm03", "collection": "authors", "collection_id": "twrer-rmm03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150728-073827459", "type": "article", "title": "The upper three-phase region in the system SiO_2 - H_2O", "author": [ { "family_name": "Kennedy", "given_name": "G. C.", "clpid": "Kennedy-G-C" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Heard", "given_name": "H. C.", "clpid": "Heard-H-C" }, { "family_name": "Newton", "given_name": "R. C.", "clpid": "Newton-R-C" } ], "abstract": "Melting relations in the system SiO_2 \u2013 H_2O were studied at high temperatures and pressures. A quadruple point for the equilibrium among quartz, tridymite, and 2 fluids was found at 1160\u00b0 C. and 1500 bars. A second quadruple point for tridymite, 2 fluids, and cristobalite is estimated to be near 1470\u00b0 C. and 400 bars. The freezing point of SiO_2 in equilibrium with 2 fluid phases is depressed from 1720\u00b0 C. at one bar to 1130\u00b0 C. at 2000 bars. This freezing point is diminished by only an additional 50\u00b0 C. with a further increase in pressure to 9700 bars. The compositions of coexisting fluids along the upper 3-phase boundary have been determined. A critical end point for the univariant equilibrium curve was found at 1080\u00b0 C. and 9700 bars with a composition of approximately 75 wt% SiO_2 to 25 wt% H_2O.", "doi": "10.2475/ajs.260.7.501", "issn": "0002-9599", "publisher": "American Journal of Science", "publication": "American Journal of Science", "publication_date": "1962-09", "series_number": "7", "volume": "260", "issue": "7", "pages": "501-521" }, { "id": "authors:tdn6g-6y385", "collection": "authors", "collection_id": "tdn6g-6y385", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131211-090759937", "type": "article", "title": "A study of the ages of the Precambrian of Texas", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Wetherill", "given_name": "G. W.", "clpid": "Wetherill-G-W" }, { "family_name": "Silver", "given_name": "L. T.", "clpid": "Silver-L-T" }, { "family_name": "Flawn", "given_name": "P. T.", "clpid": "Flawn-P-T" } ], "abstract": "Age determinations using the Sr^(87)-Rb^(87), Ar^(40)-K^(40), and Pb-U methods were made on samples of muscovite, biotite, amphibole, microcline, and zircon from igneous and metamorphic rocks from the Franklin Mountains, Hueco Mountains, Pump Station Hills, and Carrizo and Van Horn Mountains. In addition ages were determined on a number of basement cores from Texas and New Mexico. The results show that a belt of rocks of varied lithology extending from El Paso to east of the Llano uplift are all of the same age. The general age by the strontium and argon methods is 1000 to 1090 m.y.; and by the lead-uranium method on zircons it is 1150 to 1200 m.y. This event is in the same time band as the 'Grenville' orogeny in Canada and the northeastern United States and possibly should be considered part of the general 'Grenville' episode. All the data now available indicate that the orogenic event at about 1000 to 1200 m.y. is the most widespread and pervasive episode of Precambrian orogeny on the North American continent for which adequate evidence has been presented. At least one and probably two older periods of igneous activity and metamorphism occurring at 1250 and 1400 m.y. are found in the northern regions of the Texas Precambrian basement. No evidence was found for any igneous event between the early Paleozoic and the 1000-m.y. episode.", "doi": "10.1029/JZ067i010p04021", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1962-09", "series_number": "10", "volume": "67", "issue": "10", "pages": "4021-4047" }, { "id": "authors:e6ysm-1jv66", "collection": "authors", "collection_id": "e6ysm-1jv66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141015-110104691", "type": "article", "title": "Determinations d'ages absolus dans le Nord du Massif armoricain", "author": [ { "family_name": "Graindor", "given_name": "Maurice-Jacques", "clpid": "Graindor-M-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Les r\u00e9sultats ici font appara\u00eetre l'existence de plusiers p\u00e9riodes distinctes de formation de granites dans le Nord du Massif amoricain, 545 \u00e0 500 M. A., 410 et 