Meteorites contain organic compounds that occur in all known life. These compounds, commonly referred to as prebiotic compounds, include \u03b1-amino acids and are most prevalent on carbonaceous chondrites. As carbonaceous chondrites are pristine samples from early in the solar system that have not had living organisms on them, we can study the chemistry that produced \u03b1-amino acids on them to better understand the processes by which they might have formed on early Earth or on other bodies. Multiple syntheses have been put forth as routes to form amino acids on meteorites and include ice-grain chemistry on interstellar ices and Strecker synthesis in meteorite parent bodies. Prior measurements of molecular-average carbon isotope ratios (\u00b9\u00b3C/\u00b9\u00b2C) have found \u00b9\u00b3C enrichments of up to 53\u2030 in certain \u03b1-amino acids and molecular-average hydrogen isotope ratios (D/H) have found enrichments of 100s of \u2030. With this data, it has been suggested that Strecker synthesis\u2014a synthesis in which an aldehyde or ketone reacts with ammonia and cyanide to produce an \u03b1-aminonitrile that is hydrolyzed into an \u03b1-amino amide and then an \u03b1-amino acid\u2014is the primary pathway to produce \u03b1-amino acids on aqueously altered meteorites.
\r\n\r\nHere, we develop an instrument that can measure site-specific isotope ratios (SSIR) for carbon \u2014 that is the \u00b9\u00b2C/\u00b9\u00b3C at each site in a molecule \u2014 and use it to first constrain the site-specific isotope effects associated with Strecker synthesis and then the carbon SSIR of an alanine sample extracted from the Murchison meteorite. The instrument, the Q-Exactive Orbitrap, is a Fourier Transform Mass Spectrometer that has resolution of 240,000 full width-half maximum and can measure site-specific carbon isotope ratios on samples as small as 1 picomole. When we use it to measure the carbon SSIR in multiple samples of alanine produced by Strecker synthesis, we find a -20 \u2030 equilibrium isotope effect between the product alanine's C-2 site (amine carbon, \u00b9\u00b3C-depleted) reactant acetaldehyde\u2019s carbonyl carbon (\u00b9\u00b3C-enriched), a potential -15 \u2030 kinetic isotope effect on the C-1 site (eventual carboxyl carbon) for the first hydrolysis of \u03b1-aminopropanenitrile (\u00b9\u00b3C-enriched) into alaninamide (\u00b9\u00b3C-depleted), and a -15.4 \u2030 kinetic isotope effect on the C-1 carbon for the second hydrolysis step in which \u03b1-alaninamide (\u00b9\u00b3C-enriched) becomes alanine (\u00b9\u00b3C-depleted). Through conventional isotope ratio mass spectrometry, we also measure a +56.4 \u2030 equilibrium isotope effect between ammonia (\u00b9\u2075N-depleted) and the amine site on alanine (\u00b9\u2075N-enriched). When we measure the sample of alanine from the Murchison meteorite, we find site-specific carbon isotope ratios of -29 \u00b1 10 \u2030, 142 \u00b1 20 \u2030, and -36 \u00b1 20 \u2030 for the C-1, C-2, and C-3 (methyl) sites, respectively. This pattern agrees with the hypothesis that Strecker synthesis created alanine in Murchison. Combining these data with the isotope effects found for Strecker synthesis, we find initial site values of -7 \u00b1 10 \u2030, 162 \u00b1 20 \u2030, and 36 \u00b1 20 \u2030 for the C-1, C-2, and C-3 sites, respectively. With these values, we create a model of potential organic synthesis on the Murchison parent body that predicts the molecular-average \u03b4\u00b9\u00b3C values of 19 other prebiotic compounds.
\r\n\r\nFinally, we create a model that uses the previously measured molecular average carbon and deuterium isotope ratios for organics on Murchison to create models that predict site-specific and molecular average isotope ratios for organic compounds. This model finds that organic compounds with have methyl sites that are enriched in deuterium by up to 3000 \u2030 relative to other sites in the compound and that the degree of enrichment scales both with a compound class\u2019s solubility in water and with a sample\u2019s degree of aqueous alteration and terrestrial weathering. These patterns suggest that a primordial ISM-derived deuterium signal exchanges with water and that the methyl site hosts the highest amount of this enrichment due to its low acidity. The carbon model demonstrates that using only the aldehyde and cyanide values measured on Murchison and isotope effects inferred from other studies, we can predict 59 of 82 organic compounds on it (72%) that have \u03b4\u00b9\u00b3C values spanning over 149 \u2030 with an average residual of 6 \u2030. To achieve this level of prediction, the model combines Strecker synthesis, reductive amination, and oxidation of aldehydes to create straight-chain \u03b1-H hydroxy and amino acids, amines, and monocarboxylic acids with subsequent formaldehyde addition to these compounds to create branches.
", "doi": "10.7907/0hvh-xz81", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:10000", "collection": "thesis", "collection_id": "10000", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12212016-095346656", "type": "thesis", "title": "New Techniques for Noble Gas Geochronometry and Thermochronometry", "author": [ { "family_name": "Cox", "given_name": "Stephen Ellis", "orcid": "0000-0002-8819-887X", "clpid": "Cox-Stephen-Ellis" } ], "thesis_advisor": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" }, { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Noble gases were among the first species measured by mass spectrometry and interrogated for geochemical information about the solid Earth. The analytical challenge of measuring them has driven technological development in the field, and new applications have in turn followed from new developments. In the first chapter, I present developments that bolster an existing technique, the (U\u2013Th)/Ne system, by verifying the theoretical underpinnings of the method and by exploring its application in several minerals. In the second chapter, I show that the hematite (U\u2013Th)/Ne system is a sound geochronometer for use in the upper crust and a potent thermochronometer for exploring mid-crustal processes. In the third chapter I show significant advances toward using a quadrupole ion trap as a noble gas mass spectrometer, including the first static vacuum measurements. This technique provides new opportunities for low abundance noble gas measurements through its ultra low dark noise time of flight measurement approach and its high resolution, high mass range scanning capabilities. The quadrupole ion trap can measure lower concentrations of rare species like 3He and 21Ne on Earth, allowing us to make more precise determinations of cosmogenic exposure ages, and it can measure species with much higher resolution than is currently possible on most spaceflight instruments, allowing us to perform measurements on planetary surfaces and in deep space that are currently reserved to terrestrial laboratories. Finally, in the fourth chapter I demonstrate that an old, largely abandoned technique, (U\u2013Th)/He geochronometry, has useful applications now that we fully understand its limitations.", "doi": "10.7907/Z9V69GKV", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:5817", "collection": "thesis", "collection_id": "5817", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05192010-102315391", "type": "thesis", "title": "Cosmogenic \u00b3He and \u00b2\u00b9Ne Dating in Accessory Mineral Phases", "author": [ { "family_name": "Amidon", "given_name": "William Henry", "clpid": "Amidon-William-Henry" } ], "thesis_advisor": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" } ], "thesis_committee": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Lamb", "given_name": "Michael P.", "clpid": "Lamb-M-P" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The development of terrestrial cosmogenic nuclide dating has led to applications as varied as the dating of glacial moraines, establishing slip-rates on faults, measuring the erosion rates of basins, and measuring rates of soil formation. Studies in many of these fields could greatly benefit from analysis of far more samples than can be easily dated using 10Be, 26Al, and 36Cl. The rapid preparation and analysis of samples for cosmogenic 3He often allows a greater number of samples to be analyzed, but has so far been applied primarily to olivine and pyroxene in mafic rocks. Because 3He is produced in all mineral phases, it can potentially be applied in almost any lithology. The goals of this thesis is to expand the range of target lithologies suitable for cosmogenic 3He dating by calibrating production rates of cosmogenic 3He in accessory mineral phases such as apatite, zircon, and garnet. Results are presented from three calibration studies: glacial moraine boulders in the Nepal Himalaya, young rhyolite surfaces from California\u2019s Coso volcanic field, and rhyolite surfaces scoured by the Bonneville flood near Twin Falls, Idaho. Both the Nepal and Coso studies compare 3He in zircon, apatite, and garnet against 10Be in quartz, finding that higher than expected 3He concentrations are likely due to anamolous elevation scaling in the Himalaya, and to production of 3He via neutron capture on 6Li at Coso. The Idaho calibration study is unique in that it is calibrated against the age of the Bonneville outburst flood (known by 14C dating), and uses a shielded sample to definitively document Li-produced 3He components in the deep sub surface. Collectively, these studies highlight several challenges associated with cosmogenic 3He dating of accessory phases: the difficulty in measuring small amounts of cosmogenic 3He in the presence of large amounts of radiogenic 4He, the importance of production of 3He via neutron capture on 6Li, and the redistribution of energetic 3He and 3H between adjacent mineral phases. Despite these challenges, adopting a 10Be production rate of 4.51 at g-1 a-1 in quartz (Balco et al., 2008), brings three independent 3He production rate estimates into good agreement with grand means of 103 \u00b1 3, 133 \u00b1 6, and about 134 \u00b1 13 at g-1 a-1 in zircon, apatite, and spessartine garnet respectively. Such agreement suggests that these phases are suitable for cosmogenic dating. 3He in accessory phases may enable a range of unique applications including the study of ancient sediments, paleo-altimetry, and rates of chemical weathering in soils.", "doi": "10.7907/R6JB-BW27", "publication_date": "2010-06-11", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:5058", "collection": "thesis", "collection_id": "5058", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12182008-115035", "primary_object_url": { "basename": "01Guo2008PhDThesis.pdf", "content": "final", "filesize": 17906569, "license": "other", "mime_type": "application/pdf", "url": "/5058/1/01Guo2008PhDThesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Carbonate Clumped Isotope Thermometry: Applications to Carbonaceous Chondrites and Effects of Kinetic Isotope Fractionation", "author": [ { "family_name": "Guo", "given_name": "Weifu", "orcid": "0000-0002-1605-1019", "clpid": "Guo-Weifu" } ], "thesis_advisor": [ { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" } ], "thesis_committee": [ { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" }, { "family_name": "Sessions", "given_name": "Alex L.", "clpid": "Sessions-A-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Adkins", "given_name": "Jess F.", "clpid": "Adkins-J-F" }, { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "'Clumped isotope' thermometry of carbonates in the carbonaceous chondrites (CM, CI, CR and Tagish Lake) demonstrates that aqueous alteration of their parent bodies occurred from -31 to 71\u00b0C and involved reaction with fluids having \u03b418OVSMOW values of -29.7\u2030 to 11.8\u2030 and \u03b417OVSMOW of -14.9\u2030 to 7.6\u2030. Estimated carbonate formation temperatures decrease in the order: calcite > dolomite > breunnerite. Based on independent constraints on the ages of these carbonates and models of the evolution of the oxygen isotope compositions of parent body waters, I estimate that carbonate precipitation during aqueous alteration of the carbonaceous chondrite parent bodies started within 1-2 million years after the accretion of those parent bodies, and that the alteration temperatures decreased from 34\u00b0C to 18\u00b0C in the first ~4 million years and further to -20\u00b0C after a total of ~6.5 million years. Our results provide the first direct measurements of the low-temperature cooling histories of C1 and C2 carbonaceous chondrite parent bodies. Within the CM chondrite group itself, I observe a negative correlation between the \u03b413C values of CM carbonates and the \u03b418O of their formation waters, suggesting formation and escape of 13C-depleted CH4 during aqueous alteration on the CM chondrite parent bodies.
\r\n\r\nI apply ab initio transition state and statistical thermodynamics theory to study the kinetic isotope fractionations of clumped isotopologues (i.e., multiply-substituted isotopologues; I also consider singly-substituted isotopologues) associated with phosphoric acid digestion of carbonate minerals and with the degassing of CO2 from aqueous solutions. Assuming that H2CO3 is the reaction intermediate during phosphoric acid digestion of carbonate minerals, I predict at 25\u00b0C that CO2 derived from acid digestion of carbonate minerals will be 10.72\u2030 and 0.220\u2030 higher, respectively, in 18O/16O ratios and 13C-18O clumped isotope anomaly than the reactant carbonate. These predicted kinetic isotope fractionations associated with phosphoric acid digestion and their temperature dependences (for both oxygen isotope and clumped isotopologues) compare favorably with independent experimental constraints for phosphoric acid digestion of calcite. I evaluate the effect of carbonate cation compositions on phosphoric acid digestion fractionations using cluster models in which disproportionating H2CO3 interacts with adjacent cations. These cluster models underestimate the magnitude of isotope fractionations, but do successfully reproduce the general trend of variations and temperature dependences of oxygen isotope acid digestion fractionations among different carbonate minerals (suggesting I have correctly identified the basic mechanism responsible for a dependence on cation chemistry, but not the exact structural model for cation\u2014H2CO3 clusters). I further integrate our acid digestion fractionation model with previous theoretical evaluations of abundances of 13C-18O bonds in carbonate minerals, and predict the relationship between \u039447 values for CO2 extracted from carbonate minerals and the growth temperatures of those carbonates, including witherite, calcite, aragonite, dolomite and magnesite. I observe reasonable agreement between these predictions and available experimental determinations (e.g., difference of less than 0.05\u2030 over 0-50\u00b0C, for calcite).
\r\n\r\nKinetic isotope fractionation associated with HCO3- dehydration and HCO3- dehydroxylation reactions (the two pathways of CO2 degassing from aqueous solutions) are estimated with ab initio transition state theory calculations. Coupled with models of isotopic fractionations accompanying carbonate precipitation, I predict that kinetic isotope fractionation associated with CO2 degassing reactions will increase the \u03b413C and \u03b418O but decrease the relative proportion of 13C-18O bonds in carbonate minerals that precipitate from degassing solutions. Furthermore, these kinetic isotope effects are correlated with each other. For example, I predict the 13C/12C ratio of carbonate increases by 1.1-3.2\u2030 and its \u039447 value decreases by 0.017-0.026\u2030 for every 1\u2030 kinetic enrichment in its 18O/16O at 25\u00b0C, with the exact values depending on the pathway for CO2 degassing (i.e., HCO3- dehydration vs. HCO3- dehydroxylation) and on the amount of carbonate formation that accompanies CO2 degassing. These predictions compare favorably with the experimental constraints from laboratory synthesized cryogenic carbonates and speleothem-like carbonates and with the isotopic compositions of natural modern speleothems.
", "doi": "10.7907/BWC2-RH54", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:444", "collection": "thesis", "collection_id": "444", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02012007-204746", "primary_object_url": { "basename": "Thesis_Li_Final.pdf", "content": "final", "filesize": 6425083, "license": "other", "mime_type": "application/pdf", "url": "/444/1/Thesis_Li_Final.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Dynamics of the Jovian Atmosphere from Observation and Theory", "author": [ { "family_name": "Li", "given_name": "Liming", "orcid": "0000-0002-5257-9849", "clpid": "Li-Liming" } ], "thesis_advisor": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Richardson", "given_name": "Mark I.", "clpid": "Richardson-M-I" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "The atmospheric dynamics of Jupiter is studied by the Cassini observations and numerical models.
\r\n\r\nThe multi-filter imaging data sets and the global thermal maps acquired by two instruments on Cassini--the Imaging Science Subsystem (ISS) and the Cassini Composite Infrared Spectrometer (CIRS) during the Jupiter flyby, are utilized to study atmospheric activities on Jupiter including small-scale spots, the Great Red Spot (GRS), the Dark Oval (DO), the vertical structure of zonal winds, and wave propagation. These new observations enrich the library of atmospheric activities and offer more clues and constraints on theoretical studies.
\r\n\r\nA reduced-gravity quasi-geostrophic (QG) model is combined with a parameterization of moist convections based on observations, to study the interaction between moist convection and zonal jets on Jupiter and Saturn. The numerical experiments support the idea that the zonal jets get their energy from moist convective events. Strong jets in Jupiter and Saturn, which violate the barotropic stability criterion, are reproduced by assuming westward flows in the deep underlying layer. Furthermore, our simulations suggest that the width and strength of jets on Jupiter and Saturn are controlled by the classical Rhines scale and a new velocity scale determined by characteristics of moist convection.
", "doi": "10.7907/6DAY-FJ03", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:1779", "collection": "thesis", "collection_id": "1779", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05132007-103357", "primary_object_url": { "basename": "MillerThesis2007.pdf", "content": "final", "filesize": 4772897, "license": "other", "mime_type": "application/pdf", "url": "/1779/13/MillerThesis2007.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Alkaline Earth Element Partitioning in Simplified Magmatic Systems", "author": [ { "family_name": "Miller", "given_name": "Sarah Ann", "clpid": "Miller-Sarah-Ann" } ], "thesis_advisor": [ { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Trace element distributions between mineral and melt phases have proven to be important recorders of igneous differentiation histories, but this utility depends on thorough understanding of their partitioning behavior. We propose a theory for crystal-melt trace element partitioning that considers the energetic consequences of crystal-lattice strain, of multi component major-element silicate liquid mixing, and of trace element activity coefficients in melts. We demonstrate application of the theory using newly determined partition coefficients for Ca, Mg, Sr, and Ba between pure anorthite and seven CMAS liquid compositions at 1330 \u00b0C and 1 atm. By selecting a range of melt compositions in equilibrium with a common crystal composition at equal liquidus temperature and pressure, we have isolated the contribution of melt composition to divalent trace element partitioning in this simple system. The partitioning data are fit to Onuma curves with parameterizations that can be thermodynamically rationalized in terms of the melt major element activity product (aAl2O3)(aSiO22) and lattice strain theory modeling. Residuals between observed partition coefficients and the lattice strain plus major oxide melt activity model are then attributed to non-ideality of trace constituents in the liquids. The activity coefficients of the trace species in the melt are found to vary systematically with composition. Accounting for the major and trace element thermodynamics in the melt allows a good fit in which the parameters of the crystal lattice strain model are independent of melt composition.\r\n\r\nWe also present the first experimental measurements of mineral-melt radium partitioning. Ion probe analyses of coexisting anorthite and CMAS glass phases produce a molar DRa = 0.040 \u00b1 0.006 and DRa/DBa = 0.23 at 1400 \u00b0C and 1 atm. Our results indicate that lattice strain partitioning models fit the divalent (Ca, Sr, Ba, Ra) partition coefficient data of this study well, supporting previous work on crustal melting and magma chamber dynamics that has relied on such models to approximate radium partitioning behavior in the absence of experimentally determined values. ", "doi": "10.7907/90DK-3398", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:1874", "collection": "thesis", "collection_id": "1874", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05192005-000025", "primary_object_url": { "basename": "wzhr_thesis.pdf", "content": "final", "filesize": 23110022, "license": "other", "mime_type": "application/pdf", "url": "/1874/1/wzhr_thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Oxygen Isotope Studies of the Petrogenesis of Hawaiian Lavas and a Theoretical Study on Equilibrium Thermodynamics of Multiply-Substituted Isotopologues", "author": [ { "family_name": "Wang", "given_name": "Zhengrong", "clpid": "Wang-Zhengrong" } ], "thesis_advisor": [ { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" }, { "family_name": "Asimow", "given_name": "Paul David", "clpid": "Asimow-P-D" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Stolper", "given_name": "Edward M.", "clpid": "Stolper-E-M" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" }, { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" }, { "family_name": "Asimow", "given_name": "Paul David", "clpid": "Asimow-P-D" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Temporal oxygen isotope variations have been discovered in both Mauna Kea and Koolau volcanoes after detailed studies of the Hawaiian Scientific Drilling Project (HSDP-phase II) and Koolau Scientific Drilling Project (KSDP). In both volcanoes, oxygen isotope compositions of olivine phenocrysts all converge to 'Mauna Loa-like' values from depleted or enriched composition, respectively and yet, the interpretations are totally different. In the studies of HSDP core, many lines of geochemical evidences strongly indicate that low-[delta18]O values characteristic of Kea trend Hawaiian lavas are the product of contamination by hydrothermally altered rocks in the volcanic edifice. In the studies of KSDP core and submarine Koolau landslides, a full diversity of [delta18]O values correlate with trace element and radiogenic isotope compositions of host lavas. These correlations are interpreted as reflecting mixing between partial melts of high-[delta18]O and normal-[delta18]O components. A magma mixing model has been constructed to simultaneously explain the oxygen isotope, major element, trace element and radiogenic isotope variations defined by these correlations. This model indicates that the Koolau shield-building lavas are mixtures of 75~100% melt of mantle peridotite with 0~25% eclogite melt, the protolith of which is Mid-Ocean Ridge Basalt (MORB) with Depleted Mantle Model (DMM) age of at least 1.8\u00b10.3 billions years. [delta18]O value of this eclogite component is predicted to be 11.3\u00b11.5\u2030, implying it is an upper crustal (layer 1 or 2) basalt or gabbro with a low-temperature alteration history; contains a small amount of sediment; and has experienced partial melting before forming eclogite.
\r\n\r\nI also derived a method for systematically evaluating clumped-isotope effects in the abundances of all isotopologues in thermodynamically equilibrated populations of O2, CO, N2, NO, CO2 and N2O between 1000 and 193 to 77 K. This method uses Urey-type algorithms to evaluate partition functions and equilibrium constants of isotope exchange reactions, and simultaneously solves for abundance of each isotopologue of a given molecule constrained by all independent equilibria. Calculation results show that, in most cases, multiply-substituted isotopologues of these mono-molecular gases are predicted to be enriched relative to stochastic (random) distributions by ca. 1 to 2 per mil at earth-surface temperatures.
", "doi": "10.7907/zrza-wc92", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2357", "collection": "thesis", "collection_id": "2357", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06012005-135600", "primary_object_url": { "basename": "Shuster_Thesis_Final.pdf", "content": "final", "filesize": 1063593, "license": "other", "mime_type": "application/pdf", "url": "/2357/1/Shuster_Thesis_Final.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Application of Spallogenic Noble Gases Induced by Energetic Proton Irradiation to Problems in Geochemistry and Thermochronometry", "author": [ { "family_name": "Shuster", "given_name": "David Lawrence", "clpid": "Shuster-David-Lawrence" } ], "thesis_advisor": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" } ], "thesis_committee": [ { "family_name": "Adkins", "given_name": "Jess F.", "clpid": "Adkins-J-F" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" }, { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Synthetic components of 3He, 4He, and 21Ne were generated within natural minerals via irradiation with 150 and 220 MeV proton beams. Fluences of ~10^14 and ~10^16 protons/cm2 induced 3He concentrations of ~10^8 and ~10^9 atoms/mg, respectively. Controlled degassing experiments on irradiated samples of terrestrial apatite (Ca5(PO4)3F), titanite (Ca(TiO)(SiO4)), olivine ((Mg,Fe)2SiO4), goethite (FeOOH), and quartz (SiO2) demonstrate that the proton-induced nuclides are spatially uniform across samples <= 1 mm in diameter and sequential degassing quantifies solid state diffusion kinetics of helium and neon. Diffusion kinetics of proton-induced 3He in Durango apatite (Ea = 147.9 \u00b1 1.3 kJ/mol; ln(Do/a2) = 16.0 \u00b1 0.3 ln(s-1)) and Fish Canyon tuff titanite (Ea = 183.7 \u00b1 2.7 kJ/mol; ln(Do/a2) = 13.3 \u00b1 0.5 ln(s-1)), are indistinguishable from those determined for natural radiogenic 4He in the same samples. Experiments indicate that lattice damage potentially introduced via proton irradiation did not significantly modify the natural 4He diffusion kinetics in the two samples, and that the proton-induced 4He component is relatively negligible in abundance. Therefore, sequentially measured 4He/3He ratios reflect the natural spatial distribution of radiogenic 4He. Combined with a (U-Th)/He age and helium diffusion kinetics, the distribution limits the time-temperature (t-T) path a mineral experienced through geologic time. This is the basis for a new methodology called 4He/3He thermochronometry, which for apatite constrains continuous t-T paths between 80 oC and 20 oC. Proton-induced 3He diffusion parameters in olivine are: Ea = 153.8 \u00b1 1.1 kJ/mol and ln(Do/a2) = 3.0 \u00b1 0.2 ln(s-1). At 25 oC, the helium diffusion kinetics in a goethite sample (Ea = 163 \u00b1 2.4 kJ/mol; ln(Do/a2) = 26.0 \u00b1 0.6 ln(s-1)) predict 90% 4He retention over 11.8 Ma, consistent with the observed deficit gas fraction and (U-Th)/He age of 10.7 Ma. This indicates that goethite (U-Th)/He dating is a viable weathering geochronometer. In quartz, the diffusion kinetics for proton-induced 21Ne and 3He (Ea = 153.7 \u00b1 1.5 (kJ/mol); ln(Do/a2) = 15.9 \u00b1 0.3 (ln(s-1)) and Ea = 84.5 \u00b1 1.2 (kJ/mol); ln(Do/a2) = 11.1 \u00b1 0.3 (ln(s-1), respectively), indicate that cosmogenic neon will be quantitatively retained in inclusion-free quartz at Earth surface temperatures whereas cosmogenic helium will not.", "doi": "10.7907/EXV3-GG18", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:6831", "collection": "thesis", "collection_id": "6831", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02232012-115811346", "primary_object_url": { "basename": "Mukhopadhyay_s_2002.pdf", "content": "final", "filesize": 35328403, "license": "other", "mime_type": "application/pdf", "url": "/6831/1/Mukhopadhyay_s_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "I. Extraterrestrial \u00b3He in the Sedimentary Record. II. Geochemistry of Shield Stage Lavas from Kauai, Hawaii", "author": [ { "family_name": "Mukhopadhyay", "given_name": "Sujoy", "clpid": "Mukhopadhyay-Sujoy" } ], "thesis_advisor": [ { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "(I) Extraterrestrial ^3He in the sedimentary record:
\r\n\r\nAnalyses of ^3He, a tracer of interplanetary dust particles (IDPs), in marine\r\ncarbonates from the Italian Apennines exclude large, long-lived enhancement in the IDP\r\nflux between 75 Ma and 39 Ma, These data in combination with previous ^3He\r\nmeasurements preclude recurrent comet showers with periods less than 38 Myrs. The IDP\r\naccretion rate at the K-T boundary (65 Ma) is invariant and has, therefore, been used as a\r\nchronometer to estimate the duration of the K-T extinction event. Our calculation\r\nsuggests that the duration of the boundary event is 10000 \u00b1 2000 years, and the\r\ndeposition time of the impact ejecta layer is less than 60 years. These results indicate that\r\nthe mass-extinction at the K-T boundary was catastrophic, ruling out volcanism and sea\r\nlevel changes as important factors and requiring an extremely rapid faunal turnover rate.
\r\n\r\nBecause extraterrestrial ^3He is preserved in the sedimentary record for at least 480\r\nMa, the ^3He carrier phase(s) must be chemically stable on the seafloor and resist diffusion\r\nover geologic time, Our chemical leaching and step-heating experiments indicate that the\r\ncarrier phase(s) may be magnetite or more probably associated with magnetite, The\r\nassociation may be in the form of composite grains or nanometer thick rims.
\r\n\r\n(II) Geochemistry of shield stage lavas from Kauai, Hawaii:
\r\n\r\nWe measured He, Sr, Nd, Pb, and Os isotope ratios and major and trace element\r\nconcentrations in shield lavas from Kauai, Hawaii. The range of ^3He/^4He ratios (17-28\r\nR_A) measured from the Kauai shield is similar to that reported from Loihi Seamount and is clearly distinct from other Hawaiian shield volcanoes. These results challenge the\r\nprevailing notion that high ^3He/^4He ratios are restricted to the pre-shield stage of\r\nHawaiian volcanism. ^3He/^4He ratios in Kauai shield lavas vary erratically with\r\nstratigraphic position and on timescales of 100 years. These variations in ^3He/^4He ratios\r\nare correlated with variations in radiogenic isotope ratios, suggesting rapid changes in\r\nparental magma composition with time.
\r\n\r\nOur new geochemical data from Kauai shield lavas require the involvement of a\r\ndepleted mantle component that is normally sampled only during the post-shield and\r\npost-erosional stages of Hawaiian volcanism. In addition, the Kauai data support the\r\nexistence of a single high ^3He^4He reservoir in the Earth's mantle and suggest that the\r\nproportion of the high ^3He/^4He component in the Hawaiian plume has varied significantly\r\nwith time. The long-term evolution of the Hawaiian plume and the temporal variability\r\nrecorded in Kauai lavas cannot be explained by a steady-state cylindrically zoned plume\r\nand require more complex time-varying heterogeneities.
