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:16202", "collection": "thesis", "collection_id": "16202", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10062023-181634008", "primary_object_url": { "basename": "Holland_KG_1997.pdf", "content": "final", "filesize": 30615462, "license": "other", "mime_type": "application/pdf", "url": "/16202/1/Holland_KG_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Phase Changes and Transport Properties of Geophysical Materials Under Shock Loading", "author": [ { "family_name": "Holland", "given_name": "Kathleen Gabrielle", "clpid": "Holland-Kathleen-Gabrielle" } ], "thesis_advisor": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "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" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The lower mantle of the Earth is believed to be largely composed of (Mg, Fe)O (magnesiowiistite) and (Mg,Fe)SiO\u2083 (perovskite); thus the high pressure phase of (Mg,Fe)\u2082SiO\u2084 (olivine), which is believed to be perovskite plus magnesiowiistite is of geophysical interest. Radiative temperatures of single-crystal olivine starting material [(Mg_(0.9), Fe_(0.1))\u2082SiO\u2084] decreased abruptly from 7040 \u00b1 315 to 4300 \u00b1 270 K upon shock compression above 80 GPa. The data indicate that an upper bound to the solidus of the magnesiowiistite and perovskite assemblage at 4300 \u00b1 270 K is 130 \u00b1 3 GPa. These conditions correspond to those for partial melting at the base of the mantle, as has been suggested to occur within the recently discovered ultra-low-velocity zone (ULVZ) beneath the Central Pacific. We construct speculative high pressure phase diagrams for the MgO - SiO\u2082 system using experimental data from our work, and other mineral physics experiments.
\r\n\r\nIn separate experiments, time dependent shock temperatures were measured for stainless steel (SS) films sandwiched between two transparent Al\u2082O\u2083 anvils. The anvil material was the same as the driver material so that there would be symmetric heat flow from the sample. Inferred Hugoniot temperatures, T_h, of 5000 - 8500\u00b1500 Kat 222- 321 GPa are consistent with previous measurements in SS. Temperatures at the film\u00ad anvil interface (T_i), which are directly measured (rather than T_h) indicate that T_i did not decrease measurably during the approximately 250 ns that the shock wave took to traverse the Al\u2082O\u2083 anvil. Thus an upper bound is obtained for the thermal diffusivity of Al\u2082O\u2083 at the metal/anvil interface of K \u2264 14 \u00b1 5 cm\u00b2/s at 208 GPa and 2110 K. This is a factor of 1.6 lower than previously calculated values, resulting in a decrease of the inferred T_h by at least 400 K. The observed shock temperatures are combined with temperatures calculated from measured Hugoniots and are used to calculate the thermal conductivity of Al\u2082O\u2083. There was no measurable radiant-intensity decrease during the time when the shock wave propagated through the anvil; we infer from this that Al\u2082O\u2083 remained transparent while in the shocked state. Thus an Al\u2082O\u2083 anvil is sufficiently transparent for shock temperature measurements for metals, to at least 240 GPa.
\r\n\r\nFinally, shock temperature experiments employing a six-channel pyrometer were conducted on 200, 500, and 1000 \u00c5 thick films of Fe sandwiched between 3 mm thick anvils of Al\u2082O\u2083 and LiF, to measure the thermal diffusivity ratios of Al\u2082O\u2083/Fe and LiF/Fe, at high temperatures and pressures. Temperature decays of 3000 \u00b1 800 K in 250 ns were observed at Fe pressures of 194 - 303 GPa, which reflect the conduction of heat from the thin metal films into the anvil material. These results were achieved in experiments employing LiF anvils at 164 - 166 GPa and 4190 - 4220 K, and Al2O3 anvils at 196 - 303 GPa and 1410 - 2750 K. Thermal modeling of interface temperature versus time yields best fit thermal diffusivity ratios ranging from 15 \u00b1 30 to 80 \u00b1 20 (Fe/anvil) over the pressure and temperature range of the experiments. Calculated thermal conductivities for Fe, using electron gas theory, of 110 - 212 W /mK are used to calculate thermal conductivities for the anvil materials ranging from 6 to 12 W/mK. Debye theory predicts higher values of 8 to 34 W/mK. Data from previous experiments on thick (\u2265 100\u00b5m) films of Fe and stainless steel are combined with our present results from experiments on thin (\u2264 1000 \u00c5) films to infer a 5860 \u00b1 390 K Hugoniot temperature for the onset of melting of iron at 243 GPa. Our results address the question of whether radiation observed in shock temperature experiments on metals originates from the metal at the metal/ anvil interface or from the shocked anvil. We conclude that the photon flux from the shocked iron/anvil sandwich recorded in all experiments originates from the metal. Within the uncertainties of the shock temperature data, the uncertainties in shock temperatures resulting from the radiation from the anvils is negligible. This is in direct disagreement with previous conclusions of Kondo.