290 M. A.", "issn": "0001-4036", "publisher": "Gauthier-Villars, Paris", "publication": "Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences", "publication_date": "1962-05-21", "series_number": "22", "volume": "254", "issue": "22", "pages": "3875-3877" }, { "id": "authors:bff49-0rm26", "collection": "authors", "collection_id": "bff49-0rm26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141015-103634277", "type": "article", "title": "A Geochronologic Study of a Granite Pluton from the Llano Uplift, Texas", "author": [ { "family_name": "Zartman", "given_name": "R. E.", "clpid": "Zartman-R-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Granite and related pegmatite and aplite from several localities within a pluton from the Llano uplift, Texas, are being studied geochronologically. Biotite, muscovite, hornblende, microcline, plagioclase, quartz, apatite, and fluorite have been analyzed by refined chemical and mass spectrometric methods in order to determine the consistency in ages between various minerals and between different localities within an individual pluton. Field and petrologic evidence suggests that this intrusive has had a simple history of emplacement and no later metamorphism. Quadruplicate analyses on a master biotite yield K-Ar and\nRb-Sr ages reproducible to 1 per cent. In most cases K-Ar determinations on biotites, muscovites, and hornblendes and Rb-Sr determinations on biotites, muscovites, and microclines give ages which fall within a 5 per cent spread. A half-life of 1.307 X 10^9 years and a branching ratio of 0.124 are used to calculate the K-Ar ages, and Rb-Sr ages are calculated with a half-life of 50 X 10^9 years. The average age of the pluton thus determined is 1060\nm.y. K-Ar determinations on microclines give ages which are 5 to 15 per cent lower. One plagioclase from the granite gives a K-Ar age of 920 m.y. Two suites of biotites, one from pegmatites and one from a border facies of the granite, give anomalously low Rb-Sr ages. The pegmatitic biotite also has a somewhat low K-Ar age; however, the biotite from the granite gives a normal age by this method,\nas do coexisting microclines from both these rocks by the Rb-Sr method. Geologic evidence suggests that meteoric or hydrothermal fluids may have been responsible for this age discrepancy. Ages determined on a gneiss, a pegmatite cutting the gneiss, and a granite porphyry all give results approximately equal to those of the granite. No evidence\nof a significantly older basement rock or a younger igneous or metamorphic event in the area has been obtained to date.", "doi": "10.1029/JZ067i004p01627", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1962-04", "series_number": "4", "volume": "67", "issue": "4", "pages": "1664" }, { "id": "authors:9dc0v-0rf35", "collection": "authors", "collection_id": "9dc0v-0rf35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141015-101646944", "type": "article", "title": "Age measurements of the Precambrian rocks of the Death Valley-Mojave Desert region, California", "author": [ { "family_name": "Lanphere", "given_name": "Marvin", "clpid": "Lanphere-M-A" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Ar^(40)-K^(40) and Sr^(87)-R^(87) age measurements in the eastern Mojave Desert indicate two separate early Precambrian events (see table). The older event is approximately 1650 m.y. old and is evidenced by pegmatites and associated metamorphic rocks in the Mountain Pass district. Ages were measured on coarse muscovite and potassium feldspar, MP-1 and MP-2, from a pegmatite which cuts across biotite-bearing gneisses, MP-7 and MP-9. These data confirm the widespread areal extent of this ancient metamorphic terrane. Ages of biotite, MP-21 and MP-22, from the shonkinite, which intrudes the metamorphic rocks, at Mountain Pass and the Rb-Sr age of potassium feldspar, MM-3f, from granite in the Marble Mountains suggest a period of igneous intrusion in the 1350 to 1410 m.y. interval. Metamorphic rocks in the central Panamint Range have been mapped and are shown to be stratigraphically early Precambrian. K-Ar ages of approximately 80 m.y. have been measured on biotite, muscovite, and hornblende. The minerals show no memory of\na