\r\n\r\n", "doi": "10.7907/XPM2-1Q79", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6827", "collection": "thesis", "collection_id": "6827", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02172012-143736224", "primary_object_url": { "basename": "Kessel_r_2002.pdf", "content": "final", "filesize": 47941744, "license": "other", "mime_type": "application/pdf", "url": "/6827/1/Kessel_r_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "The Activity of Chromite in Multicomponent Spinels: An Experimental Study with Implications for the Metamorphic History of Equilibrated Ordinary Chondrites", "author": [ { "family_name": "Kessel", "given_name": "Ronit", "clpid": "Kessel-Ronit" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "An experimental technique for evaluating the activity of chromite in\r\nmulticomponent spinels was developed by equilibrating the spinel of interest with a Pt-alloy\r\nunder a controlled temperature and oxygen fugacity. The thermodynamic\r\nproperties of the ternary Pt-Fe-Cr system was evaluated, such that activities of Cr and Fe\r\nin an equilibrated Pt-alloy can be used to calculate the activity of chromite in the spinel of\r\ninterest.
\r\n\r\nThe ternary activity model formulation used is based on the characterization of\r\neach bounding binary system, Pt-Fe, Pt-Cr, Fe-Cr, with the addition of ternary interaction\r\nterms. The Pt-Fe and Pt-Cr systems are described as asymmetric regular solutions with\r\ninteraction parameters of W_(PtFe)=-138.0\u00b13.3, W_(FePt)=-90.8\u00b124.0, and W_(PtCr)=-129.1\u00b11.2,\r\nW_(CrPt)=-80.9\u00b14.4, and D_(PtCr)=+94.4\u00b12.5 kJ/mol (1\u03c3), respectively. Combined with\r\nliterature thermodynamic properties for the Fe-Cr system, the ternary interaction\r\nparameters in the Pt-Fe-Cr system were found to be C_(Cr)=0, C_(Pt)=+ll5.7, and C_(Fe)=-68.6\r\nkJ/mol.
\r\n\r\nUsing this technique, the metamorphic history of equilibrated ordinary chondrites\r\nwas evaluated by examining the compositions and textures of olivines, pyroxenes,\r\nspinels, and alloys. Equilibrium temperatures based on Fe-Mg exchange between olivine\r\nand spinel exhibit a range of 680-796\u00b0C in H, L, and LL ordinary chondrites spanning\r\npetrographic type 4 to 6. Type 4 chondrites in all groups record variable temperatures\r\nthat are lower than or equal to those of types 5 and 6 chondrites, implying decoupling of\r\nmetamorphic temperature from petrographic type. Cooling rates near 800\u00b0C were found to be 1-3 K/Ma, slow enough to allow continous re-equilibration of spinel grains from\r\npeak metamorphic temperatures to the olivine-spinel equilibration temperature.
\r\n\r\nThe temperature-oxygen fugacity relationships in equilibrated H chondrites were\r\nconstrained from spinel-alloy and olivine-pyroxene-alloy phase assemblages based on the\r\nmineral compositions and activity-composition models. Log_(10)f_(02) values based on the\r\nassemblage olivine-pyroxene-alloy are -1.75\u00b10.02 log units below Iron-W\u00fcstite (IW)\r\nbuffer, regardless of petrographic type. The log_(10)f_(02) values calculated based on the\r\nspinel-alloy coexistence are at least ~1.5 log units more oxidizing than those based on the\r\nolivine-pyroxene-alloy if olivine-spinel equilibration temperatures (728-820\u00b0C) are\r\nassumed. This probably indicates that closure for spinel-alloy equilibria occurred under\r\nretrograde conditions at temperatures below 700\u00b0C.
", "doi": "10.7907/0774-JM48", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:8202", "collection": "thesis", "collection_id": "8202", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04252014-150216789", "primary_object_url": { "basename": "Goreva_js_2001.pdf", "content": "final", "filesize": 30721634, "license": "other", "mime_type": "application/pdf", "url": "/8202/1/Goreva_js_2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Origin of Th/U Variations in Chondritic Meteorites", "author": [ { "family_name": "Goreva", "given_name": "Julia S.", "clpid": "Goreva-Julia-S" } ], "thesis_advisor": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Wasserburg", "given_name": "Gerald 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" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Isotope dilution thorium and uranium analyses of the Harleton chondrite show a\r\nlarger scatter than previously observed in equilibrated ordinary chondrites (EOC). The\r\nlinear correlation of Th/U with 1/U in Harleton (and all EOC data) is produced by\r\nvariation in the chlorapatite to merrillite mixing ratio. Apatite variations control the U\r\nconcentrations. Phosphorus variations are compensated by inverse variations in U to\r\npreserve the Th/U vs. 1/U correlation. Because the Th/U variations reflect phosphate\r\nampling, a weighted Th/U average should converge to an improved solar system Th/U.\r\nWe obtain Th/U=3.53 (1-mean=0.10), significantly lower and more precise than previous\r\nestimates.
\r\n\r\nTo test whether apatite also produces Th/U variation in CI and CM chondrites, we\r\nperformed P analyses on the solutions from leaching experiments of Orgueil and\r\nMurchison meteorites.
\r\n\r\nA linear Th/U vs. 1/U correlation in CI can be explained by redistribution of\r\nhexavalent U by aqueous fluids into carbonates and sulfates.
\r\n\r\nUnlike CI and EOC, whole rock Th/U variations in CMs are mostly due to Th\r\nvariations. A Th/U vs. 1/U linear correlation suggested by previous data for CMs is not\r\nreal. We distinguish 4 components responsible for the whole rock Th/U variations: (1) P\r\nand actinide-depleted matrix containing small amounts of U-rich carbonate/sulfate phases\r\n(similar to CIs); (2) CAIs and (3) chondrules are major reservoirs for actinides, (4) an\r\neasily leachable phase of high Th/U. likely carbonate produced by CAI alteration.\r\nPhosphates play a minor role as actinide and P carrier phases in CM chondrites.
\r\n\r\nUsing our Th/U and minimum galactic ages from halo globular clusters, we\r\ncalculate relative supernovae production rates for 232Th/238U and 235U/238U for different\r\nmodels of r-process nucleosynthesis. For uniform galactic production, the beginning of the\r\nr-process nucleosynthesis must be less than 13 Gyr. Exponentially decreasing production is also\r\nconsistent with a 13 Gyr age, but very slow decay times are required (less than 35 Gyr),\r\napproaching the uniform production. The 15 Gyr Galaxy requires either a fast initial\r\nproduction growth (infall time constant less than 0.5 Gyr) followed by very low decrease (decay\r\ntime constant greater than 100 Gyr), or the fastest possible decrease (\u22488 Gyr) preceded by slow in fall\r\n(\u22487.5 Gyr).
\r\n", "doi": "10.7907/hfsz-ym11", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:15066", "collection": "thesis", "collection_id": "15066", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11282022-190922104", "type": "thesis", "title": "\u00b9\u2078O/\u00b9\u2076O Studies of Short-Lived (10-25 Year), Fumarolic (>500\u00b0C) Meteoric-Hydrothermal Events in the Outflow Sheets of Ash-Flow Tuffs", "author": [ { "family_name": "Holt", "given_name": "Elizabeth Warner", "clpid": "Holt-Elizabeth-Warner" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "thesis_committee": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "\u00b9\u2078O/\u00b9\u2076O data from the 0.76 Ma Bishop Tuff outflow sheet provide evidence\r\nfor a vigorous, short-Jived (\u224810-25 years), high-temperature (400\u00b0-650\u00b0C), fumarolic\r\nmeteoric-hydrothermal event immediately following eruption. This is proved by: (1) the\r\njuxtaposition in the upper, partially welded Bishop Tuff of low-\u00b9\u2078O groundmass/glass\r\n(\u03b4\u00b9\u2078O = -5 to +3) with coexisting quartz and feldspar phenocrysts having magmatic \u03b4\u00b9\u2078O values (+8.4 \u00b1 0.3; +7.2 \u00b1 0.3); and (2) the fact that these types of \u00b9\u2078O/\u00b9\u2076O signatures\r\ncorrelate very well with the morphological features and mapped zones of fumarolic activity.\r\nTen detailed \u03b4\u00b9\u2078O-depth profiles in various parts of the Bishop Tuff outflow sheet show\r\nevidence for two types of fumarolic meteoric-hydrothermal circulation systems in the upper\r\npart of the tuff; there is a broadly based, stratigraphically bound, 20- to 40-m-thick Upper\r\nLow-\u00b9\u2078O Zone (ULZ) that straddles the contact between the Tableland Unit and the Gorges\r\nUnit, and there is also a set of localized, 40- to 80-m-thick zones in the partially welded tuff\r\nin which extremely \u00b9\u2078O-depleted rock (\u03b4\u00b9\u2078O as low as -6.5) characterizes a Deep\r\nFumarolic System (DFS). This DFS is spatially associated with steep fissures, tubular\r\nconduits, and shallow-dipping columnar joints in cylindrical volumes of rock lying beneath\r\nmore than 1000 fumarolic mounds scattered across the surface of the tuff. Both of these\r\n\u00b9\u2078O-depleted zones are concentrated over areas where the underlying Densely Welded Zone\r\n(DWZ) is particularly thick, namely above pre-Bishop Tuff paleodrainages. The DWZ\r\nremained largely hot, ductile, and impermeable during fumarolic activity, which prevented\r\nthe heated meteoric fluids from penetrating the densely welded tuff until it cooled\r\nsufficiently so that throughgoing vertical fractures provided access to the base of the ash-flow\r\nsheet (at which time the fumarolic activity appears to have rapidly terminated).\r\nWhole-rock \u03b4\u00b9\u2078O values of samples collected from the surface of the 1912 ash-flow sheet\r\nat the Valley of Ten Thousand Smokes (VTTS), Alaska show analogous \u00b9\u2078O/\u00b9\u2076O\r\nsystematics and a similar range in \u03b4\u00b9\u2078O values (-0.1 to +12.6) to surface samples collected\r\nfrom the Bishop Tuff outflow sheet (+2.5 to +16.7).", "doi": "10.7907/8vdb-7r67", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:11860", "collection": "thesis", "collection_id": "11860", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10242019-141223855", "primary_object_url": { "basename": "wasylenki-le-1999.pdf", "content": "final", "filesize": 6470569, "license": "other", "mime_type": "application/pdf", "url": "/11860/1/wasylenki-le-1999.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Partial Melting of Depleted Peridotite in the Earth's Upper Mantle and Implications for Generation of Mid-Ocean Ridge Basalts", "author": [ { "family_name": "Wasylenki", "given_name": "Laura Eileen", "orcid": "0000-0003-0333-3567", "clpid": "Wasylenki-Laura-Eileen" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "clpid": "Stolper-E-M" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" } ], "thesis_committee": [ { "family_name": "Stolper", "given_name": "Edward M.", "clpid": "Stolper-E-M" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Peridotite in the earth's upper mantle undergoes polybaric, fractional melting as it rises adiabatically beneath mid-ocean spreading ridges. As liquid is continually extracted, peridotite becomes increasingly depleted in incompatible components. The amounts and compositions of partial melts of depleted peridotite are important parameters in models of MORB petrogenesis, but have not been well-constrained previously. I present partial melting experiments on a depleted peridotite composition at 10 kbar and 1250\u20131390\u00b0C. My experiments make use of small aggregates of glassy carbon particles into which partial melt is extracted at high temperature. I have been able to analyze low degree partial melts (<10%) and quantify the effects of incompatible element depletion on the melting behavior of peridotite. Special tests of the approach to equilibrium in this study confirm the validity of the aggregate melt extraction technique, which has sparked much debate in the literature (see Chapters 2 and 3 for details).
\r\n\r\nMelts of depleted peridotite differ in important ways from melts of fertile peridotite, mostly due to lower alkali contents and chemical consequences thereof. At low melt fractions, melts of depleted peridotite have less SiO\u2082, more CaO, and higher CaO/Al\u2082O\u2083 than melts of fertile peridotite at the same melt fraction. According to these results and others in the literature, solidus temperature is a linear function of incompatible major element content. Melt fraction at cpx-out is proportional to normative cpx in source peridotite.
\r\n\r\nLiquid compositions from this study are in good agreement with calculations using the quantitative models of Kinzler and Grove (1992a), Langmuir et al. (1992), and Ghiorso and Sack (1995). Calculations of polybaric, fractional melting of primitive mantle using the models of Langmuir et al. (1992) and Asimow (1997) indicate that about half of all liquid contributed to MORB is formed by partial melting of depleted peridotite.
\r\n\r\nThe data presented in this thesis provide information about amounts and compositions of partial melts formed from depleted peridotite, an important upper mantle constituent beneath mid-ocean ridges, and can be used to improve quantitative models of MORB primary magma formation and further our understanding of MORB petrogenesis.
", "doi": "10.7907/9rx0-fn74", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:4634", "collection": "thesis", "collection_id": "4634", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11222004-140151", "type": "thesis", "title": "I. Observations and Photochemical Modeling of the Venus Middle Atmosphere. II. Thermal Infrared Spectroscopy of Europa and Callisto", "author": [ { "family_name": "Mills", "given_name": "Franklin Perry", "clpid": "Mills-Franklin-Perry" } ], "thesis_advisor": [ { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "thesis_committee": [ { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Brown", "given_name": "Michael E.", "clpid": "Brown-M-E" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The evolution of our solar system remains one of the most fascinating questions since ancient astronomers first realized that the \"stars\" which do not twinkle are planets. In the modern era, the future evolution of the Earth has become a topic that may arise even in lay conversations. For example, the effects of changes in the earth's climate and the ozone layer are debated in policy and economic discussions as well as in scientific forums. One method for assessing our understanding of the Earth's atmosphere is to examine the atmospheres of the other terrestrial planets. The atmospheres of Venus and Mars share some common features with that of the Earth, but there are important differences. These differences are important because they force us to examine the often implicit assumptions that lie within the tunable parameters that exist in all models. Consequently, studies of the atmospheric chemistry on Venus and Mars can provide a test of the degree to which our understanding of the fundamental physical and chemical principles that govern the Earth's atmosphere is correct.
\r\n\r\nThe chemistry of the Martian atmosphere has been \"solved\" to the extent that modern photochemical models [e.g., Nair et al. 1994] can reproduce the primary observable characteristics to within a factor of 2 - 3 using the results from laboratory studies of photochemical reaction rates. The chemistry of the Venus atmosphere, however, remains an \"unsolved\" problem in that the differences between the most recent generation of models [Yung and DeMore 1982] and some of the existing observations are greater than a factor of 10. The first part of this dissertation (Chapters 1, 2, and 3) combines several lines of research that focused on how the discrepancy between models and observations of the Venus atmosphere can be reduced. (The appendices for Chapter 2 are in Chapter 5.) The results provide a better understanding of the current photochemical processes in the Venus atmosphere and can serve as a baseline for future studies of its evolution.
\r\n\r\nThe intervening chapter reports observations of Europa and Callisto in the 8-l3μm wavelength region. Those observations provide constraints on the composition and/ or physical state of the surficial material on the two satellites.
\r\n\r\nPart I (Observations and Photochemical Modeling of the Venus Middle Atmosphere)
\r\n\r\nThe primary photochemical cycle of the Venus middle atmosphere (within and above the upper cloud layer) is the photolysis of C02 to form CO and oxygen atoms on the dayside followed by the reformation of C02 from CO and oxygen, primarily via catalytic reactions. Previous photochemical models-using ClOx, SOx, NOx, and HOx radicals to catalyze the reformation of C02-could qualitatively explain the stability of Venus' C02 atmosphere. Despite the powerful catalytic reactions introduced, however, none of the previous models could quantitatively explain either the low column abundance of molecular oxygen or the intense nightside air glow in the 02(a1Δ) band. The most comprehensive of the previous models, that by Yung and DeMore [1982], predicted a column abundance of molecular oxygen that was a factor of ~30 larger than the upper limit obtained the following year [Trauger and Lunine 1983], and it predicted a nightside airglow that was about three-quarters of the observed intensity. These discrepancies suggested that significant gaps remained in our understanding of the dominant chemical processes in the Venus middle atmosphere.
\r\n\r\nIn the fifteen years since these studies, new observations have provided further insight into the current state of the Venus atmosphere, and our understanding of chlorine and sulfur chemistry has improved as a result of laboratory and field studies related to the terrestrial stratosphere. One idea that had been proposed is that the abundance of 02 in the Venus atmosphere might vary by as much as a factor of 10 over time scales of years. This proposal was based on observations of S02 and SO at the top of the Venus clouds which showed a monotonic decrease in the abundances of both species from 1980 to 1995 with S02 declining by a factor of 10 and SO by a factor of 5. An alternate proposal was that rapid reactions on aerosol particles, such as
\r\n\r\nHOCl + HCl +aerosol-+ H20 + Cl2 + aerosol
\r\n\r\nwhich converts Cl from a relatively nonreactive form, HCl, to a potentially highly reactive form, Cl2, could greatly enhance the effectiveness of the chlorine catalytic reactions that oxidize CO to C02.
\r\n\r\nThis project has attempted to reconcile the differences between observations and photochemical models with regard to the oxygen budget of the Venus middle atmosphere. To examine the potential temporal variability of the 02 abundance, we attempted to detect molecular oxygen on the dayside of Venus using the Ultra-High Resolution Facility at the Anglo-Australian Telescope on 23 January 1995. We observed the 763.6325 and 763.2165 nm 02 lines at a spectral resolving power, λ⁄⁄λ, of 600000 with a square, 1.5 arc-second field of view. These observations reveal no evidence for 02 above the Venus cloud tops within our detection limit which is equivalent to a uniform vertical mixing ratio of 3 ppm. Our upper limit on the abundance of 02 in the Venus middle atmosphere is comparable to that obtained by Traub and Carlton [1974] and is a factor of ten larger (less stringent) than that obtained by Trauger and Lunine [1983] (2σ = 0.3 ppm). Within the obvious limitations imposed by the relative sensitivities of the non-detections, we find no evidence for an increase in the abundance of 02 in association with the observed decreases in S02 and SO abundances.
\r\n\r\nThe parallel branch to new observations was development of a new photochemical model for the Venus middle atmosphere that incorporates the most recent chemical kinetic rates and photoabsorption cross sections. Our one-dimensional, steady-state photochemical model can reproduce (within measurement uncertainty and temporal⁄spatial variability) the retrieved SO profile [Na et al. 1994], the retrieved S02 abundance and scale height at the cloud top [Na et al. 1994], the retrieved CO profile [Clancy and Muhleman 1991], and the observed \"global average\" 02 (a1Δ) airglow [Crisp et al. 1996] using only gas-phase chemistry if we adjust key reaction rates within their assessed one standard deviation uncertainties. Our predicted column abundance for 02 is a factor of 10 smaller than than from previous models. Our results suggest SClx and ClSOx compounds may be important in the chemistry of the upper cloud layer, and we find that Reaction G10 is not an important source of Cl2 above the cloud top.
\r\n\r\nThe current observational upper limit can be reconciled with the predictions from our photochemical model if one examines the absorption produced by our predicted 02 distribution instead of the column abundance. Our model predicts that most of the 02 in the Venus atmosphere will be located between 85 and 95 km altitude, several scale heights above the cloud top (~70-75 km altitude) and, thus, above the region in which multiple scattering is important. Radiative transfer model calculations indicate that the absorption due to our predicted 02 distribution is equivalent to that produced for a uniform vertical distribution of 02 with mixing ratio of 0.3 ppm, the two standard deviation upper limit from the observations. If the equilibrium constant for ClCO is adjusted by two standard deviations and the temperatures at 85 - 95 km altitude are decreased by ~15-20 K (two standard deviations), the predicted 02 absorption will lie below the observed one standard deviation upper limit.
\r\n\r\nPart II (Thermal Infrared Spectroscopy of Europa and Callisto)
\r\n\r\nThe trailing hemispheres of Europa and Callisto were observed and a 9- 13 μm spectrum of Europa with better spectral resolution and better signal-to-noise than was previously possible has been derived. The ratio spectrum of the two satellites has a signal-to-noise ratio of approximately 30 and spectral resolving power of approximately 50. The ratio spectrum was combined with the average Voyager 1 spectrum of Callisto from Spencer [1987a] to obtain a 9- 13 μm spectrum of Europa with signal-to-noise that is a factor of 10 better than that in the average Voyager spectrum of Europa in Spencer [1987a]. No emissivity features due to water ice are apparent at the 3% level in our Europa spectrum. The disk-integrated, effective color temperature ratio for the two satellites is consistent with previous ground-based, broadband, thermal infrared photometry. One possible explanation for the absence of features in the thermal infrared spectra of Europa (at the 3% level) and Callisto (at the 1% level) is if the surfaces of both satellites have significant abundances of small particles (≲50 micrometer in size). This explanation is consistent with most of the published observations by Galileo.
\r\n", "doi": "10.7907/NWPG-E852", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:770", "collection": "thesis", "collection_id": "770", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02262007-141751", "primary_object_url": { "basename": "Chen_g_1998.pdf", "content": "final", "filesize": 10120655, "license": "other", "mime_type": "application/pdf", "url": "/770/1/Chen_g_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "I. High pressure melting of [gamma]-iron and the thermal profile in the Earth's core. II. High pressure, high temperature equation of state of fayalite (Fe2SiO4)", "author": [ { "family_name": "Chen", "given_name": "George (Guangqing)", "clpid": "Chen-G-G" } ], "thesis_advisor": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "thesis_committee": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Stolper", "given_name": "Edward M.", "clpid": "Stolper-E-M" }, { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nThe melting curve of [...]-iron in the pressure range of 100 to 300 GPa has been derived by computing Gibbs free energies at high pressures and high temperatures from thermodynamic and equations of state (EOS) data for the [...], [...] and liquid-phases. Our calculations indicate the melting curve of iron is very sensitive to the EOS of both the solid [...] and melt phase. Our best estimate of the EOS parameters for [...]-iron are: p0 = 8.775 \u00b1 0.012 Mg/m3, [...] = 205 \u00b1 4 GPa, [...] = 4.80 \u00b1 0.01 (referenced to 12 GPa and 300 K). The calculation favors the melting curve of Boehler [1993] or Saxena et al. [1993]. Shock-wave experiments on pure iron preheated to 1573 K were conducted in 17-73 GPa range. The shock-wave equation of state of [gamma]-iron at 1573 K initial temperature can be fit with [...] = 4.102(0.015) km/s + 1.610(0.014)[...] with [...] = 7.413 \u00b1 0.012 Mg/m3. [Gamma]-iron's bulk modulus and its pressure derivative are 124.7\u00b11.1 GPa and 5.44\u00b10.06 respectively.\n\nWe present new data for sound velocities in the [gamma]- and liquid-phases. In the [gamma]-phase, to a first approximation, the longitudinal sound velocity is linear with respect to density: Vp = -3.13(0.72) + 1.119(0.084) [...] (units for Vp and [...] are km/s and Mg/m3 respectively). Melting was observed in the highest pressure (about 70-73 GPa) experiments at a calculated shock temperature of about 2775 \u00b1 160 K. This result is consistent with our calculated [...]-iron melting curve which is close to those measured by Boehler [1993] and Saxena et al. [1993]. The liquid iron sound velocity data yield a Gruneisen parameter value for liquid iron of 1.63\u00b10.28 at 9.37\u00b10.02 Mg/m3 at 71.6 GPa. The quantity [...] from our data is 15.2\u00b12.6 Mg/m3, which is within the bounds of Brown and McQueen [1986] (13.3-19.6 Mg/m3). Based on upward pressure and temperature extrapolation of our melting curve of [gamma]-iron, the estimated inner core-outer core boundary temperature is 5500\u00b1400 K, the temperature at the core-mantle boundary on the outer core side is about 3930\u00b1630 K, and the thermal boundary layer at the core-mantle boundary has a temperature difference between 400 and 1400 K.\n\nThe shock-wave equation of state of initially solid (300 K) and molten (1573 K) fayalite (Fe2SiO4, Fa) are reported in the ranges 23 to 212 GPa and 5 to 47 GPa, respectively. The 300 K data appear to undergo a phase change in the 35-55 GPa range. The density of the high pressure phase (HPP) is consistent with a dense oxide mixture. Although the initially 300 K fayalite may melt along its Hugoniot, this is not explicitly detected. Fitting the HPP Hugoniot data in the shock velocity ([...])-particle velocity ([...]) plane yields:\n\n[...] = 4.375(0.027) Mg/m3, (1)\n\n[...] = 4.07(0.22) km/s + 1.43(0.06) [...], (2)\n\nwhere [...] is the initial density. The isentropic bulk modulus [...] = 72.4 \u00b1 8.0 GPa, and its pressure derivative [...] = 4.72\u00b10.24. \n\nThe 1573 K data set yields:\n \n[...] = 3.750(0.018) Mg/m3, (3)\n \n[...] = 2.63(0.02) km/s + 1.59(0.01) [...], (4)\n\nand [...] = 25.9 \u00b1 0.4 GPa, [...] = 5.36 \u00b1 0.04. The bulk modulus compares favorably with Agee [1992a]'s result (24.4 GPa), but the pressure derivative is quite different (10.1 from Agee [1992a]).\n\nAbove 50 GPa, the high pressure regime of the Hugoniot of the solid fayalite can be fit with oxide mixture models using stishovite and FeO (either LPP or HPP). The fayalitic liquid compression data above 40 GPa are well fit with ideal mixing of partial molar volumes of stishovite and FeO (LPP or HPP), in support of the hypothesis of Rigden et al. [1989].\n\nA model basalt incorporating the liquid fayalite data shows the neutral buoyancy zone of basic silicate melts of plausible terrestrial compositions is at about 250-400 km depth based on the PREM Earth model.\n", "doi": "10.7907/z7r2-xf47", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:4033", "collection": "thesis", "collection_id": "4033", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10112005-111913", "primary_object_url": { "basename": "Wolf_ra_1997.pdf", "content": "final", "filesize": 8989655, "license": "other", "mime_type": "application/pdf", "url": "/4033/1/Wolf_ra_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The development of the (U-Th)/He thermochronometer", "author": [ { "family_name": "Wolf", "given_name": "Richmond Andrew", "clpid": "Wolf-Richmond-Andrew" } ], "thesis_advisor": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" } ], "thesis_committee": [ { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Wernicke", "given_name": "Brian P.", "clpid": "Wernicke-B-P" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "(U-Th)/He dating of apatite provides a tool for recording the low temperature (<100\u00b0C) history of the crust. A model based on stopping distances in apatite relates the fraction of alpha particles emitted from the crystal during U and Th decay to crystal size. Helium ages for different sized apatite aliquots are indistinguishable when corrected for the effects of alpha emission. Diffusion coefficients were measured by the incremental outgassing of helium from apatite. The measured range of diffusion parameters is nearly identical for apatites of different chemical composition, grain size, and grain morphology. Isothermal experiments are consistent with spherical diffusion domains which are smaller than the physical grain size.
\r\n\r\nHelium ages may reflect complex thermal histories where samples spend considerable amounts of time in the region where helium is only partially retained. Therefore, the solution to the full radiogenic helium diffusion/production equation is used to interpret helium ages instead of Dodson's (1973) closure temperature formulation. The time required to achieve a steady state between helium production and diffusion at various temperatures can be determined, as well as the range of temperatures defining the helium partial retention zone (the region where helium retentivity is most sensitive to temperature). In general, this zone resides at ~40-80\u00b0C (~2±1 km depth for typical continental geothermal gradients). This is ~35\u00b0C cooler than the analogous apatite fission track partial annealing zone.