", "doi": "10.7907/cbd3-mk54", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:15047", "collection": "thesis", "collection_id": "15047", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10252022-202940570", "primary_object_url": { "basename": "Holk_GJ_1997.pdf", "content": "final", "filesize": 201279911, "license": "other", "mime_type": "application/pdf", "url": "/15047/1/Holk_GJ_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Role of Water in the Magmatic and Tectonic Evolution of Metamorphic Core Complexes: A stable Isotope Study of the Southern Omineca Crystalline Belt, British Columbia, Canada", "author": [ { "family_name": "Holk", "given_name": "Gregory James", "clpid": "Holk-Gregory-James" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P., Jr.", "clpid": "Taylor-H-P" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" } ], "thesis_committee": [ { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Taylor", "given_name": "Hugh P., Jr.", "clpid": "Taylor-H-P" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Wernicke", "given_name": "Brian P.", "orcid": "0000-0002-7659-8358", "clpid": "Wernicke-B-P" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The oxygen isotope data in this study delineate 2 major episodes of water-rock interaction related to the metamorphic, plutonic, and tectonic development of the metamorphic core complexes in the southern Omineca belt. Episode 1 is a Paleocene pre\u00ad-extensional metamorphic/magmatic-hydrothermal event. The occurrence of isotopically uniform quartz (\u03b4\u00b9\u2078O = 12.5 \u00b1 0.5\u2030) and feldspar (10.9 \u00b1 0.7\u2030) throughout different rock types indicates that much of a 6-km-thick section of the mid-crustal Selkirk allochthon underwent internally buffered \u00b9\u2078O/\u00b9\u2076O homogenization during Paleocene melting and decompression as it moved up the Monashee decollement thrust ramp. Areas of uniform \u03b4\u00b9\u2078O are those with the most leucogranite or those subjected to severe anatexis. Only locally, in the most impermeable (or refractory) zones did 180 exchange among the rocks, leucogranite melts, and aqueous fluids fail to go to completion (i.e., in the deepest parts of the section, in a marble-rich zone, around some thick amphibolites, and in most garnets). Evidence for \u00b9\u2078O/\u00b9\u2076O heterogeneity in the protoliths of these rocks is observed in stratigraphically correlative lower-grade units elsewhere in British Columbia, as well as in garnets that coexist with isotopically homogeneous quartz. A model is introduced utilizing water as a petrologic catalyst: fluids evolved during muscovite breakdown and partial melting of pelites produce \u00b9\u2078O/\u00b9\u2076O homogenization with only minor influx of external H\u2082O; this is followed by release of magmatic H\u2082O from these melts as they crystallize (triggering further melting of adjacent feldspathic assemblages) during and after the ~20 km uplift that occurred in the thrusting event that took place just prior to detachment faulting.
\r\n \r\nEpisode 2 is a series of Eocene synextensional meteoric-hydrothermal events affecting the shallow crust along all of the major detachment faults in the region, and along some parts of the Monashee decollement; these effects were locally enhanced by added heat from some synextensional alkaline intrusions (the Coryell plutons). Very large quartz-feldspar \u00b9\u2078O/\u00b9\u2076O disequilibrium effects were imprinted upon the rocks during exchange with hot meteoric waters (initial \u03b4\u00b9\u2078O ~ -15); the mineral most affected was feldspar (\u03b4\u00b9\u2078O down to -5.0). In the Valhalla core complex, the hanging wall rocks above the Slocan Lake fault are sufficiently uniform to allow us to apply open-system kinetic oxygen isotope exchange modeling, thereby placing constraints on the duration (1-3 Ma) and integrated fluid flux (\u2265 10\u2077 cm\u00b3H\u2082O/cm\u2082rock) for this hydrothermal metamorphism.
", "doi": "10.7907/pkn3-p364", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:4607", "collection": "thesis", "collection_id": "4607", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11202003-144820", "primary_object_url": { "basename": "Asimow_pd_1997.pdf", "content": "final", "filesize": 19908356, "license": "other", "mime_type": "application/pdf", "url": "/4607/1/Asimow_pd_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "A Thermodynamic Model of Adiabatic Melting of the Mantle", "author": [ { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-Paul-David" } ], "thesis_advisor": [ { "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" } ], "thesis_committee": [ { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Gurnis", "given_name": "Michael C.", "orcid": "0000-0003-1704-597X", "clpid": "Gurnis-M-C" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Mid-ocean ridge basalts (MORB) are mixtures of melts produced over a range of pressure and temperature in a nearly adiabatic open system undergoing changes in composition as melting proceeds. Interpretation of the compositional variations observed in MORB and their correlation with geophysical aspects of the ridge therefore requires complex forward models to connect experimental observations of isothermal, isobaric batch melting of peridotite to natural compositions. Previous attempts to construct such models have relied on parameterizations of melt composition or partition coefficients and extent of melting in pressure-temperature space from experimental batch melting data. This thesis undertakes the examination of an alternative approach using thermodynamic models of silicate minerals and melts to predict equilibria under quite arbitrary constraints, including variable bulk composition and constant entropy. The liquids predicted from the thermodynamic models along polybaric paths can then be integrated to produce comprehensive forward models of MORB genesis.
