Dissertations / Theses: 'Isotope geology Sulfur Geochemistry' – Grafiati (2024)

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Thesis (M.S.)--University of Nevada, Reno, 2007.
"May, 2007." Includes bibliographical references (leaves 76-81). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

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Thesis (Ph.D.)--Indiana University, Dept. of Geological Sciences, 2006.
"Title from dissertation home page (viewed July 11, 2007)." Source: Dissertation Abstracts International, Volume: 67-08, Section: B, page: 4307. Adviser: Lisa M. Pratt.

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Thirty-five sulphur isotopic analyses have been obtained from six carbonatite-alkalic rock complexes ranging in age from 1906 Ma to 1008 Ma located within the Ontario portion of the Superior Province. Pyrrhotite, chalcopyrite and pyrite mineral separates were used. The overall range of delta 34SCDT values are from +3.4 to -4.5‰. Each complex shows its own distinct range and mean sulphur isotopic composition.The overall range in the sulphur isotopic composition in conjunction with carbon and oxygen isotopic data suggests that these carbonatites and associated silicate rocks were derived from a relatively primitive mantle source. This is consistent with previously published Sr and Nd isotopic data that suggest that the mantle source underlying the Superior Province has remained essentially a closed system from about 2700 Ma to at least 1008 Ma. The sulphur isotopic data reported here is the first ever for carbonatites from the Superior Province. (Abstract shortened by UMI.)

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[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] The formation of world-class Archean orogenic gold deposits in the Eastern Goldfields Province of Western Australia was the result of a critical combination of physical and chemical processes that modified a single and widespread ore-fluid along fluid pathways and at the sites of gold deposition. Increased gold endowment in these deposits is associated with efficient regional-scale fluid focusing mechanisms and the influence of multiple ore-depositional processes at the deposit-scale. Measurement of the complexity of geologic features, as displayed in high-quality geologic maps of uniform data density, can be used to highlight areas that influence regional-scale hydrothermal fluid flow. Useful measurements of geological complexity include fractal dimensions of map patterns, density and orientation of faults and lithologic contacts, and proportions of rock types. Fractal dimensions of map patterns of lithologic contacts and faults highlight complexity gradients. Steep complexity gradients, between domains of high and low fractal dimensions within a greenstone belt, correspond to district-scale regions that have the potential to focus the flow of large volumes of hydrothermal fluid, which is critical for the formation of significant orogenic gold mineralization. Steep complexity gradients commonly occur in greenstone belts where thick sedimentary units overly more complex patterns of lithologic contacts, associated with mafic intrusive and mafic volcanic units. The sedimentary units in these areas potentially acted as seals to the hydrothermal Mineral Systems, which resulted in fluid-pressure gradients and increased fluid flow. The largest gold deposits in the Kalgoorlie Terrane and the Laverton Tectonic Zone occur at steep complexity gradients adjacent to thick sedimentary units, indicating the significance of these structural settings to gold endowment. Complexity gradients, as displayed in surface map patterns, are an indication of three-dimensional connectivity along fluid pathways, between fluid source areas and deposit locations. Systematic changes in the orientation of crustal-scale shear zones are also significant and measurable map features. The largest gold deposits along the Bardoc Tectonic Zone and Boulder-Lefroy Shear Zone, in the Eastern Goldfields Province, occur where there are counter-clockwise changes in shear zone orientation, compared to the average orientation of the shear zone along its entire length. Sinistral movement along these shear zones resulted in the formation of district-scale dilational jogs and focused hydrothermal fluid-flow at the Golden Mile, New Celebration and Victory-Defiance deposits. Faults and lithologic contacts are the dominant fluid pathways in orogenic gold Mineral Systems, and measurements of the density of faults and contacts are also a method of quantifying the complexity of geologic map patterns on high-quality maps. Significantly higher densities of pathways in areas surrounding larger gold deposits are measurable within 20- and 5-kilometer search radii around them. Large variations in the sulfur isotopic composition of ore-related pyrites in orogenic gold deposits in the Eastern Goldfields Province are the result of different golddepositional mechanisms and the in-situ oxidation of a primary ore fluid in specific structural settings. Phase separation and wall-rock carbonation are potentially the most common mechanisms of ore-fluid oxidation and gold precipitation. The influence of multiple gold-depositional mechanisms increases the potential for significant ore-fluid oxidation, and more importantly, provides an effective means of increasing gold endowment. This explains the occurrence of negative δ34S values in ore-related pyrites in some world-class orogenic gold deposits. Sulfur isotopic compositions alone cannot uniquely define potential gold endowment. However, in combination with structural, hydrothermal alteration and fluid inclusion studies that also seek to identify multiple ore-forming processes, they can be a useful indicator. The structural setting of a deposit is also a potentially important factor controlling ore-fluid oxidation and the distribution of δ34S values in ore-related pyrites. At Victory-Defiance, the occurrence of negative δ34S(py) values in gently-dipping dilational structures, compared to more positive δ34S(py) values in steeply-dipping compressional structures, is potentially associated with different gold-depositional mechanisms that developed as a result of fluid-pressure fluctuations during different stages of the fault-valve cycle. During the pre-failure stage, when fluids are discharging from faults, fluid-rock interaction is the dominant gold-depositional mechanism. Phase separation and back-mixing of modified ore-fluid components are dominant during and immediately after faulting. Under appropriate conditions, any, or all, of these three mechanisms can oxidize orogenic gold fluids and cause gold deposition. The influence of multiple gold-depositional mechanisms during fault-valve cycles at dilational jogs, where fluid pressure fluctuations are interpreted to be most severe, can potentially explain both the large gold endowment of the giant to world-class Golden Mile, New Celebration and Victory-Defiance deposits along the Boulder-Lefroy Shear Zone, and the presence of gold-related pyrites with negative δ34S values in these deposits. This study highlights the interplay that exists between physical and chemical processes in orogenic gold Mineral Systems, during the transport of ore fluids in pathways from original fluid reservoirs to deposit sites. Potentially, a single and widespread orogenic ore-fluid could become oxidized, and lead to the formation of ore-related sulfides with variable sulfur isotopic compositions, depending on the nature and orientation of major fluid pathways, the nature of wall-rocks through which it circulates, and the precise ore-depositional processes that develop during fault-valve cycles.