\r\n\r\nApplication of the (U-Th)/He method to natural systems has provided consistent results and useful geologic information. Helium ages from the Cajon Pass Drillhole decline from 41.1 to 0.3 Ma between 526 and 2018 m depth, and appear to be in equilibrium with the present thermal gradient. This is in contrast to the previous assertion that the region is in a thermal transient resulting from recent erosion. Helium ages from Mt. San Jacinto, California, decrease monotonically from 79 to 17 Ma with sample elevation, and suggest a modest (~7\u00b0) westward tilting of the block with no evidence of rapid exhumation during this period. Helium ages from Mt. San Jacinto and Cajon Pass are younger than other available thermochronometric techniques, consistent with predictions from laboratory diffusion data.
", "doi": "10.7907/kz3w-5t57", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:4424", "collection": "thesis", "collection_id": "4424", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-091745", "primary_object_url": { "basename": "Leshin_la_1995.pdf", "content": "final", "filesize": 11818246, "license": "other", "mime_type": "application/pdf", "url": "/4424/1/Leshin_la_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Abundance and Hydrogen Isotopic Composition of Water in SNC Meteorites: Implications for Water on Mars", "author": [ { "family_name": "Leshin", "given_name": "Laurie Ann", "clpid": "Leshin-Laurie-Ann" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "thesis_committee": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Stevenson", "given_name": "David John", "clpid": "Stevenson-D-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "Caltech Distinguished Alumni Award" }, { "literal": "div_gps" } ], "abstract": "The water in the current martian atmosphere contains ~5 times more deuterium (D) than water on Earth (corresponding to a \u03b4D value of ~+4000) resulting from preferential loss of hydrogen relative to deuterium from the martian atmosphere. This thesis places constraints on the D/H of other martian water reservoirs by measuring the D/H of water in hydrous phases within the SNC meteorites, thought to be samples of martian igneous rocks.
\r\n\r\nResults from vacuum extractions of volatiles from bulk SNC samples by stepwise heating show the water yields to decrease and \u03b4D values to increase to well above terrestrial values with increasing temperature, indicative of mixing between terrestrial ~+2000 for Shergotty, the most Denriched sample. However, even the highest \u03b4D values measured may represent lower limits on the true values due to partial exchange with lighter terrestrial water.
\r\n\r\nD/H and water contents of individual amphibole, biotite and apatite grains in several SNC meteorites were measured using an ion microprobe. The amphiboles contain an order of magnitude less water than previously assumed, suggesting that SNC parent magmas may have been less hydrous than previously proposed. The \u03b4D values of the phases range from ~+500 to +4300. The variability and D-enriched nature of these values imply that the primary igneous phases have not retained a martian magmatic water signature. Rather, the high and variable D/H of the water in these phases, like that released at high temperatures from bulk SNC samples, is concluded to result from the interaction of the samples with D-enriched martian crustal fluids after crystallization, probably in an environment similar to terrestrial magmatic hydrothermal systems.
\r\n\r\nThe data presented in this thesis represent the first direct evidence for ubiquitous crustal water-igneous rock interaction on another planet. Moreover, the results imply that a large amount of water must have been lost from the martian system since water in the martian crust, in addition to the atmosphere, appears to reflect D-enrichment processes.
", "doi": "10.7907/36AJ-NW91", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4346", "collection": "thesis", "collection_id": "4346", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10312007-094538", "primary_object_url": { "basename": "McMuldroch_s_1995.pdf", "content": "final", "filesize": 6352429, "license": "other", "mime_type": "application/pdf", "url": "/4346/1/McMuldroch_s_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Circumstellar Environments of FU Orionis Stars", "author": [ { "family_name": "McMuldroch", "given_name": "Stuart", "clpid": "McMuldroch-Stuart" } ], "thesis_advisor": [ { "family_name": "Sargent", "given_name": "Anneila Isabel", "orcid": "0000-0002-4633-5098", "clpid": "Sargent-A-I" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" } ], "thesis_committee": [ { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Sargent", "given_name": "Anneila Isabel", "orcid": "0000-0002-4633-5098", "clpid": "Sargent-A-I" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Extensive observations were made of six FU Orionis objects (RNO 1B/1C, V1057 Cygni, Elias 1-12, V1515 Cygni and FU Orionis) and one pre-outburst candidate (V1331 Cygni) using the Owens Valley millimeter-wave array and the Caltech Submillimeter Observatory (CSO). Aperture synthesis maps of CO (1\u21920), \u00b9\u00b3CO (1\u21920), \u00b9\u00b3CO (2\u21921), \u00b9\u2078CO (1\u21920), and \u00b3CO (2\u21921) molecular lines and associated dust continuum emission trace the masses, kinematics and morphology of FU Orionis disks, envelopes, and outflows. Maps from the CSO delineate outflowing gas at larger spatial scales while line strengths, when input into radiative transfer models, yield column densities and fractional chemical abundances.
\r\n\r\nUnresolved 1.3 mm continuum emission from Vl331 Cygni and V1057 Cygni reveal massive circumstellar disks of 0.5 and 0.09 M\u2609, respectively. Maps of the 2.6 and 3.1 mm continuum emission reveal that RNO 1C is surrounded by a flattened dusty envelope, 5000 AU in size, with mass \u2a7e 1.1 M\u2609. No evidence is seen for multiple systems with orbital periods \u2273 4 x 10\u2074 years years.\r\n\r\nAll sources, with the exception of RNO 1B/1C are surrounded by large molecular gas envelopes between 2000-7500 AU in size, with masses ranging from 2 x 10\u207b\u00b3 to 0.36 M\u2609. Aperture synthesis maps suggest the envelopes are asymmetrically distributed. Gas kinematics around V1057 Cygni and Elias 1-12 suggest, but do not demand, that this material is rotating and possibly infalling.
\r\n\r\nOf the seven sources observed, all but FU Orionis show signs of outflowing molecular gas. No high velocity clumps or \"bullets\" are seen towards any of the sources. V1331 Cygni, V1057 Cygni, and V1515 Cygni possess arc or ring-like outflow morphologies, while emission from RNO 1B/1C and Elias 1-12 delineates filled outflow shells. All emission patterns are consistent with outflow shells being viewed at different angles. Although based on the statistics of small numbers, observations suggest shells are seen more frequently around FUors than T Tauri stars. Shell formation may therefore be caused by time-dependent events in the outflow. Cross-cutting arcs within the shell structure, seen towards RNO 1B/1C and Elias 1-12, are probably ridges of gas swept-up by the most recent outbursts, confirming the repetitive nature of FUor outbursts. Estimates of the dynamical ages of the arcs suggest that the interval between outbursts is ~5 x 10\u00b3 and 1.3 x 10\u2074 years for RNO 1B/1C and Elias 1-12 respectively, consistent with previous estimates of FUor cycling times.
\r\n\r\nComparable envelopes and shell-like outflow structure are seen towards embedded sources while envelopes surrounding T Tauri stars are smaller and less massive. This suggests FU Orionis objects are transition sources between deeply embedded and optically visible stars. The strength of the molecular outflow emission is correlated with the mass of the extended envelope; the outflow has evacuated molecular gas leaving less to be swept-up by subsequent outbursts, while envelope masses are smaller since less material is available for accretion.
\r\n\r\nChemically, fractional abundances of SiO and methanol are enhanced towards RNO 1B/1C by over an order of magnitude. Methanol is enhanced relative to HCN and H2CO towards Elias 1-12. Such large changes in fractional abundances must be caused by chemical processing. The SiO enrichments may be produced by sputtering or evaporation of dust grains in regions of directly shocked material or by chemical reactions of SiH4 after sublimation from grain surfaces. Methanol enrichments are difficult to produce in strong shocks, and may be caused by low velocity grain-grain collisions. For RNO 1B/1C, evaporation of the entire methanol rich grain mantles seems to be required; while for Elias 1-12 mantle phase changes from an amorphous ice to a clathrate hydrate can be invoked, expelling the methanol, with smaller molecules remaining trapped in the clathrate. Such low velocity collisions probably occur in the turbulent shear zones surrounding the outflowing gas.
", "doi": "10.7907/14NE-ZW09", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4375", "collection": "thesis", "collection_id": "4375", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11022007-110943", "primary_object_url": { "basename": "Gazis_ca_1995.pdf", "content": "final", "filesize": 57523337, "license": "other", "mime_type": "application/pdf", "url": "/4375/1/Gazis_ca_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "An isotopic study of the fluid flow and thermal history of the 2.8 Ma Chegem ash-flow caldera and related intrusive rocks (Caucasus Mountains, Russia)", "author": [ { "family_name": "Gazis", "given_name": "Carey Alice", "clpid": "Gazis-C-A" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "thesis_committee": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Stolper", "given_name": "Edward M.", "clpid": "Stolper-E-M" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe 2.8 Ma Chegem caldera, an 11x15 km ash-flow caldera located in the Caucasus Mountains, presents a unique opportunity to study silicic magma systems because of its combination of youth, exposure and simplicity. Rapid uplift and erosion in the region has exposed over 2 km of flatlying caldera fill, consisting of densely welded tuff (rhyolitic to dacitic), overlain by glacial deposits and andesite flows and cut by a granodiorite porphyry intrusion. The Eldjurta Granite, whose age and composition are similar to the Chegem volcanics, is exposed in an adjacent river valley 10 km to the northeast. Major Mo-W deposits located in nearby skarns have prompted mineral-exploration drillholes (to 4 km depth) in the granite. An isotopic study of the rocks of the Chegem caldera and the Eldjurta Granite has been performed to examine their petrogenesis, fluid flow and thermal histories.\r\n\r\nBiotite and sanidine [...] ages for 8 Chegem Tuff samples and the granodiorite intrusion are analytically indistinguishable at 2.82 \u00b1 0.02 Ma. Thus, the Chegem Tuff was erupted, cooled and intruded by the granodiorite within < 50,000 yrs. In the nearby Eldjurta Granite, biotite and K-feldspar [...] ages for 11 samples, including 8 from the deep drillhole (to 3970m depth) yield ages between 0.83 \u00b1 0.29 Ma and 2.78 \u00b1 0.09 Ma. A decrease in biotite ages from 1.90 \u00b1 0.24 Ma near the roof of the granite to 0.83 \u00b1 0.29 Ma at 3970m depth, apparently records the uplift and cooling history of this pluton. The ages of the upper 10 samples imply an isotherm migration rate of 13 mm/yr, probably due to a combination of downward migration of isotherms and regional uplift.\r\n\r\nOxygen isotope studies of the intracaldera tuff, including 38 samples from a continuous 1405m-stratigraphic section, reveal a striking caldera-wide stratigraphic horizon of [...]-depleted rocks in which there is extreme disequilibrium between phenocrysts and groundmass (sometimes still glassy). All quartz and feldspar phenocrysts have \"normal\" igneous [...] values of [...]8.5 and [...]7.0, respectively. Whole-rock and groundmass [...] values are as low as -4.0 and -7.7, respectively. Infrared spectroscopic analyses of glassy pumices reveal that they contain 3.3 to 4.8 wt% water. The [...] and water speciation of these glasses reflects low-temperature hydration by meteoric water, whereas some of their [...] values require higher temperature water-glass interaction.\r\n\r\nPronounced disequilibrium between coexisting feldspar and groundmass or glass has never been observed before on this scale. It requires a hydrothermal event involving large amounts of low-[...] H2O at sufficiently high temperatures and short enough time that glass exchanges thoroughly but feldspar does not. The most likely process responsible for the [...] depletions at Chegem is a high-temperature (500-600\u00b0C), short-lived (10-25 years), vigorous meteoric-hydrothermal event similar to that which occurred at the Valley of Ten Thousand Smokes, Alaska. Mass balance calculations indicate fluid fluxes of [...] mol/[...]-sec over that time period. Sr isotopic studies reveal that this hydrothermal event caused increases in whole-rock [...], possibly because the hydrothermal waters attained radiogenic Sr from crystalline rocks which were incorporated in the caldera fill during caldera collapse.\r\n\r\n[...] ratios of unaltered Chegem volcanic and intrusive rocks range from 0.7044 to 0.7060, significantly lower than values for surrounding country rock (0.7070 to 0.7319). Thus, the Chegem magmas were probably derived from the mantle or lower crust. The [...] ratios correlate with major- and trace-element trends, indicating that the Chegem magma chamber was both isotopically and compositionally zoned. Compared to the Chegem rocks, the Eldjurta Granite has higher [...] (0.7069), [...] and [...], and so must have evolved separately at some time.\r\n", "doi": "10.7907/mjb1-6r66", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:7295", "collection": "thesis", "collection_id": "7295", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11292012-100814038", "primary_object_url": { "basename": "Burt_ea_1993.pdf", "content": "final", "filesize": 56216940, "license": "other", "mime_type": "application/pdf", "url": "/7295/1/Burt_ea_1993.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Oxygen isotope studies of some sedimentary and metasedimentary rocks of the central and northern Appalachian Mountains, the Colorado Plateau, and the Ouachita Mountains", "author": [ { "family_name": "Burt", "given_name": "Emelia Anna", "clpid": "Burt-E-A" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Terrigenous sedimentary rocks from the Colorado Plateau show a relatively\r\nuniform bulk silicate \u03b4^(18)O of +14.8 with an SEM of 0.32. Shales and calcilutites in this\r\nregion have a mean bulk silicate \u03b4^(18)O of +17.7 which is significantly heavier than the\r\nmean for interbedded sandstones and siltstones. Bulk silicate \u03b4^(18)O is decoupled from\r\ncarbonate \u03b4^(18)O due to differences in mode of deposition and diagenetic behavior.
\r\n\r\nCentral Appalachian terrigenous sedimentary rocks show a surprisingly uniform\r\nbulk silicate \u03b4^(18)O of +14.8 with an SEM of 0.1. The mean bulk silicate \u03b4^(18)O for all\r\nshales (+15.2) is only 0.3 per mil heavier than the mean for all sandstones and siltstones\r\n(+14.9). The oxygen isotope uniformity of Central Appalachian sedimentary rocks is\r\nmainly a primary depositional feature that is the result of thorough, grand-scale mixing of\r\nterrigenous sediment in the Appalachian geosyncline, probably involving several cycles of\r\nsedimentation, uplift, erosion, and reworking extending over hundreds of millions of years\r\nduring the Paleozoic era. The bulk silicate \u03b4^(18)O of siltstones and shales shows a\r\nsignificant (P \u02c2 0.05) correlation with conodont color alteration index, which is a measure of\r\ndiagenetic temperature. As a result of isotopic exchange with porewater during diagenesis,\r\nthe bulk silicate \u03b4^(18)O of shales and siltstones can apparently be lowered by as much as 2.5\r\nto 4.0 per mil. These diagenetic effects contributed to the overall homogeneity of these\r\nsedimentary rocks because the shales started out at higher \u03b4^(18)O.
\r\n\r\nA reconnaissance ^(18)O/^(16)O study of 14 samples of terrigenous sedimentary rocks\r\nfrom the Ouachita Mountains suggests more inherent isotopic variation in these samples,\r\nperhaps in part as a result of greater heterogeneity of source regions. Some of the isotopic\r\nvariation also seems clearly attributable to diagenetic effects. A significant (P \u02c2 0.05)\r\ncorrelation was found between mean vitrinite reflectance, also a measure of diagenetic\r\ntemperature, and the bulk silicate \u03b4^(18)O difference between shale-sandstone pairs in three\r\ndifferent sedimentary formations.
\r\n\r\nNorthern Appalachian metasedimentary rocks show a decrease in bulk\r\nsilicate \u03b4^(18)O at garnet grade and higher. The terrigenous facies metamorphic rocks have\r\nbeen depleted in ^(18)O by about two per mil relative to their unmetamorphosed counterparts\r\nin the Central Appalachians, except where they are adjacent to carbonate-rich sections.\r\nCarbonate facies metasedimentary rocks are 5 to 6 per mil higher than interbedded\r\nterrrigenous facies rocks, but at the margins of that formation there is a distinct lowering of\r\nbulk silicate \u03b4^(18)O and carbonate \u03b4^(18)O due to influx of metamorphic hydrothermal fluids\r\nfrom the adjacent terrrigenous rocks. This is attributed to the involvement of isotopically\r\nlight fluids during metamorphism. Further work is need to elucidate the differences\r\nbetween metamorphic processes in pelitic and calcareous sediments.
\r\n\r\n\r\n", "doi": "10.7907/qgxa-rq43", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:6697", "collection": "thesis", "collection_id": "6697", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09302011-113009730", "primary_object_url": { "basename": "Dixon_je_1992.pdf", "content": "final", "filesize": 44824048, "license": "other", "mime_type": "application/pdf", "url": "/6697/1/Dixon_je_1992.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Water and carbon dioxide in basaltic magmas", "author": [ { "family_name": "Dixon", "given_name": "Jacqueline Eaby", "clpid": "Dixon-J-E" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "clpid": "Stolper-E-M" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Holloway", "given_name": "John", "clpid": "Holloway-J" }, { "family_name": "Clague", "given_name": "David", "clpid": "Clague-D" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Experiments were conducted in which basaltic melts were equilibrated with a vapor phase consisting of pure water, pure carbon dioxide, and water-carbon dioxide mixtures at\r\n1200\u00b0C and 200 to 980 bars in order to develop a basis for interpreting the behavior of these volatiles during the evolution and degassing of submarine magmas. Molar\r\nabsorptivities for the 4500 cm^(-1) band for hydroxyl groups and for the 5230 and 1630 cm^(-1) bands of molecular water were calibrated to be 0.67 \u00b1 0.04, 0.62 \u00b1 0.08, and 25 \u00b1 3 l/mole-cm, respectively. The solubility of water in MORE liquid was determined from the experiments in which MORB melt was equilibrated with pure H_20 vapor. Results are in agreement with the higher-pressure results of Hamilton et al. (1964) on Columbia River basalt. Trends observed in the concentrations of molecular water and hydroxyl groups with respect to total water concentration in the quenched, experimental, basaltic glasses are\r\nsimilar to those observed in albitic glasses (Silver and Stolper, 1989). Moreover, the concentration of molecular water measured in the quenched basaltic glasses is\r\napproximately proportional to water fugacity in all samples regardless of the composition of the vapor (X_CO_2), demonstrating that molecular water solubility in basaltic melts is closely approximated by Henry's law at pressures less than 1 kbar. Total water concentrations and\r\nthe speciation of water in vapor-saturated basaltic melt are fit by a regular ternary solution model with the coefficients for albitic glasses (Silver and Stolper, 1989), where the activity of water in the melt is given by Henry's law for molecular water. At pressures higher than\r\nabout 1 kbar, the effect of the molar volume of water in the melt (V^(0,m)_(H_2O)) on the activity of water in vapor-saturated melts is no longer negligible; a (V^(0,m)_(H_2O)) ~12 cm^3/mole fits the data of Hamilton et al. (1964).
\r\n\r\nConcentrations of CO_2 dissolved as carbonate in the experimental glasses range from 63 to 315 ppm CO_2. Carbonate was the only species of dissolved carbon observed.\r\nThe mole fraction of CO_2 in the vapor varied from 0.39 to 0.93. Concentrations of CO_2 dissolved as carbonate in the melt for all the experiments are proportional to fCO_2. The\r\ndata for pure CO_2-saturated and mixed H_2O-CO_2-saturated experiments are fit with a straight line through the origin with a slope of 40 ppm/100 bar fCO_2 (equivalent to 47\r\nppm/km water depth). These results suggest Henrian behavior for CO_2; that is, the solubility of CO_2 in the basaltic melt is essentially proportional to the fugacity of CO_2 with the same constant of proportionality whether the vapor contains pure CO_2 or H_2O + CO_2. These results do not support the widely held view that water enhances the solubility of carbon dioxide in basaltic melts.
\r\n\r\nResults of degassing calculations show that the vapor phase in equilibrium with MORB magmas at typical midoceanic eruption depths is CO_2 -rich and that the dissolved\r\nCO_2 contents should vary linearly with depth of eruption. Basaltic magmas containing < 1.0 wt. % H_2O will not degas significant quantities of water until pressures < 100 bars are reached. As water contents increase either through fractional crystallization or variations in the initial water contents. an inverse correlation is predicted between dissolved CO_2 and H_20 contents in melts saturated with a mixed H_2O-CO_2 vapor phase. These predictions were tested by examining the water and carbon dioxide concentrations in suites of basaltic glasses from the Juan de Fuca Ridge and Hawaii.
\r\n\r\nConcentrations of dissolved H_2O and CO_2 were measured in a suite of basaltic glasses from the Juan de Fuca Ridge. CO_2 contents dissolved as carbonate range from about 45 to 360 ppm by weight. In contrast to the predictions based on vapor-saturated degassing samples empted at a given depth exhibit a large range in dissolved CO_2 contents that we interpret to be the result of variable amounts of degassing. The lowest CO_2 contents at each depth are in reasonable agreement with the experimentally determined CO_2\r\nsolubility curve for basalt at low pressures. All glasses with CO_2 values higher than the experimentally determined solubility at the emption depth are oversaturated because of\r\nincomplete degassing. The highest CO_2 contents are spatially associated with the local topographic highs for each ridge segment. Lavas from relatively deep areas may have had greater opportunity to degas duIing ascent from a relatively deeper magma chamber or during late ral flow in dikes or seatloor lava flows. The highest observed CO_2\r\nconcentrations are from the axial seamount and lead to an estimate of a minimum depth to the magma chamber of 2.7 kilometers beneath the ridge axis. Water contents were not\r\nmodified during degassing and were found to behave incompatibly duIing partial melting and crystal fractionation. Variations in ratios of water to other incompatible elements suggest that water has a bulk partition coefficient similar to La duIing partial melting\r\n(~D0.010).
\r\n\r\nMajor, minor, and dissolved volatile element concentrations were measured in tholeiitic glasses from the submarine portion (puna Ridge) of the east lift zone of Kilauea Volcano, Hawaii. Dissolved H_2O and S concentrations display a wide range relative to nonvolatile incompatible elements at all depths. This range cannot be readily explained by fractional crystallization, degassing of H_2O and S during eruption on the seafloor, or source region heterogeneities. Dissolved CO_2 concentrations, in contrast, show a positive correlation with eruption depth and typically agree within error with the solubility at that\r\ndepth. Magmas along the Puna Ridge can be modelled as resulting from (1) mixing of a relatively volatile-rich, undegassed component with magmas that experienced low pressure (perhaps subaerial) degassing during which substantial H_2O, S, and CO_2 were lost, followed by (2) fractional crystallization of olivine, clinopyroxene, and plagioclase from this mixture to generate a residual liquid; and (3) further degassing, principally of CO_2 for\r\nsamples erupted deeper than 1000 m, during eruption on the seafloor. The degassed end member may form at upper levels of the summit magma chamber (assuming less than lithostatic pressure gradients), during residence at shallow levels in the crust, or during sustained summit eruptions. The final phase of degassing during eruption on the seafloor\r\noccurs slowly enough to achieve melt/vapor equilibrium during exsolution of the typically CO_2-rich vapor phase. According to the model, an average Kilauean primary magma with 16.0 % MgO should contain ~0.47 wt. % H_20 and ~900 ppm S. The model predicts that submarine lavas from wholly submarine volcanoes (i.e., Loihi), for which there is no opportunity to generate the degassed end member by low pressure degassing, will be enriched in volatiles relative to those from volcanoes whose summits have breached the sea surface (i.e., Kilauea and Mauna Loa).
\r\n", "doi": "10.7907/KPWW-6M36", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:2993", "collection": "thesis", "collection_id": "2993", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08012006-093137", "type": "thesis", "title": "I. Phase Transformations and the Spectral Reflectance of Solid Sulfur: Possible Metastable Sulfur Allotropes on Io's Surface. II. Photochemistry and Aerosol Formation in Neptune's Atmosphere", "author": [ { "family_name": "Moses", "given_name": "Julianne Ives", "orcid": "0000-0002-8837-0035", "clpid": "Moses-Julianne-Ives" } ], "thesis_advisor": [ { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" }, { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" } ], "thesis_committee": [ { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis consists of two independent papers:
\r\n\r\nPAPER I:
\r\n\r\nThe spectral reflectance of elemental sulfur is examined in a set of laboratory experiments to determine the factors that affect the transformation rate of monoclinic (\u03b2) sulfur and various other sulfur allotropes into orthorhombic (\u03b1) sulfur. The laboratory data have implications for the spectral variation and physical behavior of freshly solidified sulfur, if any exists, on Jupiter's satellite Io. Depending on its thermal history, molten sulfur on Io would initially solidify into a glassy solid or a monoclinic crystalline lattice; these forms might contain polymeric sulfur molecules as well as the more abundant S8 molecules. If freshly frozen sulfur on Io could lose heat rapidly and approach ambient dayside Io temperatures within several hours, then some of the metastable sulfur allotropes could be maintained on Io virtually indefinitely. Small droplets of sulfur ejected during plume eruptions might cool quickly enough to preserve these allotropes, but sulfur in large volcanic flows or lakes would probably remain warm long enough for phase transformations to proceed at a visible rate.
\r\n\r\nPAPER II:
\r\n\r\nPhotodissociation of methane at high levels in Neptune's atmosphere leads to the production of more complex hydrocarbon species such as ethane, acetylene, methylacetylene, propane, diacetylene, ethylacetylene, and butane. These gases diffuse to the lower stratosphere where temperatures are low enough to allow all seven of the aforementioned species to condense. Particle formation may not occur readily, however, as the vapor species become supersaturated. We present a theoretical analysis of particle formation mechanisms at conditions relevant to Neptune's troposphere and stratosphere and show that hydrocarbon nucleation is very inefficient under Neptunian conditions: saturation ratios much greater than unity are required for aerosol formation by either heterogeneous, ion-induced, or homogeneous nucleation. Thus, stratospheric hazes may form far below their saturation levels. We compare nucleation models with detailed atmospheric photochemical models in order to place realistic constraints on the altitude levels at which we expect hydrocarbon hazes or clouds to form on Neptune.
\r\n", "doi": "10.7907/S8F2-V423", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:8653", "collection": "thesis", "collection_id": "8653", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09042014-150651827", "primary_object_url": { "basename": "Blum_jd_1990.pdf", "content": "final", "filesize": 39778705, "license": "other", "mime_type": "application/pdf", "url": "/8653/1/Blum_jd_1990.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Geochemistry and Resonance Ionization of Platinum-Group Elements", "author": [ { "family_name": "Blum", "given_name": "Joel David", "clpid": "Blum-Joel-David" } ], "thesis_advisor": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "clpid": "Wasserburg-G-J" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "thesis_committee": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "clpid": "Wasserburg-G-J" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Experimental studies were conducted with the goals of 1) determining the origin of Pt-group element (PGE) alloys and associated mineral assemblages in refractory inclusions from meteorites and 2) developing a new ultrasensitive method for the in situ chemical and isotopic analysis of PGE. A general review of the geochemistry and cosmochemistry of the PGE is given, and specific research contributions are presented within the context of this broad framework.
\r\n\r\nAn important step toward understanding the cosmochemistry of the PGE is the determination of the origin of POE-rich metallic phases (most commonly \u03b5Ru-Fe) that are found in Ca, AJ-rich refractory inclusions (CAI) in C3V meteorites. These metals occur along with \u03b3Ni-Fe metals, Ni-Fe sulfides and Fe oxides in multiphase opaque assemblages. Laboratory experiments were used to show that the mineral assemblages and textures observed in opaque assemblages could be produced by sulfidation and oxidation of once homogeneous Ni-Fe-PGE metals. Phase equilibria, partitioning and diffusion kinetics were studied in the Ni-Fe-Ru system in order to quantify the conditions of opaque assemblage formation. Phase boundaries and tie lines in the Ni-Fe-Ru system were determined at 1273, 1073 and 873K using an experimental technique that allowed the investigation of a large portion of the Ni-Fe-Ru system with a single experiment at each temperature by establishing a concentration gradient within which local equilibrium between coexisting phases was maintained. A wide miscibility gap was found to be present at each temperature, separating a hexagonal close-packed \u03b5Ru-Fe phase from a face-centered cubic \u03b3Ni-Fe phase. Phase equilibria determined here for the Ni-Fe-Ru system, and phase equilibria from the literature for the Ni-Fe-S and Ni-Fe-O systems, were compared with analyses of minerals from opaque assemblages to estimate the temperature and chemical conditions of opaque assemblage formation. It was determined that opaque assemblages equilibrated at a temperature of ~770K, a sulfur fugacity 10 times higher than an equilibrium solar gas, and an oxygen fugacity 10\u2076 times higher than an equilibrium solar gas.