\r\n \r\nChapter 1 introduces the nature of the MORB modeling problem and the motivation of the thermodynamic approach in greater detail. Chapter 2 illustrates the thermodynamic approach by demonstrating that the effect of the garnet-spinel and spinelplagioclase peridotite transitions, which retard or reverse isentropic melting, can be easily understood. Chapter 3 looks at the variables affecting isentropic melt productivity (i.e., the increment of additional melting per decrement of pressure at constant entropy). I find that this quantity is likely to increase during progressive melting, punctuated by drops where phases are exhausted from the residuum. Chapter 4 extends this approach to issues of melt transport in one dimension and steady state; I evaluate the magnitude of entropy production due to gravitational dissipation and thermal interactions with migrating fractional melts and examine the effect of focused melt flow. Finally, chapter 5 deals with the compositions and mean properties of MORB obtained by integrating the compositions and melt fractions predicted by our models. We compare our results to published models of MORB compositions and consider the implications. The algorithms and source code, including subsolidus capability, added to the MELTS package of Ghiorso and Sack for these calculations are included as appendices.
", "doi": "10.7907/93RY-AN70", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:16183", "collection": "thesis", "collection_id": "16183", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09192023-212841699", "primary_object_url": { "basename": "Lee_W-J_1996.pdf", "content": "final", "filesize": 109440804, "license": "other", "mime_type": "application/pdf", "url": "/16183/1/Lee_W-J_1996.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Experimental Study on Liquid Immiscibility in Silicate-Carbonate Systems with Applications to Carbonatites", "author": [ { "family_name": "Lee", "given_name": "Woh-jer", "clpid": "Lee-Woh-jer" } ], "thesis_advisor": [ { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" } ], "thesis_committee": [ { "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": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Phase equilibrium experiments have been conducted in several silicate-carbonate systems to 2.5 GPa in order to understand the magmatic processes involved in the generation of carbonatite complexes. The studied phase fields were intersected by SiO\u2082-CaCO\u2083, NaAlSi\u2083O\u2088-CaCO\u2083, NaAlSiO\u2084-NaAlSi\u2083O\u2088-CaCO\u2083 and primitive nephelinite\u00ad (Na,Ca,Mg) carbonate, which along with the analyzed liquid and solid compositions were used to define the positions of the silicate-carbonate miscibility gap and liquidus field boundaries on various compositional projections. These boundaries exert controls on the evolution of silicate-CO\u2082 and carbonatitic magmas, and vary strongly with temperature, composition and pressure. The size of the miscibility gap decreases with increasing temperature and Mg/Ca of liquids. The extent of the Mg-free miscibility gap decreases with decreasing pressure, whereas the magnesian one shows an opposite trend. The immiscible carbonate-rich liquids could dissolve at most ~80 wt% CaCO\u2083 while still containing significant amounts of silicate and alkalis. The position of the silicate-calcite coprecipitation boundary becomes more carbonate-rich as pressure decreases, and as composition becomes more magnesian and aluminous. Calcite grew remarkably rounded in many experiments. A variety of liquid paths are compared with the field boundaries at different conditions. Partial melting of carbonated peridotite produces dolomitic carbonatites along the coprecipitation boundary, to CO\u2082-bearing, silica-undersaturated liquids in the primary silicate field. Both types of magmas could potentially ascend to the surface of the earth without much modification. None of them would reach the miscibility gap at mantle conditions. Within the crust, carbonated silicate liquids could either intersect the miscibility gap after substantial crystallization to exsolve alkali-bearing to alkalic carbonatitic liquids, or reach the coprecipitation boundary and evolve towards alkali-enrichment and silicate\u00ad depletion without immiscibility. Alkali-bearing, CaCO\u2083-rich immiscible liquids, when separating from their silicate parents, first precipitate silicate minerals during cooling until calcite is joined, and the residual liquids become more alkalic by further crystallization of calcite. It appears that most calciocarbonatites are cumulates from liquids along the coprecipitation boundary, whereas the natrocarbonatites at Oldoinyo Lengai are produced directly by immiscibility.", "doi": "10.7907/vpan-h802", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:4423", "collection": "thesis", "collection_id": "4423", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-083125", "primary_object_url": { "basename": "Ray_tw_1995.pdf", "content": "final", "filesize": 60568633, "license": "other", "mime_type": "application/pdf", "url": "/4423/1/Ray_tw_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Remote monitoring of land degradation in arid/semiarid regions", "author": [ { "family_name": "Ray", "given_name": "Terrill Wylie", "clpid": "Ray-T-W" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Blom", "given_name": "Ron", "clpid": "Blom-R" } ], "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\nLand degradation is a serious and growing problem on a world-wide scale -- 11% of the Earth's vegetated surface having suffered serious damage in the last 45 years. Human activity, especially sprinkler irrigation agriculture, can cause dramatic changes in arid regions as the fragile natural plant cover is stripped off and its root system destroyed in the process of cultivation. Satellite and airborne remote sensing data covering the Manix Basin of Eastern California over the last two decades shows that abandoned fields there suffered progressive degradation, as the topsoil eroded due to the lack of protective plant cover. Blowing sand buried and disrupted the downwind plant cover, which caused the downwind area to lose its protection against wind erosion and expanded the region of damage.