[ { "id": "authors:7wv5p-z6591", "collection": "authors", "collection_id": "7wv5p-z6591", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WASaipcp08", "type": "book_section", "title": "Magnetic Bubbles and Extramixing in Stars", "book_title": "Torino Workshop on Evolution and Nucleosynthesis in AGB Stars, 9th, and the Perugio Workshop on Nuclear Astrophysics, 2nd, 21\u201327 October 2007, Italy", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Busso", "given_name": "Maurizio", "clpid": "Busso-M" } ], "contributor": [ { "family_name": "Guandalini", "given_name": "Roald" }, { "family_name": "Palmerini", "given_name": "Sara" }, { "family_name": "Busso", "given_name": "Maurizio" } ], "abstract": "The possible role of magnetic flux tubes in transporting matter from near the H shell through the radiative zone and into the convective envelope is explored. It is shown that the required rates of mass transport necessary to provide nuclear processed material to the envelope can be achieved if large magnetic fields are present just above the H shell in AGB and RGB stars. The required fields in this zone reach 5 MG for the AGB case and 0.5-0.05 MG for the RGB case. It may thus be possible that magnetic bouyancy play a major role in providing the extra mixing needed for these stars.", "doi": "10.1063/1.2916978", "isbn": "978-0-7354-0520-2", "publisher": "American Institute of Physics", "place_of_publication": "Melville, NY", "publication_date": "2008-04-06", "pages": "295-305" }, { "id": "authors:28stx-amx97", "collection": "authors", "collection_id": "28stx-amx97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130312-151946768", "type": "book_section", "title": "Live ^(107)Pd in the Early Solar System and Implications for Planetary Evolution", "book_title": "Earth processes : reading the isotopic code", "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" } ], "contributor": [ { "family_name": "Basu", "given_name": "Asish", "clpid": "Basu-Asish" }, { "family_name": "Hart", "given_name": "Stanley R.", "clpid": "Hart-Stanley-R" } ], "abstract": "We present a report on the status of ^(107)Pd (\u03c4 = 9.4 \u00d7 10^6 y) in the early solar system and the implications of its presence for protoplanet evolution. Over the last two decades we have carried out an extensive search for the evidence of presently extinct ^(107)Pd in meteorites. From these results we conclude that: 1) ^(107)Ag^* (excess ^(107)Ag) is present in a wide variety of iron and stony-iron meteorites; 2) ^(107)Ag^* is due to the in situ decay of ^(107)Pd in these meteorites; 3) Pd-Ag metal - FeS and metal whole-rock isochrons have been established for a few meteorites; 4) the correlation observed for the total metal isochrons reflects a large variation in normal silver contents (\u223c10^3) with much small variations in Pd contents (factors of 10); 5) there is a wide range in apparent ^(107)Pd/^(108)Pd ratios but many samples show a narrow range (^(107)Pd/^(108)Pd = 1.5 \u2212 2.5 \u00d7 10^(\u22125)); and 6) there are clear cases of complex or pathologic behavior relating to some sulfides and their associated metal phases. The ^(107)Pd-^(107)Ag chronometer reflects the times of major chemical fractionation of Pd and Ag. The scenarios we have postulated to explain the Pd/Ag fractionation include two basically different fractionation processes, namely nebular and planetary. Major fractionation between Pd/Ag can only be achieved during condensation, early accretion, and metal segregation in the solar nebula. The reaction of FeNi with H_2S gas to form FeS and subsequent melting and segregation of FeNi and FeS provides a mechanism for minor (x2) fractionation. For some volatile-depleted meteorites, the processes of condensation of FeNi with isolation from later condensates effectively fractionated Pd/Ag and produced metal with a ^(108)Pd/^(109)Ag \u223c 10^4 \u2013 10^5. For other meteorites not so extensively depleted in volatiles, a smaller degree of effective Pd/Ag fractionation is produced due to the presence of later condensates which, upon planetary melting, produced metal with a ^(108)Pd/^(109)Ag \u223c 50\u2013100. Some fractionation of Pd and Ag occurred by metal-liquid, metal-crystal fractionation during crystallization in planets similar to the models of Scott [1972], Larimer and Anders [1967], and Wai and Wasson [1977]. If the variation in initial ^(107)Pd/^(108)Pd among meteorites indicates a time difference (\u0394T) in the condensation and melting-segregation of planetesimals, the data indicate a total range of \u223c12 my for many meteorites. This tight cluster includes samples of the IIAB, IIIAB, IVA, IVB, and \"anomalous\" groups, as well as mesosiderites and pallasites. However, some meteorites exhibit no evidence of ^(107)Pd. A comparison of ^(107)Pd and ^(53)Mn (\u03c4 = 5.3 \u00d7 10^6 y) chronometers on the same meteorites is possible for a few samples. In one case, ^(107)Pd/^(108)Pd and ^(53)Mn/^(55)Mn from Cape York (group IIIA) show values of \u223c2\u00d710^(\u22125). In other cases, group IIIAB irons show ^(107)Pd/^(108)Pd \u223c2\u00d710^(\u22125), but a much smaller ^(53)Mn/^(55)Mn \u223c1\u00d710^(\u22126). In addition, ^(107)Pd is absent in the metal of the Eagle Station pallasite, but has ^(53)Mn/^(55)Mn = 2.3\u00d710^(\u22126) in the Eagle Station silicates. There appear to be major discrepancies between the ^(107)Pd and ^(53)Mn chronometers. The ^(53)Mn-^(53)Cr system may be affected by the formation or equilibration of the microscopic phases containing Mn and Cr and the FeNi \"host\" during extended cooling and exsolution reaction.", "doi": "10.1029/GM095p0001", "isbn": "9780875900773", "publisher": "American Geophysical Union", "place_of_publication": "Washington, DC", "publication_date": "1996", "pages": "1-20" }, { "id": "authors:vkyb0-f6w74", "collection": "authors", "collection_id": "vkyb0-f6w74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-143656529", "type": "book_section", "title": "A unified model for terrestrial rare gases", "book_title": "Volatiles in the Earth and Solar System", "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" } ], "contributor": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" } ], "abstract": "A steady state upper mantle model for the rare gases has been constructed which explains the available observational data of mantle He, Ne, Ar, and Xe 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. The model incorporates two mantle reservoirs; an undegassed lower mantle (P) and a highly degassed upper mantle (D). Chemical species are transferred into D within mass flows from P at plumes and from the atmosphere by subduction. Rare gases in D are derived from mixing of these inflows with radiogenic nuclides produced in situ. The upper mantle is degassed at mid\u2010ocean ridges and hotspots. Flows of each isotope into D are balanced by flows out of D, so that upper mantle concentrations are in steady state. Rare gases with distinct ^3He/^4He, ^(20)Ne/^(22)Ne, ^(129)Xe/^(130)Xe, and ^(136)Xe/^(130)Xe are stored in P and are transferred into D. In P, isotopic shifts are due to decay of U\u2010 and Th\u2010 decay series nuclides, ^(40)K, ^(129)I, and ^(244)Pu over 4.5 Ga. Radiogenic ^(136)Xe in P is dominantly from ^(244)Pu. In the well\u2010outgassed D reservoir, additional isotopic shifts are due to decay of U\u2010 and Th\u2010 series nuclides and ^(40)K over a residence time of \u223c1.4 Ga. Since ^4He, ^(21)Ne, ^(40)Ar, and ^(136)Xe are produced in proportions fixed by nuclear parameters, the resulting isotopic shifts are correlated. The model predicts that the shift in ^(21)Ne/^(22)Ne in D relative to that in P is the same as that for ^4He/^3He in the respective mantle reservoirs. This is compatible with the available data for MORB and hotspots. The minimum ^(40)Ar/^(36)Ar, ^(129)Xe/^(130)Xe, and ^(136)Xe/^(130)Xe ratios in P are found to be substantially greater than the atmospheric ratios. The range in Ne, Ar, and Xe isotopes measured in MORB are interpreted as reflecting contamination of mantle rare gases by variable proportions of atmospheric rare gases. Subduction is not significant for He and Ne, but may account for a substantial fraction of Ar and Xe in D. The rare gas relative abundances in P are different than that of the atmosphere and are consistent with possible early solar system reservoirs as found in meteorites.