Precambrian age. The early Precambrian rocks show no evidence of a younger period of metamorphism. However, a younger metamorphism can be recognized in the overlying Precambrian(?) Noonday dolomite and Johnnie formation.", "doi": "10.1029/JZ067i004p01627", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1962", "series_number": "4", "volume": "67", "issue": "4", "pages": "1645" }, { "id": "authors:wkvse-9jy19", "collection": "authors", "collection_id": "wkvse-9jy19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141015-091315325", "type": "article", "title": "Crustal history and the pre-cambrian time scale", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Many bodies of data are examined in this monograph; the complexity\nof this data is evident, and the difficulties of resolving events is very great.\nThe crustal history of the earth is complex, and our understanding of the\nmechanisms of both tectonism of the emplacement and mobilization of rocks\nis poor. Nevertheless, since the ultimate goal of the science is an understanding\nof crustal history, it is important to speculate and consider various ideas\nthat treat of these processes.", "doi": "10.1111/j.1749-6632.1961.tb35525.x", "issn": "0077-8923", "publisher": "New York Academy of Sciences", "publication": "Annals of the New York Academy of Sciences", "publication_date": "1961-04", "volume": "91", "pages": "583-594" }, { "id": "authors:zgjfa-tkc51", "collection": "authors", "collection_id": "zgjfa-tkc51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141110-114319192", "type": "article", "title": "Helium, argon, and carbon in some natural gases", "author": [ { "family_name": "Zartman", "given_name": "R. E.", "clpid": "Zartman-R-E" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Reynolds", "given_name": "J. H.", "clpid": "Reynolds-J-H" } ], "abstract": "Thirty-nine samples of natural gases representing varied chemical compositions and geological occurrences were analyzed for their helium, radiogenic argon, and atmospheric argon contents. The total range in the (He/A)_(rad) ratio was found to be 1.6 to 130 with most samples having values between 6 and 25. This range of values is essentially equal to the production ratio from the uranium, thorium, and potassium in average igneous rocks and a wide variety of sediments. This indicates that all of these natural gases have obtained their radiogenic gases from rather average rock types. This is true in spite of the fact that the gases range in helium content from 37 to 62,000 ppm. \n\nA theoretical discussion of the origin of helium and argon in natural gases is given. It can be shown from the ratio of nitrogen to atmospheric argon that most of the nitrogen in these gases cannot come from the entrapment of air. From a consideration of the concentration of atmospheric argon in natural gases it is possible to estimate the proportion of gaseous and aqueous phases assuming diffusive equilibrium. \n\nThe isotopic composition of the carbon in the methane of these gases was found to be very light. It was shown that for coexisting CH_4-CO_2 pairs the carbon dioxide was always isotopically heavier.", "doi": "10.1029/JZ066i001p00277", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research", "publication_date": "1961-01", "series_number": "1", "volume": "66", "issue": "1", "pages": "277-306" }, { "id": "authors:86vwm-b0955", "collection": "authors", "collection_id": "86vwm-b0955", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WASprl60", "type": "article", "title": "Duration of Nucleosynthesis", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Fowler", "given_name": "William A.", "clpid": "Fowler-W-A" }, { "family_name": "Hoyle", "given_name": "F.", "clpid": "Hoyle-Fred" } ], "abstract": "In a recent Letter on a determination of the age of the elements, Reynolds[1] reported the important discovery of isotopically anomalous xenon in the stony meteorite Richarton. The isotopes which appear to occur in significant excess over atmospheric xenon are Xe128, Xe129, Xe130, and Xe131, with the Xe129 dominant by an order of magnitude. At present it does not appear possible to explain all of these data by any single mechanism. Because of the