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Identification of sulfur sources in an ore-forming system is important as it provides a greater understanding of how a mineral deposit forms and how best to explore for that particular type of deposit. It can also aid in the understanding of the ocean and atmosphere chemistry at the time of formation. Mass independent sulfur isotope fractionation in the Archean atmosphere provides a fingerprint for identifying non-magmatic sources of sulfur. This makes sulfur multiple isotope measurements a powerful tool for deconvolving ore-forming processes in the Archean. This thesis presents three applications of multiple sulfur isotope analysis for investigation of ore forming processes in the Archean. The first study evaluates proposed models for formation of volcanogenic massive sulfide (VMS) deposits during the Neo- and Mesoarchean, which demand little to no contribution of seawater sulfate to the ore-forming system. This is in contrast to Phanerozoic VMS systems where evidence for a seawater sulfate component is clear. We re-evaluate these models in the context of the ~2.7 Ga Noranda Camp of the Abitibi subprovince, Québec, using a combination of multiple sulfur isotope and trace element data. Sulfide samples analysed for this study have Δ33S values between -0.59 and -0.03 ‰. We interpret these negative values to reflect a sulfur component that originated in the seawater sulfate reservoir. Incorporation of this component appears to have increased during the collapse and subsequent evolution of the Noranda caldera. Higher concentrations of Se in samples with Δ33S values close to 0 ‰, and higher Fe/(Fe + Zn) values in sphalerite, are indicative of higher temperatures of formation.The second study is an investigation of sulfur sources that contributed to the formation of Cu- and Au-rich VMS deposits of the ~2.7 Ga Doyon-Bouquet-LaRonde (DBL) mining camp, also within the Abitibi subprovince. This subgroup of deposits has previously been interpreted as having a significant magmatic-hydrothermal source of ore fluids and metals. Multiple sulfur isotope analysis of deposits within the DBL mining camp, with the exception of one minor lens, indicates a very clear igneous-magmatic affinity (Δ33SV-CDT = 0.14 to +0.04 ‰), with little to no contribution from any surficial source of sulfur. In contrast, sulfide that formed at or very near the paleo-seafloor exhibits a distinct component of sulfur from the seawater sulfate reservoir (Δ33SV-CDT = 1.43 to 0.34 ‰). This study highlights the isotopic difference between the Noranda VMS deposits and those of the DBL. In addition, a lack of variation in Δ33S values between ore lenses which exhibit aluminous alteration and those that do not calls into question the characteristics with which to identify those VMS deposits that required dominant contribution of magmatic fluids.The final study examines sulfur sources within the Platreef, the main PGE bearing horizon of the Northern Limb of the Bushveld Igneous Complex (BIC), South Africa. The Platreef has a high percentage of sulfides relative to the analogous Merensky Reef in the eastern and western limbs of the BIC. It is in direct contact with underlying Neoarchean to Paleoproterozoic sediments, which are potential local sources of sulfur. However, Δ33S analysis of the Platreef sulfides identifies heterogeneous crustal sulfur contribution to the system both prior to and post-emplacement throughout the length of the Platreef.This thesis clearly demonstrates that multiple sulfur isotope analysis is a powerful tool for the identification of sulfur sources in ore forming processes of the Archean, and those involving Archean rocks, and can be applied to a range of problems and deposit types. It also highlights important issues for future consideration, including the role of seawater sulfate in the formation of Archean VMS deposits, and the characteristics of the parent magma of the BIC.
L'identification des sources de soufre dans la minéralisation est importante car elle permet de comprendre les processus et de définir la meilleure méthode d'exploration. Elle peut aussi aider à la compréhension de la chimie des océans et de l'atmosphère lors de sa formation. Le fractionnement indépendant de la masse des isotopes du soufre dans l'atmosphère de l'Archéen fournit une emprunte unique permettant d'identifier les sources de soufre non magmatiques. La nature chimique conservatrice des signatures du Δ33S en fait un outil puissant pour la déconvolution des processus minéralisateurs Archéen.Cette thèse présente trois applications de l'analyse multiple des isotopes du soufre dans l'investigation des processus de minéralisation à l'Archéen. La première étude teste les modèles de formation des sulfures massifs volcanogènes (SMV) Néo- et Mésoarchéen récemment proposés ne requérant peu ou pas d'apport de sulfate marin par rapport aux systèmes SMV du Phanérozoïque et contemporains où le sulfate marin joue un rôle important. Ces modèles sont réévalués en utilisant le camp de Noranda (~2.7 Ga), sous-province de l'Abitibi, et en combinant l'utilisation de données provenant de l'analyse des isotopes du soufre et des éléments traces.Les sulfures analysés pour cette étude ont des valeurs de δ34SV-CDT entre -14.90 et +2.49 ‰, et des valeurs de Δ33SV-CDT entre -0.59 et -0.03 ‰. Selon notre interprétation, les valeurs négatives de Δ33S sont dues à l'incorporation de soufre provenant de l'eau de mer. La proportion de soufre marin aurait augmenté durant l'affaissem*nt et l'évolution subséquente de la caldera de Noranda. Des concentrations plus élevées de Se combinées à des valeurs près de 0 ‰ et d'un haut ratio Fe/(Fe + Zn) dans les sphalérites indiquent une température de formation élevée.La deuxième étude est une investigation des sources de soufre ayant contribuées à la formation des SMV riches en Cu et en Au du camp minier Doyon-Bousquet-LaRonde (DBL; ~2.7 Ga), aussi dans la sous-province de l'Abitibi. Une source magmatique-hydrothermale de fluides minéralisateurs importante était l'interprétation donnée pour ce sous-groupe. À l'exception d'une lentille mineure, l'analyse isotopique multiple des dépôts du camp minier DBL indiquent clairement une affinité ignée-magmatique (Δ33SV-CDT = 0.14 to +0.04 ‰), avec peu ou pas de contribution de soufre provenant de la surface. Par contre, les sulfures formés sur le plancher océanique ou près de celui-ci exhibe une contribution distinctive des sulfates marins (Δ33SV-CDT = 1.43 to 0.34 ‰). D'un autre côté, l'absence de variation des valeurs du Δ33S entre des lentilles minéralisées avec une altération alumineuse et celles ne démontrant pas cette altération remet en question les l'identification des dépôts de type SMV ayant une contribution importante ou dominante de fluides magmatiques. La dernière étude examine les sources de soufre du Platreef – horizon riche en éléments du groupe platine (EGP) du flanc nord du Complexe Igné Bushveld (CIB) en Afrique du Sud. Le Platreef contient un haut pourcentage de sulfures par rapport au dépôt analogue Merensky Reef des flancs est et ouest du CIB. Il est en contact direct avec les sédiments Néoarchéens à Paléoprotérozoïques qui sont une source potentielle de soufre locale. D'un autre côté, les analyses du Δ33S des sulfures du Platreef permettent d'identifier une contribution de soufre hétérogène provenant de la croûte terrestre, avant et après la mise en place du gisem*nt.Cette étude démontre clairement que l'analyse multiple des isotopes du soufre est un outil puissant dans l'identification des sources de soufre des processus minéralisateurs de l'Archéen, ainsi que ceux impliquant des roches archéennes, et cette approche peut être appliquée à un éventail de problèmes et types de dépôt. Aussi, elle soulève des questions importantes sur le rôle du sulfate marin dans la formation des dépôts SMV de l'Archéen et les caractéristiques du magma du CIB.

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First order trends in the strontium isotopic (87Sr/86Sr) composition of seawater are controlled by radiogenic inputs from the continent and non-radiogenic inputs from exchange at mid-ocean ridges. Carbonates precipitated in seawater preserve trace amounts of strontium that record this isotope ratio and therefore record the relative importance of mid-ocean ridge and weathering chemical inputs to sea water composition. It has been proposed that environmental changes during the Ediacaran-Cambrian transition may have enabled the rapid diversification of life commonly named the “Cambrian explosion.” Proposed environmental changes include 2.5x increase in mid-ocean ridge spreading at the Ediacaran-Cambrian boundary and large continental fluxes sediment into oceans. These hypotheses rely on a poorly resolved strontium isotope curve to interpret Ediacran-Cambrian seawater chemistry. A refined strontium isotope curve through this time period may offer insight into the environmental conditions of the early Cambrian. New age models and detailed mapping in the Zavkhan terrane in west-central Mongolia provide the context necessary for robust geochemical analysis. This study aims to better resolve the coarse strontium isotope curve for the early Cambrian period by analyzing carbonate sequences in the Zavkhan basin. These carbonate sections are rapidly deposited, have undergone little diagenesis, and are likely to preserve a primary seawater signal. Strontium isotope analysis of these sequences was carried out to determine changes in hydrothermal activity and weathering fluxes during this time period. Recompiling these data with a global dataset of strontium isotopes through this time period indicates a stable strontium isotope signal through much of the early Cambrian. These data do not support previous hypotheses attributing the driving mechanism for the early Cambrian transition from Mg-dominated to Ca-dominated seas to increased sea floor spreading rates.

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Hydrogeochemical analyses of the thermal waters at Hotsprings Cove, west coast Vancouver Island, reveal the presence of a stable geothermal reservoir. Temperature (50.5$\sp\circ$C), and aqueous geochemical data are nearly identical to those dating back to 1898. $\delta\sp $O-D plots indicate local recharge for these thermal waters, whereas radiocarbon isotopes suggest mean residence times of several thousand years and modification by sulphate-reducing bacteria. Bromide/chloride ratios, when considered with tritium and $\sp{34}$S data, are indicative of minor seawater mixing near the discharge zone. Binary mixing models, with local recharge waters and local seawater as end-member components, point to maximum local seawater contributions of about 1% and 4% for Hotsprings Cove and associated Mate Island thermal waters, respectively. Most chemical and isotopic geothermometer estimates are 90$\sp\circ$C. The Ahouset hotspring, located 12 km south of Hotsprings Cove has low total dissolved solids, a pH of 10.05, and a different geochemistry. Data from the Selkirk Range show a consistent sodium-sulphate geochemistry among the three hotsprings sampled in the Kuskanax Batholith. All waters have low bicarbonate content. $\sp $C values in excess of 100 pmc at the Nakusp hotspring imply incorporation of $\sp $C-active DIC from soil zone organics entrained during recharge, with possible additional $\sp $C contributions occurring due to sulphate reduction and incorporation of soil zone organics during mixing with non-thermal groundwaters near discharge. $\sp $C-derived mean residence times for the sulphide-rich waters of Halcyon hotspring are also short; possibly ${\sim}$1000 years. Geothermometer estimates for all three springs are consistent and fall into two groups, one group near ${\sim}$90$\sp\circ$C and the other between 115$\sp\circ$C and 155$\sp\circ$C. (Abstract shortened by UMI.)