\r\n\r\nDiffusion rates between -\u03b3Ni-Fe and \u03b5Ru-Fe metal play a critical role in determining the time (with respect to CAI petrogenesis) and duration of the opaque assemblage equilibration process. The diffusion coefficient for Ru in Ni (DRuNi) was determined as an analog for the Ni-Fe-Ru system by the thin-film diffusion method in the temperature range of 1073 to 1673K and is given by the expression:
\r\n\r\nDRuNi (cm\u00b2 sec\u207b\u00b9) = 5.0(\u00b10.7) x 10\u207b\u00b3 exp(-2.3(\u00b10.1) x 10\u00b9\u00b2 erg mole\u207b\u00b9/RT) where R is the gas constant and T is the temperature in K. Based on the rates of dissolution and exsolution of metallic phases in the Ni-Fe-Ru system it is suggested that opaque assemblages equilibrated after the melting and crystallization of host CAI during a metamorphic event of \u2265 10\u00b3 years duration. It is inferred that opaque assemblages originated as immiscible metallic liquid droplets in the CAI silicate liquid. The bulk compositions of PGE in these precursor alloys reflects an early stage of condensation from the solar nebula and the partitioning of V between the precursor alloys and CAI silicate liquid reflects the reducing nebular conditions under which CAI were melted. The individual mineral phases now observed in opaque assemblages do not preserve an independent history prior to CAI melting and crystallization, but instead provide important information on the post-accretionary history of C3V meteorites and allow the quantification of the temperature, sulfur fugacity and oxygen fugacity of cooling planetary environments. This contrasts with previous models that called upon the formation of opaque assemblages by aggregation of phases that formed independently under highly variable conditions in the solar nebula prior to the crystallization of CAI.
\r\n\r\nAnalytical studies were carried out on PGE-rich phases from meteorites and the products of synthetic experiments using traditional electron microprobe x-ray analytical techniques. The concentrations of PGE in common minerals from meteorites and terrestrial rocks are far below the ~100 ppm detection limit of the electron microprobe. This has limited the scope of analytical studies to the very few cases where PGE are unusually enriched. To study the distribution of PGE in common minerals will require an in situ analytical technique with much lower detection limits than any methods currently in use. To overcome this limitation, resonance ionization of sputtered atoms was investigated for use as an ultrasensitive in situ analytical technique for the analysis of PGE. The mass spectrometric analysis of Os and Re was investigated using a pulsed primary Ar\u207a ion beam to provide sputtered atoms for resonance ionization mass spectrometry. An ionization scheme for Os that utilizes three resonant energy levels (including an autoionizing energy level) was investigated and found to have superior sensitivity and selectivity compared to nonresonant and one and two energy level resonant ionization schemes. An elemental selectivity for Os over Re of \u2265 10\u00b3 was demonstrated. It was found that detuning the ionizing laser from the autoionizing energy level to an arbitrary region in the ionization continuum resulted in a five-fold decrease in signal intensity and a ten-fold decrease in elemental selectivity. Osmium concentrations in synthetic metals and iron meteorites were measured to demonstrate the analytical capabilities of the technique. A linear correlation between Os\u207a signal intensity and the known Os concentration was observed over a range of nearly 10\u2074 in Os concentration with an accuracy of ~ \u00b110%, a millimum 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 PGE) 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 PGE by fire assay fusion.
\r\n\r\nPhase equilibria and diffusion experiments have provided the basis for a reinterpretation of the origin of opaque assemblages in CAI and have yielded quantitative information on conditions in the primitive solar nebula and cooling planetary environments. Development of the method of resonance ionization of sputtered atoms for the analysis of Os has shown that this technique has wide applications in geochemistry and will for the first time allow in situ studies of the distribution of PGE at the low concentration levels at which they occur in common minerals.
", "doi": "10.7907/KXRF-AQ49", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:8781", "collection": "thesis", "collection_id": "8781", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03182015-092735941", "primary_object_url": { "basename": "Anderson_ww_1990.pdf", "content": "final", "filesize": 31311830, "license": "other", "mime_type": "application/pdf", "url": "/8781/1/Anderson_ww_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "High Pressure States in Condensed Matter: I. High Pressure Behavior of the Iron-Sulfur System with Applications to the Earth's Core. II. Empirical Equation of State for Organic Compounds at High Pressures", "author": [ { "family_name": "Anderson", "given_name": "William Wyatt", "clpid": "Anderson-William-Wyatt" } ], "thesis_advisor": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" } ], "thesis_committee": [ { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Part I:
\r\n\r\nThe earth's core is generally accepted to be composed primarily of iron, with an admixture of other elements. Because the outer core is observed not to transmit shear waves at seismic frequencies, it is known to be liquid or primarily liquid. A new equation of state is presented for liquid iron, in the form of parameters for the 4th order Birch-Murnaghan and Mie-Gr\u00fcneisen equations of state. The parameters were constrained by a set of values for numerous properties compiled from the literature. A detailed theoretical model is used to constrain the P-T behavior of the heat capacity, based on recent advances in the understanding of the interatomic potentials for transition metals. At the reference pressure of 105 Pa and temperature of 1811 K (the normal melting point of Fe), the parameters are: \u03c1 = 7037 kg/m3, KS0 = 110 GPa, KS' = 4.53, KS\" = -.0337 GPa-1, and \u03b3 = 2.8, with \u03b3 \u221d \u03c1-1.17. Comparison of the properties predicted by this model with the earth model PREM indicates that the outer core is 8 to 10 % less dense than pure liquid Fe at the same conditions. The inner core is also found to be 3 to 5% less dense than pure liquid Fe, supporting the idea of a partially molten inner core. The density deficit of the outer core implies that the elements dissolved in the liquid Fe are predominantly of lower atomic weight than Fe. Of the candidate light elements favored by researchers, only sulfur readily dissolves into Fe at low pressure, which means that this element was almost certainly concentrated in the core at early times. New melting data are presented for FeS and FeS2 which indicate that the FeS2 is the S-hearing liquidus solid phase at inner core pressures. Consideration of the requirement that the inner core boundary be observable by seismological means and the freezing behavior of solutions leads to the possibility that the outer core may contain a significant fraction of solid material. It is found that convection in the outer core is not hindered if the solid particles are entrained in the fluid flow. This model for a core of Fe and S admits temperatures in the range 3450K to 4200K at the top of the core. An all liquid Fe-S outer core would require a temperature of about 4900 K at the top of the core.
\r\n\r\nPart II.
\r\n\r\nThe abundance of uses for organic compounds in the modern world results in many applications in which these materials are subjected to high pressures. This leads to the desire to be able to describe the behavior of these materials under such conditions. Unfortunately, the number of compounds is much greater than the number of experimental data available for many of the important properties. In the past, one approach that has worked well is the calculation of appropriate properties by summing the contributions from the organic functional groups making up molecules of the compounds in question. A new set of group contributions for the molar volume, volume thermal expansivity, heat capacity, and the Rao function is presented for functional groups containing C, H, and O. This set is, in most cases, limited in application to low molecular liquids. A new technique for the calculation of the pressure derivative of the bulk modulus is also presented. Comparison with data indicates that the presented technique works very well for most low molecular hydrocarbon liquids and somewhat less well for oxygen-bearing compounds. A similar comparison of previous results for polymers indicates that the existing tabulations of group contributions for this class of materials is in need of revision. There is also evidence that the Rao function contributions for polymers and low molecular compounds are somewhat different.
", "doi": "10.7907/7dsx-ed25", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:7994", "collection": "thesis", "collection_id": "7994", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10172013-085025235", "primary_object_url": { "basename": "Polanskey_ca_1989.pdf", "content": "final", "filesize": 19873642, "license": "other", "mime_type": "application/pdf", "url": "/7994/1/Polanskey_ca_1989.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "I. Impact Spallation Experiments: Fracture Patterns and Spall Velocities. II. Craters in Carbonate Rocks: An Electron Paramagnetic Resonance Analysis of Shock Damage", "author": [ { "family_name": "Polanskey", "given_name": "Carol Ann", "clpid": "Polanskey-Carol-Ann" } ], "thesis_advisor": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "thesis_committee": [ { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This work is divided into two independent papers.
\r\n\r\nPAPER 1.
\r\n\r\nSpall velocities were measured for nine experimental impacts into San Marcos gabbro targets. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles were iron, aluminum, lead, and basalt of varying sizes. The projectile masses ranged from a 4 g lead bullet to a 0.04 g aluminum sphere. The velocities of fragments were measured from high-speed films taken of the events. The maximum spall velocity observed was 30 m/sec, or 0.56 percent of the 5.4 km/sec impact velocity. The measured velocities were compared to the spall velocities predicted by the spallation model of Melosh (1984). The compatibility between the spallation model for large planetary impacts and the results of these small scale experiments are considered in detail.
\r\n\r\nThe targets were also bisected to observe the pattern of internal fractures. A series of fractures were observed, whose location coincided with the boundary between rock subjected to the peak shock compression and a theoretical \"near surface zone\" predicted by the spallation model. Thus, between this boundary and the free surface, the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.
\r\n\r\nPAPER 2.
\r\n\r\nCarbonate samples from the nuclear explosion crater, OAK, and a terrestrial impact crater, Meteor Crater, were analyzed for shock damage using electron paramagnetic resonance, EPR. The first series of samples for OAK Crater were obtained from six boreholes within the crater, and the second series were ejecta samples recovered from the crater floor. The degree of shock damage in the carbonate material was assessed by comparing the sample spectra to spectra of Solenhofen limestone, which had been shocked to known pressures.
\r\n\r\nThe results of the OAK borehole analysis have identified a thin zone of highly shocked carbonate material underneath the crater floor. This zone has a maximum depth of approximately 200 ft below sea floor at the ground zero borehole and decreases in depth towards the crater rim. A layer of highly shocked material is also found on the surface in the vicinity of the reference bolehole, located outside the crater. This material could represent a fallout layer. The ejecta samples have experienced a range of shock pressures.
\r\n\r\nIt was also demonstrated that the EPR technique is feasible for the study of terrestrial impact craters formed in carbonate bedrock. The results for the Meteor Crater analysis suggest a slight degree of shock damage present in the \u03b2 member of the Kaibab Formation exposed in the crater walls.
", "doi": "10.7907/3rgr-f070", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:7994", "collection": "thesis", "collection_id": "7994", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10172013-085025235", "primary_object_url": { "basename": "Polanskey_ca_1989.pdf", "content": "final", "filesize": 19873642, "license": "other", "mime_type": "application/pdf", "url": "/7994/1/Polanskey_ca_1989.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "I. Impact Spallation Experiments: Fracture Patterns and Spall Velocities. II. Craters in Carbonate Rocks: An Electron Paramagnetic Resonance Analysis of Shock Damage", "author": [ { "family_name": "Polanskey", "given_name": "Carol Ann", "clpid": "Polanskey-Carol-Ann" } ], "thesis_advisor": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "thesis_committee": [ { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This work is divided into two independent papers.
\r\n\r\nPAPER 1.
\r\n\r\nSpall velocities were measured for nine experimental impacts into San Marcos gabbro targets. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles were iron, aluminum, lead, and basalt of varying sizes. The projectile masses ranged from a 4 g lead bullet to a 0.04 g aluminum sphere. The velocities of fragments were measured from high-speed films taken of the events. The maximum spall velocity observed was 30 m/sec, or 0.56 percent of the 5.4 km/sec impact velocity. The measured velocities were compared to the spall velocities predicted by the spallation model of Melosh (1984). The compatibility between the spallation model for large planetary impacts and the results of these small scale experiments are considered in detail.
\r\n\r\nThe targets were also bisected to observe the pattern of internal fractures. A series of fractures were observed, whose location coincided with the boundary between rock subjected to the peak shock compression and a theoretical \"near surface zone\" predicted by the spallation model. Thus, between this boundary and the free surface, the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.
\r\n\r\nPAPER 2.
\r\n\r\nCarbonate samples from the nuclear explosion crater, OAK, and a terrestrial impact crater, Meteor Crater, were analyzed for shock damage using electron paramagnetic resonance, EPR. The first series of samples for OAK Crater were obtained from six boreholes within the crater, and the second series were ejecta samples recovered from the crater floor. The degree of shock damage in the carbonate material was assessed by comparing the sample spectra to spectra of Solenhofen limestone, which had been shocked to known pressures.
\r\n\r\nThe results of the OAK borehole analysis have identified a thin zone of highly shocked carbonate material underneath the crater floor. This zone has a maximum depth of approximately 200 ft below sea floor at the ground zero borehole and decreases in depth towards the crater rim. A layer of highly shocked material is also found on the surface in the vicinity of the reference bolehole, located outside the crater. This material could represent a fallout layer. The ejecta samples have experienced a range of shock pressures.
\r\n\r\nIt was also demonstrated that the EPR technique is feasible for the study of terrestrial impact craters formed in carbonate bedrock. The results for the Meteor Crater analysis suggest a slight degree of shock damage present in the \u03b2 member of the Kaibab Formation exposed in the crater walls.
", "doi": "10.7907/3rgr-f070", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:8004", "collection": "thesis", "collection_id": "8004", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10222013-084818842", "primary_object_url": { "basename": "weathers-dl_1989.pdf", "content": "final", "filesize": 22257906, "license": "other", "mime_type": "application/pdf", "url": "/8004/4/weathers-dl_1989.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Sputtering by Multiply-Charged Ions, and Preferential Sputtering of Isotopic Mixtures", "author": [ { "family_name": "Weathers", "given_name": "Duncan Lee", "clpid": "Weathers-Duncan-Lee" } ], "thesis_advisor": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "thesis_committee": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Goodstein", "given_name": "David L.", "clpid": "Goodstein-D-L" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Collector-type experiments have been conducted to investigate two different aspects of sputtering induced by keV ions. The first study looked for possible ejection mechanisms related to the primary charge state of the projectile. Targets of CsI and LiNbO\u2083 were bombarded with 48 keV Arq+, and a Au target was bombarded with 60 keV Arq+, for q = 4, 8, and 11. The collectors were analyzed using heavy-ion Rutherford backscattering spectroscopy to determine the differential angular sputtering yields; these and the corresponding total yields were examined for variations as a function of projectile charge state. For the Au target, no significant changes were seen, but for the insulating targets slight (~10%) enhancements were observed in the total yields as the projectile charge state was increased from 4+ to 11+.
\r\n\r\nIn the second investigation, artificial \u2079\u00b2Mo/\u00b9\u2070\u2070Mo targets were bombarded with 5 and 10 keV beams of Ar\u207a and Xe\u207a to study the isotopic fractionation of sputtered neutrals as a function of emission angle and projectile fluence. Using secondary ion mass spectroscopy to measure the isotope ratio on the collectors, material ejected into normal directions at low bombarding fluences (~ 10\u00b9\u2075 ions cm\u207b\u00b2) was found to be enriched in the light isotope by as much as ~70\u2030 compared to steady state. Similar results were found for secondary Mo ions sputtered by 14.5 keV O\u207b. For low-fluence 5 keV Xe\u207a bombardment, the light-isotope enrichment at oblique angles was ~20\u2030 less than the corresponding enrichment in the normal direction. No angular dependence could be resolved for 5 keV Ar\u207a projectiles at the lowest fluence. The above fractionation decreased to steady-state values after bombarding fluences of a few times 10\u00b9\u2076 ions cm\u207b\u00b2, with the angular dependence becoming more pronounced. The fractionation and total sputtering yield were found to be strongly correlated, indicating that the above effects may have been related to the presence of a modified target surface layer. The observed effects are consistent with other secondary ion measurements and multiple-interaction computer simulations, and are considerably larger than predicted by existing analytic theory.
", "doi": "10.7907/5bf6-s278", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:237", "collection": "thesis", "collection_id": "237", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01192007-082647", "type": "thesis", "title": "An \u00b9\u2078O/\u00b9\u2076O Study of Mesozoic and Early Tertiary Granitic Batholiths of the Southwestern North American Cordillera", "author": [ { "family_name": "Solomon", "given_name": "George Cleve", "clpid": "Solomon-George-Cleve" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "thesis_committee": [ { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Abundant evidence from previous studies indicates that, as long as samples are collected well away from pluton margins, the whole-rock \u03b4\u00b9\u2078O value of an unaltered granitic pluton is not likely to vary by more than \u00b10.5 per mil from the original \u00b9\u2078O/\u00b9\u2076O composition of its source rocks. Therefore, granitic plutons may be viewed as \"remote-sensing probes\" which sample deep portions of the continental crust or upper mantle, and \u00b9\u2078O/\u00b9\u2076O studies of such plutons can provide detailed information on lithologic boundaries at depth. This thesis presents approximately 350 new \u00b9\u2078O/\u00b9\u2076O analyses of whole-rock and quartz powders from Mesozoic and Cenozoic granitic plutons in the Northern Great Basin (NGB) and Southern Basin and Range (SBR) provinces of the western United States. The samples were collected along two broad, regional traverses eastward from the Sierra Nevada Batholith (SNB) and the Peninsular Ranges Batholith (PRB) in California: (1) the NGB traverse from western Nevada, near Carson City, eastward to the area around Salt Lake City, Utah; (2) the SBR traverse in southeastern California (SECA), eastward from the Central and Eastern Transverse Ranges across the Mojave Desert to the Colorado River, and then southeastward into southern Arizona. Where available, wholerock major-element geochemistry, [\u03b5Nd, and (\u2078\u2077Sr/\u2078\u2076Sr)i analyses of the same samples by other workers are integrated with these \u00b9\u2078O/\u00b9\u2076O analyses. In addition, several hundred whole-rock \u00b9\u2078O/\u00b9\u2076O analyses and, where available, Nd and Sr isotopic data, have been taken from the literature and combined with the new results to compile a data base that provides virtually complete reconnaissance coverage of the batholithic terranes in the Cordillera of southwestern North America.
\r\n\r\nSamples in the southern Arizona part of the SBR traverse were collected from Jurassic, late Cretaceous, and early Tertiary granitic plutons emplaced well within mapped boundaries of the > 1.5 Ga craton. The Jurassic plutons are metaluminous, alkali-calcic, epizonal syenites, monzodiorites and granodiorites (avg. whole-rock \u03b4\u00b9\u2078O: +6.7 to +7.4). The late Cretaceous plutons are metaluminous hornblende-bearing monzogranites and granodiorites (+7.4 < \u03b4\u00b9\u2078O < +9.9). The early Tertiary (Laramide) plutons are all peraluminous, leucocratic, two-mica granites (+8.2 < \u03b4\u00b9\u2078O < +9.0), which exhibit synkinematic and post-kinematic features. The Cretaceous suite is sliqhtly more \u00b9\u2078O-enriched and less oxidized than the Jurassic suite. The peraluminous two-mica granites, which are mineralogically closest to typical S-type plutons (as defined in SE Australia), have distinctly lower \u03b4\u00b9\u2078O values than most S-type granitic rocks throughout the world. We therefore classify all of these Arizona granites as basically I-type; there is no isotopic evidence for a major, pelitic, S-type source in southern Arizona. The two-mica granites probably represent highly fractionated \"first-melts\" of cratonal basement, while the epizonal Jurassic and Cretaceous plutons probably formed from \"drier\" melts that originated deeper in the crust.
\r\n\r\nThe samples in the Transverse Ranges and the SECA part of the SBR traverse were obtained from Triassic monzonites and syenogranites, Jurassic granodiorites and monzogranites, and late Cretaceous granodiorites, monzogranites, and two-mica granites. Most of these plutons are alkalicalcic to alkalis and were intruded upward through Precambrian basement rocks, with the exception of Cretaceous calc-alkaline monzogranites and rare two-mica granites emplaced west of cratonal basement rocks in the San Bernardino Mountains (SBM) and San Gabriel Mountains (SGM). The Triassic plutons (e.g. Mt. Lowe pluton) have uniformly low \u03b4\u00b9\u2078O values (+6.7 to +8.0). The Jurassic and Cretaceous magmas had \u03b4\u00b9\u2078O values between +6.7 and +9.3, including the two-mica granites of the Old Woman Mountains (+7.2 to +9.3), Cadiz Valley Batholith (+7.7 to +9), Chemehuevi Mountains (+7.8), and eastern SBM (+8.8 to +8.9). As in southern Arizona, these \"cratonal\" two-mica granites have lower \u03b4\u00b9\u2078O values than typical S-type plutons. In contrast, the Cretaceous plutons emplaced west of mapped cratonal basement in the SBM and SGM have high \u03b4\u00b9\u2078O values, between +8.5 and +10.8. This east-west change in primary whole-rock \u03b4\u00b9\u2078O marks a fundamental, regional \u00b9\u2078O/\u00b9\u2076O boundary, which we believe can be used to map the western edge of the craton in the Cordillera of the southwestern USA. The whole-rock \u03b4\u00b9\u2078O values of the plutons in the fault-reconstructed SGM terrane, the SBM terrane, and in the Little San Bernardino Mountains (LSB) can be contoured in a systematic fashion, and these contours are subparallel to the aforementioned regional \u00b9\u2078O/\u00b9\u2076O boundary.
\r\n\r\nNearly all of the Jurassic plutons in the SBR traverse were emplaced into shallow volcanic centers, and they show characteristics related to calderas, including hydrothermal alteration by heated low-\u00b9\u2078O meteoric waters. The altered plutons have \u03b4\u00b9\u2078O values ranging from -3.4 to +5.7, and where sampling density permits, contouring of \u03b4\u00b9\u2078O values reveals map patterns similar to those found at other meteoric-hydrothermal centers throughout the world. The best-studied of these Jurassic centers in this work is the Rodman-Ord Mountains (ROM) area, where the distinctive \u00b9\u2078O/\u00b9\u2076O map patterns produced by the Jurassic hydrothermal events have been used to estimate approximately 3 to 4 km of left-lateral strike-slip displacement along the late Cenozoic Camp Rock Fault. These SBR calderas are apparently part of a major Jurassic rift-system that extends from southeastern Arizona to the California-Nevada border. The low \u03b4\u00b9\u2078O values of the altered Jurassic plutons in SECA indicate that the paleoclimate in that portion of the rift was typical of mountainous regions today.
\r\n\r\nThe Oligocene to Jurassic plutons in the NGB traverse in Nevada and Utah are the same samples analyzed by Farmer and DePaolo (1983) in their Nd-Sr isotopic study of NGB plutonism: (1) calc-alkaline, metaluminous granodiorites and monzogranites intrude eugeoclinal Paleozoic allochthonous terranes between the SNB and the Roberts Mountain Thrust; (2) calc-alkaline, metaluminous to peraluminous granodiorites, monzogranites and two-mica granites intrude miogeoclinal terranes between the Roberts Mountain Thrust and the first outcrops of > 1.5 Ga cratonal basement going east; (3) alkali-calcic monzodiorites, granodiorites, and monzogranites intrude cratonal shelf sediments deposited on > 1.5 Ga craton in northeastern Nevada and western Utah. The primary, whole-rock \u03b4\u00b9\u2078O values in the first of the above groups exhibit the same geographic systematics discovered by Taylor and Silver (1978) for the PRB in southern and Baja California. There is a sharp, north-trending \u00b9\u2078O/\u00b9\u2076O boundary in western Nevada, analogous to the longitudinal \"\u00b9\u2078O-step\" down the center of the PRB. West of this boundary, the NGB plutons have \u03b4\u00b9\u2078O values that are uniformly lower than +8.5, and east of this boundary the plutons have \u03b4\u00b9\u2078O > +8.5, ranging up to +13.2. The highest \u00b9\u2078O/\u00b9\u2076O areas coincide with the second of the above groups, particularly where two-mica granite plutons occur. Just east of the Utah border, the third group of plutons exhibits \u03b4\u00b9\u2078O values < +9, and farther inland, \u03b4\u00b9\u2078O decreases to values as low as +6.7. This eastern boundary is inferred to be the same one we observe in the eastern Transverse Ranges in SECA.
\r\n\r\nWe use the \u00b9\u2078O/\u00b9\u2076O data from the NGB and SBR traverses, combined and augmented with literature-derived data on the PRB, SNB, and Idaho Batholith to provide a framework for viewing the subcrustal distribution of petrotectonic assemblages in much of the western United States. In conjunction with the Nd-, Pb- and Sr-isotopic signatures, the \u00b9\u2078O/\u00b9\u2076O data are used to map isotopic variations in the source regions of these plutons. This method yields a well-constrained model for the continental crust (especially when compared with earlier models that do not take into account the \u00b9\u2078O/\u00b9\u2076O values). Such studies are particularly helpful in constraining rock-types in these source regions, because \u00b9\u2078O/\u00b9\u2076O variations in rocks arise in a totally different manner than do the radiogenic isotope variations, which are mostly dependent upon age and upon various trace element concentrations.
\r\n\r\nAs discovered in the PRB by Taylor and Silver (1978), the \u03b4\u00b9\u2078O values of granitic rocks in the western United States define a series of sharp isotopic boundaries, independent of pluton lithologies, between different geographic groupings of granitic plutons. These are extremely well defined for the Cretaceous magmatic arc, for which three north-trending belts of plutons exist: (1) a Western Zone (WZ) of low-\u00b9\u2078O plutons with +5.5 < \u03b4\u00b9\u2078O < +8.5; (2) a Central Zone (CZ) of high-\u00b9\u2078O plutons with \u03b4\u00b9\u2078O between +8.5 and +13.2; and (3) an Eastern Zone (EZ) with variable \u03b4\u00b9\u2078O, typically lower than +9.0, but locally exhibiting plutonic centers with \u03b4\u00b9\u2078O > +9.0 (commonly associated with metamorphic core complexes). When (\u2078\u2077Sr/\u2078\u2076Sr)i values are taken into account, the Central Zone in the NGB must be divided into two geographic and geochemical entities; one lying west of a north-trending (\u2078\u2077Sr/\u2078\u2076Sr)i \"step\" (< 0.7080 to the west and > 0.7100 to the east), and one between this \u2078\u2077Sr/\u2078\u2076Sr \"step\" and the CZ-EZ boundary. The westernmost part is here termed the Central V-type subzone (CZ-V), and the eastern part is termed the Central S-type subzone (CZ-S). The CZ-S subzone is not present (except on a very small, local scale) south of approximately latitude 37\u00b0N, but it makes up approximately half of the Central Zone in the NGB, and dominates the CZ in the Idaho Batholith, north of the NGB. In contrast, the CZ-V subzone extends along the entire length of the Cordillera in the western USA, although it is very narrow north of 40\u00b0N latitude in the western portions of the Idaho Batholith.
\r\n\r\nThe three geographic \u00b9\u2078O/\u00b9\u2076O zones have boundaries coincident with several fundamental geologic features. The WZ occurs west of the quartz diorite line of Moore (1959) while the CZ is centered on the thickest portions of the late Precambrian-early Phanerozoic (0.3 to 1.5 Ga) Cordilleran geosyncline. The CZ in general lies east of the quartz diorite line, and west of the western limits of > 1.5 Ga Precambrian crystalline basement. The CZ-V subzone lies within the area of the geosyncline characterized by accreted terranes and dominated by eugeoclinal lithologies, whereas the CZ-S subzone appears to be associated with late Proterozoic miogeoclinal metasedimentary rocks. The EZ is located east of the western limit of older (> 1.5 Ga) crystalline basement and east of the thick geosynclinal sedimentary section. The EZ hosts most of the major porphyry copper deposits of the region, whereas the CZ hosts the known tungsten-skarn deposits.