\nThe ^3He/^(22)Ne and ^(20)Ne/^(36)Ar ratios of P are within the range for meteorites with 'solar' Ne isotope compositions. The ^(130)Xe/^(36)Ar ratio of the lower mantle is greater than that of the atmosphere and may be as high as the ratio found for meteoritic 'planetary' rare gases. In the model, atmospheric rare gas isotope compositions are distinct from those of the mantle. If the Earth originally had uniform concentrations of rare gases, degassing of the upper mantle would have provided only a small proportion of the nonradiogenic rare gases presently in the atmosphere. The remainder was derived from late\u2010accreted material with higher concentrations of rare gases. However, radiogenic ^(129)Xe and ^(136)Xe abundances imply a substantial loss of rare gases up to \u223c10^8 years after meteorite formation either from the early Earth or from late\u2010accreting protoplanetary materials. Rare gases must have been lost during accretion and the moon\u2010forming impact, so that nonradiogenic rare gases in the atmosphere must have been supplied by subsequently accreted material with nonradiogenic Xe, possibly from comets. Fractionation of atmospheric Xe isotopes relative to other early solar system components occurred either on late\u2010accreting materials or during loss from the Earth.", "doi": "10.1063/1.48750", "isbn": "1-56396-409-0", "publisher": "American Institute of Physics", "place_of_publication": "Woodbury, NY", "publication_date": "1995", "pages": "56-69" }, { "id": "authors:tatay-rx904", "collection": "authors", "collection_id": "tatay-rx904", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120927-152403804", "type": "book_section", "title": "Systematics of the odd-even effect in the resonance ionization of Os and Ti", "book_title": "Resonance Ionization Spectroscopy 1992", "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": "G. A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" } ], "contributor": [ { "family_name": "Miller", "given_name": "Charles M.", "clpid": "Miller-C-M" }, { "family_name": "Parks", "given_name": "J. E.", "clpid": "Parks-J-E" } ], "abstract": "Measurements of the odd-even effect in the mass spectrometric analysis of Ti and\nOs isotopes by resonance ionization mass spectrometry have been performed for \u0394J = + 1, 0 and -1 transitions. Under saturating conditions of the ionization and for \u0394J = + 1 transitions odd-even\neffects are reduced below the 0.5% level. Depending on the polarization state of the laser large\nodd isotope enrichments are observed for \u0394J = 0 and -1 transitions which can be reduced below\nthe 0.5% level by depolarization of the laser field.", "isbn": "9780750302302", "publisher": "IOP", "place_of_publication": "Bristol, England", "publication_date": "1992-05", "pages": "127-130" }, { "id": "authors:dsde6-pej30", "collection": "authors", "collection_id": "dsde6-pej30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120927-160017193", "type": "book_section", "title": "Measurement of isotopic ratios by resonance ionization mass spectrometry\n in the presence of optical isotope shifts", "book_title": "Resonance Ionization Spectroscopy 1992", "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": "G. A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" } ], "contributor": [ { "family_name": "Miller", "given_name": "Charles M.", "clpid": "Miller-C-M" }, { "family_name": "Parks", "given_name": "Jame E.", "clpid": "Parks-J-E" } ], "abstract": "The effect of optical isotope shifts on Os and Ti isotopic ratio measurements by\nresonance ionization mass spectrometry has been investigated. Conditions with regard to laser\nbandwidth and intensity and the reproducibility of laser wavelength setting have been evaluated\nwich allowed Os and Ti isotopic ratios to be obtained with an accuracy better than 0.4%.", "isbn": "9780750302302", "publisher": "IOP", "place_of_publication": "Bristol, England", "publication_date": "1992-05", "pages": "229-232" }, { "id": "authors:2r1ed-k2794", "collection": "authors", "collection_id": "2r1ed-k2794", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150331-082201029", "type": "book_section", "title": "Presolar (?) Corundum in the Orgueil Meteorite", "author": [ { "family_name": "Huss", "given_name": "G. R.", "orcid": "0000-0003-4281-7839", "clpid": "Huss-G-R" }, { "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": "Stone", "given_name": "J.", "clpid": "Stone-J" } ], "abstract": "The discovery in chondritic meteorites of diamond, SiC, and poorly crystallized graphite that formed around other stars demonstrated conclusively that presolar dust survived the formation of the solar system to be incorporated into meteorites. The presolar nature of these grains is shown by the highly unusual isotopic compositions of their constituent elements. To date, all recognized types of presolar grains have been carbon rich and apparently formed around carbon stars, those with C/O greater than 1. The discovery of the first oxygen-rich grain with isotopic characteristics consistent with a presolar origin is reported. Oxygen-rich grains presumably form only around stars with C/O less than 1.", "publisher": "Lunar and Planetary Institute", "publication_date": "1992-03" }, { "id": "authors:5svgk-vs935", "collection": "authors", "collection_id": "5svgk-vs935", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120928-160139432", "type": "book_section", "title": "Systematics of isotope ratio measurements with resonant laser photoionization sources", "book_title": "Applied spectroscopy in material science II", "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" } ], "contributor": [ { "family_name": "Golden", "given_name": "William G.", "clpid": "Golden-W-G" } ], "abstract": "Sources of laser-induced even-even and odd-even isotopic selectivity in the resonance ionization mass\nspectroscopy of Os and Ti have been investigated experimentally for various types of transitions. A set\nof conditions with regard to laser bandwidth and frequency tuning, polarization state and intensity was\nobtained for which isotopic selectivity is either absent or reduced below the 2 % level.", "doi": "10.1117/12.59314", "isbn": "0-8194-0782-8", "publisher": "Society of Photo-optical Instrumentation Engineers", "place_of_publication": "Bellingham, WA", "publication_date": "1992-01", "pages": "211-222" }, { "id": "authors:nx0ac-7rz95", "collection": "authors", "collection_id": "nx0ac-7rz95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230105-224018445", "type": "book_section", "title": "Silicon, carbon, and nitrogen isotopic studies of silicon carbide in carbonaceous and enstatite chondrites", "book_title": "Stable isotope geochemistry : a tribute to Samuel Epstein", "author": [ { "family_name": "Stone", "given_name": "J.", "clpid": "Stone-J" }, { "family_name": "Hutcheon", "given_name": "I. D.", "clpid": "Hutcheon-Ian-D" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "contributor": [ { "family_name": "Taylor", "given_name": "H. P., Jr.", "clpid": "Taylor-H-P-Jr" }, { "family_name": "O'Neil", "given_name": "J. R.", "clpid": "O'Neil-J-R" }, { "family_name": "Kaplan", "given_name": "I. R.", "clpid": "Kaplan-I-R" } ], "abstract": "Both carbonaceous and enstatite chondrites contain complex populations of silicon carbide (SiC) grains. SiC in carbonaceous chondrites contains highly anomalous Si, C, and N. Individual SiC grains and aggregates of sub-micron SiC analysed in this study show variations in \u03b4\u00b2\u2079Si and \u03b4\u00b3\u2070Si exceeding 120 per mil, \u03b4\u00b9\u00b3C values ranging from -300 to +24,500, and \u03b4\u00b9\u2075N values between -390 and -960. This range of isotopic compositions suggests that the total SiC population consists of families of grains formed in a variety of stellar sites (ZINNER et al., 1989; TANG et al., 1989). One such family, common to Orgueil and Murchison, and distinguished by a platy surface morphology, contains consistently anomalous Si defining a binary mixing array in the Si three-isotope diagram. \n\nOn formation, these grains incorporated varying proportions of two exotic Si components, one enriched in \u00b2\u2078Si, the other in \u00b2\u2079Si and \u00b3\u2070Si relative to normal Si. Grains belonging to this family are consistently enriched in \u00b9\u00b3C and \u00b9\u2074N relative to the solar isotopic compositions of these elements. The most plausible source for these grains is the circumstellar envelope of a low-mass red giant star on the Asymptotic Giant Branch (AGB)(GALLINO et al., 1990). In this case, the \u00b2\u2078Si-rich component represents the seed composition preserved in the stellar envelope, to which was added \u00b2\u2079Si and \u00b3\u2070Si produced by neutron capture during He-burning. Enrichments in \u00b9\u00b3C and \u00b9\u2074N are attributable to proton capture following convective dredge-down of H into the top of the He layer. The poor correlation of C and N with Si isotopes in the platy SiC grains suggests condensation over a number of convective mixing episodes, which enriched the stellar envelope in \u00b9\u00b3C and \u00b9\u2074N to differing degrees. \n\nSilicon carbide grains in Indarch differ in size and surface texture from those found in the carbonaceous chondrites. None of the Indarch grains analysed in this study contains isotopically anomalous Si or C, an observation difficult to reconcile with high concentration of the \u00b2\u00b2Ne-rich component, Ne-E(H), found in Indarch acid residues (Huss, 1990). The grains analysed in this study either belong to a SiC family distinct from that presumed to host Ne-E(H), or formed in a region characterised by isotopically normal Si and C but anomalous Ne. In the former case, a solar-system origin for the grains analysed in this work cannot be ruled out.", "isbn": "9780941809023", "publisher": "Geochemical Society", "place_of_publication": "San Antonio, TX", "publication_date": "1991", "pages": "487-504" }, { "id": "authors:73q71-d5810", "collection": "authors", "collection_id": "73q71-d5810", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200929-120358894", "type": "book_section", "title": "A possible relationship between extinct \u00b2\u2076Al and \u2075\u00b3Mn in meteorites and early solar activity", "book_title": "Nuclear Astrophysics", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Arnould", "given_name": "M.", "clpid": "Arnould-M" } ], "contributor": [ { "family_name": "Hillebrandt", "given_name": "Wolfgang", "clpid": "Hillebrandt-W" }, { "family_name": "Kuhfu\u00df", "given_name": "Rudolf", "clpid": "Kuhfu\u00df-R" }, { "family_name": "M\u00fcller", "given_name": "Ewald", "clpid": "M\u00fcller-E" }, { "family_name": "Truran", "given_name": "James W.", "clpid": "Truran-J-W" } ], "abstract": "Much excitement in the meteoritic and astrophysical communities has been raised by the discovery in a small fraction of the meteoritic material of isotopic anomalies ascribable to nuclear effects. A special class of those anomalies relates to the in-situ decay of now-extinct short-lived (t_(1/2) \u2264 10\u2078 yr) radionuclides. One of the most important of those cases is \u00b2\u2076Al [(t_1/2) = 7.05 x 10\u2075, following Norris et al. (1983)]. The short time scale for \u00b2\u2076Al has been used as the measure of time between the injection of freshly synthesized nuclei into a dense molecular cloud and its collapse. As reviewed by e.g. Wasserburg and Papanastassiou (1982), Wasserburg (1985) or Papanastassiou (1985), the (\u00b2\u2076Al/\u00b2\u2077Al)\u2080 abundance ratio at the time T\u2080 of crystallization is 5 x 10\u207b\u2075. Lower values have been found and are attributed to time differences or to heterogeneities in the solar nebula. There is some difficulty in maintaining large primary heterogeneities on the scale of 100 km in the solar nebula after collapse. There are also problems in relating the inferred abundances of short-lived nuclei with a simple or coherent set of nuclear astrophysical processes and sources. Strong evidence also exists for the presence of \u00b9\u2070\u2077Pd (t_(1/2) = 6.5 x 10\u2076 yr) with (\u00b9\u2070\u2077Pd/\u00b9\u2070\u2078Pd)\u2080 = 2 x 10\u207b\u2075 in the early solar system (Kelly and Wasserburg 1978; Kaiser and Wasserburg 1983; Chen and Wasserburg 1983). As evidence of \u00b9\u2070\u2077Pd is found in iron meteorites, the time scale for this nuclide is related to the formation of small planetary objects.", "doi": "10.1007/bfb0016587", "isbn": "978-3-540-18279-5", "publisher": "Springer", "place_of_publication": "Berlin", "publication_date": "1987", "pages": "262-276" }, { "id": "authors:7zp49-qbh54", "collection": "authors", "collection_id": "7zp49-qbh54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130909-151752715", "type": "book_section", "title": "Early Archean Sm-Nd model ages from a tonalitic gneiss, northern Michigan", "book_title": "Selected studies of Archean gneisses and Lower Proterozoic rocks, southern Canadian Shield", "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" } ], "contributor": [ { "family_name": "Morey", "given_name": "G. B.", "clpid": "Morey-G-B" }, { "family_name": "Hanson", "given_name": "Gilbert N.", "clpid": "Hanson-G-N" } ], "abstract": "Sm-Nd model ages on a whole-rock sample of the gneiss at\nWatersmeet, Michigan, show that these rocks were added to the\ncontinental crust about 3,600 m.y. ago. These model ages are\ncalculated by assuming that the rocks were derived from a mantle\nreservoir with the Sm/Nd ratio of CHUR, which corresponds approximately\nto the chondritic ratio. These data confirm the U-ThPb\nzircon results that indicated a minimum age of 3,410 m.y. and\npossibly an age as old as 3,800 m.y. This study further illustrates\nthe utility of Sm-Nd model ages in deciphering the history of complex\nPrecambrian terranes.", "doi": "10.1130/SPE182-p135", "isbn": "9780813721828", "publisher": "Geological Society of America", "place_of_publication": "Boulder, CO", "publication_date": "1980", "pages": "135-138" }, { "id": "authors:gzq6t-psw24", "collection": "authors", "collection_id": "gzq6t-psw24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150702-073323853", "type": "book_section", "title": "Isotopic Heterogeneities in the Solar System", "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": "Lee", "given_name": "Typhoon", "clpid": "Lee-Typhoon" } ], "abstract": "The nature of isotopic anomalies in solar system material is discussed\nwith emphasis on correlated anomalies in refractory elements. Evidence\nfor the existence of short-lived radioactive nuclides in the early solar system\nis given and is used to estimate the time scale for the last injection\nof freshly synthesized nuclear material. It is shown that the early solar\nnebula was incompletely mixed and contained debris which was injected\nfrom a stellar source at most a few million years prior to the formation of\nthe solar system. It appears that the average solar system material is made\nup of ambient interstellar material which was deficient in certain nuclear\nspecies to which was added a small fraction of freshly synthesized material.\nIt is this mixture which now makes up the bulk solar system. At the\npresent time there may still remain both substantial and subtle isotopic differences\nbetween the sun, the terrestrial planets, and volatile-rich planetary\nbodies including comets. The isotopic variations which are observed\nreflect slightly different proportions of nuclei from different stellar sources\nwhich were locally well mixed and homogenized prior to or during the formation\nof the early solar nebula condensates. The process of local homogenization\napparently destroyed most pre-solar dust grains but preserved\nthe distinctive average isotopic character of the local regions. Substantial\nisotopic differences existed between the cool gas and some condensed\nmatter. This is manifest in major chemical and some associated isotopic\nalteration of the early condensates.", "publisher": "Universite de Liege", "publication_date": "1979" }, { "id": "authors:j6s14-68w77", "collection": "authors", "collection_id": "j6s14-68w77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230105-391189000.2", "type": "book_section", "title": "\u00b3\u2079Ar-\u2074\u2070Ar and Rb-Sr age determinations on quaternary volcanic rocks from the roman volcanic province", "author": [ { "family_name": "Radicati di Brozolo", "given_name": "F.", "clpid": "Radicati-di-Brozolo-F" }, { "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" } ], "contributor": [ { "family_name": "Zartman", "given_name": "Robert E.", "clpid": "Zartman-Robert-E" } ], "abstract": "We report \u00b3\u2079Ar-\u2074\u2070Ar and Rb-Sr analyses\nperformed on mineral separates from very young\n(~350,000 yr) tuffs from the potassic Roman\nvolcanic province to establish the feasibility\nof age measurements on potassic minerals with\nthe high precision necessary for good stratigraphic\ndefinition. Several outcrops of the\nVilla Senni tuff in the Albano volcanic complex\nwere sampled. The tuff contains fresh leucite\nand biotite crystals 0.1 - 1 cm in size and\nminor amounts of amphibole. Leucite and biotite\nseparates were irradiated for the \u00b3\u2079Ar-\u2074\u2070Ar\nanalyses with a fast neutron fluence of ~7 x\n10\u00b9\u2074 n cm\u00b2 in the TRIGA reactor facility at the\nUniversity of California, Berkeley. The Be 4 M\nstandard muscovite (Steiger, 1964; Lanphere and\nDalrymple, 1965) was used as the irradiation\nmonitor . Neutron fluence inhomogeneities were\nmonitored by measuring the \u2075\u2078Co \u03b3 activity\ninduced in Ni wires that were placed in known\npositions. The monitor \u2074\u2070Ar/K ratio is reported\nwith an uncertainty of ~4 percent, which\naffects the absolute ages of our samples. The\nerrors in the relative ages from the ma ss\nspectrometric analyses and the fluence normalizations\namount to approximately 8000 years (2\u03c3).