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Eocene dykes intruding the Ladakh batholith were sampled along the southern margin of the Trans-himalayan plutonic arc in Ladakh, NW-India. Approximately 30 dykes were encountered in the 40 km trail between Leh and Hemis Shugpachan. The dykes in the east of the field are trending E to NE and those in the west trending N to NW, exhibiting sub-parallel orientations within each area. Eighteen dykes were sampled (two of them multiple times) and subjected to petrographic, geochemical and isotopic analyses. They exhibit various degrees of differentiation from basaltic to rhyolitic compositions and are mainly composed of plagioclase, quartz, hornblende (s.l.) and/or biotite and magnetite. Furthermore, dykes in the eastern part of the field area contain quartz xenocrysts resulting from crustal assimilation, while no relict quartz was found in the west. The dykes exhibit alteration phases and features suggesting that they underwent autometamorphism, i.e. hydration reactions due to igneous cooling. Whereas the dykes in the east of the field area record low-T alteration, the mineral parageneses in the west are typical for alteration at elevated temperatures typical for greenschist metamorphic facies. Al-in-hornblende barometry performed on Magnesio-hornblende and Tschermakitic-hornblende phenocrysts of the least altered dyke indicates formation in upper-amphibolite metamorphic facies conditions and pressures of about 6 kbar corresponding to an intrusion depth of approximately 20 km.Major and trace element analyses and Rb-Sr and Sm-Nd isotope analyses revealed a stunning variability in geochemistry and isotopic composition amongst the coeval dykes. All dykes exhibit LREE enrichment and HREE depletion as well as negative Tb and Nb anomalies characteristic for subduction-related intrusives and extrusives. Their REE patterns support a clear subdivision into chemically distinct groups. The group hypothesis was further tested and found valid using statistical tools designed to assess similarity/dissimilarity amongst individuals of a group with a common ancestor, such as hierarchical cluster analysis and multidimensional scaling. The dykes are cogenetic, but clearly not consanguineous, i.e. have not formed from one, progressively differentiating magma chamber.The variability observed in Sr-Nd isotopes can be explained by the dykes having undergone differing degrees of crustal assimilation. In particular the dykes in the east containing quartz xenocrysts show negative iiNd) and positive N(Sr) values caused by crustal assimilation, whereas the dykes in the west with no quartz xenocrysts exhibit positive qqNd) and N(Sr) near zero. 39Ar-40Ar dating by incremental heating of several hornblende-bearing dykes revealed crystallization ages between 50 and 54 Ma, whereas two biotite-bearing dykes gave ages of 45 and 37 Ma, likely to be cooling or recrystallisation ages.The combination of structural field evidence with petrographic, petrologic, geochemical, isotopic and geochronological analyses demonstrates that the dykes, although sharing a common origin, i.e. having formed in the same tectonic setting at roughly the same time, have undergone further geological processes leading to an unexpected diversification of the dykes. These findings provide ample scope for further in-depth and breadth investigations on “late-magmatic dykes” in the future.
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The Southern Uplands of Scotland is interpreted as a Lower Palaeozoic accretionary complex which formed on the northern margin of the Iapetus Ocean. Seven conglomerates which contain detritus derived from the north-west, from sources on the Laurentian continental margin, were studied. Granite clasts in five of the conglomerates have distinct petrographic and geochemical characteristics which indicate that separate source areas supplied detritus to the Southern Uplands at different times. The Llandeilo Corsewall Point and Caradoc Glen Afton conglomerates, which occur in Tracts 1 and 2 of the Northern Belt, contain granite clasts that yield similar Rb-Sr whole-rock isochron ages (c. 1,200 Ma, 600-660 Ma and c. 475 Ma) and similar Sm-Nd model ages. This suggests that the clasts in the two conglomerates were derived from related sources. Some of the granite clasts in the early Ashgill Shinnel Formation conglomerate, which occurs in Tract 3 of the Northern Belt, resemble those in the Corsewall Point conglomerate, but most are petrographically and geochemically distinct, and yield younger Sm-Nd model ages. The lower Llandovery Pinstane Hill conglomerate occurs in Tract 4 of the Central Belt, and contains granitic detritus which yields a Rb-Sr whole-rock isochron age of 458 ± 26 Ma and has similar characteristics to the clasts in the Shinnel Formation conglomerate. The granite clasts in the Corsewall Point and Glen Afton conglomerates are of a different age to the granite intrusions of northern Scotland, and are unlikely to have been derived from this region. Conglomerates in the Midland Valley contain granite clasts with different petrographic and isotopic characteristics to those supplied to the Southern Uplands during the Llandeilo and Caradoc. However, north-west Newfoundland has a similar igneous history to that recorded by the Southern Uplands clasts, which could be derived from this region. The clasts supplied to the Shinnel Formation and Pinstane Hill conglomerates during the Ashgill and Llandovery have more in common with the granitic detritus in the Midland Valley. Thus, the Southern Uplands form a distinct Caledonian terrane which was south-east of Newfoundland in the Llandeilo, and was affected by sinistral strike-slip displacements during and after accretion.

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The nature of Cu isotope fractionation in natural Cu-Fe-S minerals was investigated through acid ferric sulfate leaching of copper ore from Morenci, Arizona. Copper isotope composition of the derived solutions varies from δ⁶⁵Cu = 0.47‰ to 5.21‰ over the course of progressive copper extraction. High δ⁶⁵Cu values characterize solutions collected in the first half of the leach, while the solutions collected between 35% and 45% copper recovery exhibit lower δ⁶⁵Cu values. This general pattern was observed for both bacterially-mediated and abiotic leaching. Sulfate solutions derived from dissolving pure djurleite show variable Cu isotope compositions as well, although the range is protracted from δ⁶⁵Cu = 0.01‰ to 1.21‰. As the Cu:S ratio of the remaining sulfide decreases, crystal structure parameters change as mineralogy passes through a series of nonstoichiometric copper sulfides. Mineralogy converges to yarrowite near 44% copper dissolution. Crystal chemical studies show that distribution of the two copper-sulfur bond coordination geometries, triangular planar and tetrahedral, in the copper sulfides, approximately corresponds to changes in δ⁶⁵Cu of the leachates. In particular, the proportion of CuS3 relative to CuS4 groups decreases from Cu/S = 2.00 (chalcocite) to 1.40 (geerite). Between Cu/S = 1.40 to 1.00 (covellite), the relative proportion of CuS3 groups increases slightly. Connection between coordination number and Cu isotope fractionation implies affinity of CuS₃ groups for the heavier, ⁶⁵Cu, isotope. This can be justified through bond length-bond strength arguments. Solutions from bornite dissolution vary from δ⁶⁵Cu = -0.79‰ to 1.14‰, with the largest values associated with solutions from early stage of reaction (up to 15% copper removal). Around 25% dissolution, δ⁶⁵Cu of the solution approaches that of the original bornite (δ⁶⁵Cu = 0.02‰). This is explained by disappearance of all remaining CuS₃ groups. Sulfur isotope compositions of solutions and sulfides derived from djurleite leaching were determined to investigate the possibility of intra-mineral fractionation. Very soon after reaction initiation, δ³⁴S of both sulfur reservoirs reach a steady-state with sulfate solutions about 2‰ enriched in ³⁴S relative to residual sulfide. Unlike the case of Cu isotopes, the main partitioning affecting S isotopes is exchange between sulfate and sulfide.