\r\n\r\nBecause the amount and kind of plant cover is an important marker both of where wind erosion has occurred and where it is likely to occur in the future, especially designed satellite monitoring systems should be able to sense to signatures of undisturbed and disturbed vegetation cover in arid regions. However, this problem cannot be addressed by standard vegetation indices, because of the adaptation of arid region plants to the scarcity of water. Furthermore, weekly to monthly sampling will be necessary because blowing sand visible to satellite remote sensing is highly dependent on the local weather, and this can change within a few months. A new vegetative index suitable for arid regions is proposed for the wavelength region from 0.4-1.0 [...].\r\n\r\nThe detection and identification of arid region plant communities requires a highly calibrated remote sensing system with higher spectral resolution than that currently offered by Landsat Thematic Mapper. The way in which regions of blowing sand can appear and disappear with rapidity demonstrates the need for a remote monitoring system that can survey large areas on a regular basis. Such a system must be supported by focused ground observations and a continuing analysis of the satellite data.\r\n", "doi": "10.7907/65EA-Y568", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "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: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:6347", "collection": "thesis", "collection_id": "6347", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04222011-143434002", "type": "thesis", "title": "Geologic and isotopic investigations of the early Cretaceous Sierra Nevada Batholith, Tulare Co., CA, and the Ivrea Zone, NW Italian Alps: examples of interaction between mantle-derived magma and continental crust", "author": [ { "family_name": "Knott", "given_name": "Diane Clemens", "clpid": "Knott-D-C" } ], "thesis_advisor": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" } ], "thesis_committee": [ { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Stolper", "given_name": "Edward M.", "clpid": "Stolper-E-M" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Two igneous suites containing layered ultramafic-mafic cumulates were investigated with the intent to characterize the parental magma and to identify processes significant to the petrogenesis of these rocks. In both study areas, the early Cretaceous Sierra Nevada batholith and the Ivrea Zone, isotopic systematics of the cumulates were found to preserve the characteristics of the mantle-derived parental magma and to record the effects of fractional crystallization and assimilation. Modeling the relative importance of these processes and characterization of the material derived from the mantle are necessary to understanding the growth of the continental crust.
\r\n\r\nGeologic mapping of 110 mi2 of the 125 to 110 Ma Stokes Mountain region reveals the presence of layered cumulate megaxenoliths and two coeval ring dike complexes. Petrographic analysis and geochemical modeling of 125 dominantly mafic and intermediate samples demonstrate the comagmatic nature of this suite. Combined oxygen, strontium and neodymium analysis of 22 samples indicates, however, that each ring complex was fed by an isotopically distinct parental magma (\u03b5Nd(115) = +6.1, Sri = 0.70338, \u03b418O = 6.6\u2030 ; (\u03b5Nd(115) = +5.7, Sri = 0.70372, \u03b418O = 6.7\u2030) both of which were derived from a variably contaminated, depleted mantle source. Minor assimilation of continentally-derived metasediments and mafic-ultramafic material of the Kings-Kaweah ophiolite further affected the isotopic evolution of the two subsuites. Hydrothermal alteration in the subvolcanic environment is recorded only by rare stoped xenoliths of 120 Ma hypabyssal intrusives.
\r\n\r\nLate Hercynian (\u2248300 - 270 Ma) magmatism produced the 10 km thick Mafic Complex lying at the base of the Ivrea-Strona-Ceneri crustal cross section. \u03b418O analysis of 237 whole rock samples and 26 mineral separates reveals that presumably early intrusions into the cool crust preserve the depleted mantle signature of the modeled parental magma (\u03b5Nd(115) = +7, Sri = 0.703, \u03b418O = 6.5\u2030) while later intrusions assimilated significant amounts of the 10 - 12\u2030 metapelite. Subsequent intrusion of voluminous basaltic magma fonned a large, convecting magma chamber in which assimilation was concentrated within boundary layers. Such lower crustal production of high-18O (\u03b418O = 8 - 10\u2030) mafic magmas is suggested as contributing to the petrogenesis of upper crustal Permian granites.
\r\n", "doi": "10.7907/AA6N-EY25", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "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:6048", "collection": "thesis", "collection_id": "6048", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09242010-084738829", "type": "thesis", "title": "Some Problems in Mantle Structure and Dynamics. Part 1. Inversion for Depth Variation of Spectra of Mantle Compressional and Shear Velocity Heterogeneity. Part 2. Physical Model of Source Region of Subduction Zone Volcanism", "author": [ { "family_name": "Davies", "given_name": "John Huw", "clpid": "Davies-John-Huw" } ], "thesis_advisor": [ { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" } ], "thesis_committee": [ { "family_name": "Helmberger", "given_name": "Donald V.", "clpid": "Helmberger-D-V" }, { "family_name": "Clayton", "given_name": "Robert W.", "orcid": "0000-0003-3323-3508", "clpid": "Clayton-R-W" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Part 1. The scatter in ISC P- and S-wave travel-time residuals was inverted to give a measure of the data-set's incoherent noise and the depth variation of the spectra of the Earth's seismic heterogeneity. The P- and S-wave models are similar in pattern with most of their power shallower than 400km. The power generally decreases with depth and is lowest around 1500-2600km depth. Both models show a slight increase locally below the 670km discontinuity. The long-wavelength half-width (l<50) is around 500km through the upper mantle increasing to around 1200km in the lowermost mantle. The variance in the travel-time residuals requires that (\u03b41nV\u209b/ \u03b41n V\u209a) \u2248 2, if they are correlated. Our results suggest values as high as 5 from 60-1400km; these could be correct but our preferred explanation is that it's a result of poor depth resolution of the shallowest layer and a difference in the spectral resolution of the two studies.