\nWe have analyzed the samples for Ar using the\nstepwise heating technique. Typically we used\neight steps plus a high-temperature (~1650\u00b0C)\nre-extraction step which was never noticeably\nabove the blank level. The first observation to\nbe made is that the bulk \u2074\u2070Ar/\u00b3\u2076Ar ratios of\nleucites are much higher than those of biotites\n(leucites ~5,000; biotites ~360).", "doi": "10.3133/ofr78701", "publisher": "United States Geological Survey", "publication_date": "1978-08" }, { "id": "authors:3crd7-byf22", "collection": "authors", "collection_id": "3crd7-byf22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221129-193075600.1", "type": "book_section", "title": "Evidence for \u00b2\u2076Al in the Solar System", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-D-A" }, { "family_name": "Lee", "given_name": "T.", "clpid": "Lee-T" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "contributor": [ { "family_name": "Delsemme", "given_name": "A. H.", "clpid": "Delsemme-A-H" } ], "abstract": "We review the evidence for the presence of short lived \u00b2\u2076Al (^\u03c4(1/2) = 0.72 \u00d7 10\u2076 years) in the early solar system. Large excesses of \u00b2\u2076Mg of up to 5% have been found in Ca-Al rich inclusions of the Allende meteorite. The Mg excesses correlate well with \u00b2\u2077Al/\u00b2\u2074Mg and in two cases they are found in high purity separates of coarse grained Al-rich minerals which tend to exclude Mg. The data demonstrate that \u00b2\u2076Al was present in the early solar system. Mechanisms for addition of \u00b2\u2076Al to the solar nebula or for production within an active solar system are required within a few million years of condensation of small (centimeter sized) objects. The \u00b2\u2076Al abundance in Allende inclusions is high enough to provide for effective melting of kilometer size bodies or larger, if such bodies accreted early enough (a few million years) to incorporate the \u00b2\u2076Al.", "doi": "10.1017/s0252921100070275", "publisher": "University of Toledo", "publication_date": "1977-12" }, { "id": "authors:y29jw-hmd38", "collection": "authors", "collection_id": "y29jw-hmd38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221223-213502133", "type": "book_section", "title": "Stratigraphic processes in the lunar regolith - additional insight from neutron fluence measurements on bulk soils and lithic fragments from the deep drill cores", "book_title": "Proceedings of the Eighth Lunar Science Conference", "author": [ { "family_name": "Curtis", "given_name": "David B.", "clpid": "Curtis-David-B" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Three of the Apollo missions sampled 2-3 m sections of the regolith with deep drill cores. Measurements of the integrated neutron exposure, the fluence, of bulk samples from these cores provided considerable insight into the processes of sedimentation, erosion and mixing in the lunar regolith. We have attempted to gain further knowledge about the nature of the lunar gardening processes by measuring the fluences in lithic fragments and selected bulk samples (<300 \u03bcm soils) from the Apollo 15 and 17 deep drill cores. \n\nAdditional measurements on bulk samples from the Apollo 15 core have increased the spatial resolution of the depth dependence of fluence in this section. The new data more fully define the very smooth profile that was originally measured by Russ et al. (1972). The exact correspondence between this well-defined fluence profile and the depth dependence of the lunar neutron flux leaves virtually no doubt that all but the top few decimeters of this vertical section of the regolith had lain undisturbed for about half a billion years prior to its retrieval by the Apollo 15 astronauts. \n\nFluences in soil breccias appear to reflect the average fluence of materials which comprise them rather than the residence time of the lithic fragments in the regolith. By contrast, fluences in millimeter sized pebbles of basalt are, on the average, less than in bulk samples from the same depths in the cores. The difference manifests an average residence time in the regolith that is ~300 m.y. less for igneous pebbles than for fine-grained soils (<300 \u03bcm). \n\nThe difference in the regolith residence times between the igneous pebbles and the bulk samples in the Apollo 15 core has established an upper limit of 750 m.y. on the stratigraphic age of the cored materials. The lower limit of 420 m.y. was previously determined assuming the section to have been emplaced by very rapid sedimentation. \n\nOne basaltic fragment from the Apollo 17 drill stem has a relative regolith residence time which conflicts with a very long stratigraphic history that had been proposed to describe the fluence profile in the core. An alternative model describing rapid sedimentation in the last 200 m.y. is believed to be a more accurate description of the processes that formed this stratigraphic section. \n\nBoth the Apollo 15 and 17 cores appear to contain thick slabs of material that were laid down rather rapidly. Materials throughout the length of each slab have had nearly identical average residence times in the regolith. There must be lunar gardening processes that can deposit at least 2-3 m of well-mixed material in a relatively short time.", "isbn": "9780080220529", "publisher": "Pergamon Press", "place_of_publication": "New York, NY", "publication_date": "1977-03", "pages": "3575-3593" }, { "id": "authors:csw08-d8d71", "collection": "authors", "collection_id": "csw08-d8d71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221223-214402361", "type": "book_section", "title": "Rb-Sr and Sm-Nd chronology and genealogy of mare basalts from the Sea of Tranquility", "book_title": "Proceedings of the Eighth Lunar Science Conference", "author": [ { "family_name": "Papanastassiou", "given_name": "D. A.", "clpid": "Papanastassiou-Dimitri-A" }, { "family_name": "DePaolo", "given_name": "D. J.", "clpid": "DePaolo-Donald-J" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Rb-Sr and Sm-Nd ages of two Apollo 11 mare basalts are 3.64 \u00b1 0.05 and 3.57 \u00b1 0.03 AE for high-K basalt 10072, and 4.01 \u00b1 0.11 and 3.88 \u00b1 0.06 AE for low-K basalt 10062. Rb-Sr, Sm-Nd, and \u2074\u2070Ar-\u00b3\u2079Ar ages are in good agreement and show an extensive time interval for filling of the Sea of Tranquility, presumably by thin lava flows, in agreement with similar observations for the Ocean of Storms. The older ages indicate that mare filling may have started prior to the Imbrium event. Initial Sr and Nd isotopic compositions on Apollo 11 basalts identify at least two parent sources producing basalts. The low-K basalts may have been produced from a single reservoir over an extended time interval. The Sm-Nd isotopic data demonstrate that low-K and high-Ti basalts from Apollo 11 and 17 have been derived from totally distinct reservoirs while low-Ti Apollo 15 mare basalt sources have Sm/Nd similar to the sources of Apollo 11 basalts. It appears that groupings of mare basalt based on Ti content and on isotopic data do not coincide. Apollo 11 high-K basalts show no significant Sm/Nd fractionation near the time of crystallization in contrast to characteristically large Rb/Sr fractionation for these basalts.", "isbn": "9780080220529", "publisher": "Pergamon Press", "place_of_publication": "New York, NY", "publication_date": "1977-03", "pages": "1639-1672" }, { "id": "authors:8yqr0-68z18", "collection": "authors", "collection_id": "8yqr0-68z18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141008-094651986", "type": "book_section", "title": "Transport and erosional processes in the Taurus-Littrow Valley -- Inferences from neutron fluences in surface soils", "book_title": "Proceedings of the Eighth Lunar Science Conference", "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": "Isotopic abundances of Gd and Sm have been measured in 15 surface soils from the\nApollo 17 site in the Taurus-Littrow Valley. Generally the fluences at this site are similar to fluences\nmeasured in surface soils from other sites. Fluences calculated from the isotopic shifts directly\nreflect the origin of the soils. Materials with very low fluences are from the ejecta blankets of fresh\ndeep craters. Soils composed predominantly of comminuted basalt, other than the ejecta from deep\ncraters, have fluences that are distinctly lower than soils which contain significant proportions of\nhighland materials.