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Models suggest that global warming will cause an intensification of the hydrologic cycle, but they are poor at predicting changes in the frequency of short, intense precipitation events at the regional to local scale. High-resolution stable isotope measurements across tree rings have shown potential for resolving precipitation at sub-annual resolution, but identification of single intense precipitation events across multiple tree rings has proven elusive. In this work, I report 218 high-resolution carbon isotope (δ¹³C) measurements made across eight growth rings of two Pinus trees cored in southern Louisiana. Tree rings were targeted for the presence and absence of extreme rainfall associated with land-falling tropical cyclones within 100 km of the study site. Comparison of the δ¹³C record to meteorological data yields a significant correlation (r = -0.576, p = 0.0004) with monthly precipitation and δ¹³C value measured across the rings. Significant, intra-ring declines of >1‰ are associated with monthly precipitation > 200 mm that cannot be resolved by low-resolution sampling. Comparing the effects of sample resolution on δ¹³C patterns suggests that wide-ringed samples are preferred for identifying precipitation events at sub-seasonal resolution. Recent technical and methodological advancements allow for more rapid preparation and analysis of intra-ring δ ¹³C data and provide opportunity for quantifying sub-seasonal environmental information within high-resolution tree-ring datasets. This work indicates the potential for quantifying changes in the magnitude and frequency of extreme precipitation events at individual sites from long-term intra-ring δ ¹³C records.

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In the southern White Pine Range (SWPR) silica is found to have been deposited from hydrothermal solution within the Currant Gap Detachment fault (CGD). Silica has been observed to occur in three modes of deposition: (1) narrow veins within the lower plate Pole Canyon limestone, (2) bulk silicification of carbonates and (3) breccia matrix found in proximity to the CGD.

Through stable isotope analysis of oxygen from quartz samples and hydrogen from fluid inclusions we see that there is a history of meteoric waters penetrating into the Lower Pole Canyon Formation, in the lower plate of the CGD. This study reveals that silica in the SWPR formed from aqueous fluids at temperatures between 260 °C and 315 °C within lower plate quartz veins and 150 °C to 300 °C within the upper plate of the CGD. These temperature ranges are in line with what would be expected in a brittle regime (T < 350 °C).

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The scarcity of water resources in Jordan poses difficulties for the development of the country and its relationship with its neighbours. Thermal groundwaters recently identified in the northern part of the country represent a 40 MCM/y resources for exploitation to meet the increasing demand for water. These thermal groundwaters are found in three well fields (Mukhebeh, JRV and Ramtha) and were investigated to determine their recharge origin, mean subsurface residence times, and the source of heat. They discharge in the northern part of Jordan Rift Valley and the rifted Yarmouk Valley, which are low elevation (50 to 150 m below sea level) zones of recent tectonism and volcanic activity. The range of temperatures is 30 and 56$\sp\circ$C and salinities vary between 500 and 2500 mg/l. Non-thermal groundwaters within the study area have also been studied. In particular shallow groundwater in adjacent highlands region (Ajloun Mountains) are examined to determine their role in recharge to those regional flow systems. The principal aquifer is the Upper Cretaceous B2/A7 group, a package of carbonate formations with high kerogen content at depth. This aquifer outcrops in the Ajloun Mountains and flanking regions and is confined by overlying marls in the down gradient regions. A deeper sandstone aquifer underlies the study area and hosts thermal groundwater which was sampled in the Ramtha area. The major geochemical processes in the subsurface have generated various geochemical facies in the thermal waters. These include carbonate dissolution to calcite saturation in the recharge areas. The thermal groundwater in Mukhebeh and JRV well fields are found to be chemically similar to the carbonate groundwater from Ajloun mountains recharge area. All thermal waters are characterized by sulphate reduction, driven by oxidation of kerogen. Sulphate is of marine evaporite origin dissolved from within the aquifer with a component of volcanogenic sulphur. Some thermal waters have also Na-Cl salinity component related to evaporite dissolution. The thermal waters are of meteoric provenance, originating as rain falling over the carbonate highlands in Jordan and Syria. The $\delta\sp $O and $\delta$D isotopic data show that all thermal groundwaters are largely associated with Eastern Mediterranean Meteoric Water Line, signifying recharge under the climate regime which dominates today in Jordan. The exception is groundwater from the deep sandstone aquifer which is associated with Global Meteoric Water Line, signifying recharge during Pleistocene time. The isotopic composition of groundwater suggests two distinct recharge areas for the Mukhebeh well field: Ajloun Mountains (Jordan) and Mount Hermon (Syria). (Abstract shortened by UMI.)

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The end-Ordovician was a critical time in Earth history and marked the occurrence of a mass extinction and a period of continental glaciation. The Ellis Bay Formation on Anticosti Island in Quebec represents up to 100 meters of relatively undisturbed, continuous, low latitude, shallow water carbonate ramp deposits that span the Hirnantian Stage and terminate close to the Ordovician-Silurian (O-S) boundary. In this study, approximately 400 samples of micritic limestones were collected from six Ellis Bay sections ranging from the basin margin to more distal basin center of the Anticosti Basin. delta13C and delta18O isotopic ratios were measured from these samples and integrated within a recently proposed framework of sequence stratigraphy and biostratigraphy for the Ellis Bay Formation. The measured delta13C values in most sections show a positive excursion (∼2‰) in the lower Ellis Bay Formation followed by a larger excursion (∼4‰) in the upper Ellis Bay Formation. The delta 13C profile of the Ellis Bay Formation on Anticosti Island exhibits a pattern similar to those of other profiles in graptolite-rich Hirnantian basinal successions from the rest of the world. The delta13C record on Anticosti Island is not consistent with predictions and observations based on current models that describe the state and evolution of the global carbon cycle during the Late Ordovician.

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This thesis develops and applies new techniques for reconstructing past environments from the speleothem archive. Chapter 3 introduces Ca isotopes as a novel palaeo-aridity proxy. Recent dripwater, farmed calcite and bedrock data show that, in the modern environment, 36% of initial dripwater Ca is removed by prior calcite precipitation at the HS4 dripsite (Heshang Cave, Central China). A speleothem record spanning the 8.2kyr event suggests this value increased to 60% during the event, in response to a decrease in effective rainfall of approximately a third. Modern Ca isotope systematics, and the cycling of other Group II metals, are studied further in Chapter 4. Data from Heshang Cave monitoring samples explore the temporal and spatial controls on these proxy systems. Results highlight the importance of secondary calcite as a potential source of dripwater metals, as well as the significant contribution of particulate calcite to bulk dripwater chemistry. At the HS4 dripsite, over a third of bulk dripwater Ca is present as particulate calcite. This influences bulk dripwater Ca concentrations and isotopes, as well as potentially impacting speleothem growth and chemistry. Chapters 5 introduces CaveCalc, a new numerical model for dripwater and speleothem chemistry and isotopes based on PHREEQC. Key strengths of CaveCalc include its ability to model multiple proxy systems in a single framework, the ability to quantify the extent of open-system dissolution, and the extensible nature of its design. Chapter 6 applies CaveCalc to disentangling the controls on dripwater and speleothem δ¹³C values. Model results are compared with speleothem data. At Heshang Cave, anomalously high δ¹³C is quantitatively explained as the result of CO₂ degassing and prior calcite precipitation, an interpretation made possible by the availability of coupled δ¹³C, a¹⁴C and Ca isotope data. This approach provides a powerful tool to help researchers better interpret dripwater and speleothem δ¹³C data.