\r\n\r\nPart 2. Thermal modeling of a generic subduction zone suggests that the oceanic crust does not melt extensively to be the source of subduction zone magmas. The slab dehydrates and the water is transported laterally into the wedge by a mechanism involving transport fixed in amphiboles and vertical porous flow when free. This water generates melting at the amphibole saturated solidus. Melting reaches a maximum at the hottest geotherm, which also caps the source region. Melts depart the source region in cracks whose direction of propagation is perpendicular to the least compressive stress. For a corner flow regime this leads to focusing of melt towards the wedge corner. The model correctly predicts the location of, the volcanic front. The melt and residue provide buoyancy that leads to local flow reversal and modulates the volcanism with a period of \u2248 1Ma. Estimates suggest more water is subducted than reappears in extrusive volcanics. We suggest the excess water is stored in melts trapped deeper in the section that later become the precursors of granitic and tonalitic plutons.
", "doi": "10.7907/1pkp-t397", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "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:8006", "collection": "thesis", "collection_id": "8006", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10232013-113130725", "type": "thesis", "title": "Chemical and Mineralogical Characterization of Micro-Inclusions in Diamonds", "author": [ { "family_name": "Navon", "given_name": "Oded", "clpid": "Navon-Oded" } ], "thesis_advisor": [ { "family_name": "Wasserburg", "given_name": "Gerald J.", "clpid": "Wasserburg-G-J" }, { "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": "Armstrong", "given_name": "John T.", "clpid": "Armstrong-John-T" }, { "family_name": "Hutcheon", "given_name": "Ian D.", "clpid": "Hutcheon-Ian-D" }, { "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": "Wasserburg", "given_name": "Gerald J.", "clpid": "Wasserburg-G-J" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Secondary-ion mass spectrometry (SIMS), electron probe analysis (EPMA), analytical scanning electron microscopy (SEM) and infrared (IR) spectroscopy were used to determine the chemical composition and the mineralogy of sub-micrometer inclusions in cubic diamonds and in overgrowths (coats) on octahedral diamonds from Zaire, Botswana, and some unknown localities.
\r\n\r\nThe inclusions are sub-micrometer in size. The typical diameter encountered during transmission electron microscope (TEM) examination was 0.1-0.5 \u00b5m. The micro-inclusions are sub-rounded and their shape is crystallographically controlled by the diamond. Normally they are not associated with cracks or dislocations and appear to be well isolated within the diamond matrix. The number density of inclusions is highly variable on any scale and may reach 10\u00b9\u00b9 inclusions/cm\u00b3 in the most densely populated zones. The total concentration of metal oxides in the diamonds varies between 20 and 1270 ppm (by weight).
\r\n\r\nSIMS analysis yields the average composition of about 100 inclusions contained in the sputtered volume. Comparison of analyses of different volumes of an individual diamond show roughly uniform composition (typically \u00b110% relative). The variation among the average compositions of different diamonds is somewhat greater (typically \u00b130%). Nevertheless, all diamonds exhibit similar characteristics, being rich in water, carbonate, SiO\u2082, and K\u2082O, and depleted in MgO. The composition of micro-inclusions in most diamonds vary within the following ranges: SiO\u2082, 30-53%; K\u2082O, 12-30%; CaO, 8-19%; FeO, 6-11%; Al\u2082O\u2083, 3-6%; MgO, 2-6%; TiO\u2082, 2-4%; Na\u2082O, 1-5%; P\u2082O\u2085, 1-4%; and Cl, 1-3%. In addition, BaO, 1-4%; SrO, 0.7-1.5%; La\u2082O\u2083, 0.1-0.3%; Ce\u2082O\u2083, 0.3-0.5%; smaller amounts of other rare-earth elements (REE), as well as Mn, Th, and U were also detected by instrumental neutron activation analysis (INAA). Mg/(Fe+Mg), 0.40-0.62 is low compared with other mantle derived phases; K/AI ratios of 2-7 are very high, and the chondrite-normalized Ce/Eu ratios of 10-21 are also high, indicating extremely fractionated REE patterns.
\r\n\r\nSEM analyses indicate that individual inclusions within a single diamond are roughly of similar composition. The average composition of individual inclusions as measured with the SEM is similar to that measured by SIMS. Compositional variations revealed by the SEM are larger than those detected by SIMS and indicate a small variability in the composition of individual inclusions. No compositions of individual inclusions were determined that might correspond to mono-mineralic inclusions.
\r\n\r\nIR spectra of inclusion- bearing zones exhibit characteristic absorption due to: (1) pure diamonds, (2) nitrogen and hydrogen in the diamond matrix; and (3) mineral phases in the micro-inclusions. Nitrogen concentrations of 500-1100 ppm, typical of the micro-inclusion-bearing zones, are higher than the average nitrogen content of diamonds. Only type IaA centers were detected by IR. A yellow coloration may indicate small concentration of type IB centers.