\r\n\r\nThe isotopic data suggest that the Cordilleran granitic plutons are derived from varying proportions of the following major end-member components (largely by simple two-component mixing): (1) upper mantle and/or subducted oceanic crust, either an Oceanic Island Arc (OIA), or MORB-type source, with \u03b4\u00b9\u2078O = +6 to +7, (\u2078\u2077Sr/\u2078\u2076Sr)i ~ 0.702 to 0.704, and \u03b5Nd ~ +2 to +7; (2) \"eugeosynclinal\" sediments and altered volcanic rocks (SAV-type sources) with \u03b4\u00b9\u2078O = +10 to +13.5, (\u2078\u2077Sr/\u2078\u2076Sr)i ~ 0.705 to 0.710, and \u03b5Nd = -2 to -9; (3) \"miogeosynclinal\" continental margin sediments (MCM), with \u03b4\u00b9\u2078O > +10, (\u2078\u2077Sr/\u2078\u2076Sr)i > 0.715, and \u03b5Nd < -9; (4) some type of \"model lithospheric component\" in the lower continental crust (LCC, > 1.5 Ga) and/or upper mantle (SCL), having evolved, crustal characteristics and (\u2078\u2077Sr/\u2078\u2076Sr)i of about 0.705 to 0.710, with \u03b4\u00b9\u2078O values of +6.0 to +8.0 in the SBR and +7.5 to +9 in the NGB, and \u03b5Nd = -6 and -12 in the NGB and -4 and -10 in the SBR; and (5) mid-level continental crust of the craton (MCC) with \u03b4\u00b9\u2078O = +8 to +10, (\u2078\u2077Sr/\u2078\u2076Sr)i > 0.715, and \u03b5Nd < -12 to as low as -20. The latter values depend on the age of the crust.
\r\n\r\nThe simplest way to characterize each geographic \u00b9\u2078O/\u00b9\u2076O zone is by simple two-component melt-solid or solid-solid mixing of source-region materials, although the lack of specific isotopic data on the actual end-members precludes a rigorous evaluation of the relative importance of assimilation-fractional crystallization (AFC) processes. Western Zone: OIA-SAV with OIA dominant. Central V-type subzone: OIA-SAV with SAV dominant. Central S-type subzone: dominantly MCM with minor SAV, LCC, and OIA(?). Eastern Zone: dominantly LCC/SCL with widely varying proportions of some other end-members, such as MCC and/or a modified OIA mantle component (i.e., one that is older and more LIL-enriched than Cretaceous OIA or MORB, and thus one with a relatively high Sr content and high \u2078\u2077Sr/\u2078\u2076Sr ratio).
\r\n\r\nPrevious workers place the \"edge of the craton\" beneath the -0.706 (Kistler and Peterman, 1978) or -0.708 (Farmer and DePaolo, 1983) (\u2078\u2077Sr/\u2078\u2076Sr)i boundaries. However, we suggest that, in the NGB the (\u2078\u2077Sr/\u2078\u2076Sr)i \"step\" (0.708) is not the edge of the craton, but instead is probably a structural discontinuity that has juxtaposed an accreted terrane of eugeosynclinal volcanic and volcanogenic sedimentary rocks on the west against a late Precambrian sedimentary terrane on the east. The sharpness of this boundary implies that it is either the edge of an ancient rift-zone (Kistler and Peterman, 1978), a strike-slip fault, or a suture zone. The hypothetical late Precambrian metasedimentary basin that we infer east of the \u2078\u2077Sr/\u2078\u2076Sr \"step\" could represent an in-filled pull-apart basin, which opened during southward transport of the \"Mojavia\" terrane of Bennett and DePaolo (1987), thus explaining the east-trending boundary between the CZ and EZ that extends all the way across south-central Nevada.
\r\n\r\nThe isotopic differences inferred for the deep continental crustal sources (LCC/SCL) in the NGB (\u03b4\u00b9\u2078O = +7 to +9) and SBR (\u03b4\u00b9\u2078O = +6 to +8) bear on the structure of the craton. The \u03b4\u00b9\u2078O of the LCC/SCL component in SECA is similar to that in southern Arizona, implying that the \u00b9\u2078O/\u00b9\u2076O composition of LCC/SCL in the SBR was acquired after any of the hypothetical tectonic movements that shifted \"Mojavia\" from the NGB southward into southeastern California (Bennett and DePaolo, 1987). This means that: (1) a relatively low-\u00b9\u2078O source could have underplated the SBR (including Mojavia) after tectonic emplacement of \"Mojavia\" athwart the southern Arizona region; or (2) previous fusion events at 1.4 Ga and 1.1 Ga could have modified the SBR deep sources, such that the \u03b4\u00b9\u2078O of the LCC/SCL underneath the SBR was lowered relative to the equivalent zone in the NGB.
", "doi": "10.7907/T831-NP65", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:7536", "collection": "thesis", "collection_id": "7536", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03212013-080648923", "type": "thesis", "title": "Water in Silicate Glasses", "author": [ { "family_name": "Silver", "given_name": "Lynn Alison", "clpid": "Silver-Lynn-Alison" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Eckert", "given_name": "Hellmut", "clpid": "Eckert-Hellmut" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The speciation of water in a variety of hydrous silicate glasses, including simple and rhyolitic compositions, synthesized over a range of experimental conditions with up to 11 weight percent water has been determined using infrared spectroscopy. This technique has been calibrated with a series of standard glasses and provides a precise and accurate method for determining the concentrations of molecular water and hydroxyl groups in these glasses.
\r\n\r\nFor all the compositions studied, most of the water is dissolved as hydroxyl groups at total water contents less than 3-4 weight percent; at higher total water contents, molecular water becomes the dominant species. For total water contents above 3-4 weight percent, the amount of water dissolved as hydroxyl groups is approximately constant at about 2 weight percent and additional water is incorporated as molecular water. Although there are small but measurable differences in the ratio of molecular water to hydroxyl groups at a given total water content among these silicate glasses, the speciation of water is similar over this range of composition. The trends in the concentrations of the H-bearing species in the hydrous glasses included in this study are similar to those observed in other silicate glasses using either infrared or NMR spectroscopy.
\r\n\r\nThe effects of pressure and temperature on the speciation of water in albitic glasses have been investigated. The ratio of molecular water to hydroxyl groups at a given total water content is independent of the pressure and temperature of equilibration for albitic glasses synthesized in rapidly quenching piston cylinder apparatus at temperatures greater than 1000\u00b0C and pressures greater than 8 kbar. For hydrous glasses quenched from melts cooled at slower rates (i.e., in internally heated or in air-quench cold seal pressure vessels), there is an increase in the ratio of molecular water to hydroxyl group content that probably reflects reequilibration of the melt to lower temperatures during slow cooling.
\r\n\r\nMolecular water and hydroxyl group concentrations in glasses provide information on the dissolution mechanisms of water in silicate liquids. Several mixing models involving homogeneous equilibria of the form H\u2082O + O = 2OH among melt species have been explored for albitic melts. These models can account for the measured species concentrations if the effects of non-ideal behavior or mixing of polymerized units are included, or by allowing for the presence of several different types of anhydrous species.
\r\n\r\nA thermodynamic model for hydrous albitic melts has been developed based on the assumption that the activity of water in the melt is equal to the mole fraction of molecular water determined by infrared spectroscopy. This model can account for the position of the water-saturated solidus of crystalline albite, the pressure and temperature dependence of the solubility of water in albitic melt, and the volumes of hydrous albitic melts. To the extent that it is successful, this approach provides a direct link between measured species concentrations in hydrous albitic glasses and the macroscopic thermodynamic properties of the albite-water system.
\r\n\r\nThe approach taken in modelling the thermodynamics of hydrous albitic melts has been generalized to other silicate compositions. Spectroscopic measurements of species concentrations in rhyolitic and simple silicate glasses quenched from melts equilibrated with water vapor provide important constraints on the thermodynamic properties of these melt-water systems. In particular, the assumption that the activity of water is equal to the mole fraction of molecular water has been tested in detail and shown to be a valid approximation for a range of hydrous silicate melts and the partial molar volume of water in these systems has been constrained. Thus, the results of this study provide a useful thermodynamic description of hydrous melts that can be readily applied to other melt-water systems for which spectroscopic measurements of the H-bearing species are available.
", "doi": "10.7907/z336-zw46", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:11789", "collection": "thesis", "collection_id": "11789", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09032019-144830666", "primary_object_url": { "basename": "Fine_GJ_1986.pdf", "content": "final", "filesize": 42465709, "license": "other", "mime_type": "application/pdf", "url": "/11789/1/Fine_GJ_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Carbon Dioxide in Synthetic and Natural Silicate Glasses", "author": [ { "family_name": "Fine", "given_name": "Gerald Jonathan", "clpid": "Fine-Gerald-Jonathan" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Infrared spectroscopy has been used to study the speciation of CO2 in both synthetic silicate glasses quenched from melts held at high temperatures and pressures and in natural basaltic glasses. In glasses near the NaAlO2-SiO2 join, absorption bands resulting from the antisymmetric stretches of both molecular CO2 (2352 cm-1) and CO2-3 (1610 cm-1 and 1375 cm-1) are observed. The latter are attributed to distorted Na-carbonate ionic-complexes. Molar absorptivities for each of the absorption bands have been determined; these molar absorptivities allow the quantitative determination of species concentrations in sodium aluminosilicate glasses with a precision on the order of several percent of the amount present. The accuracy of the method is estimated to be \u00b115-20% at present.
\r\n\r\nThe ratio of molecular CO2 to CO2-3 in sodium aluminosilicate glasses varies little for each silicate composition over the range of total dissolved CO2 contents (0-1.5%), pressures (15-33 kbar) and temperatures (1400-1560\u00b0C) studied. This ratio is, however, a strong function of silicate composition, increasing both with decreasing Na2O content along the NaAlO2-SiO2 join and with decreasing Na2O content in peraluminous compositions off the join.
\r\n\r\nThe molar absorptivities determined for sodium aluminosilicate glasses have also been used to measure the concentrations of CO2 in albitic (NaAlSi3O8) glasses quenched from melts equilibrated with CO2 vapor at high pressures (15-30 kbar) and temperatures (1450-1625\u00b0C). The results show that total CO2 solubility increases with increasing pressure at constant temperature. Both molecular CO2 and CO2-3 concentrations increase with pressure. At constant pressure, the solubility of molecular CO2 decreases with temperature while the concentration of CO2-3 increases. The net effect is that total CO2 solubility is not significantly dependent on temperature, decreasing slightly with increasing temperature at constant pressure.
\r\n\r\nThe speciation of CO2 in both synthetic Ca \u00b1 Mg-composition glasses and natural basaltic glasses contrasts with the case of CO2-bearing sodium aluminosilicate glasses. CO2 is inferred to be dissolved in these glasses as distorted Ca- or Mg-carbonate ionic-complexes that result in unique infrared absorption bands at 1515 cm-1 and 1435 cm-1. The molar absorptivities for each of these absorption bands were also determined. No detectable molecular CO2 is dissolved in these glasses.
\r\n\r\nInfrared spectroscopic measurements of species concentrations in glasses provide insights into the molecular level processes accompanying CO2 solution in melts and can be used to test and constrain thermodynamic models of CO2-bearing melts. CO2 speciation in silicate melts can be modelled by equilibria between molecular CO2, CO2-3, and oxygen species in the melts. Consideration of the thermodynamics of such equilibria can account for the observed linear relationship between molecular CO2 and carbonate concentrations in sodium aluminosilicate glasses, the absence of molecular CO2 in Ca \u00b1 Mg silicate glasses, the proposed linear relationship between total dissolved CO2 content and the activity of CO2 in melts, and observed variations in CO2 solubility in melts.
\r\n\r\nDissolved CO2 contents of natural basaltic glasses can also be determined from the intensities of the carbonate absorption bands at 1515 cm-1 and 1435 cm-1. The uncertainty of the method is estimated to be \u00b115% of the amount present. The infrared technique is a powerful tool for the measurement of dissolved CO2 contents in natural basaltic glasses since it is nondestructive, can be aimed at regions of glass a few tens of micrometers in size, and discriminates between dissolved carbonate and carbon present as carbonate alteration, contained in fluid inclusions or adsorbed on the glass.
\r\n\r\nA set of submarine basaltic glasses dredged from a variety of locations contain 0-400 ppm dissolved CO2, measured using the infrared technique. These concentrations are lower than most previous reports for similar basaltic glasses. No general relationship is observed between dissolved CO2 content and depth of magmatic eruption.
", "doi": "10.7907/xmqc-xv31", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:11789", "collection": "thesis", "collection_id": "11789", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09032019-144830666", "primary_object_url": { "basename": "Fine_GJ_1986.pdf", "content": "final", "filesize": 42465709, "license": "other", "mime_type": "application/pdf", "url": "/11789/1/Fine_GJ_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Carbon Dioxide in Synthetic and Natural Silicate Glasses", "author": [ { "family_name": "Fine", "given_name": "Gerald Jonathan", "clpid": "Fine-Gerald-Jonathan" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Infrared spectroscopy has been used to study the speciation of CO2 in both synthetic silicate glasses quenched from melts held at high temperatures and pressures and in natural basaltic glasses. In glasses near the NaAlO2-SiO2 join, absorption bands resulting from the antisymmetric stretches of both molecular CO2 (2352 cm-1) and CO2-3 (1610 cm-1 and 1375 cm-1) are observed. The latter are attributed to distorted Na-carbonate ionic-complexes. Molar absorptivities for each of the absorption bands have been determined; these molar absorptivities allow the quantitative determination of species concentrations in sodium aluminosilicate glasses with a precision on the order of several percent of the amount present. The accuracy of the method is estimated to be \u00b115-20% at present.
\r\n\r\nThe ratio of molecular CO2 to CO2-3 in sodium aluminosilicate glasses varies little for each silicate composition over the range of total dissolved CO2 contents (0-1.5%), pressures (15-33 kbar) and temperatures (1400-1560\u00b0C) studied. This ratio is, however, a strong function of silicate composition, increasing both with decreasing Na2O content along the NaAlO2-SiO2 join and with decreasing Na2O content in peraluminous compositions off the join.
\r\n\r\nThe molar absorptivities determined for sodium aluminosilicate glasses have also been used to measure the concentrations of CO2 in albitic (NaAlSi3O8) glasses quenched from melts equilibrated with CO2 vapor at high pressures (15-30 kbar) and temperatures (1450-1625\u00b0C). The results show that total CO2 solubility increases with increasing pressure at constant temperature. Both molecular CO2 and CO2-3 concentrations increase with pressure. At constant pressure, the solubility of molecular CO2 decreases with temperature while the concentration of CO2-3 increases. The net effect is that total CO2 solubility is not significantly dependent on temperature, decreasing slightly with increasing temperature at constant pressure.
\r\n\r\nThe speciation of CO2 in both synthetic Ca \u00b1 Mg-composition glasses and natural basaltic glasses contrasts with the case of CO2-bearing sodium aluminosilicate glasses. CO2 is inferred to be dissolved in these glasses as distorted Ca- or Mg-carbonate ionic-complexes that result in unique infrared absorption bands at 1515 cm-1 and 1435 cm-1. The molar absorptivities for each of these absorption bands were also determined. No detectable molecular CO2 is dissolved in these glasses.
\r\n\r\nInfrared spectroscopic measurements of species concentrations in glasses provide insights into the molecular level processes accompanying CO2 solution in melts and can be used to test and constrain thermodynamic models of CO2-bearing melts. CO2 speciation in silicate melts can be modelled by equilibria between molecular CO2, CO2-3, and oxygen species in the melts. Consideration of the thermodynamics of such equilibria can account for the observed linear relationship between molecular CO2 and carbonate concentrations in sodium aluminosilicate glasses, the absence of molecular CO2 in Ca \u00b1 Mg silicate glasses, the proposed linear relationship between total dissolved CO2 content and the activity of CO2 in melts, and observed variations in CO2 solubility in melts.
\r\n\r\nDissolved CO2 contents of natural basaltic glasses can also be determined from the intensities of the carbonate absorption bands at 1515 cm-1 and 1435 cm-1. The uncertainty of the method is estimated to be \u00b115% of the amount present. The infrared technique is a powerful tool for the measurement of dissolved CO2 contents in natural basaltic glasses since it is nondestructive, can be aimed at regions of glass a few tens of micrometers in size, and discriminates between dissolved carbonate and carbon present as carbonate alteration, contained in fluid inclusions or adsorbed on the glass.
\r\n\r\nA set of submarine basaltic glasses dredged from a variety of locations contain 0-400 ppm dissolved CO2, measured using the infrared technique. These concentrations are lower than most previous reports for similar basaltic glasses. No general relationship is observed between dissolved CO2 content and depth of magmatic eruption.
", "doi": "10.7907/xmqc-xv31", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:16216", "collection": "thesis", "collection_id": "16216", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10272023-170924439", "primary_object_url": { "basename": "Rigden_SM_1986.pdf", "content": "final", "filesize": 48886487, "license": "other", "mime_type": "application/pdf", "url": "/16216/1/Rigden_SM_1986.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Determination of the Equation of State of Molten Silicates at High Pressures Using Shock-Wave Techniques", "author": [ { "family_name": "Rigden", "given_name": "Sally Miranda", "clpid": "Rigden-Sally-Miranda" } ], "thesis_advisor": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Hager", "given_name": "Bradford H.", "clpid": "Hager-B-H" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Shock wave (Hugoniot) equation-of state experiments have been carried out on molten silicates in the petrologically important system CaMgSi\u2082O\u2086-CaAl\u2082Si\u2082O\u2088 via the projectile impact method. An RF heating technique was developed to heat silicate samples contained in pure Mo containers to the necessary high initial temperatures (up to 1773 K). Thermocouple techniques, a refractory sample holding system and optical shutter systems, were developed to allow utilization of a propellant gun apparatus at impact velocities ranging from 1.0 to 2.5 km sec\u207b\u00b9 corresponding to shock pressures of 4 to 40 GPa. The methodology for taking into account the effect of the Mo container in measuring the equation of state of the molten silicate is explicitly derived.
\r\n\r\nResults on molten diopside (CaMgSi\u2082O\u2086), anorthite (CaAl\u2082Si\u2082O\u2088) and an inter\u00ad mediate composition (36 mole % CaAl\u2082Si\u2082O\u2088, 64 mole % CaMgSi\u2082O\u2086: An_(0.36)Di_(0.64)) are presented. Reduction of the Hugoniot data for these materials to third-order Birch-\u00adMurnaghan isentropes yields 1 atm bulk moduli (K_s) in the range 18-24 GPa which are in good agreement with bulk moduli recently measured by ultrasonic methods at 1 atm and similar temperatures. The pressure derivatives of bulk modulus (K') vary\r\nfrom 5-7. Shock temperature calculations for An_(0.36)Di_(0.64) indicate temperatures of 2400-2600 K at ~25 GPa. The Hugoniot states are believed to lie metastably in the liquid field on the basis of measured bulk modulus, calculated Hugoniot density of a solid of the same composition and estimated crystallization times.
\r\n\r\nThe measured equation of state data for molten diopside is used in conjunction with other thermochemical data to constrain the diopside solidus via the Clausius\u00ad Clapeyron equation at pressures up to 20 GPa. The present data are consistent with\r\n measured fusion curve data of others to 5 GPa. Above ~10 GPa, a marked shallowing of the solidus is predicted as the difference in volume between crystalline and mol\u00adten diopside in equilibrium approaches zero.
\r\n\r\nComparison of the results for molten diopside with those from the intermediate composition indicates that the liquids exhibit ideal mixing behavior with respect to volume to within \u00b12% up to ~40 Gpa. Gradual changes in coordination of Al\u00b3\u207a and Si\u2074\u207a from tetrahedral at low pressures to octahedral at high pressures are believed to occur during compression of these materials. The integrated compressibility as reflected in the values of K_s and K' is related to the proportion of tetrahedrally coordinated cations at low pressure, and the volume at ~40 GPa is from 100-110% of that of a mixture of the dense, high-pressure phases MgSiO\u2083 (perovskite), CaSiO\u2083 (perovskite), Al\u2082P\u2083 (corundum) and SiO\u2082 (stishovite).
\r\n\r\nImportant petrological implications of our results include: (1) basic to ultrabasic melts become denser than olivine- and pyroxene-rich mantle at pressures of 6-10 GPa, and (2) there is a maximum depth from which basaltic melt can rise buoyantly within terrestrial planetary interiors.
", "doi": "10.7907/5v04-ws14", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:8686", "collection": "thesis", "collection_id": "8686", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10092014-111031305", "type": "thesis", "title": "Solar Photospheric and Coronal Abundances from Solar Energetic Particle Measurements", "author": [ { "family_name": "Breneman", "given_name": "Hugh Herbert, III", "clpid": "Breneman-Hugh-Herbert-III" } ], "thesis_advisor": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" } ], "thesis_committee": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Whaling", "given_name": "Ward", "clpid": "Whaling-W" }, { "family_name": "McKeown", "given_name": "Robert D.", "clpid": "McKeown-R-D" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "div_pma" } ], "abstract": "Observations of solar energetic particles (SEPs) from 22 solar flares in the 1977-1982 time period are reported. The observations were made by the Cosmic Ray Subsystem on board the Voyager 1 and 2 spacecraft. SEP abundances have been obtained for all elements with 3 \u2264 Z \u2264 30 except Li, Be, B, F, Sc, V, Co and Cu, for which upper limits have been obtained. Statistically meaningful abundances of several rare elements (e.g., P, Cl, K, Ti, Mn) have been determined for the first time, and the average abundances of the more abundant elements have been determined with improved precision, typically a factor of three better than the best previous determinations.
\r\n\r\nPreviously reported results concerning the dependence of the fractionation of SEPs relative to photosphere on first ionization potential (FIP) have been confirmed and amplified upon with the new data. The monotonic Z-dependence of the variation between flares noted by earlier studies was found to be interpretable as a fractionation, produced by acceleration of the particles from the corona and their propagation through interplanetary space, which is ordered by the ionic charge-to-mass ratio Q/ M of the species making up the SEPs. It was found that Q/M is the primary organizing parameter of acceleration and propagation effects in SEPs, as evidenced by the dependence on Q/M of time, spatial and energy dependence within flares and of the abundance variability from flare to flare.
\r\n\r\nAn unfractionated coronal composition was derived by applying a simple Q/M fractionation correction to the observed average SEP composition, to simultaneously correct for all Q/M-correlated acceleration/propagation fractionation of SEPs. The resulting coronal composition agrees well with current XUV/X-ray spectroscopic measurements of coronal composition but is of much higher precision and is available for a much larger set of elements. Compared to spectroscopic photospheric abundances, the SEP-derived corona appears depleted in C and somewhat enriched in Cr (and possibly Ca and Ti).
\r\n\r\nAn unfractionated photospheric composition was derived by applying a simple FIP fractionation correction to the derived coronal composition, to correct for the FIP-associated fractionation of the corona during its formation from photospheric material. The resulting composition agrees well with the photospheric abundance tabulation of Grevesse (1984) except for an at least ~50% lower abundance of C and a significantly greater abundance of Cr and possibly Ti. The results support the Grevesse photospheric Fe abundance, about 50% higher than meteoritic and earlier solar values. The SEP-derived photospheric composition is not generally of higher precision than the available spectroscopic data, but it relies on fewer physical parameters and is available for some elements (C, N, Ne, Ar) which cannot be measured spectroscopically in the photosphere.
", "doi": "10.7907/4mma-e885", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:8686", "collection": "thesis", "collection_id": "8686", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10092014-111031305", "type": "thesis", "title": "Solar Photospheric and Coronal Abundances from Solar Energetic Particle Measurements", "author": [ { "family_name": "Breneman", "given_name": "Hugh Herbert, III", "clpid": "Breneman-Hugh-Herbert-III" } ], "thesis_advisor": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" } ], "thesis_committee": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Whaling", "given_name": "Ward", "clpid": "Whaling-W" }, { "family_name": "McKeown", "given_name": "Robert D.", "clpid": "McKeown-R-D" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "div_pma" } ], "abstract": "Observations of solar energetic particles (SEPs) from 22 solar flares in the 1977-1982 time period are reported. The observations were made by the Cosmic Ray Subsystem on board the Voyager 1 and 2 spacecraft. SEP abundances have been obtained for all elements with 3 \u2264 Z \u2264 30 except Li, Be, B, F, Sc, V, Co and Cu, for which upper limits have been obtained. Statistically meaningful abundances of several rare elements (e.g., P, Cl, K, Ti, Mn) have been determined for the first time, and the average abundances of the more abundant elements have been determined with improved precision, typically a factor of three better than the best previous determinations.
\r\n\r\nPreviously reported results concerning the dependence of the fractionation of SEPs relative to photosphere on first ionization potential (FIP) have been confirmed and amplified upon with the new data. The monotonic Z-dependence of the variation between flares noted by earlier studies was found to be interpretable as a fractionation, produced by acceleration of the particles from the corona and their propagation through interplanetary space, which is ordered by the ionic charge-to-mass ratio Q/ M of the species making up the SEPs. It was found that Q/M is the primary organizing parameter of acceleration and propagation effects in SEPs, as evidenced by the dependence on Q/M of time, spatial and energy dependence within flares and of the abundance variability from flare to flare.
\r\n\r\nAn unfractionated coronal composition was derived by applying a simple Q/M fractionation correction to the observed average SEP composition, to simultaneously correct for all Q/M-correlated acceleration/propagation fractionation of SEPs. The resulting coronal composition agrees well with current XUV/X-ray spectroscopic measurements of coronal composition but is of much higher precision and is available for a much larger set of elements. Compared to spectroscopic photospheric abundances, the SEP-derived corona appears depleted in C and somewhat enriched in Cr (and possibly Ca and Ti).
\r\n\r\nAn unfractionated photospheric composition was derived by applying a simple FIP fractionation correction to the derived coronal composition, to correct for the FIP-associated fractionation of the corona during its formation from photospheric material. The resulting composition agrees well with the photospheric abundance tabulation of Grevesse (1984) except for an at least ~50% lower abundance of C and a significantly greater abundance of Cr and possibly Ti. The results support the Grevesse photospheric Fe abundance, about 50% higher than meteoritic and earlier solar values. The SEP-derived photospheric composition is not generally of higher precision than the available spectroscopic data, but it relies on fewer physical parameters and is available for some elements (C, N, Ne, Ar) which cannot be measured spectroscopically in the photosphere.
", "doi": "10.7907/4mma-e885", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:3133", "collection": "thesis", "collection_id": "3133", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08152006-132531", "primary_object_url": { "basename": "Piepgras_dj_1984.pdf", "content": "final", "filesize": 13047842, "license": "other", "mime_type": "application/pdf", "url": "/3133/1/Piepgras_dj_1984.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Isotopic Composition of Neodymium in the Marine Environment: Investigations of the Sources and Transport of Rare Earth Elements in the Oceans", "author": [ { "family_name": "Piepgras", "given_name": "Donald John", "clpid": "Piepgras-Donald-John" } ], "thesis_advisor": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "thesis_committee": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Patterson", "given_name": "Clair C.", "clpid": "Patterson-C-C" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In this study, the isotopic composition of neodymium in the marine environment has been determined from analysis of marine ferromanganese precipitates and seawater. An initial survey of the isotopic composition of Nd in the marine environment was made utilizing the analyses of authigenic ferromanganese sediments. These included ferromanganese nodules, metalliferous sediments, and hydrothermal ferromanganese crust deposits. Large variations in \u03b5Nd(0) values are observed which exhibit a clear separation of the ocean basin. Nd isotopic variations within an ocean basin fall within a relatively small, well defined range which is characteristic of the ocean basin sampled. Based on these results, the following average 143Nd/144Nd ratios for the ocean basins have been determined: Atlantic Ocean, \u03b5Nd(0) \u2248 -12; Indian Ocean, \u03b5Nd(0) \u2248 -8; Pacific Ocean, \u03b5Nd(0) \u2248 -3. These values are considerably lower than \u03b5Nd(0) values associated sources having oceanic mantle affinities, indicating that the REE in the oceans are dominated by continental sources. Therefore, the variations must reflect primarily the age and 147Sm/144Nd ratio of the continental masses being sampled.
\r\n\r\nDirect measurements of the isotopic composition of Nd in seawater samples from the Atlantic and Pacific are in excellent agreement with the values determined from the ferromanganese sediments indicating that these sediments accurately reflect the isotopic composition of Nd dissolved in seawater. The results clearly demonstrate the existence of distinctive Nd isotopic differences in waters of the major ocean basins. These values correspond to a difference in the absolute abundance of 143Nd between the Atlantic and the Pacific Oceans of ~ 10(6) atoms 143Nd per gram of seawater. In addition to the isotopic differences observed between the ocean basins, smaller but distinctive variations are observed in the water column of both the Pacific and the Atlantic, indicating different sources of REE at different levels in the water column. 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.