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Over the course of my PhD, I developed the analytical capability to measure calcium isotopes at the University of Cambridge and analyzed calcium isotopes in a range of fluids and minerals in modern and past environments. After discussing my methodological development, I report my work in the glacial precursor to the Dead Sea. Here, the calcium isotope composition of aragonite varies synchronously with lake level fluctuations over the last 70,000 years. My numerically reconstructed lake calcium budget led me to conclude that 20,000 years ago, the Dead Sea was wetter than modern conditions, rather than colder and drier, as had previously been proposed. The primary focus of my PhD research was understanding the sedimentary sink for carbon. The formation of authigenic carbonate in marine sediments is caused by the microbial degradation of organic matter. I used pore fluid measurements and a numerical model to identify zones of authigenic carbonate precipitation. This knowledge was then combined with an understanding of the microbial processes that occur beneath the seafloor to determine the link between microbial activity and authigenic carbonate formation. Two processes, sulfate reduction and the anaerobic oxidation of methane were determined to be the main drivers of authigenic carbonate precipitation. In order to assess the importance of the carbon isotope signal imparted by each of the two identified processes, I created Artificial Neural Networks to predict the areal extent of authigenic carbonate precipitation and the dominant microbial process driving the precipitation. My ANNs identified that 37% of the modern seafloor is precipitating authigenic carbonate, which leads to a flux of 1.2*10^12 moles of carbon per year, of which 88% is due to the anaerobic oxidation of methane, and 12% is due to sulfate reduction. This represents 2-3% of the modern global carbon deposition, however I was able to show that this would be significantly higher in the geological past when ocean conditions were vastly different to how they are today. Finally, I conclude by proposing that some variations in the global carbon cycle in the past can be explored by linking marine calcium concentrations to authigenic carbonate formation and the flux of alkalinity from the seafloor.

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Thesis (Ph. D.)--Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, 1987.
Funding was provided by the National Science Foundation under grants OCE 15270 and OCE 16082.

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Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2000.
"September 1999."
Includes bibliographical references.
Geochemical studies are fundamental for understanding how the dynamic Earth works and evolves. These studies place constraints on the composition, formation, age, distribution, evolution and scales of geochemically distinct reservoirs such as the Earth's crust, mantle and core. In this dissertation the strategy has been to work on a broad range of topics to evaluate crustal and mantle processes. This study presents Re-Os systematics to constrain the composition, formation and age of the lower continental crust and the mantle lithosphere, examines melt inclusion from oceanic island basalts to evaluate the scale of the mantle heterogeneities, and uses U-series isotope to constrain geodynamic parameters, such as the upwelling velocities and porosities of mantle plumes. The lower continental crust plays a pivotal role in understanding the composition and evolution of the continental crust and the petrogenesis of continental basalts.
by Alberto Edgardo Saal.
Ph.D.

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Morenci is located in southeast Arizona. Copper grade hypogene mineralization averages 0.15%; one or more generations of supergene enrichment have increased mineralization to 0.96%. Intense supergene alteration has made it difficult to determine phyllosilicate paragenesis. The purpose of this study is to differentiate hypogene from supergene phyllosilicates. Forty-nine samples from five drill holes were obtained for petrographic, geochemical, mineralogical, and stable isotope data. Petrographic examination, X-ray diffraction and X-ray powder camera techniques established alteration of feldspars to kaolinite, montmorillonite, and sericite. Whole rock analyses using XRF determined cationic gains and losses that correspond with kaolinite and sericite. Stable isotopes of oxygen and hydrogen using kaolinite and sericite from 14 samples were tested to determine provenance of water. Stable isotope data show a trimodal distribution of phyllosilicates consistent with early hypogene alteration of magmatic origin, and two generations of supergene enrichment due to meteoric waters.

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The fluid history of serpentinites from three locations in the Franciscan Complex, San Rafael Mountains, California is evaluated with petrologic and stable isotope data that allow interpretation of the serpentinization history and tectonic origin of these rocks. Petrologic evidence shows that most samples were originally serpentinized in a relatively low temperature seafloor hydrothermal environment, but some rocks underwent subsequent recrystallization. Data obtained from serpentine-magnetite geothermometry indicate that the serpentinization temperatures ranged from 168°C to 306°C. Oxygen isotopic values suggest that the serpentinites may have originated in a forearc setting. Hydrogen isotopic values obtained do not reflect the original conditions of serpentinization, but indicate that the rocks subsequently underwent isotopic exchange with meteoric water once they were emplaced onto the continent.

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Underlying all applications of sulfur isotope analyses is our understanding of isotope systematics. This dissertation tests some fundamental assumptions and assertions, drawn from equilibrium theory and a diverse body of empirical work on biochemical kinetics, as applied to the multiple sulfur isotope systematics of microbial sulfate reduction. I take a reductionist approach, both in the questions addressed and experimental approaches employed. This allows for a mechanistic, physically consistent interpretation of geological and biological sulfur isotope records. The goal of my work here is to allow interpreters a more biologically, chemically and physically parsimonious framework to decipher the signals coded in modern and ancient sulfur isotope records.
Earth and Planetary Sciences

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Lead isotope ratios of ores and igneous rocks in the Central and Southern Andes show a large-scale geographic pattern related to magmatic source processes. This pattern changes in the Northern Andes for reasons that are not well understood; this study is an investigation of potential causes of this change. Deep ocean sediment samples from the Nazca Plate were analyzed for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb, and the data were compared with published data on central Andean ores and ores and igneous rocks from Ecuador. Lead isotopic compositions of the Nazca Plate sediments are quite hom*ogenous and are a close match with Andean ore lead in the coastal arc from central Perú through south-central Chile. However, the lead isotope ratios of the sediment samples are much lower than northern Perú and Ecuador ores. Variations in sediment composition are probably not the source of the northern Andean ore lead isotope pattern.

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The Bandelierkop Formation of the Southern Marginal Zone (SMZ) of the Limpopo Belt consists of metamorphosed ultramafic, mafic and sedimentary rocks. Metamorphic conditions indicated by the petrography of these different rock groups are consistent with upper amphibolite to granulite facies. The ultramafic and mafic rocks are geochemically akin to peridotitic-pyroxenitic intrusive rocks and high-Mg basalts respectively. Metamorphism of these two rock groups in the SMZ was an essentially closed system process, except for the highly volatile phases such as H₂O and CO₂. The metasediments appear to represent a sequence of high (Mg+Fe)-greywackes and/or deep-water shales with minor amounts of iron formation material. The unusually mafic character of the metasediments can be ascribed to a high ultramafic + mafic source component to the original sediment. Some modification of the major and trace element compositions of the pelitic rocks has been caused by the removal of partial melts and the metamorphism of the pelitic rocks is not therefore considered to have occurred under closed system conditions. Variable extraction of partial melts is implied by the chemical variations shown by the pelitic rocks and is also suggested by the presence of large pegmatitic felsic bodies which are commonly found close to the pelitic rocks. Detailed petrographic study of the Bandelierkop Formation rocks suggests an increase in metamorphic grade, and/or a decrease in water activity, from south to north within the Southern Marginal Zone. Peak metamorphic conditions of 730°C + 65°C at pressures of 6.1 ± 1.5 kbars may be deduced from a careful application of several cation thermometers and barometers on selected mineral analyses. A rigorous application of garnet-biotite thermometry to the pelitic rocks indicates that the transition from orthoamphibole gneisses in the south to orthopyroxene-bearing rocks in the north of the SMZ terrane, is a function of changing biotite composition and/or decreasing water activities rather than an increase in metamorphic temperatures. In contrast to the major and trace element data, the stable isotope data for the ultramafic and mafic rocks in the SMZ indicate open system behaviour for some of these rocks, but closed system behaviour for the pelites. Extraction of SO to 70% partial melts from the pelitic rocks, should not, however, have affected the δ¹⁸O value of the restite. Petrological and stable isotope data in the SMZ rocks are consistent with retrogression in all these rocks and open system behaviour for oxygen in some ultramafic and mafic rocks, being caused by the crystallization and accompanying fluid release of melts produced during prograde metamorphism of the pelitic rocks. Small scale (-5 to 30m's) heterogeneity is implied by both oxygen and carbon stable isotope compositions of closely spaced rock samples, even for those collected from within large "shear zones", suggesting small fluid/rock ratios for most of the samples in the high-grade terrane or heterogeneous stable isotopic compositions of the fluids. Furthermore, a similarity in mineral-mineral stable isotope fractionation factors is observed for all the pelitic rocks, including the orthoamphibole gneisses found immediately south of the orthopyroxene isograd. These features preclude the presence of pervasive fluid infiltration after peak metamorphism. Two implications are, that granulite facies metamorphism in the SMZ terrane was not caused by an influx of mantle derived CO₂-rich fluid and, that the orthoamphibole gneisses are not retrogressed equivalents of the granulites found to the north of the orthopyroxene isograd. It is suggested that this isograd represents a change in the water activities of the rocks during metamorphism. Apparent disequilibria in mineral - mineral stable isotope fractionations observed amongst different minerals within any one pelitic rock, may be explained by a combination of the crystallization of residual melt within these rocks and oxygen diffusion amongst minerals which have not reached their oxygen-closure. The concordant quartz-plagioclase, quartz-biotite and plagioclase-biotite oxygen isotope equilibration temperatures are taken to represent minimum crystallization temperatures for the melts (-560°C), while successively higher quartz-orthopyroxene, quartz-amphibole and quartz-garnet oxygen isotope equilibration temperatures are a function of increasing closure temperatures for the orthopyroxene, amphibole and garnet respectively. The minimum estimate to peak metamorphic temperatures is given by the quartz-garnet oxygen isotope temperature averaging 736 + 52°C. If oxygen diffusion experiments performed in hydrothermal systems are appropriate for the SMZ rocks, then cooling rates for the SMZ terrane could have been as low as 12 to 25°C/My over a temperature range of 480 to 600°C. Stable isotope modeling of hypothetical fluids that may have been in equilibrium with the high-grade rocks, suggests that a mixture of CO₂ and H₂O, with CO₂/H₂O mole ratios > 0.1 can precipitate both quartz and carbonate of stable isotope composition similar to those determined for quartz and carbonate from the mineralized Archaean lode gold deposits of the Murchison and Pietersburg greenstone belts. A model involving granulite facies metamorphism, partial melt extraction and subsequent release of fluids, Au, K and S upon crystallization of such melts, appears to be viable for gold mineralization occuring in the adjacent lower grade greenstone belts and in the high-grade terrane of the Southern Marginal Zone.