\nDifferences in the chemical composition of the irradiated material can account for differences in\nmeasured fluence in basaltic soils from the valley floor and highland soils from the South Massif. To\npermit a direct comparison of the irradiation history of materials with different chemical compositions,\nwe have calculated \"normalized\" fluences, i.e., the neutron fluence which the sample\nwould have if it had been irradiated in a standard chemical composition. The similarity of the\nresulting normalized fluences indicates similar regolith residence times for these two types of\nmaterials.\nHigher than average normalized fluences in soils containing a constituent from the North Massif\nmay reflect erosion and/or burial rates on the slopes of the massif that are less than the average\nburial rate of all the soils that have been sampled. A correlation between fluence and distance from\nthe bottom of the North Massif suggests the erosional processes deposit highland soils from near the\nsurface far into the valley, while materials of deeper origin are deposited close to the bottom of the\nmassif.", "isbn": "9780080220529", "publisher": "Pergamon Press", "place_of_publication": "New York, NY", "publication_date": "1977", "pages": "3045-3057" }, { "id": "authors:k6185-0g764", "collection": "authors", "collection_id": "k6185-0g764", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221129-190644082", "type": "book_section", "title": "Rb-Sr age of troctolite 76535", "book_title": "Proceedings of the Seventh Lunar Science Conference", "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": "We have studied the Rb-Sr systematics for the troctolite 76535 in phases covering a wide range of Rb and Sr concentrations. The Rb-Sr data define a precise linear array for most of the samples. Excluding two samples which are distinctly anomalous we obtain a line corresponding to an age of 4.61 \u00b1 0.07 AE and an initial \u2078\u2077Sr/\u2078\u2076Sr of 0.69900 + 0.00003. The Rb-Sr age of 4.55 \u00b1 0.10 AE for the dunite (72417) and the Rb-Sr age of the troctolite are in approximate agreement and permit an interpretation that these rocks formed during a single major lunar differentiation which presumably produced an anorthositic-gabbroic lunar crust and layered upper mantle. Other dating methods (K-Ar, Sm-Nd) yield distinctly younger ages for the troctolite of 4.25 AE which are not in agreement with the Rb-Sr age. The causes of this discrepancy are not understood. The U-Pb system shows a young disturbance in the neighborhood of ~4.0 AE. Whereas the K-Ar ages could previously be considered as due to partial degassing of 76535 during the terminal lunar cataclysm, the Sm-Nd data cannot easily be interpreted in this fashion. Assuming that the ages of 4.61 and 4.25 AE are meaningful, our preferred interpretation is that the troctolite was formed at 4.61 AE and remained at elevated temperatures until 4.25 AE at which time it was excavated by a major impact. Throughout the interval 4.61-4.25 AE, \u2074\u2070Ar diffused out of the rock and Sm and Nd exchanged chemically and isotopically; however, Rb-Sr systems protected inside olivine crystals remained closed. Except for some inconclusive U-Pb results and peculiarities in the \u2074\u2070Ar-\u00b3\u2079Ar data there are no results which clearly show that the troctolite was affected by the terminal lunar cataclysm.", "isbn": "9780080217710", "publisher": "Pergamon Press", "place_of_publication": "New York, NY", "publication_date": "1976-03", "pages": "2035-2054" }, { "id": "authors:79a1s-gx595", "collection": "authors", "collection_id": "79a1s-gx595", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221129-184538218", "type": "book_section", "title": "Rb-Sr study of a lunar dunite and evidence for early lunar differentiates", "book_title": "Proceedings of the Sixth Lunar Science Conference", "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 isochron is defined by data on a set of rock chip samples and handpicked mineral\nseparates of the dunite clast 72417. Although this rock has undergone a complex multistage history, the\ndata yield a well-defined age of 4.55 \u00b1 0.10 AE and an initial \u2078\u2077Sr/\u2078\u2076Sr, I = 0.69900 \u2213 0.00004. These\nobservations estab\u03bcsh the dunite as an early lunar differentiate. The I value must be representative of\nthe early lunar upper mantle and offers no evidence of I values for the moon significantly lower than\nBABI. Trace-element correlations show that the dunite contains at least three distinct phases with\ndifferent Rb/Sr and, therefore, the isochron is not simply a mixing line. Samples of the dunite have\nextremely low K/Rb ~100 (by weight) as compared to most lunar rocks and minerals and require that\nthe dunite were derived from a distinctive magma. Samples of the host breccia of the dunite indicate\nthat the breccia was formed or disturbed at times younger than 4.10 AE but show that isotopic\nhomogenization was not achieved over distances as short as 1 mm. The lack of significant element\nmigration during metamorphism of the breccia is consistent with the preservation of the ancient Rb-Sr\nage of the dunite through the last stage of metamorphism at the geometrical scale studied.\nData are presented which show that mineral separation procedures, using organic liquids, cause the\ndifferential dissolution of Rb and Sr from phases in the dunite. In general, the use of organic liquids in\nmineral separation may seriously disturb the isotopic systems.", "isbn": "9780080205663", "publisher": "Pergamon Press", "place_of_publication": "New York, NY", "publication_date": "1975-03", "pages": "1467-1489" }, { "id": "authors:e6zfv-06w98", "collection": "authors", "collection_id": "e6zfv-06w98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221123-215902709", "type": "book_section", "title": "U-Th-Pb systematics on lunar rocks and inferences about lunar evolution and the age of the moon", "book_title": "Proceedings of the Fifth Lunar Science Conference", "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": "All of the available data on terra rocks define a striking linear array when plotted on the U-Pb evolution diagram with a generally limited scatter around a reference isochron which intersects the concordia curve at 4.42 and 3.95 AE and defines an initial radiogenic \u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb of I_(Pb) = 1.45. In addition to the observed wide range of 201Pbf06Pb (0.4-1.45) the samples exhibit a vast range for \u03bc = \u00b2\u00b3\u2078U/\u00b2\u2070\u2074Pb from 0.9 to 10\u2074 which is generally correlated with the degree of discordance. On the basis of similar observations, on a limited number of terra rocks, we had previously inferred that a major impact had caused global metamorphism in the lunar crust. The more extensive results presented here demonstrate that the terra rocks in general fall on the linear array although it is not clear as to how much of the scatter reflects lunar processes and how much is due to insufficient precision in some of the existing data. The data array is taken as an evidence for the validity of the terminal lunar cataclysm hypothesis which ascribes large-scale metamorphism at --3.9 AE to a period of intense bombardment of an ancient lunar crust, effecting element redistribution and extensive mobilization of Pb. A time interval of up to 200 m.y. (3.8-4.0 AE) is assigned to the duration of the terminal cataclysmic bombardment during which several of the major ringed basins may have been formed. Some of the impacted materials lost almost all their