\r\n\r\nThe isotopic composition of Nd was determined in seawater samples from the Drake Passage in order to monitor the exchange of REE between the Pacific and Atlantic Oceans. The Antarctic Circumpolar Current, which flows eastward through this passage, represents the primary conduit through which the major ocean basins communicate with each other. The isotopic composition of Nd is found to be uniform with depth at all stations and corresponds to \u03b5Nd(0) \u2243 -9.0. This value 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. 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.
\r\n\r\nThe concentration of Nd exhibits a regular increase with depth at all locations studied. In contrast, Nd isotopic compositions can exhibit substantial variations in the water column which vary depending on the location. Where isotopic differences in the water column occur, substantial lateral transport of REE from different sources and at different levels in the water column is required to maintain these differences. It is shown that the concentration gradients are established without significantly affecting the isotopic distribution, and that the enrichment of Nd in the deep water cannot be a result of resolution of REE scavenged from surface waters.
\r\n\r\nThe isotopic distributions are compared to water mass analyses based on temperature and salinity characteristics in the water column at the various sampling locations. It is shown that differences in isotopic compositions in the water column are well correlated with changes in the temperature and salinity characteristics. Thus, the isotopic distributions are fully consistent with the circulation of major water masses. This indicates that while Nd is nonconservative in concentration, the isotopic composition is conserved and can be used as a tracer for studying the origin and circulation of water masses.
\r\n\r\nThe results of these studies have provided some important contributions to the understanding of trace element transport in the oceans. First, the Nd isotopic differences in the water column clearly indicate that transport of Nd from the surface to the deep ocean cannot account for the observed increase in concentration of Nd with depth. These isotopic differences must be maintained by lateral transport of the REE and indicates that the concentration gradients of the REE and possibly other trace elements must also be related in part to lateral transport processes. Second, the close correlation observed between changes in Nd isotopic compositions and temperature-salinity relationships in the water column indicates that the lateral transport of REE in the oceans is directly related to the origin and flow of water masses. Thus, the isotopic composition of Nd in seawater is shown to be a useful tracer for studying the sources of injection and transport of trace elements in the oceans.
\r\n\r\nIn addition to the seawater studies, the concentrations and isotopic compositions of Nd and Sr were determined in hydrothermal solutions emanating from hot springs on the crest of the East Pacific Rise at 21\u00b0N and at Guaymas Basin, Gulf of California. This study represents the first effort to measure the Nd isotopic compositions in hydrothermal solutions. Endmember samples (T = 350\u00b0C) from 21\u00b0N exhibit a small range in \u03b5Sr values from -13.4 to -15.7. Correcting to CMg = 0, the pure hydrothermal solutions are estimated to have \u03b5Sr \u2243 -18. These results indicate that the fluids have undergone extensive but not complete exchange with Sr in the depleted oceanic crust (\u03b5Sr \u2243 -30). CSr ranges from 5.8 to 8.7 ppm and is similar to seawater (7.6 ppm) indicating that there must be buffering. Hydrothermal solutions from Guaymas Basin (T = 315\u00b0C) rise through several hundred meters of sediment before reaching the sea floor. One sample from here has \u03b5Sr = +5.8, indicating that the solutions have reacted first with oceanic crust and then sediments. The high Sr concentration in this sample (19.3 ppm) is consistent with late stage interaction between the ascending fluid and carbonate rich sediments.
\r\n\r\nNd shows a wide range in concentration and isotopic compositions in solutions from 21\u00b0N. CNd ranges from 20 to 659 pg/g, indicating substantial enrichments of Nd over typical seawater concentrations of ~3 to 4pg/g. \u03b5Nd ranges from -10.8 to +7.9. The data clearly show substantial contributions of Nd from depleted oceanic crust to many of the samples analyzed. In spite of enrichments in Nd of up to about 100 times seawater, none of the samples have \u03b5Nd values equal to MORB (\u03b5Nd \u2243 +10). One sample from Guaymas Basin has \u03b5Nd = -11.4 consistent with leaching of Nd from sediments derived from old, continental sources. There is some inconsistency in the Nd isotopic data indicating that there is a possibility of contamination during sampling and/or handling of the solutions.
", "doi": "10.7907/GATW-C580", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:3133", "collection": "thesis", "collection_id": "3133", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08152006-132531", "primary_object_url": { "basename": "Piepgras_dj_1984.pdf", "content": "final", "filesize": 13047842, "license": "other", "mime_type": "application/pdf", "url": "/3133/1/Piepgras_dj_1984.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Isotopic Composition of Neodymium in the Marine Environment: Investigations of the Sources and Transport of Rare Earth Elements in the Oceans", "author": [ { "family_name": "Piepgras", "given_name": "Donald John", "clpid": "Piepgras-Donald-John" } ], "thesis_advisor": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "thesis_committee": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Patterson", "given_name": "Clair C.", "clpid": "Patterson-C-C" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In this study, the isotopic composition of neodymium in the marine environment has been determined from analysis of marine ferromanganese precipitates and seawater. An initial survey of the isotopic composition of Nd in the marine environment was made utilizing the analyses of authigenic ferromanganese sediments. These included ferromanganese nodules, metalliferous sediments, and hydrothermal ferromanganese crust deposits. Large variations in \u03b5Nd(0) values are observed which exhibit a clear separation of the ocean basin. Nd isotopic variations within an ocean basin fall within a relatively small, well defined range which is characteristic of the ocean basin sampled. Based on these results, the following average 143Nd/144Nd ratios for the ocean basins have been determined: Atlantic Ocean, \u03b5Nd(0) \u2248 -12; Indian Ocean, \u03b5Nd(0) \u2248 -8; Pacific Ocean, \u03b5Nd(0) \u2248 -3. These values are considerably lower than \u03b5Nd(0) values associated sources having oceanic mantle affinities, indicating that the REE in the oceans are dominated by continental sources. Therefore, the variations must reflect primarily the age and 147Sm/144Nd ratio of the continental masses being sampled.
\r\n\r\nDirect measurements of the isotopic composition of Nd in seawater samples from the Atlantic and Pacific are in excellent agreement with the values determined from the ferromanganese sediments indicating that these sediments accurately reflect the isotopic composition of Nd dissolved in seawater. The results clearly demonstrate the existence of distinctive Nd isotopic differences in waters of the major ocean basins. These values correspond to a difference in the absolute abundance of 143Nd between the Atlantic and the Pacific Oceans of ~ 10(6) atoms 143Nd per gram of seawater. In addition to the isotopic differences observed between the ocean basins, smaller but distinctive variations are observed in the water column of both the Pacific and the Atlantic, indicating different sources of REE at different levels in the water column. 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.
\r\n\r\nThe isotopic composition of Nd was determined in seawater samples from the Drake Passage in order to monitor the exchange of REE between the Pacific and Atlantic Oceans. The Antarctic Circumpolar Current, which flows eastward through this passage, represents the primary conduit through which the major ocean basins communicate with each other. The isotopic composition of Nd is found to be uniform with depth at all stations and corresponds to \u03b5Nd(0) \u2243 -9.0. This value 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. 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.
\r\n\r\nThe concentration of Nd exhibits a regular increase with depth at all locations studied. In contrast, Nd isotopic compositions can exhibit substantial variations in the water column which vary depending on the location. Where isotopic differences in the water column occur, substantial lateral transport of REE from different sources and at different levels in the water column is required to maintain these differences. It is shown that the concentration gradients are established without significantly affecting the isotopic distribution, and that the enrichment of Nd in the deep water cannot be a result of resolution of REE scavenged from surface waters.
\r\n\r\nThe isotopic distributions are compared to water mass analyses based on temperature and salinity characteristics in the water column at the various sampling locations. It is shown that differences in isotopic compositions in the water column are well correlated with changes in the temperature and salinity characteristics. Thus, the isotopic distributions are fully consistent with the circulation of major water masses. This indicates that while Nd is nonconservative in concentration, the isotopic composition is conserved and can be used as a tracer for studying the origin and circulation of water masses.
\r\n\r\nThe results of these studies have provided some important contributions to the understanding of trace element transport in the oceans. First, the Nd isotopic differences in the water column clearly indicate that transport of Nd from the surface to the deep ocean cannot account for the observed increase in concentration of Nd with depth. These isotopic differences must be maintained by lateral transport of the REE and indicates that the concentration gradients of the REE and possibly other trace elements must also be related in part to lateral transport processes. Second, the close correlation observed between changes in Nd isotopic compositions and temperature-salinity relationships in the water column indicates that the lateral transport of REE in the oceans is directly related to the origin and flow of water masses. Thus, the isotopic composition of Nd in seawater is shown to be a useful tracer for studying the sources of injection and transport of trace elements in the oceans.
\r\n\r\nIn addition to the seawater studies, the concentrations and isotopic compositions of Nd and Sr were determined in hydrothermal solutions emanating from hot springs on the crest of the East Pacific Rise at 21\u00b0N and at Guaymas Basin, Gulf of California. This study represents the first effort to measure the Nd isotopic compositions in hydrothermal solutions. Endmember samples (T = 350\u00b0C) from 21\u00b0N exhibit a small range in \u03b5Sr values from -13.4 to -15.7. Correcting to CMg = 0, the pure hydrothermal solutions are estimated to have \u03b5Sr \u2243 -18. These results indicate that the fluids have undergone extensive but not complete exchange with Sr in the depleted oceanic crust (\u03b5Sr \u2243 -30). CSr ranges from 5.8 to 8.7 ppm and is similar to seawater (7.6 ppm) indicating that there must be buffering. Hydrothermal solutions from Guaymas Basin (T = 315\u00b0C) rise through several hundred meters of sediment before reaching the sea floor. One sample from here has \u03b5Sr = +5.8, indicating that the solutions have reacted first with oceanic crust and then sediments. The high Sr concentration in this sample (19.3 ppm) is consistent with late stage interaction between the ascending fluid and carbonate rich sediments.
\r\n\r\nNd shows a wide range in concentration and isotopic compositions in solutions from 21\u00b0N. CNd ranges from 20 to 659 pg/g, indicating substantial enrichments of Nd over typical seawater concentrations of ~3 to 4pg/g. \u03b5Nd ranges from -10.8 to +7.9. The data clearly show substantial contributions of Nd from depleted oceanic crust to many of the samples analyzed. In spite of enrichments in Nd of up to about 100 times seawater, none of the samples have \u03b5Nd values equal to MORB (\u03b5Nd \u2243 +10). One sample from Guaymas Basin has \u03b5Nd = -11.4 consistent with leaching of Nd from sediments derived from old, continental sources. There is some inconsistency in the Nd isotopic data indicating that there is a possibility of contamination during sampling and/or handling of the solutions.
", "doi": "10.7907/GATW-C580", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:11236", "collection": "thesis", "collection_id": "11236", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10172018-114703911", "primary_object_url": { "basename": "Hofmeister_AM_1984.pdf", "content": "final", "filesize": 138472836, "license": "other", "mime_type": "application/pdf", "url": "/11236/1/Hofmeister_AM_1984.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A Spectroscopic and Chemical Study of the Coloration of Feldspars by Irradiation and Impurities, Including Water", "author": [ { "family_name": "Hofmeister", "given_name": "Anne Marie", "clpid": "Hofmeister-Anne-Marie" } ], "thesis_advisor": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Kamb", "given_name": "W. Barclay", "clpid": "Kamb-W-B" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Natural smoky color or smoky color induced by ionizing radiation develops only in potassium feldspars (KAlSi3O8) free of water bound in the feldspar structure. Neither fluid inclusion water nor \u2261SiOH have an effect. The optical absorption spectra of the smoky color consist of polarized bands at 11600, 16200, 19100, and 27200 cm-1, whose integrated intensities are linearly correlated with the integrated intensity of a broad, asymmetric first derivative at geff = 2.027 in electron paramagnetic resonance (EPR) spectra. This hole center forms only in KAlSi3O8 without structurally bound H2O, and in microcline is resolved into an asymmetric six-line pattern at geff = 2.024 and a single derivative at geff = 2.009 which are Si-O- -K and a hole shared between two nonbonding oxygens (NBO) on Si. In analogy to coloring in quartz and glass, the 11600 cm-1 band is caused by a hole trapped between two NBO's on silicon, the 16200 and 27200 cm-1 bands are due to the Si-O- -K center, and the 19100 cm-1 band results from a hole trapped on an oxygen attached to two aluminums. Smoky centers do not develop in feldspars with structural water because irradiation mobilizes protons which, while diffusing, destroy centers in their path, and finally then settle in sites similar to their original site. Smoky color also develops in sodic plagioclases, but high Al content inhibits its formation in labradorite.
\r\n\r\nAmazonite color is intrinsic and controlled by an absorption minimum between three overlapping bands in the ultraviolet and a broad band in \u03b2 at 630, or one UV band and a broad band in \u03b2 at 720 nm, or both superimposed. Comparison of EPR to optical integrated intensities shows that all three colors are connected with a first derivative at geff = 1.56 and two satellites of about 1/7 intensity at geff of 1.83 and 1.39. Analysis of the EPR pattern shows that this center is Pb3+ 31% of the time, with the hole located on coordinating oxygens for the remaining 69%. This center is only produced in samples which have in addition to Pb, H2O structurally bound in the lattice. The dependence of color intensity on the smaller molar concentration of structural water or lead implies that lead and structural water in a 1:1 ratio produce color centers in amazonite. The first order reaction kinetics of amazonite color formation by irradiation and the observation that water is not consumed in the process suggests that Pb2+ is oxidized to Pb3+ by the product OH of the irradiation-induced dissociation of water while H concurrently destroys a hole center on an oxygen, and is followed by the regeneration of the water molecule. The kinetics also show that the radiation necessary for the coloration is provided by internal decay of 40K. The two end-member color types (630 or 720 nm) occur for microcline or orthoclase local structure, respectively. Al/Si disorder increases first locally, and then overall as larger amounts Pb or H2O are incorporated, so that crystals with intermediate Pb contents have both color types. A spectrally similar blue radiation color also occurs for Pb-bearing sodic plagioclases.
\r\n\r\nGemmy labradorite phenocrysts from one Steens Mountain basalt flow in Rabbit Basin, Oregon, sometimes possess a pink schiller, or more rarely a transparent red or green coloration. Direct microprobe analysis of the schiller flakes show that these are metallic copper. XRF analysis of the different colored zones revealed that only the copper content varies with color: colorless samples, or sections of crystals, have 0-35 ppm Cu; greens average 80 ppm Cu; reds average 135 ppm Cu; while schiller bearing labradorites have 50 to 240 ppm Cu. Spectral similarity of the red color to copper-ruby color of glass shows that the red arises from the intrinsic absorption of colloidal Cuo particles that are too small to scatter light (ca. 4 to 22 nm). Spectra from the green regions strongly resemble that of amazonite. Because the temperature of exsolution is subsolidus and proportional to Cu content, diffusion proceeds more rapidly for crystals with higher Cu content and results in formation of larger particles. The Cuo reduction at low temperature (800\u00b0C) involves formation of hole center (O-) that is captured by Pb2+ to form the green amazonite color (Pb3+). At high temperatures (~ 900 to 1100\u00b0C) the reduction of Cu is controlled by whatever reactions occur in the basalt to keep fO2 along the QFM buffer. Migration of Cuo may cause the variation of Cu concentrations in a single sample; but the variation of Cu content among different crystals suggests that the composition of the megacrysts was not constant and changed in response to an increasing copper content in the melt as crystallization of the labradorite proceeded.
\r\n\r\nThe coloration process in feldspar strongly resembles that in glasses for both radiation colors (smoky) and exsolution phenomena (Cuo colloids, Cuo schiller) and also that of radiation colors in other crystalline solids (smoky quartz, Pb3+ or Tl2+ in KCl). Although quartz and glass are structurally and chemically similar to feldspar, KCl is not, suggesting that for the most part it is the behavior of the chemical impurity on an atomic level which controls the coloring mechanism.
\r\n", "doi": "10.7907/bj75-5674", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:7461", "collection": "thesis", "collection_id": "7461", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02042013-113709002", "primary_object_url": { "basename": "Gladstone-gr-1983.pdf", "content": "final", "filesize": 23291604, "license": "other", "mime_type": "application/pdf", "url": "/7461/1/Gladstone-gr-1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Radiative Transfer and Photochemistry in the Upper Atmosphere of Jupiter", "author": [ { "family_name": "Gladstone", "given_name": "George Randall", "clpid": "Gladstone-George-Randall" } ], "thesis_advisor": [ { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" } ], "thesis_committee": [ { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The upper atmosphere of Jupiter, from the tropopause to well above the homopause, is investigated as to its compositional structure and vertical mixing parameters. Constraints are obtained through the study of the radiative transfer of ultraviolet resonance lines and continuum radiation. These constraints and others are then used in the modeling of the hydrocarbon photochemistry of Jupiter.
\r\n\r\nA direct finite difference numerical solution for the equation of radiative transfer is developed for use in planetary atmospheres. The procedure uses a plane-parallel atmosphere, and can treat partial frequency redistribution (for use in the radiative transfer of optically thick resonance lines), inhomogeneity, external or internal sources, and various boundary conditions. Isotropic scattering is assumed, but in the case of no frequency redistribution, a Rayleigh phase function may be used. A program utilizing this solution is tested against more powerful and elaborate methods. This program is then applied to the Lyman-\u03b1 aurora of Jupiter, and detailed line profiles are presented.
\r\n\r\nUsing this program, a study is made of the UV reflection spectrum of Jupiter as measured by the International Ultraviolet Explorer. Detailed modeling reveals the mixing ratios of C2H2, C2H6, and C4H2 to be (1.0 \u00b1 0.1) x 10-7, (6.6 \u00b1 5.3) x 10-6, and (2.9 \u00b1 2.0) x 10-10, respectively in the pressure region between \u223c 3 and 40 mbar. Upper limits in this pressure region for the mixing ratios of C2H4 and NH3 were determined to be (3.9 \u00b1 4.93.9) x 10-10 and (4.2 \u00b1 6.74.2 x 10-9, respectively. An upper limit to the optical depth of dust above the tropopause, assuming it is well mixed, is 0.2 \u00b1 0.30.2 and an upper limit on the dayglow emission by the Lyman bands of H2 is 1.4 \u00b1 2.41.4 kiloRayleighs. Comparison with Voyager results suggests that the scale height of C2H2 in the region 150-10 mbar is approximately twice that of the bulk atmosphere, consistent with the IUE observation of cosine-like limb darkening in the north-south direction on Jupiter in the UV.
\r\n\r\nThe resonant scattering of the solar He I 584 \u00c5 emission line by the upper Jovian atmosphere is investigated next. The observed intensity of this scattered line depends directly on the eddy diffusion for vertical mixing (Kh) and the temperature (Th) at the homopause. Using the temperature profile determined by the Voyager UVS experiment, a value of Kh = 1.3 x 106 cm2s-1 \u00b1 30% is obtained. If the temperature profile was the same during the Pioneer 10 encounter with Jupiter, then Kh \u2248 1 x 108 cm2 s-1 at that time. The He 584 \u00c5 brightness is found not to depend strongly on the gradients of either the eddy diffusion or temperature profiles. A semi-analytical expression for computing the He 584 \u00c5 brightness for a constant-K, constant-T atmosphere is derived and compared with calculations by other authors. It is speculated that the apparent decrease in Kh by two orders of magnitude between the Pioneer and Voyager encounters may be the result of an increase in the pole-to-equator circulation in the thermosphere, perhaps driven by the solar cycle.
\r\n\r\nThe above results are used as constraints for a one-dimensional photochemical-diffusive model of the hydrocarbon chemistry in Jupiter's upper atmosphere. The important chemical cycles and pathways among the C and C2 species are outlined and it is shown that the amount of methane dissociation resulting from acetylene photochemistry is comparable to the amount that is due to direct photolysis. Profiles for the major observed hydrocarbon species are calculated and their sensitivity to eddy diffusion profile, chemistry, and solar UV flux is examined. A best fit to the eddy diffusion profile of the upper atmosphere during the Voyager encounters is found to be given by K = 1.3 x 106(2.17 x 1013/n)0.5 cm2 s-1 (where n is the total number density), which implies a vertical mixing time at the tropopause of ~ 50 years. It is shown that polyacetylene formation driven by acetylene photochemistry in the models presented here is capable of producing the observed abundance of Danielson dust in the stratosphere of Jupiter. The disk-averaged Lyman-\u03b1 albedo of the the preferred model is calculated to be ~ 8 kiloRayleighs, almost a factor of two lower than the Voyager observed value of ~ 14 kiloRayleighs. This may indicate the need for an increased flux of atomic hydrogen from the thermosphere over the already present source from EUV and soft electron dissociation of H2. Such a flux is available from the auroral regions if there exists a pole-to-equator flow in the thermosphere as postulated earlier. Finally, a brief consideration of the auroral chemistry concludes that more lab studies of ion-neutral and ion-electron recombination reactions are needed before a meaningful study of that problem may be undertaken.
", "doi": "10.7907/pzzp-2209", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:7461", "collection": "thesis", "collection_id": "7461", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02042013-113709002", "primary_object_url": { "basename": "Gladstone-gr-1983.pdf", "content": "final", "filesize": 23291604, "license": "other", "mime_type": "application/pdf", "url": "/7461/1/Gladstone-gr-1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Radiative Transfer and Photochemistry in the Upper Atmosphere of Jupiter", "author": [ { "family_name": "Gladstone", "given_name": "George Randall", "clpid": "Gladstone-George-Randall" } ], "thesis_advisor": [ { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" } ], "thesis_committee": [ { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The upper atmosphere of Jupiter, from the tropopause to well above the homopause, is investigated as to its compositional structure and vertical mixing parameters. Constraints are obtained through the study of the radiative transfer of ultraviolet resonance lines and continuum radiation. These constraints and others are then used in the modeling of the hydrocarbon photochemistry of Jupiter.
\r\n\r\nA direct finite difference numerical solution for the equation of radiative transfer is developed for use in planetary atmospheres. The procedure uses a plane-parallel atmosphere, and can treat partial frequency redistribution (for use in the radiative transfer of optically thick resonance lines), inhomogeneity, external or internal sources, and various boundary conditions. Isotropic scattering is assumed, but in the case of no frequency redistribution, a Rayleigh phase function may be used. A program utilizing this solution is tested against more powerful and elaborate methods. This program is then applied to the Lyman-\u03b1 aurora of Jupiter, and detailed line profiles are presented.
\r\n\r\nUsing this program, a study is made of the UV reflection spectrum of Jupiter as measured by the International Ultraviolet Explorer. Detailed modeling reveals the mixing ratios of C2H2, C2H6, and C4H2 to be (1.0 \u00b1 0.1) x 10-7, (6.6 \u00b1 5.3) x 10-6, and (2.9 \u00b1 2.0) x 10-10, respectively in the pressure region between \u223c 3 and 40 mbar. Upper limits in this pressure region for the mixing ratios of C2H4 and NH3 were determined to be (3.9 \u00b1 4.93.9) x 10-10 and (4.2 \u00b1 6.74.2 x 10-9, respectively. An upper limit to the optical depth of dust above the tropopause, assuming it is well mixed, is 0.2 \u00b1 0.30.2 and an upper limit on the dayglow emission by the Lyman bands of H2 is 1.4 \u00b1 2.41.4 kiloRayleighs. Comparison with Voyager results suggests that the scale height of C2H2 in the region 150-10 mbar is approximately twice that of the bulk atmosphere, consistent with the IUE observation of cosine-like limb darkening in the north-south direction on Jupiter in the UV.
\r\n\r\nThe resonant scattering of the solar He I 584 \u00c5 emission line by the upper Jovian atmosphere is investigated next. The observed intensity of this scattered line depends directly on the eddy diffusion for vertical mixing (Kh) and the temperature (Th) at the homopause. Using the temperature profile determined by the Voyager UVS experiment, a value of Kh = 1.3 x 106 cm2s-1 \u00b1 30% is obtained. If the temperature profile was the same during the Pioneer 10 encounter with Jupiter, then Kh \u2248 1 x 108 cm2 s-1 at that time. The He 584 \u00c5 brightness is found not to depend strongly on the gradients of either the eddy diffusion or temperature profiles. A semi-analytical expression for computing the He 584 \u00c5 brightness for a constant-K, constant-T atmosphere is derived and compared with calculations by other authors. It is speculated that the apparent decrease in Kh by two orders of magnitude between the Pioneer and Voyager encounters may be the result of an increase in the pole-to-equator circulation in the thermosphere, perhaps driven by the solar cycle.
\r\n\r\nThe above results are used as constraints for a one-dimensional photochemical-diffusive model of the hydrocarbon chemistry in Jupiter's upper atmosphere. The important chemical cycles and pathways among the C and C2 species are outlined and it is shown that the amount of methane dissociation resulting from acetylene photochemistry is comparable to the amount that is due to direct photolysis. Profiles for the major observed hydrocarbon species are calculated and their sensitivity to eddy diffusion profile, chemistry, and solar UV flux is examined. A best fit to the eddy diffusion profile of the upper atmosphere during the Voyager encounters is found to be given by K = 1.3 x 106(2.17 x 1013/n)0.5 cm2 s-1 (where n is the total number density), which implies a vertical mixing time at the tropopause of ~ 50 years. It is shown that polyacetylene formation driven by acetylene photochemistry in the models presented here is capable of producing the observed abundance of Danielson dust in the stratosphere of Jupiter. The disk-averaged Lyman-\u03b1 albedo of the the preferred model is calculated to be ~ 8 kiloRayleighs, almost a factor of two lower than the Voyager observed value of ~ 14 kiloRayleighs. This may indicate the need for an increased flux of atomic hydrogen from the thermosphere over the already present source from EUV and soft electron dissociation of H2. Such a flux is available from the auroral regions if there exists a pole-to-equator flow in the thermosphere as postulated earlier. Finally, a brief consideration of the auroral chemistry concludes that more lab studies of ion-neutral and ion-electron recombination reactions are needed before a meaningful study of that problem may be undertaken.
", "doi": "10.7907/pzzp-2209", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:9275", "collection": "thesis", "collection_id": "9275", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11122015-102557568", "primary_object_url": { "basename": "Mendenhall-mh-1983.pdf", "content": "final", "filesize": 12531558, "license": "other", "mime_type": "application/pdf", "url": "/9275/1/Mendenhall-mh-1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "High Energy Heavy Ion Induced Enhanced Adhesion", "author": [ { "family_name": "Mendenhall", "given_name": "Marcus Holden", "orcid": "0000-0001-6236-8212", "clpid": "Mendenhall-Marcus-Holden" } ], "thesis_advisor": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Goodstein", "given_name": "David L.", "clpid": "Goodstein-D-L" }, { "family_name": "LoSecco", "given_name": "John M.", "clpid": "LoSecco-John-M" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "The work described in this thesis represents an attempt to summarize to date the information collected on the process of high energy heavy ion induced enhanced adhesion. Briefly, the process involves the irradiation of materials covered by thin (\u227e 3 \u03bcm) films with high energy (E > 200 keV / nucleon) heavy ion beams (such as Fluorine or Chlorine). Enhanced adhesion has been observed on all material combinations tested, including metal on metal, metal on semiconductor, metal on dielectric and dielectric on dielectric systems. In some cases, the enhancement can be quite large, so that a film that could be wiped off a substrate quite easily before irradiation can withstand determined scrubbing afterwards.
\r\n\r\nVery little is understood yet about this adhesion mechanism, so what is presented are primarily observations about systems studied, and descriptions of the actual preparation and irradiation of samples used. Some discussion is presented about mechanisms that have been considered but rejected.