existence of these four anomalies, it is difficult to conclude that the Xe129 excess is simply the product of I129 decay.", "doi": "10.1103/PhysRevLett.4.112", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "1960-02-01", "series_number": "3", "volume": "4", "issue": "3", "pages": "112-114" }, { "id": "authors:w121h-ffw15", "collection": "authors", "collection_id": "w121h-ffw15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221129-180010170", "type": "article", "title": "Ages in the Precambrian Terrane of Death Valley, California", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Wetherill", "given_name": "G. W.", "clpid": "Wetherill-George-W" }, { "family_name": "Wright", "given_name": "Lauren A.", "clpid": "Wright-Lauren-A" } ], "abstract": "The Sr\u2078\u2077-Rb\u2078\u2077 and A\u2074\u2070-A\u2074\u2070 ages of minerals contained in three pre-Pahrump igneous and metamorphic rocks were determined. The results indicate an event at 1.7 X 10\u2079 years. Since the rock types investigated have distinct continental affinities, it is concluded that continental growth has not occurred in this area since that time. Concordant ages obtained on two rocks gave results in disagreement with the observed field relationships.", "issn": "0022-1376", "publisher": "University of Chicago Press", "publication": "Journal of Geology", "publication_date": "1959-11", "series_number": "6", "volume": "67", "issue": "6", "pages": "702-708" }, { "id": "authors:qvcx4-08s17", "collection": "authors", "collection_id": "qvcx4-08s17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221213-626467500.4", "type": "article", "title": "The A\u00b3\u00b3 content of two potassium minerals", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Bieri", "given_name": "R.", "clpid": "Bieri-R" } ], "abstract": "Gerling, Levskii and Afanasyeva (1956) have presented evidence indicating the presence of A\u00b3\u2078 in potassium micas and feldspars. Their data indicate that the A\u00b3\u2078/K ratio is constant for potassium minerals of a given age and that this ratio increases regularly with the age of the sample. They state that the observed data may be explained by assuming that K\u00b3\u2078 occurs in nature with an abundance of K\u00b3\u2078/K = 1 x 10\u207b\u00b9\u2070 and that the K\u00b3\u2078 has along lived isomeric state (K\u00b3\u2078 ->- A\u00b3\u2078 + \u03b2+; t1/2 = 7\u00b770 x 10\u2078 yr). The only known isomers of K\u00b3\u2078 have half lives of the order of minutes. Because of the implications of their conclusion, we have investigated the A\u00b3\u2078 content of two minerals--MMI, a muscovite mica from Dickinson Co., Michigan, U.S.A., and N-45, a lepidolite from Bikita Quarry, So. Rhodesia.", "doi": "10.1016/0016-7037(58)90020-6", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1958-11", "series_number": "1-2", "volume": "15", "issue": "1-2", "pages": "157-159" }, { "id": "authors:z7dgp-qdk61", "collection": "authors", "collection_id": "z7dgp-qdk61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221114-172446482", "type": "article", "title": "The Solubility of Quartz in Supercritical Water as a Function of Pressure", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "The solubility of SiO\u2082 in supercritical H\u2082O as a function of pressure is discussed a dilute solutionlin a regular lattice gas. It is shown that the reaction SiO\u2082 + 2H\u2082O = Si(OH)\u2084 is compatible with the experimental data from 0.3 to 2 kilobars pressure. It is shown that a simple power law, x = f(T)p\u207f should not in general obtain for solutions in the neighborhood of the critical point. An expression is given for the fugacity of solutes as a function of pressure in terms of certain structural parameters and the equation of state of the solvent.", "issn": "0022-1376", "publisher": "University of Chicago Press", "publication": "Journal of Geology", "publication_date": "1958-09", "series_number": "5", "volume": "66", "issue": "5", "pages": "559-578" }, { "id": "authors:3f9rp-76c07", "collection": "authors", "collection_id": "3f9rp-76c07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-34759700.2", "type": "article", "title": "The solubility of quartz at high