Pb and consequently fall on the concordia curve at the lower intersection. The mobilized Pb was deposited and/or incorporated in other rocks which became discordant. Some rocks are dominated by this labile Pb and lie close to the intercept (e.g. 15415). While the target rocks may be of variable age and the mobilized Pb not have a unique isotopic composition the gross isotopic composition of the radiogenic comp.Jnent of the mobilized lead (I_(Pb) ~ 1.45) presumably represents the average value of \u00b2\u2070\u2077Pb/\u00b2\u2070\u2076Pb in the lunar crust at ~3.8-3.9 AE. This I_(Pb) is consistent with its production in a single stage in the time span 4.4-3.9 AE. The upper intersection of the linear array with the concordia curve appears well defined by the fact that two terra rocks and one mare basalt are concordant by the U-Th-Pb method at 4.42 AE indicating a very strong possibility that this is close to the actual time of differentiation of the lunar crust. A firm interpretation of the upper intersection is not yet possible. It must be recognized, however, that from the point of view of the U-Th-Pb systematics that it is not possible to distinguish between differentiates produced by magmatic activity at ~ 3.9 AE and those rocks produced in cataclysmic impact metamorphism. Thus, a sample might fall accidentally on the array without having a genetic relationship to terra rocks on the array. This might apply to the orange soil and basalt 75055 which plot on the reference isochron. New data on two lunar basalts show that the \u00b2\u2070\u2074Pb concentration levels are much lower than reported previously.", "isbn": "9780080183183", "publisher": "Pergamon Press", "place_of_publication": "New York, NY", "publication_date": "1974-03", "pages": "1571-1599" }, { "id": "authors:yg2w3-s2170", "collection": "authors", "collection_id": "yg2w3-s2170", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221123-214402416", "type": "book_section", "title": "High resolution argon analysis of neutron-irradiated Apollo 16 rocks and separated mineral", "book_title": "Proceedings of the Fifth Lunar Science Conference", "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": "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": "Ar analyses are reported for detailed thermal release studies on neutron-irradiated samples of mineral separates and a whole sample of breccia 65015 and rock fragments 67483,15-2 and 60503,3-3. \n\nThe \u00b3\u2077Ar release patterns show a single release peak at ~800\u00b0C for 65015 plagioclase and a distinctive release peak at ~1200\u00b0C for 65015 pyroxene. 60% of the \u00b3\u2077Ar is released from the pyroxene above 1000\u00b0C, whereas only 15% of the 39 Ar is released above this temperature. From a graph of \u2074\u2070Ar/\u00b3\u2079Ar ages versus \u00b3\u2077Ar, the anomalously low ages of high-temperature releases, which are a common feature in \u2074\u2070Ar/\u00b3\u2079Ar age spectra of lunar samples, can be associated with the unique high-temperature release of \u00b3\u2077Ar from the pyroxene. \n\nThe age spectrum of 65015 plagioclase plotted versus \u00b3\u2077Ar shows a plateau at 3.98 AE and then rises with a sharp ascent to a maximum of 4.47 AE for the last stages of gas release that correlates with the proportion of ancient relict plagioclase as determined by Rb-Sr analyses. This confirms the existence of ancient lithic fragments within this metaclastic rock and indicates that the protolith of 65015 contained plagioclase fragments older than 4.47 AE and the 65015 breccia was severely metamorphosed in an event at 3.98 AE. The time interval between this metamorphic event and the event dated by Luna 20 samples (neutron-irradiated with 65015) is 80 m.y. These events occurred at distinctly separate times and presumably represent the times of formation of the Nectaris and Crisium basins, respectively. The terminal lunar cataclysm involved at least two separate major impact events.", "isbn": "9780080183183", "publisher": "Pergamon Press", "place_of_publication": "New York, NY", "publication_date": "1974-03", "pages": "1419-1449" }, { "id": "authors:b07ae-00y19", "collection": "authors", "collection_id": "b07ae-00y19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221123-204758941", "type": "book_section", "title": "\u2074\u2070Ar/\u00b3\u2079Ar measurements in Apollo 16 and 17 samples and the chronology of metamorphic and volcanic activity in the Taurus-Littrow region", "book_title": "Proceedings of the Fourth Lunar Science Conference", "author": [ { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Jessberger", "given_name": "E. K.", "clpid": "Jessberger-E-K" }, { "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": "Argon analyses are reported for neutron irradiated whole samples and mineral separates of Apollo 16 crystalline rock 68415, Apollo 17 basaltic rock 75055 and fragment 75083,3,3, breccia 76055, soil 74241 and orange glass from soil 74220, giving gas retention and exposure ages of these samples as\nwell as information on the systematic variations of all Ar isotopes necessary to evaluate these ages. \n\nAn age of 3.97 \u00b10.04 AE is determined for the metamorphosed breccia 76055 which probably dates the time of extensive metamorphism in the impact forming the Serenitatis basin. The moon was evidently bombarded by many large bodies about 3.95 AE ago, forming most of the major mare basins and smaller multi-ring basins over a period of less than 10\u2078 years. \n\nA well-defined age of 3.78\u00b10.04 AE obtained on a plagioclase separate of basalt 75055 and a less precise age of 3.70\u00b10.09 for the basaltic fragment 75083,3,3 are evidence of flooding by basalt lava in the Taurus-Littrow region 3.7-3.8 AE ago. These ages are similar to the ages of some Mare Tranquilitatis basalts and do not extend the 3.1-3.9 AE range of lunar magmatic activity previously determined. \n\nThe isotopic variations in Ar released from 74220 were complex, but separable into two distinctly different arrays at intermediate and high temperatures. A gas retention age of 3.54\u00b10.05 AE was determined over the intermediate release containing 47% of the total \u00b3\u2079Ar*. The correspondence of this age with the period of lunar magmatism is suggestive evidence for a volcanic origin of the orange glass and possibly a significant fraction of the glass particles observed at other sites. \n\nThe apparent age of 68415 is not well determined by the whole sample Ar release. A maximum apparent age of 3.86 AE in the intermediate release is similar to a precise Rb-Sr age of 3.84 AE. The apparent age plateau at 4.09 AE in the intermediate release from the plagioclase is atypically higher than the Rb-Sr age. Anomalous Ar isotopic variations are observed in the Ar release from both 68415 plagioclase and the high temperature release from the 74220 glass. Both have high Cl contents, and in both apparent ages are higher than anticipated from other criteria, suggesting inherited \u2074\u2070Ar. The possibility of a complex multistage origin for 68415 must be investigated. \n\nFormation times of 95 m.y. ago for Camelot Crater and 30 m.y. ago for Shorty Crater are inferred from the cosmic-ray exposure ages of the associated samples 75055 and 74220, respectively. The exposure age for the soil fragment 75083,3,3 is 310 m.y., for the breccia 76055 is 140 m.y., and for the soil 74241 is 300 m.y. No well-defined exposure age could be determined for 68415.", "isbn": "9780080179094", "publisher": "Caltech Library", "publication_date": "1973-03", "pages": "1725-1756" }, { "id": "authors:4fg5g-ms862", "collection": "authors", "collection_id": "4fg5g-ms862", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221123-193724255", "type": "book_section", "title": "Ar\u2074\u2070-Ar\u00b3\u2079 systematics in rocks and separated minerals from Apollo 14", "book_title": "Proceedings of the Third Lunar Science Conference", "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": "The Ar\u2074\u2070-Ar\u00b3\u2079 dating technique has been applied to separated minerals (plagioclase, pyroxene, quintessence and an \"ilmenite\" concentrate), and whole rock samples of Apollo 14 rocks 14310 and 14073. Plagioclase shows the best gas retention characteristics, with no evidence of anomalous behavior and only a small amount of gas loss in the initial release. Ages determined from the plagioclase of 14310 and 14073 are (3.87 \u00b1 0.05) and (3.88 \u00b1 0.05) AE respectively. Low