\r\n", "doi": "10.7907/99pd-7q77", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:7441", "collection": "thesis", "collection_id": "7441", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01252013-152959933", "type": "thesis", "title": "Carbon Monoxide in the Atmospheres of the Terrestrial Planets", "author": [ { "family_name": "Clancy", "given_name": "Robert Todd", "clpid": "Clancy-Robert-Todd" } ], "thesis_advisor": [ { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" } ], "thesis_committee": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Moffet", "given_name": "Alan Theodore", "clpid": "Moffet-A-T" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Microwave spectra of carbon monoxide (12CO) in the mesosphere of Venus were measured in December of 1978; May and December of 1980; and January, September, and November of 1982. These spectra are analyzed to provide mixing profiles of CO in the Venus mesosphere and best constrain the mixing profile of CO between ~ 100 and 80 kilometers altitude. From the January 1982 measurement (which, of all our spectra, best constrains the abundance of CO below 80 km altitude) we find an upper limit for the CO mixing ratio below 80 kilometers altitude that is 2-3 times smaller than the stratospheric ( ~ 65 km) value of 4.5 \u00b1 1.0 x 10-5 determined by Connes et al. (1968) in 1967, indicating a possible long-term change in the lower atmospheric concentration of CO.
\r\n\r\nIntercomparison among the individual CO profiles derived from our spectra indicates considerable short-term temporal and/or spatial variation in the profile of CO mixing in the Venus mesosphere above 80 kilometers. A more complete comparison with previously published CO microwave spectra from a number of authors (Kakar et al., 1976; Gulkis et al., 1977: Schloerb et al., 1980; Wilson and Klein, 1981; Schloerb et al., 1981) specifies the basic diurnal nature of mesospheric CO variability. CO abundance above ~ 95 kilometers in the Venus atmosphere shows approximately a factor of 2-4 enhancement on the nightside relative to the dayside of Venus. The magnitude of this nightside CO bulge is in good agreement with the dynamical modeling results of Dickinson and Ridley (1977), indicating that subsolar to antisolar circulation proposed for the thermosphere of Venus by Dickinson and Ridley extends to below 100 km altitude in the Venus mesosphere. Furthermore, peak nightside CO abundance above ~ 95 kilometers occurs very near to the antisolar point on Venus (local time of peak CO abundance above ~ 95 kilometers occurs at 0.6+0.7-0.6 hours after midnight on Venus), strongly suggesting that retrograde zonal flow is substantially reduced at an altitude of 100 kilometers in the Venus mesosphere.
\r\n\r\nBy contrast, CO abundances between 80 and 90 kilometers altitude show a maximum that is shifted from the antisolar point towards the morning side of Venus (local time of peak CO abundance between 80 and 90 kilometers occurs at 8.5 \u00b1 1.0 hours past midnight on Venus). The magnitude of the diurnal variation of CO abundance between 80 and 90 kilometers is again, approximately a factor of 2-4. Given the recombination of CO strongly peaks in this altitude region (Yung and DeMore, 1982), we investigated the possible effects of diurnal photochemistry as a driving force for diurnal CO variations between 70 and 90 kilometers from model calculations. We find that the likely magnitude of diurnal CO variability due to photochemistry and vertical eddy diffusion is smaller than that indicated by the microwave data, and that such variations cannot predict the observed phase behavior of the diurnal variations. Photochemical models invariably predict peak CO abundances in the afternoon rather than morning hours on Venus. However, a simple model for the circulation of the Venus mesosphere is presented to explain the observed diurnal variations of CO both above 90 kilometers altitude and between 80 and 90 kilometers altitude. We propose that the subsolar to antisolar circulation of the Venus thermosphere (and the resulting nightside enhancement of CO) persists down to altitudes of ~ 80 kilometers. Above ~ 90 kilometers zonal flow is small and the nightside CO bulge remains centered near the antisolar point on Venus. Below ~ 90 kilometers altitude retrograde zonal wind velocities increase abruptly to several tens of meters/sec displacing the nightside enhancement of CO towards the morningside of Venus.
\r\n\r\nWe also present a J = 1 \u2192 2 spectrum of 13CO absorption in the mesosphere of Venus. This 13CO spectrum was measured at the same time as our high quality, January 1982 12CO spectrum. Radiative transfer models employing a single pressure-temperature model of the Venus mesosphere are fit to both the 13CO and 12CO spectra. The 12CO spectrum is used to specify the altitude distribution of CO. Subsequently, we solve for the ratio 12CO/13CO = 185 in order to best fit the 13CO spectrum. Based on an extensive error analysis we believe that the standard deviation of this value is \u00b1 69. This result applies only to the mesosphere of Venus, i.e. from 80 to 110 km. Values of the 12CO/13CO ratio measured deeper in the Venus atmosphere are closer to the terrestrial value of 89. We suggest several fractionation mechanisms in order to account for the difference between our result and the terrestrial value. However, as yet, none of these mechanisms is known to produce significant fractionation of CO isotopes in the upper atmosphere of Venus.
\r\n\r\nIn January of 1982 we measured a microwave spectrum of CO in the Martian atmosphere utilizing the rotational J = 1 \u2192 2 transition of CO. We have analyzed our data and reanalyzed the microwave spectra of Kakar et al. (1967, measured in 1975) and Good and Schloerb (1981, measured in 1980) in order to constrain estimates of the temporal variability of CO abundance in the Martian atmosphere. Long-term (\u2273 1 year) variations in CO abundance have been predicted on the basis of possible variations in eddy diffusion (McElroy and Donahue, 1972) and/or condensible HxOy compounds (Hunten, 1974) in the Martian atmosphere. Our values of CO column density from the data of Kakar et al., Good and Schloerb, and our own are 1.7 \u00b1 0.9 x 1020 cm-2, 3.0 \u00b1 1.0 x 1020 cm-2, and 4.6 \u00b1 2.0 x 1020 cm-2, respectively. The most recent estimate of CO column density from the 1967 infrared spectra of Connes et al. (1969) is 2.0 \u00b1 0.8 x 1020 cm-2 (Young and Young, 1977). The large uncertainties given for the microwave measurements are due primarily to uncertainty in the difference between the continuum brightness temperature and atmospheric temperatures of Mars. We have accurately calculated the variation among the observations of the continuum (surface) brightness temperature of Mars which is primarily a function of the observed aspect of Mars. A more difficult problem to consider is variability of global atmospheric temperatures among the observations, particularly the effects of global dust storms and the ellipticity of the orbit of Mars. The large error bars accompanying our estimates of CO column density from the three sets of microwave measurements are primarily caused by an assumed uncertainty of \u00b1 10 K in our atmospheric temperature model due to possible dust in the atmosphere. A qualitative consideration of seasonal variability of global atmospheric temperatures among the measurements suggests that there is not strong evidence for variability of the column abundance of CO on Mars, although variability of 0-100% over a time scale of several years is allowed by the data set. The implication for the variability of Mars O2 (which is directly tied to photodissociation of CO2) is, crudely, a factor of two less. We find that the altitude distribution of C) in the atmosphere of Mars is not well constrained by any of the spectra, although our spectrum is marginally better fit by an altitude increasing profile of CO mixing ratios.
\r\n\r\nFinally, we consider variations in the CO content of the terrestrial mesosphere. The Earth's mesospheric carbon monoxide was observed in absorption against the Moon in early December of 1979 and late January of 1982 at a wavelength of 1.3 mm, and in early December of 1980 at a wavelength of 2.6 mm. The January 1982 spectrum was also measured in emission with very high signal-to-noise ratios. The observed wavelengths correspond to the respective rotational transitions of CO, J = 1 \u2192 2 and J = 0 \u2192 1. No significant change in the column density of CO above ~ 65 km is found between the 1979 and 1980 observations, but the January 1982 measurement indicates an ~ 30% reduction in column density relative to the December observations. Inversion of the spectra did not provide unique CO mixing ratio profiles for a direct quantitative comparison of December 1979 and 1980 and January 1982 profiles, due to limited signal-to-noise ratios for the 1979, 1980 observations. One of the best constrained mixing profiles published to date is presented for the very high signal-to-noise January 1982 emission spectrum. Comparison with other published spectra of mesospheric CO suggests a large seasonal variation (~ a factor of 2-4) in the column density of CO above 65 km, with a maximum in winter and a minimum in summer. The phase of this seasonal variation in CO abundance is opposite to the phase of seasonal variation in insolation suggesting that a hemispheric pattern of circulation is responsible for seasonal variations in the Earth's mesosphere.
\r\n\r\nWe summarize by noting the very different time scales for variations of CO in the upper atmospheres of Venus, the Earth, and Mars. The long diurnal period of Venus produces a very strong diurnal variation in mesospheric CO which is driven primarily by subsolar to antisolar circulation. CO in the terrestrial mesosphere shows strong seasonal variation which is apparently produced by seasonally driven meridional circulation. By contrast, if atmospheric CO does vary on Mars, it is most likely controlled by long-term changes in the chemistry and/or vertical mixing in the Martian atmosphere.
", "doi": "10.7907/mf7e-1581", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:8685", "collection": "thesis", "collection_id": "8685", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10092014-110007312", "primary_object_url": { "basename": "Krombel_ke_1983.pdf", "content": "final", "filesize": 19761889, "license": "other", "mime_type": "application/pdf", "url": "/8685/1/Krombel_ke_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Relative Abundances of Sn, Te, Xe, Ba, and Ce in the Cosmic Radiation", "author": [ { "family_name": "Krombel", "given_name": "Keith E.", "clpid": "Krombel-Keith-E" } ], "thesis_advisor": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" } ], "thesis_committee": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" }, { "family_name": "Barnes", "given_name": "Charles A.", "clpid": "Barnes-C-A" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "div_pma" } ], "abstract": "Elements with even atomic number (Z) in the interval 50 \u2264 Z \u2264 58 have been resolved in the cosmic radiation using the Heavy Nuclei Experiment on the HEAO-3 satellite. Their relative abundances have been compared with the results expected from pure r-process material, pure s-process material, and solar system material, both with and without a modification due to possible first ionization potential effects. Such effects may be the result of the preferential acceleration, and hence enhancement in the cosmic rays, or those elements having low first ionization potentials. We find that our measurements are inconsistent with pure r-process material at the greater than 98% confidence level whether or not the first ionization potential adjustments are made.
\r\n\r\nIn addition, we have compared our results with mixtures having varying ratios of pure r-process material to pure s-process material. We find that, if no first ionization potential effects are included,
\r\n\r\n(r/s)CRS/(r/s)SS = 0.20+0.18-0.14
\r\n\r\nwhere CRS refers to the cosmic ray source and SS refers to the solar system, consistent with having an almost pure s-process source. If the first ionization potential adjustments are applied
\r\n\r\n(r/s)CRS/(r/s)SS = 1.5+1.1-0.7
\r\n\r\nconsistent with a solar system mixture.
", "doi": "10.7907/h4fg-6z05", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:8685", "collection": "thesis", "collection_id": "8685", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10092014-110007312", "primary_object_url": { "basename": "Krombel_ke_1983.pdf", "content": "final", "filesize": 19761889, "license": "other", "mime_type": "application/pdf", "url": "/8685/1/Krombel_ke_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Relative Abundances of Sn, Te, Xe, Ba, and Ce in the Cosmic Radiation", "author": [ { "family_name": "Krombel", "given_name": "Keith E.", "clpid": "Krombel-Keith-E" } ], "thesis_advisor": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" } ], "thesis_committee": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" }, { "family_name": "Barnes", "given_name": "Charles A.", "clpid": "Barnes-C-A" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "div_pma" } ], "abstract": "Elements with even atomic number (Z) in the interval 50 \u2264 Z \u2264 58 have been resolved in the cosmic radiation using the Heavy Nuclei Experiment on the HEAO-3 satellite. Their relative abundances have been compared with the results expected from pure r-process material, pure s-process material, and solar system material, both with and without a modification due to possible first ionization potential effects. Such effects may be the result of the preferential acceleration, and hence enhancement in the cosmic rays, or those elements having low first ionization potentials. We find that our measurements are inconsistent with pure r-process material at the greater than 98% confidence level whether or not the first ionization potential adjustments are made.
\r\n\r\nIn addition, we have compared our results with mixtures having varying ratios of pure r-process material to pure s-process material. We find that, if no first ionization potential effects are included,
\r\n\r\n(r/s)CRS/(r/s)SS = 0.20+0.18-0.14
\r\n\r\nwhere CRS refers to the cosmic ray source and SS refers to the solar system, consistent with having an almost pure s-process source. If the first ionization potential adjustments are applied
\r\n\r\n(r/s)CRS/(r/s)SS = 1.5+1.1-0.7
\r\n\r\nconsistent with a solar system mixture.
", "doi": "10.7907/h4fg-6z05", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:10832", "collection": "thesis", "collection_id": "10832", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04252018-105910410", "type": "thesis", "title": "Dynamic Properties of Carbonates and Applications to Cratering Processes", "author": [ { "family_name": "Vizgirda", "given_name": "Joana Marija", "clpid": "Vizgirda-Joana-Marija" } ], "thesis_advisor": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The response of carbonate minerals and rocks under shock compression is investigated using equation of state, shock metamorphism, and crater morphology studies. Coralline limestone samples from Cactus Crater, a nuclear explosion crater on Runit Island in Eniwetok Atoll, are used in the investigations of shock deformation as well as the crater structural study. Carbonate minerals and rocks shocked in the laboratory to known dynamic stress levels are used to calibrate shock pressures in the Cactus samples.
\r\n\r\nVery low shock pressure deformation effects are detected in the explosively and laboratory shocked samples by two bulk sample techniques: electron spin resonance (ESR) and powder X-ray diffraction. According to ESR studies on calcite from Cactus Crater samples, peak shock pressures of 4.5\u00b10.5 GPa were experienced by the material beneath the crater. Aragonite peak broadening analyses of powder X-ray diffraction spectra allows differentiation between two modes of material deformation, mosaicism (or reduction of crystallite size) and strain; both of these effects are detected in Cactus and in laboratory shocked samples. According to the X-ray analysis, peak pressures of 3\u00b11.5 GPa were experienced by the Cactus samples. A phase transition model, based on the variation of mosaicism and strain effects with shock pressure, is proposed. According to this model, residual strain in aragonite increases (crystallite size remaining approximately the same) until a threshold pressure of 8 to 10 GPa, corresponding to a phase transition, is reached; release from shock states above this pressure results in a discontinuous decrease in crystallite size and strain.
\r\n\r\nThe diagenetic high to low magnesium calcite transition boundary occurring in the immediate subsurface of Runit Island is used as a stratigraphic tracer to determine structural features beneath Cactus Crater, including the amount of permanent downward displacement, the presence of a 10 m thick breccia lens which is disturbed and extensively mixed in-situ, and a possible central uplift feature. Applying the Bingham plastic model to Cactus Crater gives a yield strength of approximately 1 bar for the shock-wave engulfed limestone rock; this value is similar to the yield strength of many clays, and suggests a partially liquefied state for the water-saturated limestone immediately after passage of the shock wave.
\r\n\r\nThe first aragonite Hugoniot equation of state data are presented. A Hugoniot elastic limit at 2.5\u00b10.8 GPa and a phase transition at 6.5\u00b11.5 GPa are observed. Above 10 GPa, the aragonite and calcite Hugoniots are approximately coincident, suggesting the transformation of both CaCO3 polymorphs to the same high pressure phase. Release adiabats centered at shock pressures above 18 GPa yield pressure-density isentropes which suggest possible dissociation, i.e. CO2 release, during the decompression process. These experimental data disagree with theoretical calculations, which predict incipient vaporization upon release from shock pressures of 55 and 33 GPa on the aragonite and calcite Hugoniots, respectively. Results from release adiabat experiments on calcite agree with the aragonite data and suggest vaporization upon unloading from shock pressures of approximately 37 GPa; a mass balance calculation using the experimental calcite release paths indicates that 45% of the CaCO3 has dissociated upon release to 0.2 GPa pressures.
\r\n\r\n", "doi": "10.7907/dat3-9s72", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:7482", "collection": "thesis", "collection_id": "7482", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02152013-145142740", "type": "thesis", "title": "Viscosity Structure of the Lithospheres of Ganymede, Callisto, and Enceladus, and of the Earth's Upper Mantle", "author": [ { "family_name": "Passey", "given_name": "Quinn R.", "clpid": "Passey-Quinn-R" } ], "thesis_advisor": [ { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" } ], "thesis_committee": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Hager", "given_name": "Bradford H.", "clpid": "Hager-B-H" }, { "family_name": "Shoemaker", "given_name": "Eugene Merle", "clpid": "Shoemaker-E-M" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Craterform and related features on Ganymede and Callisto include bowl-shaped craters, craters with nearly fiat floors, craters with central peaks, craters with central pits, basins, crater palimpsests and penepalimpsests, and giant multiring systems of ridges and furrows. The large majority of all craters larger than 20 km diameter have a central pit. The pits are interpreted as formed by prompt collapse of transient central peaks. Most craters, in all size ranges, are highly flattened as a consequence of topographic relaxation by slow viscous or plastic flow.
\r\n\r\nAnalysis of the global distribution of craters and multiring structures on Callisto reveal that the large multiring structures are concentrated in the leading hemisphere, whereas craters are depleted here. Calculations of model crater retention ages based on a sample of 2000 craters \u2265 30 km in diameter show that the mean age of Callisto's surface is between 4.0 and 4.2 Gy. Variations in the surface ages, derived from different diameter craters, suggests that larger craters are not retained from as early a period in time as were the smaller craters; this is in agreement with the results predicted by viscous relaxation theory where large wavelength features relax at a faster rate than do small wavelength features. Most of the variations in the observed distribution of craters can be explained satisfactorily by the effects due to the formation of multiring structures, and on the viscous relaxation of craters beneath an insulating regolith.
\r\n\r\nAbout 1000 topographic profiles of craters on Ganymede and Callisto were obtained by photoclinometry. Fresh craters on Ganymede and Callisto have depth-to-diameter ratios and rim height-to-diameter ratios similar to those of fresh lunar craters, but most craters are much shallower. Small craters have not flattened or relaxed as much as have large craters; comparison of the crater profiles with the results from theoretical of crater relaxation studies in a viscous medium, allows determination of the viscosity at the surfaces of Ganymede and Callisto, and, also, determination of the viscosity gradient with depth. The derived mean surface viscosity for the lithospheres of Ganymede and Callisto is 1.0 \u00b1 0.5 x 1026 poise. For Ganymede, the estimated thermal gradient at ~3.9 Gya was \u2265 8 K/km; the thermal gradient can be modelled as decreasing approximately exponentially with time, with an e-folding time of about 108 years; the estimated present thermal gradient is \u2264 2.0 K/km. For Callisto, the thermal gradient was \u2265 3 K/km at ~4.1 GYA and the decrease in the thermal gradient can be modelled as an exponential dropoff with an e-folding time between about 5 x 107 and 2 x 108 years; the estimated present thermal gradient on Callisto \u2264 1.5 K/km.
\r\n\r\nHigh resolution Voyager II images of Enceladus reveal that some regions on its surface are highly cratered; the most heavily cratered surfaces probably date back into a period of heavy bombardment. The forms of many of the craters, on Enceladus, are similar to those of fresh lunar craters, but many of the craters are much shallower in depth, and the floors of some craters are bowed up. Analysis of the forms of the flattened craters on Enceladus suggests that the viscosity at the top of the lithosphere, in the most heavily cratered regions, is between 1024 and 1025 poise. The exact time scale for the collapse of the craters is not known, but probably was between 100 My and 4 Gy. The flattened craters are located in regions in which the heat flow was (or is) higher than in the adjacent terrains. Because the temperature at the top of the lithosphere of Enceladus would be less than, or equal to that of Ganymede and Callisto, if it is covered by a thick regolith, and because the required viscosity, on Enceladus, is one to two orders of magnitude less than for Ganymede and Callisto, it can be concluded that the lithospheric material, on Enceladus, is different from that of Ganymede and Callisto. Enceladus possibly has a mixture of ammonia ice and water ice in the lithosphere, whereas the lithospheres of Ganymede and Callisto are composed primarily of water ice.
\r\n\r\nNew field measurements of elevation of Provo-level and Bonneville-level shoreline terraces, of Lake Bonneville, provide data for reanalysis of isostatic rebound in the Lake Bonneviile basin. Analysis of the differential rebound between the Provo shoreline (maximum rebound of 43 m) and the Bonneville shoreline (maximum rebound of 69 m) requires that the latter be an equilibrium shoreline. From the new data, the best estimate of the upper limit of effective viscosity of the uppermost mantle, assuming a half-space model and a 2000 year time interval between the Bonneville and Provo shorelines, is 2 x 1019 N sec m-2 (2 x 1020 poise). In addition, comparison of shoreline rebound profiles, for both shorelines, with theoretical plate flexure models indicates that the mean flexural rigidity of the Basin and Range lithosphere in this region is 1 x 1023 N m, or slightly less.
\r\n\r\n\r\n\r\n", "doi": "10.7907/A31H-FJ81", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:7482", "collection": "thesis", "collection_id": "7482", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02152013-145142740", "type": "thesis", "title": "Viscosity Structure of the Lithospheres of Ganymede, Callisto, and Enceladus, and of the Earth's Upper Mantle", "author": [ { "family_name": "Passey", "given_name": "Quinn R.", "clpid": "Passey-Quinn-R" } ], "thesis_advisor": [ { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" } ], "thesis_committee": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Hager", "given_name": "Bradford H.", "clpid": "Hager-B-H" }, { "family_name": "Shoemaker", "given_name": "Eugene Merle", "clpid": "Shoemaker-E-M" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Craterform and related features on Ganymede and Callisto include bowl-shaped craters, craters with nearly fiat floors, craters with central peaks, craters with central pits, basins, crater palimpsests and penepalimpsests, and giant multiring systems of ridges and furrows. The large majority of all craters larger than 20 km diameter have a central pit. The pits are interpreted as formed by prompt collapse of transient central peaks. Most craters, in all size ranges, are highly flattened as a consequence of topographic relaxation by slow viscous or plastic flow.
\r\n\r\nAnalysis of the global distribution of craters and multiring structures on Callisto reveal that the large multiring structures are concentrated in the leading hemisphere, whereas craters are depleted here. Calculations of model crater retention ages based on a sample of 2000 craters \u2265 30 km in diameter show that the mean age of Callisto's surface is between 4.0 and 4.2 Gy. Variations in the surface ages, derived from different diameter craters, suggests that larger craters are not retained from as early a period in time as were the smaller craters; this is in agreement with the results predicted by viscous relaxation theory where large wavelength features relax at a faster rate than do small wavelength features. Most of the variations in the observed distribution of craters can be explained satisfactorily by the effects due to the formation of multiring structures, and on the viscous relaxation of craters beneath an insulating regolith.
\r\n\r\nAbout 1000 topographic profiles of craters on Ganymede and Callisto were obtained by photoclinometry. Fresh craters on Ganymede and Callisto have depth-to-diameter ratios and rim height-to-diameter ratios similar to those of fresh lunar craters, but most craters are much shallower. Small craters have not flattened or relaxed as much as have large craters; comparison of the crater profiles with the results from theoretical of crater relaxation studies in a viscous medium, allows determination of the viscosity at the surfaces of Ganymede and Callisto, and, also, determination of the viscosity gradient with depth. The derived mean surface viscosity for the lithospheres of Ganymede and Callisto is 1.0 \u00b1 0.5 x 1026 poise. For Ganymede, the estimated thermal gradient at ~3.9 Gya was \u2265 8 K/km; the thermal gradient can be modelled as decreasing approximately exponentially with time, with an e-folding time of about 108 years; the estimated present thermal gradient is \u2264 2.0 K/km. For Callisto, the thermal gradient was \u2265 3 K/km at ~4.1 GYA and the decrease in the thermal gradient can be modelled as an exponential dropoff with an e-folding time between about 5 x 107 and 2 x 108 years; the estimated present thermal gradient on Callisto \u2264 1.5 K/km.
\r\n\r\nHigh resolution Voyager II images of Enceladus reveal that some regions on its surface are highly cratered; the most heavily cratered surfaces probably date back into a period of heavy bombardment. The forms of many of the craters, on Enceladus, are similar to those of fresh lunar craters, but many of the craters are much shallower in depth, and the floors of some craters are bowed up. Analysis of the forms of the flattened craters on Enceladus suggests that the viscosity at the top of the lithosphere, in the most heavily cratered regions, is between 1024 and 1025 poise. The exact time scale for the collapse of the craters is not known, but probably was between 100 My and 4 Gy. The flattened craters are located in regions in which the heat flow was (or is) higher than in the adjacent terrains. Because the temperature at the top of the lithosphere of Enceladus would be less than, or equal to that of Ganymede and Callisto, if it is covered by a thick regolith, and because the required viscosity, on Enceladus, is one to two orders of magnitude less than for Ganymede and Callisto, it can be concluded that the lithospheric material, on Enceladus, is different from that of Ganymede and Callisto. Enceladus possibly has a mixture of ammonia ice and water ice in the lithosphere, whereas the lithospheres of Ganymede and Callisto are composed primarily of water ice.
\r\n\r\nNew field measurements of elevation of Provo-level and Bonneville-level shoreline terraces, of Lake Bonneville, provide data for reanalysis of isostatic rebound in the Lake Bonneviile basin. Analysis of the differential rebound between the Provo shoreline (maximum rebound of 43 m) and the Bonneville shoreline (maximum rebound of 69 m) requires that the latter be an equilibrium shoreline. From the new data, the best estimate of the upper limit of effective viscosity of the uppermost mantle, assuming a half-space model and a 2000 year time interval between the Bonneville and Provo shorelines, is 2 x 1019 N sec m-2 (2 x 1020 poise). In addition, comparison of shoreline rebound profiles, for both shorelines, with theoretical plate flexure models indicates that the mean flexural rigidity of the Basin and Range lithosphere in this region is 1 x 1023 N m, or slightly less.
\r\n\r\n\r\n\r\n", "doi": "10.7907/A31H-FJ81", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:10816", "collection": "thesis", "collection_id": "10816", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04182018-111515439", "primary_object_url": { "basename": "Cooper_BH_1982.pdf", "content": "final", "filesize": 89211376, "license": "other", "mime_type": "application/pdf", "url": "/10816/1/Cooper_BH_1982.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Erosion of Ice Films by Energetic Ions", "author": [ { "family_name": "Cooper", "given_name": "Barbara Hope", "clpid": "Cooper-Barbara-Hope" } ], "thesis_advisor": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "thesis_committee": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Weinberg", "given_name": "William Henry", "clpid": "Weinberg-W-H" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We measured the sputtering yields of ice films by 19F ions in the electronic stopping power energy regime. The yield was a function of the incident energy and charge state of the F beam, but did not vary for tar\u00adget thicknesses ranging from about 30-70 x 1016H2O/cm2, or substrate tem\u00adperatures from 10-60\u00b0K.
\r\n\r\nThe energy dependence of the yield demonstrates that the sputtering mechanism is related to the electronic stopping power of the incident ion in the ice film. The detailed nature of this dependence is not understood. Predictions of thermal models and ion explosion models are compared to the experimental results.
\r\n\r\nOur F data on ice is compared to H and He sputtering of ice. We also review results from the literature where sputtering of other dielectric targets with ions in the electronic stopping power regime have been studied.
\r\n\r\nPossible connections with nuclear track formation in dielectrics and laser annealing are discussed. We also briefly mention the applications of enhanced sputtering of dielectrics; for example, in non-destructive desorption of large biomolecules and in astrophysical environments where frozen gas surf aces are bombarded by energetic ion fluxes.
\r\n", "doi": "10.7907/yyye-qc47", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:3203", "collection": "thesis", "collection_id": "3203", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08232006-143453", "type": "thesis", "title": "I. Ancient Arctic Ice Does Not Contain Large Excesses of Natural Lead. II. Chronological Variations in Lead and Barium Concentrations and Lead Isotopic Compositions in Sediments of Four Southern California Off-Shore Basins", "author": [ { "family_name": "Ng", "given_name": "Chihang Amy", "clpid": "Ng-Chihang-Amy" } ], "thesis_advisor": [ { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Patterson", "given_name": "Clair C.", "clpid": "Patterson-C-C" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Part I This study settled the dispute and proved beyond doubt that excess lead today is 300-fold instead of the 5-fold, as proposed by other investigators, greater than prehistoric time. And, virtually all of the present-day excess of lead above natural levels was shown to be caused by industrial lead emissions to the atmosphere.