\r\n\r\nThe absorption due to the micro-inclusions in all diamonds produces similar spectra and indicates the presence of hydrated sheet silicates (most likely, Fe-rich clay minerals), carbonates (most likely calcite), and apatite. Small quantities of molecular CO\u2082 are also present in most diamonds. Water is probably associated with the silicates but the possibility of its presence as a fluid phase cannot be excluded. Characteristic lines of olivine, pyroxene and garnet were not detected and these phases cannot be significant components of the inclusions. Preliminary quantification of the IR data suggests that water and carbonate account for, on average, 20-40 wt% of the micro-inclusions.
\r\n\r\nThe composition and mineralogy of the micro-inclusions are completely different from those of the more common, larger inclusions of the peridotitic or eclogitic assemblages. Their bulk composition resembles that of potassic magmas, such as kimberlites and lamproites, but is enriched in H\u2082O, CO\u207c\u2083, K\u2082O, and incompatible elements, and depleted in MgO.
\r\n\r\nIt is suggested that the composition of the micro-inclusions represents a volatile-rich fluid or a melt trapped by the diamond during its growth. The high content of K, Na, P, and incompatible elements suggests that the trapped material found in the micro-inclusions may represent an effective metasomatizing agent. It may also be possible that fluids of similar composition are responsible for the extreme enrichment of incompatible elements documented in garnet and pyroxene inclusions in diamonds.
\r\n\r\nThe origin of the fluid trapped in the micro-inclusions is still uncertain. It may have been formed by incipient melting of a highly metasomatized mantle rocks. More likely, it is the result of fractional crystallization of a potassic parental magma at depth. In either case, the micro-inclusions document the presence of highly potassic fluids or melts at depths corresponding to the diamond stability field in the upper mantle. The phases presently identified in the inclusions are believed to be the result of closed system reactions at lower pressures.
", "doi": "10.7907/A88J-S465", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "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:9925", "collection": "thesis", "collection_id": "9925", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09132016-161520143", "primary_object_url": { "basename": "Hill_ri_1984.pdf", "content": "final", "filesize": 201454228, "license": "other", "mime_type": "application/pdf", "url": "/9925/1/Hill_ri_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Petrology and Petrogenesis of Batholithic Rocks, San Jacinto Mountains, Southern California", "author": [ { "family_name": "Hill", "given_name": "Robert Ian", "clpid": "Hill-Robert-Ian" } ], "thesis_advisor": [ { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" } ], "thesis_committee": [ { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Hager", "given_name": "Bradford H.", "clpid": "Hager-B-H" }, { "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" }, { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "A combined field and laboratory study of plutonic rocks from the San Jacinto Mountains of southern California was conducted in order to investigate the nature and origins of strontium and oxygen isotope heterogeneities within batholithic rocks.
\r\n\r\nGeological mapping has allowed differentiation of three major and many minor masses of plutonic rock. Contacts between units are offset up to 6 km by faults of the Neogene San Jacinto fault system, which has a total right-lateral displacement of 29\u00b11 km. The early small intrusives range from olivine gabbro through granite. They were intruded by three larger plutons of relatively homogeneous biotite-hornblende-titanite tonalite. The oldest major intrusive unit, Unit I, is an elongate body of dimensions 40x8 km. Before complete solidification it was intruded by Unit II, an irregular tabular mass 25 km long and a few kilometers wide. Unit III, in turn, intruded Unit II before it was completely solidified, producing a roughly rectangular mass 20x12 km that appears to funnel in downwards.
\r\n\r\nMineral foliations and banding, schlieren, and xenolith orientations within each unit usually parallel the nearest contact. Alignment of foliations and apparent flow-sorting and scour features seem to reflect flow patterns within each chamber. Mlfic synplutonic dikes (quartz diorite to tonalite) intruded into the tonalites, and were commonly broken up and redistributed as linearly extensive xenolith trains. From these relationships it is interpreted that: 1) magma adjacent to pluton walls had considerable yield strength, as it could fracture to allow dike emplacement; 2) magmatic flow adjacent to pluton walls was capable of moving material some distances (up to km) to create the xenolith trains; and 3), that the dikes are potentially the feeders through which material was added to the inflating magma chambers. Each major tonalite unit spans a limited compositional range of from mafic tonalite (Colour Index > 15) to low-K granodiorite (Colour Index < 10). Volumetrically minor felsic differentiates extend the compositional range through to granodiorite. Units I and II average slightly more mafic overall compositions than does Unit III. All units are comprised of plagioclase (An30-40) [50-55%], quartz[20-30%], K-feldspar[1-8%], biotite (10-15%], hornblende[0-5%], titanite[0-2%] and accessory zircon, apatite, allanite and ilmenite. Variations in mineral abundances are geographically systematic only within Unit III, which grades from marginal mafic tonalite to central low-K granodiorite.
\r\n\r\nMineral compositions throughout the major tonalites are remarkably uniform. The An content of the bulk plagioclase falls from An40 \u00b1 1 in the most mafic tonalites to An30 in low-K granodiorites; Mg/(Mg + Fe) of biotite and hornblende drop similarly from 0.44 to 0.36. The entire observed range of plagioclase compositions within the major tonalites is An44 to An25 (and to An47 in mafic xenoliths). The sole opaque mineral is almost pure ilmenite. This homogeneity of mineral compositions implies remarkable stability of physico-chemical conditions throughout crystallization of each unit.