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Thesis (B. Sc.(Hons))--University of Adelaide, Dept. of Geology and Geophysics, 1998.
National Grid Reference 1:250 000 Geological Series Sheet SI 53-2 and Sheet SI 53-6. Includes bibliographical references (6 leaves ).

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The Rosita Hills volcanic centre is an alkali-calcic mid-Tertiary caldera complex overlying ortho- and paragneissic basem*nt on the eastern margin of the Wet Mountains graben in southcentral Colorado. There were two mineralising events at the Rosita centre. Au, Ag and base metal mineralisation occurred in a phreatomagmatic breccia pipe at the northern margin of the complex. Later, Ag and base metal mineralisation occurred in veins in the centre of the complex. Mapping, petrological and XRD studies outline 4 alteration facies related to hydrothermal activity at the centre. Propylitic/argillic, K-feldspar-sericitic, advanced argillic and silicic alteration assemblages are recognised. The areas of most intense alteration are controlled by the dominant structural trends within the caldera. Sub-volcanic magma movement is postulated as the dominant cause of the fracture patterns. A lithogeochemical grid survey for Au, Ag, Sr, Rb, Cu, Pb, Zn and Mn across areas of hydrothermal alteration reveal complex patterns indicative of multi-stage hydrothermal activity. District-wide Sr, Zn and Mn depletions are related to the propylitic/argillic alteration. Au, Ag, Rb and Cu enhancements are related to the K-feldspar-sericite alteration. Late stage advanced argillic alteration modified the trace element dispersion patterns by leaching previously formed enhancements. Stable isotope studies (O and H) of whole rock and mineral separate (quartz and sericite) samples from veins and hydrothermal eruption breccias show that the hydrothermal fluid had both meteoric and magmatic components. δD values from whole rock samples show a crudely concentric pattern centring on areas of sericitic and advanced argillic alteration in the middle of the lithogeochemical grid. Fluid inclusion data from vein gangue minerals (quartz, baryte and sphalerite) and from silicified rock in the advanced argillic alteration zone again show that the hydrothermal fluid had more than one component fluid. A highly saline, high temperature fluid occurs in quartz associated with base metal mineralisation. Less saline inclusions occur in the upper parts of the system in the silicic alteration. The data indicate that mixing of these two end-member fluids precipitated the vein mineralisation. The source of metals in the Bassick breccia pipe orebody was a highly differentiated magma body underlying the breccia pipe. Incipient ring faulting probably controlled the emplacement of the magma. Other similar breccia pipes in Colorado are postulated as overlying Cu-Mo porphyry mineralisation. The source of the metals in the Rosita vein orebodies was the volcanic host rocks (and the Precambrian basem*nt?). The Rosita Hills vein mineralisation shows features typical of adularia-sericite systems in the western United States. The Au:Ag ratio in these deposits can be related to the origins of the crust underlying the deposits.

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Hf, Sr, Nd and Pb isotopes, and major, trace and rare earth elements (REE) were determined for a suite of peridotite and pyroxenite xenoliths, constituent garnet and clinopyroxene and the host Nikos kimberlite (100 Ma) from Somerset Island, in order to constrain the chemical and isotopic composition of the lithosphere beneath the northern Canadian craton. The refractory Nikos peridotites are characterized by high olivine forsterite contents (avg. Fo = 92.3) and depletions in incompatible major elements (Fe, Al, Ca), but are enriched in incompatible trace elements, such as large ion lithophile elements (LILE) and light rare earth elements (LREE), while having approximately chondritic heavy rare earth element (HREE) contents. Mass balance calculations using REE contents of clinopyroxene and garnet indicate that calculated LREE abundances for the Nikos xenoliths are significantly lower (e.g. Nd ~50%) than those of the analyzed whole-rocks. These results suggest the presence of small amounts of a kimberlite-related LREE-rich interstitial component (i.e. ~1% kimberlite liquid and/or ~0.01% apatite) to account for the excess LREE abundances, with little effect on the HREE budgets of the xenoliths.
The 143Nd/144Nd(0.1Ga) (0.51249--0.51276) isotopic compositions of the Nikos peridotites are little variable and overlap those of the Nikos kimberlite at the time of sample transport. The low-temperature peridotites (<1100°C) that sample the shallow lithosphere are characterized by more radiogenic 176Hf/177Hf(0.1Ga) (0.28296--0.28419) and Pb (206Pb/204Pb (0.1Ga) = 17.82--19.03), but lower 87Sr/ 86Sr(0.1Ga) (0.7047--0.7066) isotopic ratios than those of the high-temperature peridotites (>1100°C; 0.28265--0.28333; 17.18--18.30; 0.7064--0.7085, respectively). Incompatible trace element compositions of the xenoliths confirm this depth stratification indicating that shallow and deep (>160 km) Somerset lithosphere are characterized by distinct chemical and isotopic characteristics.
The Lu-Hf isotope compositions of the low-temperature peridotites plot along a 2.8 Ga reference isochron, which is consistent with an interpretation that the shallow Somerset lithosphere stabilized in the Archean to depth of ~150 km. The deep lithospheric mantle, which is probably younger, does not share the same petrogenetic history and may contain recycled material (altered oceanic crust and sedimentary component?). The Hf isotope compositions for the shallow low-temperature peridotites indicate that part of the lithosphere beneath the Canadian craton is characterized by more radiogenic Hf isotope signatures than estimates for "depleted" mantle.

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Stable isotope analysis of thirty-five samples from the Northwestern Coast Mountains indicates a complex fluid history related to terrane accretion, metamorphism, and magmatism. The greenschist to amphibolite facies metasedimentary rocks from the Western Metamorphic Belt have variable δD and δ ¹⁸O values that appear to be in isotopic equilibrium with metamorphic fluids at low water-rock ratio conditions. Carbon isotope values indicate organic rich protoliths. Stable isotope values from the Coast Shear Zone indicate the involvement of both magmatic and meteoric-hydrothermal fluids during deformation, in contrast to meteoric-free fluid systems related to Au-mineralization along strike to the north (Goldfarb et al., 1988). The Coast Mountain Batholith and Central Gneiss Complex have hom*ogeneous δD and δ ¹⁸O values that indicate magmatic fluids at low water-rock ratio (Magaritz and Taylor, 1976). Further to the east, large amounts of meteoric-hydrothermal fluids circulated through a network of ductile-to-brittle normal faults (Andronicos et al., 2003; Heah, 1990).