\r\n\r\nConcentrations of lead and potassium were determined in a series of ice samples taken in sequence from the outside to the interior of several >2000 year old ice cores drilled from the Greenland and Antarctic ice sheets. Concentrations of lead and potassium were observed to decrease continuously in going from the exterior to the interior of the cores, which indicated that surface contamination had penetrated to the interior of the core, making it impossible to determine the original concentration of lead in the ice. Concentrations measured at the centers of these cores must therefore represent upper limits of lead concentration originally present in the ice. There are l.6 ng Pb/kg ice in 5000 year old Greenland ice and l.4 ng Pb/kg in 2000 year old Antarctic ice.
\r\n\r\nThese data verified the earlier findings reported by Murozumi et al. (1969) of <1 ng Pb/kg ice in 800 B.C. Greenland ice near Camp Tuto and also at New Byrd Station. Our findings also support their observation of a continual progressive increase of lead concentration with time even before 1900 A.D. These new data refuted the high concentration values of 45 ng Pb/kg ice and 70 ng Pb/kg ice reported by Herron et al. (1977) and Cragin et al. (1975) in pre-1900 Greenland ice and their claims of no concentration change with time before 1900. These new data also refute the lead concentration values of 26 ng Pb/kg ice reported by Boutron and Lorius (1979) in snow strata of Dome C, Antarctica for the period 1914 to 1974 and their claims that this high lead concentration is natural and has been present since ancient times.
\r\n\r\nPotassium concentrations at the center of the ice core are 2 x 103 ng K/kg ice in 5000 year old Greenland ice and 9 x 102 ng K/kg ice in the 2000 year old Antarctic ice. The decrease in potassium concentrations within the central third of the core was, unlike that for lead, relatively small, indicating the potassium contamination effects were not large within the central portions of the cores.
\r\n\r\nPart II This study documented the chronological changes of lead and barium fluxes from the Los Angeles Urban Complex to adjacent San Nicolas, Santa Barbara, Santa Monica, and San Pedro coastal basins; and identified industry as the sources of the excess lead and barium.
\r\n\r\nThe natural deposition fluxes of acid leachable lead in Santa Barbara, Santa Monica, and San Pedro basins were about 0.7, 0.1 and 0.2 \u00b5g Pb/cm2 respectively. A model, using clay as a major transport vehicle for soluble lead, was proposed to explain the large lead flux within the Santa Barbara basin compared to the other basins. Sedimentation fluxes of industrial and natural leachable lead within these three basins today are 3- to l0-fold greater, being about 2.1, 1.1 and 1.8 \u00b5g Pb/cm2 yr respectively. Directly deposited large sewage particles account for 0%, 66%, and 75% of the industrial lead deposition fluxes respectively. Isotopic compositions of the excess leachable lead change in accordance with corresponding known changes of isotopic compositions of industrial lead in the Los Angeles atmosphere. Lead remaining in the acid leached sediment residues originates from igneous and clay minerals, exhibing no changes in concentration or isotopic composition since pre-industrial times.
\r\n\r\nDeposition fluxes of total barium among the three basins were proportional to mass deposition fluxes before 1950. Afterwards, there are barium concentration maxima with time in both Santa Monica and San Pedro basin sediments that are attributable to industrial sewage rather than to erosion from barium-rich sedimentary evaporite strata exposed locally along the shore. A slight increase of barium concentration in present-day Santa Barbara basin sediments may reflect dispersal of barium rich drilling mud from local drilling operations.
", "doi": "10.7907/mn3s-dd97", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:9260", "collection": "thesis", "collection_id": "9260", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10292015-112154529", "primary_object_url": { "basename": "Dumke_MF_1982.pdf", "content": "final", "filesize": 21433583, "license": "other", "mime_type": "application/pdf", "url": "/9260/1/Dumke_MF_1982.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Sputtering of the Gallium-Indium Eutectic Alloy in the Liquid Phase", "author": [ { "family_name": "Dumke", "given_name": "Mark Frederick", "clpid": "Dumke-Mark-Frederick" } ], "thesis_advisor": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "thesis_committee": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Gomez", "given_name": "Ricardo", "clpid": "Gomez-R" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We have measured sputtering yields and angular distributions of sputtered atoms from both the solid and liquid phases of gallium, indium, and the gallium-indium eutectic alloy. This was done by Rutherford backscattering analysis of graphite collector foils. The solid eutectic target shows a predominance of indium crystallites on its surface which have to be sputtered away before the composition of the sputtered atoms equals the bulk target composition. The size of the crystallites depends upon the conditions under which the alloy is frozen. The sputtering of the liquid eutectic alloy by 15 keV Ar+ results in a ratio of indium to gallium sputtering yields which is 28 times greater than would be expected from the target stoichiometry. Furthermore, the angular distribution of gallium is much more sharply peaked about the normal to the target surface than the indium distribution. When the incident Ar+ energy is increased to 25 keV, the gallium distribution broadens to the same shape as the indium distribution. With the exception of the sharp gallium distribution taken from the liquid eutectic at 15 keV, all angular distributions from liquid targets fit a cos2 \u03b8 function. An ion-scattering-spectroscopy analysis of the liquid eutectic alloy reveals a surface layer of almost pure indium. A thermodynamic explanation for this highly segregated layer is discussed. The liquid eutectic alloy provides us with a unique target system which allows us to estimate the fraction of sputtered material which comes from the first monolayer of the surface.
", "doi": "10.7907/psdd-pp78", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:9260", "collection": "thesis", "collection_id": "9260", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10292015-112154529", "primary_object_url": { "basename": "Dumke_MF_1982.pdf", "content": "final", "filesize": 21433583, "license": "other", "mime_type": "application/pdf", "url": "/9260/1/Dumke_MF_1982.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Sputtering of the Gallium-Indium Eutectic Alloy in the Liquid Phase", "author": [ { "family_name": "Dumke", "given_name": "Mark Frederick", "clpid": "Dumke-Mark-Frederick" } ], "thesis_advisor": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "thesis_committee": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Gomez", "given_name": "Ricardo", "clpid": "Gomez-R" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We have measured sputtering yields and angular distributions of sputtered atoms from both the solid and liquid phases of gallium, indium, and the gallium-indium eutectic alloy. This was done by Rutherford backscattering analysis of graphite collector foils. The solid eutectic target shows a predominance of indium crystallites on its surface which have to be sputtered away before the composition of the sputtered atoms equals the bulk target composition. The size of the crystallites depends upon the conditions under which the alloy is frozen. The sputtering of the liquid eutectic alloy by 15 keV Ar+ results in a ratio of indium to gallium sputtering yields which is 28 times greater than would be expected from the target stoichiometry. Furthermore, the angular distribution of gallium is much more sharply peaked about the normal to the target surface than the indium distribution. When the incident Ar+ energy is increased to 25 keV, the gallium distribution broadens to the same shape as the indium distribution. With the exception of the sharp gallium distribution taken from the liquid eutectic at 15 keV, all angular distributions from liquid targets fit a cos2 \u03b8 function. An ion-scattering-spectroscopy analysis of the liquid eutectic alloy reveals a surface layer of almost pure indium. A thermodynamic explanation for this highly segregated layer is discussed. The liquid eutectic alloy provides us with a unique target system which allows us to estimate the fraction of sputtered material which comes from the first monolayer of the surface.
", "doi": "10.7907/psdd-pp78", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:3930", "collection": "thesis", "collection_id": "3930", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10052006-093021", "type": "thesis", "title": "Studies of the Geochemical Similarity of Plutonium and Samarium and Their Implications for the Abundance of \u00b2\u2074\u2074Pu in the Early Solar System", "author": [ { "family_name": "Jones", "given_name": "John Hume", "clpid": "Jones-John-Hume" } ], "thesis_advisor": [ { "family_name": "Patterson", "given_name": "Clair C.", "clpid": "Patterson-C-C" } ], "thesis_committee": [ { "family_name": "Patterson", "given_name": "Clair C.", "clpid": "Patterson-C-C" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "PuD and SmD have been measured for diopsidic pyroxene and whitlockite in the system Di-An-Ab (\u00b1 Ca3(PO4)2). PuD was determined by fission track radiography and SmD was determined on the same samples by beta radiography. The analytical difficulties encountered in using photographic emulsions to determine beta fluences have been studied in detail. These studies have resulted in a technique which should be generally applicable to the radiography of low energy beta emitters (Appendix I).
\r\n\r\nPuD and SmD for clinopyroxene are 0.17 and 0.31, respectively, at about 1250\u00b0C and SmD/PuD = 1.9. The addition of 1.4% P2O5 to the DiAnAb system lowers SmD and PuD by factors of 1.5 and 2.0, respectively; this P2O5 addition raises the SmD/PuD ratio to 2.6. PuD and SmD for whitlockite are 3.8 and 6.4, respectively.
\r\n\r\nThe problem of approach to interfacial equilibrium is discussed in detail, and D values of crystals grown using various thermal histories are compared. Whitlockite D values appear to be independent of thermal history, implying a close approach to equilibrium at the crystal-liquid interface. Differences are seen between pyroxene D values for different thermal histories, and these variations are compared to the results of a simple kinetic disequilibrium model. The result of this comparison suggests that interfacial equilibrium was closely approached and that variations in pyroxene D values are mainly due to the temperature dependence of partitioning. This appears to be true for both Sm and Pu, even though the partitioning of other elements (e.g. Al) may be influenced by kinetic disequilibrium.
\r\n\r\nThe magnitudes of SmD and PuD and (\u2264 0.3) for clinopyroxene imply that Pu and the light REE's are difficult to fractionate during ordinary igneous processes. 244Pu/238U ratio measurements of meteorites are reviewed in light of the results of this study and a 244Pu/238U ratio of 0.005 \u00b1 0.002 for the early solar system is favored. This is supportive of the 244Pu/238U ratio calculated by Marti et al. (1977) and suggests that the Podosek (1970a) value of 0.015 is invalid.
\r\n", "doi": "10.7907/qwv9-t340", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:3930", "collection": "thesis", "collection_id": "3930", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10052006-093021", "type": "thesis", "title": "Studies of the Geochemical Similarity of Plutonium and Samarium and Their Implications for the Abundance of \u00b2\u2074\u2074Pu in the Early Solar System", "author": [ { "family_name": "Jones", "given_name": "John Hume", "clpid": "Jones-John-Hume" } ], "thesis_advisor": [ { "family_name": "Patterson", "given_name": "Clair C.", "clpid": "Patterson-C-C" } ], "thesis_committee": [ { "family_name": "Patterson", "given_name": "Clair C.", "clpid": "Patterson-C-C" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "PuD and SmD have been measured for diopsidic pyroxene and whitlockite in the system Di-An-Ab (\u00b1 Ca3(PO4)2). PuD was determined by fission track radiography and SmD was determined on the same samples by beta radiography. The analytical difficulties encountered in using photographic emulsions to determine beta fluences have been studied in detail. These studies have resulted in a technique which should be generally applicable to the radiography of low energy beta emitters (Appendix I).
\r\n\r\nPuD and SmD for clinopyroxene are 0.17 and 0.31, respectively, at about 1250\u00b0C and SmD/PuD = 1.9. The addition of 1.4% P2O5 to the DiAnAb system lowers SmD and PuD by factors of 1.5 and 2.0, respectively; this P2O5 addition raises the SmD/PuD ratio to 2.6. PuD and SmD for whitlockite are 3.8 and 6.4, respectively.
\r\n\r\nThe problem of approach to interfacial equilibrium is discussed in detail, and D values of crystals grown using various thermal histories are compared. Whitlockite D values appear to be independent of thermal history, implying a close approach to equilibrium at the crystal-liquid interface. Differences are seen between pyroxene D values for different thermal histories, and these variations are compared to the results of a simple kinetic disequilibrium model. The result of this comparison suggests that interfacial equilibrium was closely approached and that variations in pyroxene D values are mainly due to the temperature dependence of partitioning. This appears to be true for both Sm and Pu, even though the partitioning of other elements (e.g. Al) may be influenced by kinetic disequilibrium.
\r\n\r\nThe magnitudes of SmD and PuD and (\u2264 0.3) for clinopyroxene imply that Pu and the light REE's are difficult to fractionate during ordinary igneous processes. 244Pu/238U ratio measurements of meteorites are reviewed in light of the results of this study and a 244Pu/238U ratio of 0.005 \u00b1 0.002 for the early solar system is favored. This is supportive of the 244Pu/238U ratio calculated by Marti et al. (1977) and suggests that the Podosek (1970a) value of 0.015 is invalid.
\r\n", "doi": "10.7907/qwv9-t340", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:8689", "collection": "thesis", "collection_id": "8689", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10092014-153207228", "primary_object_url": { "basename": "Zumberge_JF_1981.pdf", "content": "final", "filesize": 15101550, "license": "other", "mime_type": "application/pdf", "url": "/8689/1/Zumberge_JF_1981.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A Balloon Measurement of the Isotopic Composition of Galactic Cosmic Ray Boron, Carbon, and Nitrogen", "author": [ { "family_name": "Zumberge", "given_name": "James Frederick", "clpid": "Zumberge-James-Frederick" } ], "thesis_advisor": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" } ], "thesis_committee": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "div_pma" } ], "abstract": "The isotopic compositions of galactic cosmic ray boron, carbon, and nitrogen have been measured at energies near 300 MeV amu-1, using a balloon-borne instrument at an atmospheric depth of ~ 5 g cm-2. The calibrations of the detectors comprising the instrument are described. The saturation properties of the cesium iodide scintilla tors used for measurement of particle energy are studied in the context of analyzing the data for mass. The achieved rms mass resolution varies from ~ 0.3 amu at boron to ~ 0.5 amu at nitrogen, consistent with a theoretical analysis of the contributing factors. Corrected for detector interactions and the effects of the residual atmosphere, the results are 10B/B = 0.33+0.17-0.11, 13C/C = 0.06+0.13-0.01, and 15N/N = 0.42+0.19-0.17. A model of galactic propagation and solar modulation is described. Assuming a cosmic ray source composition of solar-like isotopic abundances, the model predicts abundances near earth consistent with the measurements.
\r\n", "doi": "10.7907/22yw-v483", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:8689", "collection": "thesis", "collection_id": "8689", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10092014-153207228", "primary_object_url": { "basename": "Zumberge_JF_1981.pdf", "content": "final", "filesize": 15101550, "license": "other", "mime_type": "application/pdf", "url": "/8689/1/Zumberge_JF_1981.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A Balloon Measurement of the Isotopic Composition of Galactic Cosmic Ray Boron, Carbon, and Nitrogen", "author": [ { "family_name": "Zumberge", "given_name": "James Frederick", "clpid": "Zumberge-James-Frederick" } ], "thesis_advisor": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" } ], "thesis_committee": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "div_pma" } ], "abstract": "The isotopic compositions of galactic cosmic ray boron, carbon, and nitrogen have been measured at energies near 300 MeV amu-1, using a balloon-borne instrument at an atmospheric depth of ~ 5 g cm-2. The calibrations of the detectors comprising the instrument are described. The saturation properties of the cesium iodide scintilla tors used for measurement of particle energy are studied in the context of analyzing the data for mass. The achieved rms mass resolution varies from ~ 0.3 amu at boron to ~ 0.5 amu at nitrogen, consistent with a theoretical analysis of the contributing factors. Corrected for detector interactions and the effects of the residual atmosphere, the results are 10B/B = 0.33+0.17-0.11, 13C/C = 0.06+0.13-0.01, and 15N/N = 0.42+0.19-0.17. A model of galactic propagation and solar modulation is described. Assuming a cosmic ray source composition of solar-like isotopic abundances, the model predicts abundances near earth consistent with the measurements.
\r\n", "doi": "10.7907/22yw-v483", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:8634", "collection": "thesis", "collection_id": "8634", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08132014-153838558", "primary_object_url": { "basename": "Yapp 1980.pdf", "content": "final", "filesize": 41055352, "license": "other", "mime_type": "application/pdf", "url": "/8634/1/Yapp 1980.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Variations and Climatic Significance of D/ H Ratios in the Carbon-Bound Hydrogen of Cellulose in Trees", "author": [ { "family_name": "Yapp", "given_name": "Crayton Jeffery", "clpid": "Yapp-Crayton-Jeffery" } ], "thesis_advisor": [ { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "thesis_committee": [ { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Lowenstam", "given_name": "Heinz A.", "clpid": "Lowenstam-H-A" }, { "family_name": "Patterson", "given_name": "Clair C.", "clpid": "Patterson-C-C" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The \u03c3D values of nitrated cellulose from a variety of trees\r\ncovering a wide geographic range have been measured. These measurements\r\nhave been used to ascertain which factors are likely to cause \u03c3D\r\nvariations in cellulose C-H hydrogen.
\r\n\r\nIt is found that a primary source of tree \u03c3D variation is the\r\n\u03c3D variation of the environmental precipitation. Superimposed on this\r\nare isotopic variations caused by the transpiration of the leaf water\r\nincorporated by the tree. The magnitude of this transpiration effect\r\nappears to be related to relative humidity.
\r\n\r\nWithin a single tree, it is found that the hydrogen isotope\r\nvariations which occur for a ring sequence in one radial direction may\r\nnot be exactly the same as those which occur in a different direction.\r\nSuch heterogeneities appear most likely to occur in trees with asymmetric\r\nring patterns that contain reaction wood. In the absence of reaction\r\nwood such heterogeneities do not seem to occur. Thus, hydrogen isotope\r\nanalyses of tree ring sequences should be performed on trees which do\r\nnot contain reaction wood.
\r\n\r\nComparisons of tree \u03c3D variations with variations in local climate\r\nare performed on two levels: spatial and temporal. It is found that\r\nthe \u03c3D values of 20 North American trees from a wide geographic range\r\nare reasonably well-correlated with the corresponding average annual\r\ntemperature. The correlation is similar to that observed for a\r\ncomparison of the \u03c3D values of annual precipitation of 11 North\r\nAmerican sites with annual temperature. However, it appears that this\r\ncorrelation is significantly disrupted by trees which grew on poorly\r\ndrained sites such as those in stagnant marshes. Therefore, site\r\nselection may be important in choosing trees for climatic interpretation\r\nof \u03c3D values, although proper sites do not seem to be uncommon.
\r\n\r\nThe measurement of \u03c3D values in 5-year samples from the tree ring\r\nsequences of 13 trees from 11 North American sites reveals a variety\r\nof relationships with local climate. As it was for the spatial \u03c3D vs\r\nclimate comparison, site selection is also apparently important for\r\ntemporal tree \u03c3D vs climate comparisons. Again, it seems that poorly-drained\r\nsites are to be avoided. For nine trees from different \"well-behaved\"\r\nsites, it was found that the local climatic variable best\r\nrelated to the \u03c3D variations was not the same for all sites.
\r\n\r\nTwo of these trees showed a strong negative correlation with the\r\namount of local summer precipitation. Consideration of factors likely\r\nto influence the isotopic composition of summer rain suggests that\r\nrainfall intensity may be important. The higher the intensity, the\r\nlower the \u03c3D value. Such an effect might explain the negative\r\ncorrelation of \u03c3D vs summer precipitation amount for these two trees.\r\nA third tree also exhibited a strong correlation with summer climate,\r\nbut in this instance it was a positive correlation of \u03c3D with summer\r\ntemperature.
\r\n\r\nThe remaining six trees exhibited the best correlation between \u03c3D\r\nvalues and local annual climate. However, in none of these six cases\r\nwas it annual temperature that was the most important variable. In\r\nfact annual temperature commonly showed no relationship at all with\r\ntree \u03c3D values. Instead, it was found that a simple mass balance\r\nmodel incorporating two basic assumptions yielded parameters which\r\n\r\nproduced the best relationships with tree \u03c3D values. First, it was\r\nassumed that the \u03c3D values of these six trees reflected the \u03c3D values\r\nof annual precipitation incorporated by these trees. Second, it was\r\nassumed that the \u03c3D value of the annual precipitation was a weighted\r\naverage of two seasonal isotopic components: summer and winter. Mass\r\nbalance equations derived from these assumptions yielded combinations\r\nof variables that commonly showed a relationship with tree \u03c3D values\r\nwhere none had previously been discerned.
\r\n\r\nIt was found for these \"well-behaved\" trees that not all sample\r\nintervals in a \u03c3D vs local climate plot fell along a well-defined\r\ntrend. These departures from the local \u03c3D VS climate norm were defined\r\nas \"anomalous\". Some of these anomalous intervals were common to trees\r\nfrom different locales. When such widespread commonalty of an anomalous\r\ninterval occurred, it was observed that the interval corresponded to\r\nan interval in which drought had existed in the North American Great\r\nPlains.
\r\n\r\nConsequently, there appears to be a combination of both local and\r\nlarge scale climatic information in the \u03c3D variations of tree cellulose\r\nC-H hydrogen.
\r\n", "doi": "10.7907/FFSK-YC27", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:8092", "collection": "thesis", "collection_id": "8092", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02202014-142721576", "type": "thesis", "title": "Oxygen, Carbon, and Hydrogen Isotope Studies of Contact Metamorphism", "author": [ { "family_name": "Shieh", "given_name": "Yuch-Ning", "clpid": "Shieh-Yuch-Ning" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "thesis_committee": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The O18/O16, C13/C12, and D/H ratios have been determined for\r\nrocks and coexisting minerals from several granitic plutons and their contact\r\nmetamorphic aureoles in northern Nevada, eastern California, central Colorado,\r\nand Texas, with emphasis on oxygen isotopes. A consistent order of O18/O16, C13/C12, and D/H enrichment in coexisting minerals, and a correlation between isotopic fractionations among coexisting mineral pairs are in general\r\nobserved, suggesting that mineral assemblages tend to approach isotopic\r\nequilibrium during contact metamorphism. In certain cases, a correlation is\r\nobserved between oxygen isotopic fractionations of a mineral pair and sample\r\ndistance from intrusive contacts. Isotopic temperatures generally show good\r\nagreement with heat flow considerations. Based on the experimentally\r\ndetermined quartz-muscovite O18/O16 fractionation calibration curve, temperatures are\r\nestimated to be 525 to 625\u00b0C at the contacts of the granitic stocks\r\nstudied.
\r\n\r\nSmall-scale oxygen isotope exchange effects between intrusive and\r\ncountry rock are observed over distances of 0.5 to 3 feet on both sides of the\r\ncontacts; the isotopic gradients are typically 2 to 3 per mil per foot. The\r\ndegree of oxygen isotopic exchange is essentially identical for different\r\ncoexisting minerals. This presumably occurred through a diffusion-controlled\r\nrecrystallization process. The size of the oxygen isotope equilibrium systems\r\nin the small-scale exchanged zones vary from about 1.5 cm to 30 cm. A\r\nxenolith and a re-entrant of country rock projecting into on intrusive hove\r\nboth undergone much more extensive isotopic exchange (to hundreds of feet);\r\nthey also show abnormally high isotopic temperatures. The marginal portions\r\nof most plutons have unusually high O18/O16 ratios compared to \"normal\"\r\nigneous rocks, presumably due to large-scale isotopic exchange with meta-sedimentary\r\ncountry rocks when the igneous rocks were essentially in a molten\r\nstate. The isotopic data suggest that outward horizontal movement of H2O\r\ninto the contact metamorphic aureoles is almost negligible, but upward movement\r\nof H2O may be important. Also, direct influx and absorption of water from the\r\ncountry rock may be significant in certain intrusive stocks.
\r\n\r\nExcept in the exchanged zones, the O18/O16 ratios of pelitic rocks\r\ndo not change appreciably during contact metamorphism, even in the cordierite\r\nand sillimanite grades; this is in contrast to regional metamorphic rocks which\r\ncommonly decrease in O18 with increasing grade. Low O18/O16 and C13/C12\r\nratios of the contact metamorphic marbles generally correlate well with the\r\npresence of calc-silicate minerals, indicating that the CO2 liberated during\r\nmetamorphic decarbonation reactions is enriched in both O18 and C13 relative to the carbonates.
\r\n\r\nThe D/H ratios of biotites in the contact metamorphic rocks and their\r\nassociated intrusions show a geographic correlation that is similar to that shown\r\nby the D/H ratios of meteoric surface waters, perhaps indicating that meteoric\r\nwaters were present in the rocks during crystallization of the biotites.
\r\n\r\n", "doi": "10.7907/JJY7-J871", "publication_date": "1969", "thesis_type": "phd", "thesis_year": "1969" }, { "id": "thesis:8092", "collection": "thesis", "collection_id": "8092", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02202014-142721576", "type": "thesis", "title": "Oxygen, Carbon, and Hydrogen Isotope Studies of Contact Metamorphism", "author": [ { "family_name": "Shieh", "given_name": "Yuch-Ning", "clpid": "Shieh-Yuch-Ning" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "thesis_committee": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Burnett", "given_name": "Donald S.", "orcid": "0000-0001-9521-8675", "clpid": "Burnett-D-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The O18/O16, C13/C12, and D/H ratios have been determined for\r\nrocks and coexisting minerals from several granitic plutons and their contact\r\nmetamorphic aureoles in northern Nevada, eastern California, central Colorado,\r\nand Texas, with emphasis on oxygen isotopes. A consistent order of O18/O16, C13/C12, and D/H enrichment in coexisting minerals, and a correlation between isotopic fractionations among coexisting mineral pairs are in general\r\nobserved, suggesting that mineral assemblages tend to approach isotopic\r\nequilibrium during contact metamorphism. In certain cases, a correlation is\r\nobserved between oxygen isotopic fractionations of a mineral pair and sample\r\ndistance from intrusive contacts. Isotopic temperatures generally show good\r\nagreement with heat flow considerations. Based on the experimentally\r\ndetermined quartz-muscovite O18/O16 fractionation calibration curve, temperatures are\r\nestimated to be 525 to 625\u00b0C at the contacts of the granitic stocks\r\nstudied.
\r\n\r\nSmall-scale oxygen isotope exchange effects between intrusive and\r\ncountry rock are observed over distances of 0.5 to 3 feet on both sides of the\r\ncontacts; the isotopic gradients are typically 2 to 3 per mil per foot. The\r\ndegree of oxygen isotopic exchange is essentially identical for different\r\ncoexisting minerals. This presumably occurred through a diffusion-controlled\r\nrecrystallization process. The size of the oxygen isotope equilibrium systems\r\nin the small-scale exchanged zones vary from about 1.5 cm to 30 cm. A\r\nxenolith and a re-entrant of country rock projecting into on intrusive hove\r\nboth undergone much more extensive isotopic exchange (to hundreds of feet);\r\nthey also show abnormally high isotopic temperatures. The marginal portions\r\nof most plutons have unusually high O18/O16 ratios compared to \"normal\"\r\nigneous rocks, presumably due to large-scale isotopic exchange with meta-sedimentary\r\ncountry rocks when the igneous rocks were essentially in a molten\r\nstate. The isotopic data suggest that outward horizontal movement of H2O\r\ninto the contact metamorphic aureoles is almost negligible, but upward movement\r\nof H2O may be important. Also, direct influx and absorption of water from the\r\ncountry rock may be significant in certain intrusive stocks.
\r\n\r\nExcept in the exchanged zones, the O18/O16 ratios of pelitic rocks\r\ndo not change appreciably during contact metamorphism, even in the cordierite\r\nand sillimanite grades; this is in contrast to regional metamorphic rocks which\r\ncommonly decrease in O18 with increasing grade. Low O18/O16 and C13/C12\r\nratios of the contact metamorphic marbles generally correlate well with the\r\npresence of calc-silicate minerals, indicating that the CO2 liberated during\r\nmetamorphic decarbonation reactions is enriched in both O18 and C13 relative to the carbonates.
\r\n\r\nThe D/H ratios of biotites in the contact metamorphic rocks and their\r\nassociated intrusions show a geographic correlation that is similar to that shown\r\nby the D/H ratios of meteoric surface waters, perhaps indicating that meteoric\r\nwaters were present in the rocks during crystallization of the biotites.
\r\n\r\n", "doi": "10.7907/JJY7-J871", "publication_date": "1969", "thesis_type": "phd", "thesis_year": "1969" } ]