\r\n\r\nMajor and trace element abundances reflect the general homogeneity of these rocks. Most have SiO2 in the range 63-68 wt.%; minor felsic differentiates extend to 71 wt.%. 60% of analyzed samples from Unit III fall in the restricted compositional range 66-68 wt.% SiO2; the majority of samples from Units I and II are more mafic than this. Major elements (excepting K2O) define excellent linear arrays on Harker diagrams. K2O shows a diffuse curvilinear pattern. Trace elements generally considered \"compatible\" (including the transition metals), and Sr also define linear arrays on Harker diagrams. Other trace elements, especially Ba, Rb, Pb, Th, U and REE show more complex behaviour. \"Mafic\" tonalites, (<65.5 wt.% SiO2) have simply covarying trace element endowments. Minor felsic differentiates, collected on the basis of field evidence for in situ fractionation, have higher Si, K, Rb, Ba, U and Th. \"Normal\" tonalites (66.5 < SiO2 < 70.0) have trace element and K endowments intermediate between the mafic tonalites and the felsic differentiates.
\r\n\r\nMafic tonalites, comprising about half the exposed rocks, crystallized from liquids which derived their geochemical characteristics before injection into the high-level magma chambers. The minor felsic differentiates are considered end-products of fractional crystallization within the magma chamber; the \"normal\" tonalites are interpreted as crystallizing from liquids of intermediate character, i.e., mixtures of \"primitive\" and fractionated liquids.
\r\n\r\nMeasured primary \u03b418O values vary from +9.0 to +10.6. Metasedimentary country rocks have \u03b418O values of +11.5 to +13.5. Exchange of oxygen between plutons and country rock is minor and limited to narrow border zones. Within Unit III primary \u03b418O correlates with position. A marginal zone of variable values (+9.0-+10.0) gives way to regularly increasing values (+10.0-+10.5) inwards. Primary \u03b418O correlates with Colour Index. Within the central part of Unit III the observed range in \u03b418O values can be explained by crystallization of modally variable rocks from a liquid of constant 18O/16O (to\u00b10.2 per mil). The \u03b418O values of the more mafic marginal rocks (and of mafic rocks from Units I and II) also correlate with Colour Index; lower SiO2 rocks have lower \u03b4180. This correlation cannot simply result from varying mineral abundances, but must reflect variations in \u03b4180 values of the liquids from which these rocks crystallized.
\r\n\r\nCalculated initial 87Sr/86Sr (Sri) varies substantially among rocks from each major tonalite unit (Unit I: 0.7060-0.7076; Unit II: 0.7060-0.7074; Unit III: 0.7058-0.7073). These variations appear geographically regular at the kilometer scale within each pluton. The complex patterns, however, differ fundamentally from the general regular west-to-east increase in Sri reported for the batholith (Early and Silver, 1973), and observed in the small early intrusives from the San Jacinto Mountains (0.7057-0.7077). Sri within these rocks shows no identified correlation with other geochemical and petrological parameters.
\r\n\r\nThe Sr isotope data indicate that melt production, transport, and crystallization processes combined were not capable of completely homogenizing initial variations in Sri within the liquids from which these rocks crystallized. This further implies that either the time scale for convection was large compared to that for crystallization, or that the length scale for convection was small compared to the size of the plutons. Field evidence suggests considerable flow within the magma chamber; estimation of rheological parameters suggest that flow was within a laminar flow convective regime.
\r\n\r\nThe combined observations are compatible with crystallization from an intermittently recharged, continuously fractionating system. Recharge tended to buffer both the thermal and chemical properties of liquids within the magma chamber; it gave a mechanism for introducing isotopic variations that are incorporated into this continuously crystallizing system. The mafic dikes are suggested to be conduits through which some of these liquids were injected into the various magma chambers. Chemical buffering by continued recharge is also compatible with the observation that the majority of these rocks have geochemical features interpreted as resulting from the action of processes prior to injection of liquids into the high-level magma chambers.
\r\n\r\nRocks with low Sri (0.7058-0.7068) generally have intermediate \u03b418O values (+9.7-+10.3), and fall near the low-\u03b418O side of the batholithic trend defined by Taylor and Silver (1978). Rocks with high Sri (>0.7072) cover the entire observed range in \u03b418O values (+9.0-+10.6), and overlap the field defined for the San Jacinto - Santa Rosa Mountains block by Taylor and Silver. These data require involvement of material from three isotopically distinct source materials in the generation of these rocks. Two of these components (one with low Sri, low \u03b418O; one with high Sri, high \u03b418O) are common to the bulk of the batholith to the south and west. The third (high Sri, low \u03b418O) seems unique to the San Jacinto - Santa Rosa Mountains block; its relative importance within the San Jacinto rocks appears to correlate negatively with SiO2, suggesting that it was associated with relatively mafic liquids. The oxygen isotopic data imply that as much as 35% of this component may be present in some rocks. This component has isotopic and inferred geochemical characteristics compatible with old, slightly enriched (in Rb relative to Sr) subcontinental lithosphere. The low-Sri, low-\u03b418O component appears to be either (or both) normal depleted mantle or (subducted) oceanic crust. Tile oxygen data imply that the third (high-Sri, high-\u03b418O) component has had a prior history at the Earth's surface; it could be either sediment, or igneous material altered at low temperatures such as hydrothermally altered oceanic crust. Geochemical features (K, Rb, LREE abundances) appear more compatible with sedimentary material.