apparent ages at low release temperatures, which are frequently observed in whole rock Ar\u2074\u2070-Ar\u00b3\u2079 experiments on lunar basalts, are shown here to be principally due to gas loss in the high-K interstitial glass (quintessence) phase, confirming earlier suggestions. The decrease in apparent ages in the high temperature release previously observed in several total rock samples of Apollo 14 basalts has been identified with the pyroxene. \n\nPlagioclase is also found to be the most suitable mineral for the determination of cosmic ray exposure ages, and exposure ages of 280 and 113 million years are found for 14310 and 14073, respectively, indicating that these rocks, which are very similar in many respects, have different exposure histories. The relative production rates of Ar\u00b3\u2078 from Fe and Ca have been determined from a comparison of pyroxene and plagioclase measurements.", "isbn": "9780262120647", "publisher": "MIT Press", "place_of_publication": "Cambridge, MA", "publication_date": "1972-01", "pages": "1589-1612" }, { "id": "authors:nf2yr-kdy23", "collection": "authors", "collection_id": "nf2yr-kdy23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221123-170945414", "type": "book_section", "title": "The irradiation history of lunar samples", "book_title": "Proceedings of the Second Lunar Science Conference", "author": [ { "family_name": "Burnett", "given_name": "D. S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Huneke", "given_name": "J. C.", "clpid": "Huneke-J-C" }, { "family_name": "Podosek", "given_name": "F. A.", "clpid": "Podosek-Frank-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": "From new data on Apollo 12 samples illustrated in this paper and data available in the literature, the galactic cosmic ray and solar wind exposure of lunar samples has been investigated by means of rare gas and Gd isotopic measurements. Neutron exposures obtained from Gd isotopic measurements on Apollo 11 and Apollo 12 soil samples are the same to within 10% and Xe/(Ba + 1.65 Ce) to within 40%. These data permit regolith mixing depths of 10-20 meters to be calculated for the Apollo 11 and Apollo 12 sites. The Apollo 12 double core shows only a small, but significant, gradient in neutron exposure (~10% larger at the bottom). Consequently, the core could not have been stratified in its present configuration for more than 50 x 10\u2076 yr. Apollo 12 rocks have neutron exposures which are similar to the Apollo 11 rocks. No variations in neutron exposure are observed for samples from different depths in 12002. \n\nStrong evidence for a range in irradiation depths for lunar rocks is obtained from the relative yields of rare gas spallation products and neutron dosages calculated from the measured Gd isotopic variations. However, it appears that the average irradiation depths were not large (probably ~60 cm). Almost all rocks must have resided at depths greater than ~4 meters most of the time since their original crystallization. \n\nAn internally consistent set of spallation product exposure ages has been calculated for 14 Tranquillity Base rocks. Six of seven \"low-K\" rocks appear to be grouped with an exposure age of around 100 m.y. \n\nThermal release data show large variations (~\u0394M/M) in the composition of SUCOR (surface correlated) Kr and Xe indicating that SUCOR may not be well defined. SUCOR Xe appears to be complex and may contain, in addition to solar wind, additional components from the lunar atmosphere (for example, fission Xe) which have been implanted by solar wind action.", "isbn": "9780262120517", "publisher": "MIT Press", "place_of_publication": "Cambridge, MA", "publication_date": "1971-01", "pages": "1671-1679" }, { "id": "authors:jqp0v-bfs06", "collection": "authors", "collection_id": "jqp0v-bfs06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221115-162438073", "type": "book_section", "title": "Comparative study of Li, Na, K, Rb, Cs, Ca, Sr and Ba abundances in achondrites and in Apollo 11 lunar samples", "book_title": "Proceedings of the Apollo 11 Lunar Science Conference", "author": [ { "family_name": "Tera", "given_name": "F.", "clpid": "Tera-Fouad" }, { "family_name": "Eugster", "given_name": "O. J.", "clpid": "Eugster-Otto-J" }, { "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": "This study provides analytically precise abundance data for Li, Na, K, Rb, Cs, Ca, Sr and Ba in five lunar rocks, a breccia and the lunar soil. For comparison, analyses have also been made for eight eucrites, Angra dos Reis, and a terrestrial basalt. \n\nThe chemical compositions of lunar rocks fall into two distinct groups which can be clearly distinguished by their K concentrations. A parallel grouping is also found for concentrations of Li, Rb, Cs and Ba which is the same as that observed for K. These elements plus many others can be shown to reside in interstitial phases. Gross abundance features, e.g. the Ba enhancement relative to carbonaceous chondrites, reflect the composition of the lunar crust. It is not possible to precisely form the soil by a mixture of the two rock types. A component with high Rb, Cs and Ba relative to K is required. Breccias form a well-defined chemical group whose composition can be described as a mixture of soil and high K rocks. There is no evidence for differential volatilization of alkalis between the rocks and the soil. \n\nCompared to carbonaceous chondrites, Ca, Sr, Ba and Li are strongly enhanced and Rb and Cs are systematically depleted relative to K in a similar manner in both lunar samples and achondrites. \n\nSimilar abundance patterns are found in terrestrial basalts. The concentrations of K, Rb, Cs and Ba in the lunar samples are distinctly higher than the achondrites. The Na (and Ca) concentrations of achondrites and lunar samples are essentially equal. \n\nWe conclude that the composition of the moon as a whole is characterized by relative abundances for these elements that are distinct from those found in chondrites.", "isbn": "9780080163925", "publisher": "Pergamon Press", "place_of_publication": "New York, NY", "publication_date": "1970-01", "pages": "1637-1657" }, { "id": "authors:m0hxe-mnh55", "collection": "authors", "collection_id": "m0hxe-mnh55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220617-20418900", "type": "book_section", "title": "The Status of Isotopic Age Determinations on Iron and Stone Meteorites", "book_title": "Meteorite Research", "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" } ], "contributor": [ { "family_name": "Millman", "given_name": "Peter M.", "clpid": "Millman-Peter-M" } ], "abstract": "A discussion of the ages determined by various methods is given. The results of \u2078\u2077Rb-\u2078\u2077Sr, and \u2074\u2070K-\u2074\u2070Ar ages on the silicate phases of iron meteorites are summarized as well as the internal isochrons on stone meteorites. The data for Kodaikanal are reviewed and the importance of recognizing events of intermediate age in the formation of planetary objects is emphasized. It is shown that it is possible to resolve time events by high precision Sr measurements to 5 x 10\u2077 years for chondrites.", "doi": "10.1007/978-94-010-3411-1_38", "isbn": "978-94-010-3413-5", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "1969", "pages": "467-479" }, { "id": "authors:3ztv8-43s02", "collection": "authors", "collection_id": "3ztv8-43s02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130903-145842040", "type": "book_section", "title": "Geochronology, and isotopic data bearing on development of the continental crust", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "contributor": [ { "family_name": "Hurley", "given_name": "Patrick M.", "clpid": "Hurley-P-M" } ], "abstract": "I will present some ideas and problems regarding the evolution of\nthe crust of the earth and will also attempt a prognosis of the application\nof isotopic techniques to the understanding of geological processes.