temperatures and pressures; discussion", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Wood", "given_name": "John A.", "clpid": "Wood-John-A" } ], "abstract": "In a recent paper by J. A. Wood, Jr. (this Journal, v. 256, p. 40, 1958) a theoretical discussion of the experimental data on the solubility of quartz in water was presented.", "doi": "10.2475/ajs.256.6.438", "issn": "0002-9599", "publisher": "American Journal of Science", "publication": "American Journal of Science", "publication_date": "1958-06", "series_number": "6", "volume": "256", "issue": "6", "pages": "438" }, { "id": "authors:tcgbs-dpy06", "collection": "authors", "collection_id": "tcgbs-dpy06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141015-084729348", "type": "article", "title": "The solubility of quartz at high temperatures and pressures", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Wood", "given_name": "John A., Jr", "clpid": "Wood-J-A-Jr" } ], "abstract": "In a recent paper by J. A. Wood, Jr. (this Journal, v. 256, p. 40, 1958) a theoretical discussion of the experimental data on the solubility of quartz in water was presented.", "doi": "10.2475/ajs.256.6.438", "issn": "0002-9599", "publisher": "American Journal of Science", "publication": "American Journal of Science", "publication_date": "1958-06", "series_number": "6", "volume": "256", "issue": "6", "pages": "438" }, { "id": "authors:d2gyk-2v517", "collection": "authors", "collection_id": "d2gyk-2v517", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200505-085157720", "type": "article", "title": "A\u2074\u2070/K\u2074\u2070 Ages of Micas and Feldspars from the Glenarm Series near Baltimore, Maryland", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Pettijohn", "given_name": "F. J.", "clpid": "Pettijohn-F-J" }, { "family_name": "Lipson", "given_name": "J.", "clpid": "Lipson-J" } ], "abstract": "The inner zone of the central Appalachian Mountains is a belt of metamorphic and plutonic rocks which crop out in the Blue Ridge province and underlie most of the Piedmont province. In southeastern Pennsylvania and adjacent parts of Maryland, the oldest rock is the Baltimore gneiss, which forms domical uplifts surrounded and overlain by the Glenarm series. This series consists of a basal quartzite (Setters) overlain by a marble (Cockeysville) and a thick series of mica schists (Wissahickon and Peters Creek) of sedimentary origin but including in some places altered volcanics (1). The Glenarm group is locally cut by pegmatite, granite, and other plutonic rocks.", "doi": "10.1126/science.126.3269.355", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1957-08-23", "series_number": "3269", "volume": "126", "issue": "3269", "pages": "355-357" }, { "id": "authors:7frgm-9fa53", "collection": "authors", "collection_id": "7frgm-9fa53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130530-132414545", "type": "article", "title": "The Effects of H_2O in Silicate Systems", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "A theoretical discussion of the role of water in simple silicate melts is presented. It is shown that to a good\napproximation in the region T \u2248 1,000\u00b0 C., P < 2.3 X 10^3 bars, both the solubility of water in an NaAlSi_3O_8\nmelt and the depression of the freezing point of albite from such a melt are grossly governed by a perfect-solution\nlaw. A more detailed theory is presented in which the entropy of mixing for an ideal mixture of the\nbridging oxygen atoms of the silicate with the oxygen atoms of the water is calculated. This model is shown\nto be in good agreement with the observed phase diagram of the NaAlSi_3O_8-H_2O system.", "issn": "0022-1376", "publisher": "University of Chicago Press", "publication": "Journal of Geology", "publication_date": "1957-01", "series_number": "1", "volume": "65", "issue": "1", "pages": "15-23" }, { "id": "authors:pf77r-a3y08", "collection": "authors", "collection_id": "pf77r-a3y08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221111-678968900.5", "type": "article", "title": "A\u2074\u2070-K\u2074\u2070 dating of igneous rocks and sediments", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hayden", "given_name": "R. J.", "clpid": "Hayden-R-J" }, { "family_name": "Jensen", "given_name": "Kenneth