\r\n\r\nThese data are compatible with, but do not prove, a model for this source region as being a mixture of normal depleted mantle, oceanic crust, old slightly enriched \"subcontinental lithosphere\", and subducted sediment. This model source contains variously 0-35% (oxygen atom basis) subcontinental lithosphere, up to 25% sedimentary component, and apparently requires material of both basaltic (oceanic crust) and depleted mantle composition to balance isotope systematic systematics.
\r\n\r\nTile combined data show 1) that the source volumes for the batholithic rocks were heterogeneous at the scale of hundreds of meters or greater, 2) that the effects of these source heterogeneities were at least partially preserved throughout melt production, transport, and crystallization, and 3) that the net effect of a persistent recharge-fractional crystallization process within the magma chambers was to buffer the composition of the bulk of the rock near that of the early-crystallizing solids.
", "doi": "10.7907/9x01-1n85", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:11270", "collection": "thesis", "collection_id": "11270", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11092018-122937399", "primary_object_url": { "basename": "Aines_RD_1984.pdf", "content": "final", "filesize": 87616479, "license": "other", "mime_type": "application/pdf", "url": "/11270/1/Aines_RD_1984.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Trace Hydrogen in Minerals", "author": [ { "family_name": "Aines", "given_name": "Roger Deane", "clpid": "Aines-Roger-Deane" } ], "thesis_advisor": [ { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "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": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Trace hydrogen in minerals most frequently occurs bonded to oxygen. The resulting water and hydroxyl (OH-) affect and play a role in a variety of mineral properties and reactions. This thesis examines the occurrence of trace hydrogen in nominally anhydrous minerals, the mechanisms by which trace hydrogen participates in reactions and controls properties, and the changes that occur in hydrogen speciation and siting as a function of temperature. The principal tool used in this study is infrared (IR) spectroscopy because of its sensitivity to the highly polar O-H bond, yielding quantitative information on concentration, and symmetry, speciation, and siting information.
\r\n\r\nThe speciation of trace hydrogen in garnet and low temperature natural and synthetic quartz is examined in detail. In garnet hydrogen occurs as the hydrogarnet substitution, four hydroxyl groups replacing a silicate tetrahedron. This substitution is extremely common among natural garnets. Concentrations range from 0.05 to 0.20 wt. % (as H2O) in garnets from most occurrences, including garnets from the mantle. This trace hydrogen is truly dissolved. The hydrogen found in natural and synthetic quartz formed at low temperature can occur as either hydroxyl or molecular water. The molecular water is the active participant in hydrolytic weakening of quartz, but it is not truly dissolved. It occurs as small groups of molecules (approximately 5 to 200) which were trapped during rapid growth.
\r\n\r\nTwo properties of minerals affected by trace hydrogen are strength and radiation response. Molecular water may be responsible for weakening of other minerals as well as quartz. Both water and hydroxyl participate in radiation response of minerals. In metamict zircon, water stabilizes local charge imbalance formed when bonds are broken. Water enters the crystal after a threshold of damage occurs, and reacts with broken bonds to form hydroxyl groups. These must reform molecular water and be expelled before recrystallization occurs during heating. In quartz, molecular water is strongly correlated with the formation of citrine color during irradiation, but inhibits the formation of the amethyst color center Fe4+. Apparently molecular hydrogen forms during radiolysis of the water, and reduces the Fe4+. Several hydroxyl sites in topaz are strongly correlated with the formation of brown color upon irradiation. The unifying theme in all these reactions is the extreme mobility of hydrogen and the ease with which different oxygen-hydrogen species may be formed in silicates.
\r\n\r\nThe behavior of trace hydrogen at temperatures of geologic interest has been examined using high temperature infrared spectroscopy. Direct observations of speciation, concentration, and properties have been made up to 1200\u00b0C. In muscovite there is no change in hydrogen speciation or site up to the dehydration point, as expected. However, in cordierite and beryl water reversibly partitions into a gas-like state above 400\u00b0C, and the formation of this new state controls the dehydration behavior. In topaz, hydroxyl groups have been observed converting to new sites at temperatures above 500\u00b0C. In orthoclase feldspar, one type of molecular water dehydrates at 200\u00b0C, while a second type converts irreversibly to a new hydrous species above 600\u00b0C.
\r\n\r\nThere is no evidence for the existence of hydrogen species other than hydroxyl and water in silicate minerals. The hydrogarnet substitution (four hydroxyl groups in a tetrahedral configuration) is common in garnets and may be important in other orthosilicates. The most common hydrous species in nominally anhydrous silicates (aside from fluid inclusions and alteration) are: small groups of trapped water molecules; individual water molecules occupying voids in the structure of minerals; hydroxyl occurring in a charge balancing role such as AlO3OH substituting for SiO4; hydroxyl neutralizing substitutional atoms, e.g., LiOH; and hydroxyl groups formed from the reaction of broken bonds with water as in radiation damaged minerals. There is no evidence for the presence of the oxonium ion, H3O+, in common minerals, and the existing evidence for the occurrence of molecular hydrogen may better be explained by the presence of water or hydroxyl groups.
", "doi": "10.7907/n7vk-f724", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" } ]