\nThis dissertation might well be entitled \"Pride and Prejudice\"; it will\nbe my implicit assumption that the use of physicochemical techniques\nand principles, when used with a sound geologic knowledge, has and\nwill help solve important existing problems and will also create new\nproblems and new fields which are themselves an integral part of the\nscience of geology.", "publisher": "MIT Press", "publication_date": "1966" }, { "id": "authors:pf36r-kfx14", "collection": "authors", "collection_id": "pf36r-kfx14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221115-400096200.1", "type": "book_section", "title": "Spontaneous Fission Xenon in Natural Gases", "book_title": "Fluids in Subsurface Environments", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Mazor", "given_name": "E.", "clpid": "Mazor-E" } ], "abstract": "Isotopic enrichments of Xe\u00b9\u00b3\u00b2, Xe\u00b9\u00b3\u2074, and Xe\u00b9\u00b3\u2076 were found in a number of natural gases and are attributed to the spontaneous fission of U\u00b2\u00b3\u2078. The ratio of spontaneous-fission xenon to atmospheric xenon and the ratio of spontaneous fission xenon to He are discussed in terms of a solubility model. It is shown that the isotopic enrichments can be explained in terms of the solubility model and a preferential release of He as compared to XegF by a factor ranging up to three. An estimate is made of the present flux of spontaneous-fission.", "doi": "10.1306/m4360c17", "isbn": "9781629812335", "publisher": "American Association of Petroleum Geologists", "place_of_publication": "Tulsa, OK", "publication_date": "1965-01-01", "pages": "386-398" }, { "id": "authors:94ae5-bmd22", "collection": "authors", "collection_id": "94ae5-bmd22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160125-145554089", "type": "book_section", "title": "Redistribution of Strontium and Rubidium Isotopes during Metamorphism, World Beater Complex, Panamint Range, California", "author": [ { "family_name": "Lanphere", "given_name": "M. A.", "clpid": "Lanphere-M-A" }, { "family_name": "Wasserburg", "given_name": "G. J. F.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Albee", "given_name": "A. L.", "clpid": "Albee-A-L" }, { "family_name": "Tilton", "given_name": "G. R.", "clpid": "Tilton-G-R" } ], "contributor": [ { "family_name": "Craig", "given_name": "H.", "clpid": "Craig-Harmon" }, { "family_name": "Miller", "given_name": "S. L.", "clpid": "Miller-S-L" }, { "family_name": "Wasserburg", "given_name": "G. J.", "clpid": "Wasserburg-G-J" } ], "abstract": "An earlier Precambrian gneiss dome in the Panamint Range of California and its\nmantle of later Precambrian and Paleozoic rocks have been metamorphosed in late\nMesozoic time. Uranium-lead analyses of zircons indicate the primary age of the older\ngneiss to be about 1800 m.yrs and the age of a younger cross-cutting granite to be about\n1300 to 1400 m.yrs. Potassium-argon ages on biotite give ages ranging from 103-130\nm.yrs. Rubidium-strontium isotopic studies of all the constituent minerals and their\nassociated total rocks yielded biotite-total rock isochrons indicating ages ranging from\n64 to 156 m.yrs. All of the total rock ages deviate considerably from the apparent\nprimary age indicated by the zircon ages. The intercept values of Sr^(87)/Sr^(86) for the isochrons\nfrom the various rocks range from 0.85 to 1.08.\n\nNearly complete isotopic homogenization of strontium has occurred locally during\nthis metamorphic episode for all mineral systems except apatite and muscovite. The\n\"total rock systems\" were open in some cases, including samples as large as 85 kg. There\nis obvious mineralogic and field evidence for metamorphism in the mantling sediments\nbut no evidence for gross recrystallization and mobilization in either the mantling\nrocks or the underlying gneiss and granite. Even though original textures and structures,\nboth sedimentary and igneous are preserved, the observed homogenization of strontium\nindicates that extensive migration of strontium occurred and affords a sensitive test\nof metamorphism. Conditions causing the redistribution of strontium in the gneiss did\nnot lower the lead-uranium ratios of the zircons by more than 30%.\nA basic dike of later Precambrian age was found to contain radiogenic strontium\ndue to partial equilibration with the neighboring gneiss. This rock gives an apparent\nage of 31.4 x 10^9 yrs and presents evidence for strontium transport over a distance of\n5m.", "publisher": "North Holland", "publication_date": "1964" }, { "id": "authors:1bqkj-a3g85", "collection": "authors", "collection_id": "1bqkj-a3g85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141008-100731638", "type": "book_section", "title": "Spontaneous fission xenon in natural gases", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Mazor", "given_name": "E.", "clpid": "Mazor-E" } ], "contributor": [ { "family_name": "Tongiorgi", "given_name": "Ezio", "clpid": "Tongiorgi-E" } ], "abstract": "In the study of natural gases it is particularly important to\nbe able to distinguish between terrestrial juvenile components\nand those which are of atmospheric origin. The most positive\nidentification of juvenile components is made from studying the\nisotopic enrichments of those elements which are produced by\nnaturally occurring nuclear processes. Such results may indicate\nthe presence of components which have never been mixed with\nthe atmosphere. Rather extensive studies have been made by\nvarious workers on He^4 and Ar^(40) produced by radioactive decay\n(ALDRICH and NIER 1948, BOATO, CARERI, and SANTANGELO 1957,\nWASSERBURG, CZAMANSKE, FAUL and HAYDEN 1957, DAMON and\nKULP 1958, ZARTMAN, WASSERBURG and REYNOLDS 1961, WASSERBURG,\nMAZOR, and ZARTMAN 1963). In addition to these decay products,\nthe spontaneous fission of U^(238) also contributes, xenon and\nkrypton as gaseous daughter products. These spontaneous fission\n(and neutron fission) products have been detected in minerals by\nseveral workers (KHLOPIN, GERLING and BARANOVSKYA 1947,\n1948, MACNAMARA and THODE 1950, WETHERILL 1953, FLEMING\nand THODE 1953, GERLING and SHOKOLIVKOV 1959, GERLING, SHOKOLIKOV,\nand MAKAROCHKIN 1959, YOUNG and THODE 1960). In\na recent study by BUTLER, JEFFERY, REYNOLDS and WASSERBURG\n(1963) spontaneous fission xenon was found both in samples of\ngranite and in two samples of natural gases. More recently CLARKE and THODE (1963) have studied some terrestrial natural gases and\nfound contributions of spontaneous fission xenon.", "publisher": "Consiglio nazionale delle ricerche", "publication_date": "1963" }, { "id": "authors:smjkc-c7c03", "collection": "authors", "collection_id": "smjkc-c7c03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140505-073540214", "type": "book_section", "title": "Isotopic and Chemical Composition of Some Terrestrial Natural Gases", "author": [ { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Mazor", "given_name": "E.", "clpid": "Mazor-E" }, { "family_name": "Zartman", "given_name": "R. E.", "clpid": "Zartman-R-E" } ], "contributor": [ { "family_name": "Geiss", "given_name": "Johannes", "clpid": "Geiss-J" }, { "family_name": "Goldberg", "given_name": "Edward D.", "clpid": "Goldberg-E-D" } ], "abstract": "A variety of natural gases was analyzed for their content of argon, helium, hydrogen,\ncarbon dioxide, methane and heavier hydrocarbons, along with the isotopic compositions\nof their argon and carbon. It is found that most natural gases, including\nsamples from geothermal areas, have a (He^4/A^( 40))rad ratio which is close to the production\nratio in normal rocks. Glacial drift gases were found to have a distinctive\nchemistry and contain no detectable radiogenic argon.\nThe observed atmospheric argon contents of all gases, including very high pressure\nsources, are found to be compatible with a simple solubility model.\nUsing the measured ratios of (He^4/A ^(40))rad, a calculation of the mean life of He^4\nin the atmosphere was made of 5 x 10^5 \u2264 \u03c4 He^4 \u2264 2.5 x 10^7 years.", "publisher": "North-Holland Pub. Co.", "publication_date": "1963" }, { "id": "authors:420yn-tz131", "collection": "authors", "collection_id": "420yn-tz131", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141002-134957051", "type": "book_section", "title": "Argon^(40):Potassium^(40) Dating", "author": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "contributor": [ { "family_name": "Faul", "given_name": "Henry", "clpid": "Faul-H" } ], "abstract": "The element potassium has three naturally occurring isotopes,\npotassium^(39), potassium^(40), and potassium^(41), with atomic abundances\nof 93.08, 0.0119, and 6.9, respectively (Nier, 1950). Of these, potassium^(40)\nis radioactive with a decay constant \u03bb = 0.55 X 10^(-9) year^(-1)\n(see Birch, 1951; Burch, 1953). Potassium^(40) decays by K-electron\ncapture to argon^(40) with the emission of a gamma and by beta emission\nto calcium^(40) (see Figure 3.1).", "publisher": "Wiley", "publication_date": "1954" } ]