J.", "clpid": "Jensen-Kenneth-J" } ], "abstract": "The discrepancy in A\u2074\u2070/K\u2074\u2070 ratios between micas and feldspars reported by Wetherill has been confirmed. Assuming no A\u2074\u2070 to be inherited by potassium minerals, a branching ratio of 0.113 is calculated from dated mica samples. This implies that the micas investigated have retained 85% or more of their argon. The branching ratio of R = 0.085 is interpreted to be an empirical calibration constant which corrects for argon loss. The A\u2074\u2070/K\u2074\u2070\nratios in four authigenic minerals have been determined and the ages are found to be in reasonable agreement with the times assigned to the geologic periods by Holmes.", "doi": "10.1016/0016-7037(56)90041-2", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1956-09", "series_number": "3", "volume": "10", "issue": "3", "pages": "153-165" }, { "id": "authors:ehjha-k9806", "collection": "authors", "collection_id": "ehjha-k9806", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WETpr56", "type": "article", "title": "Decay Constants of K40 as Determined by the Radiogenic Argon Content of Potassium Minerals", "author": [ { "family_name": "Wetherill", "given_name": "G. W.", "clpid": "Wetherill-G-W" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Aldrich", "given_name": "L. T.", "clpid": "Aldrich-L-T" }, { "family_name": "Tilton", "given_name": "G. R.", "clpid": "Tilton-G-R" } ], "abstract": "It is shown that the potassium-argon age of young minerals depends almost linearly on the decay constant for electron capture in K40 and is very insensitive to the decay constant for beta emission. This fact permits calculation of \u03bbe by comparing the concordant uranium-lead age of cogenetic uraninite with A40/K40 ratios found in young samples of mica. It is found that \u03bbe=(0.557\u00b10.026)\u00d710^-10 yr^-1. Similar comparisons with older mica samples indicate that satisfactory agreement with the uraninite ages are obtained by use of this value of \u03bbe together with \u03bb\u03b2=(0.472\u00b10.05)\u00d710^-9 yr^-1. It is concluded that there is no conflict between the decay constants inferred by this geological method and those found by direct counting experiments.", "doi": "10.1103/PhysRev.103.987", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1956-08-15", "series_number": "4", "volume": "103", "issue": "4", "pages": "987-989" }, { "id": "authors:1p0a8-z1d32", "collection": "authors", "collection_id": "1p0a8-z1d32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221129-216858600.1", "type": "article", "title": "Time Interval between Nucleogenesis and the Formation of Meteorites", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hayden", "given_name": "R. J.", "clpid": "Hayden-R-J" } ], "abstract": "While determining the radiogenic argon-40 content of the Beardsley chondritic meteorite, a mass spectrometric search for xenon-129 produced by decay of iodine-129 was made. The total amount of xenon which was observed was 5 \u00d7 10\u207b\u2079 c.c. (s.t.p.) from a 29.86-gm. meteorite sample. Within the limits of experimental error, this xenon had a normal isotopic composition. The ratio of xenon to argon-36 was in essential agreement with that found in air, indicating that this xenon was due to atmospheric contamination. Since a 30 per cent increase in the abundance of xenon-129 over that observed in normal xenon would have been observable, this indicates that radiogenic xenon-129 was present in this meteorite to less than 1.3 \u00d7 10\u207b\u00b9\u00b9 c.c. (s.t.p.)/gm. H. E. Suess and M. G. Inghram (personal communication) have suggested that if the meteorites had been formed soon after the formation of the elements, they would contain an excess of xenon-129 due to decay of iodine-129.", "doi": "10.1038/176130b0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1955-07-16", "series_number": "4472", "volume": "176", "issue": "4472", "pages": "130-131" }, { "id": "authors:pg8pz-rs971", "collection": "authors", "collection_id": "pg8pz-rs971", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221121-941303200.1", "type": "article", "title": "Time Interval between Nucleogenesis and the Formation of Meteorites", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hayden", "given_name": "R. J.", "clpid": "Hayden-R-J" } ], "abstract": "While determining the radiogenic argon-40 content of the Beardsley chondritic meteorite, a mass spectrometric search for xenon-129 produced by decay of iodine-129 was made. The total amount of xenon which was observed was 5 \u00d7 10\u207b\u2079 c.c. (s.t.p.) from a 29.86-gm. meteorite sample. Within the limits of experimental error, this xenon had a normal isotopic composition. The ratio of xenon to argon-36 was in essential agreement with that found in air, indicating that this xenon was due to atmospheric contamination. Since a 30 per cent increase in the abundance of xenon-129 over that observed in normal xenon would have been observable, this indicates that radiogenic xenon-129 was present in this meteorite to less than 1.3 \u00d7 10\u207b\u00b9\u00b9 c.c. (s.t.p.)/gm. H. E. Suess and M. G. Inghram (personal communication) have suggested that if the meteorites had been formed soon after the formation of the elements, they would contain an excess of xenon-129 due to decay of iodine-129.", "doi": "10.1038/176130b0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1955-07", "series_number": "4472", "volume": "176", "issue": "4472", "pages": "130-131" }, { "id": "authors:m23nx-0m234", "collection": "authors", "collection_id": "m23nx-0m234", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221111-678968900.3", "type": "article", "title": "A\u2074\u2070-K\u2074\u2070 dating", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hayden", "given_name": "R. J.", "clpid": "Hayden-R-J" } ], "abstract": "The A\u2074\u2070/K\u2074\u2070 ratios and the Pb-U ages of various co-existing potassium feldspars and uraninites were determined. It was found that with a branching ratio \u03bbe\u03bb\u03b2 = 0.085 \u00b1 0.005 and a decay constant \u03bb = 0.55 x 10\u207b\u2079, the A\u2074\u2070/K\u2074\u2070 ages could be brought into agreement with the Pb-U ages for samples ranging from 260 to 1860 m.y. Ko evidence was found for the loss of argon by diffusion from potassium feldspars.", "doi": "10.1016/0016-7037(55)90045-4", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1955-02", "series_number": "1-2", "volume": "7", "issue": "1-2", "pages": "51-60" }, { "id": "authors:etn7r-syw28", "collection": "authors", "collection_id": "etn7r-syw28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WASpr55", "type": "article", "title": "Age of Meteorites by the A40 \u2014 K40 Method", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hayden", "given_name": "R. J.", "clpid": "Hayden-R-J" } ], "abstract": "The ages of two stony meteorites were determined by measuring the A40/K40 ratio using an isotopic dilution technique. With a branching ratio \u03bbe/\u03bb\u03b2=0.085 and a decay constant \u03bb=0.55\u00d710^-9 yr^-1, the ages obtained were (4.82\u00b10.20)\u00d710^9 and (4.58\u00b10.20)\u00d710^9 years.", "doi": "10.1103/PhysRev.97.86", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1955-01-01", "series_number": "1", "volume": "97", "issue": "1", "pages": "86-87" }, { "id": "authors:r705x-2sw29", "collection": "authors", "collection_id": "r705x-2sw29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WASpr54", "type": "article", "title": "The Branching Ratio of K40", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Hayden", "given_name": "R. J.", "clpid": "Hayden-R-J" } ], "abstract": "Attempts to measure the branching ratio of K40 by determining the A40/K40 ratio in potassium minerals of supposedly known age were recently reported by Russell, Shilibeer, Farquhar, and Mousuf [1] and by Mousuf [2]. These results indicated a branching ratio of 0.06\u00b10.006. Other recent determinations of \u03bbK/\u03bb\u03b2 by counting methods [3] and by determining the A40/Ca40 ratio in geologically old potassium salts [4] are in agreement with a value of 0.13.", "doi": "10.1103/PhysRev.93.645", "issn": "0031-899X", "publisher": "Physical Review", "publication": "Physical Review", "publication_date": "1954-02-01", "series_number": "3", "volume": "93", "issue": "3", "pages": "645" } ]