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Major and trace metal loading to mountains in the western US depends on dust sources, intensity of storms and their availability for transport during snowmelt and runoff. Previous work has been conducted on dust production, composition, and its affect on solar radiation and timing of snow melt. This study was conducted to 1) examine temporal and spatial variability in dust chemistry; 2) evaluate form and availability of major and trace elements in dust; and 3) identify potential dust sources affecting mountains in Utah and Nevada. Spring and summertime dust was collected across northern Utah over the course of three years (2013-2015). Additional dust samples were collected from eastern Nevada for comparison. All samples were analyzed for mineralogy. The spring dust samples were also leached with 1 M acetic acid, 0.8 M nitric acid, and aqua regia and analyzed for 87Sr/86Sr ratios and concentrations of 40+ trace and major elements. Nearly all dust samples were enriched in playa-associated elements (U, Mg, Li, Ca, Sr, As) and anthropogenic elements (Sb, Mn, Zn, Cu, Pb, Se, Cd) relative to average upper continental crust. Leachate results showed that nearly 60% Ca, Sr, and Cd mass is potentially available for transport during snowmelt and that the rare earth elements could be mobilized under lower pH conditions in the soil zone. A major dust event on 17 March 2014 that was sampled across the study area showed spatially variable trace element concentrations and 87Sr/86Sr ratios, indicating that dust deposited to mountain snowpack originated from multiple upwind desert dust source areas. The NOAA HYSPLIT model was used to calculate back trajectories for this dust event and showed potential dust sources ranged from the Sevier, West and Great Salt Lake deserts in Utah and the Snake River Plain in Idaho. In contrast, multivariate statistical analysis showed that over the course of the study samples had unique geochemical signatures within each sample area. These findings suggest that spatial variability is more important than temporal variability in terms of the chemistry of dust deposition. With increasing populations and land use change in the western US, the short and long term effects of aeolian dust deposition to mountain environments need to continual monitored and constrained.

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This study is concerned with the Pb-isotope compositions of galena samples from Pb-Zn occurrences in southern Turkey. The purpose is to i) provide chronologic information for ore deposition, ii) investigate the likely source(s) of lead in oredeposits, and iii) examine the possible control of tectonic setting and crustal basem*nt on Pb-isotope compositions. The data used in the study belongs to thedeposits located in Taurides (Zamanti, KahramanmaraS, Malatya, Elazig, Bitlis), with additional data from Nigde Massif and Hakkari Area.The mineralizations are dominantly carbonate-hosted Pb-Zn deposits formed as fracture and karst fillings and, in some places, parralel to bedding. Ore minerals are mainly Zn-oxides and minor Zn, Pb-sulphides.The Pb-isotope compositions, as evaluated in terms of their configuration with respect to reference crustal growth curves and reference isochrons on conventional Pb-isotope diagrams, point to U/Pb ratios greater than average crustal values (and close to the Western Mediterranean Crustal Growth Curve) forall the deposits, indicating upper crustal source for Pb. However, some of the deposits (AfSin-KahramanmaraS
Oreks, D&uuml
ndarli, AgcaSar and skarn type deposits to the south of &Ccedil
adirkaya in Zamanti (Kayseri-Adana)
Keban-Elazig) appear to have magmatic inputs in their genesis. Relatively old deposits are likely Paleozoic (Cafana-Malatya and T&uuml
rksevin-KahramanmaraS), Late Paleozoic-Early Mesozoic (Kalek&ouml
y-Zamanti) and Mesozoic (Hakkari) in age. The rest of the deposits (most of the occurrences in Zamanti, Nigde,KahramanmaraS, Elazig and Bitlis) are likely of Cenozoic age. The Pb-isotope compositions are, in general, similar to those from other occurrences in the Mediterranean Belt.

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As ever-increasing levels of carbon dioxide alter the chemistry of the Earth’s atmosphere, understanding the global carbon cycle becomes increasingly important. A particularly important component is the riverine carbon cycle, as rivers are the primary conduits for dissolved inorganic carbon from terrestrial watersheds to ocean basins. Stable carbon isotopes (13C/12C) were collected weekly and input into the mixing model IsoSource to delineate seasonal carbon sourcing along two nested basins in the upper Green River System, Kentucky. In the more siliciclastic upstream catchment, dissolved inorganic carbon (DIC) was primarily derived from soil respiration (34%). Groundwater dissolving carbonate bedrock and carbonate dissolution/precipitation reactions contributed 31% and 11%, respectively. The more carbonate-dominated downstream catchment also was influenced greatly by soil respiration (35%). Due to the more pronounced levels of carbonate bedrock, carbonate reactions contributed double that of the upstream catchment (20%), with groundwater contributing 22%. Seasonally, the upstream basin gathered most DIC from soil respiration from late spring to winter. Early spring precipitation and still limited photosynthesis caused the primary carbon sourcing to shift to groundwater. Downstream, the primary source throughout the entire study period was soil respiration. Collectively, this study provides insight into the carbon cycling process in a mid-latitude, karstic river using carbon isotope sourcing to aid in the quantification of global carbon flux in the critical zone.

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Thesis (M.S.)--Miami University, Dept. of Geology, 2003.
Title from first page of PDF document. Document formatted into pages; contains viii, 105 p. : ill. Includes bibliographical references (p. 83-91).

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Geology
M.S.
Urbanization affects in-stream biogeochemical processes that control nutrient export. Attempts to restore urban streams will not be successful unless the biological and physical controls on water quality are thoroughly understood. The objective of this study was to identify the relative influences of tributary dilution, groundwater discharge, and biological processing on nitrate concentrations in an urban stream during high and low flow periods. A wastewater treatment plant (WTP) on Pennypack Creek, an urban stream near Philadelphia, PA, increases nitrate concentrations to a mean of 8.5 mg-l-1 (as N). Concentrations decrease to 5.5 mg-l-1 about 7.5 km downstream. Reaches along this distance were sampled for nitrate concentration and delta-15N at fine spatial intervals to determine the reasons for this decrease. To quantify the effects of dilution, samples were collected from tributaries, groundwater springs, and upstream and downstream of tributaries or groundwater discharge zones identified through terrain analysis and continuous temperature modeling. These methods were also used to identify and sample reaches along which hyporheic flow occurred, where nitrate biological processing is often concentrated. In addition, loggers were installed at closely spaced sites to monitor daily fluctuations in nitrate, dissolved oxygen, and related parameters, which provided further indications of biological processing. Longitudinal sampling revealed decreases in nitrate concentration of 2 and 6.5 mg-l-1 during high and low flow, respectively. During high flow, delta-15N varied from 9.5 to 10.5 per mille downstream of the WTP, while delta-15N varied from 10.14 to 11.06 per mille throughout this reach during low flow. Mixing analysis indicated that groundwater discharge and biological processing both control nitrate concentration during both flow periods. Larger declines in nitrate concentration were observed during low flow than during high flow, and delta-15N fell between biological and groundwater signatures, indicating that both processes were enhanced. Continuous nitrate concentrations displayed distinct diurnal cycles often out-of-phase with dissolved oxygen cycles, indicating autotrophic processing. However, shifts occurred in nitrate cycle timing at a weekly scale wherein daily maximum concentrations were observed as many as 6 hours closer to noon than previously. These shifts were comparable to shifts observed across seasons in other studies, and by the end of the summer, nitrate and dissolved oxygen cycles were in-phase. Furthermore, shifts in nitrate cycles could not be linked to shifts in daily fluctuations of WTP discharge. Longitudinal sampling and continuous monitoring suggest that biological processing is an important control on nitrate concentrations in urban systems, though documenting its signature may be complicated by groundwater discharge and anthropogenic inputs.
Temple University--Theses

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Abstract:

Hydrothermal systems on active volcanoes can be studied through characterization of the emitted fluids and surface discharges using major element and isotopic compositions of fumaroles and thermal springs within the volcanic area. This thesis aims at understanding the geochemistry of the existing hydrothermal systems of Kanlaon, Biliran and Bulusan volcanoes in the Philippines and the contribution of magma degassing in the formation of fluids circulating within the hydrothermal system. This study also aims at improving the geochemical monitoring program of PHIVOLCS by suggesting parameters to use in evaluating the volcano’s activity and their evolution that may lead to volcanic unrest.Kanlaon volcano’s extensive hydrothermal system evolved into two distinct hydrothermal systems independent of each other. A mature hydrothermal system represented by Pataan thermal area is characterized by neutral Na + K chloride (bicarbonate) fluids and an immature system, represented by Hagdan is characterized by the presence of acid-sulfate waters. Chemical and isotopic analyses were performed on thermals waters to classify the samples that are linked to the existence of these two hydrothermal systems. Using Cl-SO4-HCO3 relative abundances, Kanlaon’s thermal waters are classified as acid sulfate, acid sulfate-chloride, neutral chloride, and neutral bicarbonate waters. The linear trend formed by Na + K and Cl of Pataan and Mambucal samples can be explained by groundwater/meteoric dilution. This is consistent with the light sulfur isotopic signatures between δ34S = -3.4 ‰ and +1.2 ‰ of the mature hydrothermal system. This implies that the origin of sulfur is linked to the surficial oxidation of H2S. In contrast, the immature hydrothermal system shows significantly heavier sulfur isotopic composition (δ34S = +8.2 ‰), which indicates that sulfur may have originated from the disproportionation of magmatic SO2 or from the fractionation between hydrothermal sulfate and sulfide (SO42-/H2S) pairs that have achieved isotopic equilibrium.On Biliran Volcano, the area of Vulcan thermal grounds exhibits the greatest thermal activity. Thermal waters of Biliran are classified into 6 types based on their geochemistry and location on the ground. Location 1 is composed of summit springs and location 2-6 are springs found along the periphery of the volcano with varying distances from the summit springs. Immature waters are discharging from the springs located at the summit. These are the acid sulfate-chloride waters. The high concentration of SO42- and Cl- is a clear indication of the presence of magmatic HCl, H2S, and SO2. The high δ34S (+14.7 ‰ to +26.6 ‰) values suggest that these fluids were formed from the disproportionation of magmatic SO2. The acidity of the summit springs is coming from the HCl which is a contribution from the degassed magma at depth. Mature neutral (SO42- - HCO3-) Cl springs are found away from the summit moving towards the margins of the neutralization zone. Neutral Cl fluids evolved from progressive neutralization of previously acidic fluid by water-rock interaction that migrated laterally and emerged as bicarbonate waters in the periphery of the volcano. Mt. Bulusan hydrothermal system is complex and tends to show the signature of a deep neutral Cl fluid. Based on Cl and SO42-, there are two groups of springs and these are found in two different locations. Type I springs are located on Mt. Bulusan close to the crater. The predominance of HCO3- and SO42- can be associated with shallow interactions and processes (i.e. boiling of hydrothermal fluids producing steam) that modify the fluid of meteoric in origin. Major gases such as CO2(g) and H2S(g) are incorporated in the groundwater via condensation. Type II springs are located on the periphery of the volcano, far from the location of Type I springs. These springs are characterized by the presence of Cl- and HCO3- ions at concentration levels greater than SO42- concentrations. The low solubility of CO2 allows the gas phase to be transported over long distances and converted to HCO3-. The origin of Type II fluids can either be through adsorption of CO2-bearing gases, or condensation of CO2-rich geothermal steam. The proximity of one Type II spring to sea level can have a bearing on the origin of Cl- in the fluids, but the fact that all Cl- composition of these springs are quite uniform, this means that the chloride must have come from one source and that it is highly unlikely to receive any contribution from seawater. This is also supported by the Cl/B and Cl/Li composition of Type II springs. Mt. Bulusan does not have ‘pure’ neutral chloride water signature but rather a mixture of neutral Cl waters and HCO3-rich waters.
Le travail de thèse est consacré à l’étude de systèmes hydrothermaux de volcans actifs qui ont été caractérisés grâce à l’étude géochimique (éléments majeurs et composition isotopique) des fluides hydrothermaux émis en surface de zones volcaniques. L’objectif principal de la thèse est l’interprétation de la composition géochimique des fluides hydrothermaux présents dans 3 systèmes actifs :les volcans Kanlaon, Biliran et Bulusan aux Philippines. Cette étude a également pour but d’améliorer le programme de monitoring de l’activité volcanique du PHIVOLCS (Philippine Institute of Volcanology and Seismology) en proposant des paramètres géochimiques utiles à l’évaluation de l’état d’activité d’un volcan et qui peuvent également fournir de signaux précurseurs d’une activité éruptive. Dans le cas du Volcan Kanlaon, la présence de deux systèmes hydrothermaux distincts a été mise en évidence grâce à l’analyse géochimique et isotopique des eaux thermales présentes dans le massif volcanique. Un système hydrothermal « mature » caractérisé par des fluides neutres chlorures (Na+K/Cl) est présent sous la zone hydrothermale de Pataan. Le deuxième système hydrothermal, situé dans la zone de Hagdan, présente au contraire des propriétés d’un système « immature » dominé par des fluides de type acide sulfate. En comparant les abondances relatives en Cl-SO4-HCO3, différents types de composition de sources thermales sont observées :acide sulfate, acide sulfate-chlorure, neutre chlorure et neutre bicarbonate. La corrélation linéaire qui existe entre les alcalins (Na+K) et les chlorures dans les échantillons de Pataan et de Mambucal suggère une origine identique et un processus de simple dilution par des eaux d’origine météoritique. D’autre part, la signature isotopique des sulfates à Mambucal avec une gamme de valeurs de δ34S entre -3.4 ‰ et +1.2 ‰ est typique de l’oxydation à proximité de la surface de l’H2S et tend à confirmer le caractère « mature » du système hydrothermal. La signature isotopique contrastée des sulfates de Hagdan avec un δ34S = +8.2 ‰ suggère que l’origine du soufre dans ce système « immature » pourrait être liée soit à la disproportionation du SO2 d’origine magmatique soit résulté d’un fractionnement isotopique à l’équilibre au niveau du sytème hydrothermal de la paire SO42-/H2S.Dans le cas du volcan Biliran, l’activité hydrothermal principale est située dans la zone sommitale de Vulcan. 6 types de composition géochimique différents ont été mis en évidence. Dans la zone sommitale de l’édifice volcanique, des eaux « immatures » de type acide sulfate-chlorure ont été identifiées. Les concentrations élevées en SO42- et Cl- suggèrent une contribution magmatique et la présence de HCl, H2S and SO2 émis par le dégazage d’une intrusion magmatique superficielle. Les valeurs élevées en δ34S (+14.7 ‰ à +26.6 ‰) suggèrent clairement que les sulfates proviennent de la réaction de disproportionation de SO2 d’origine magmatique. D’autre part, les valeurs d’acidité de ces sources sont nettement corrélées à l’abondance des chlorures et donc à la contribution d’HCl gazeux d’origine magmatique. En périphérie de la zone sommitale, les sources chaudes sont caractérisées par des eaux « matures » de type (SO42- - HCO3-) + Cl- dont l’acidité est largement neutralisée. Des fluides neutre chlorures provenant de la neutralisation progressive de fluides acides par interaction avec les roches encaissantes et enrichis en bicarbonates sont également présents dans les zones périphériques du volcan Biliran.Le système hydrothermal du Mt. Bulusan est complexe mais tend à révéler la présence d’un réservoir profond de composition neutre chlorure. Deux groupes de sources chaudes distincts sont présents dans deux zones distinctes de l’édifice volcanique. Sur base des compositions en Cl et SO42-, deux groupes distincts de sources chaudes ont été observées. Le type I, localisé à proximité du cratère du Bulusan, est caractérisé par la prédominance de HCO3- et SO42- et pourrait résulter de la condensation et dissolution de vapeurs (H20(g), CO2(g) et H2S(g)) essentiellement hydrothermales par des eaux superficielles d’origine météoritique. Le type II, observé beaucoup plus en périphérie de l’édifice volcanique, se distingue par l’abondance des ions Cl- et HCO3- qui dominent largement les concentrations en SO42-. L’origine des sources chaudes de type II est liée à la condensation/dissolution de vapeurs hydrothermales riches en gaz carbonique, le CO2 ayant, en raison de sa plus faible réactivité chimique, la faculté de diffuser latéralement sur de longue distance au sein d’un édifice volcanique. La proximité de certaines sources de type II avec la mer tend à suggérer une origine marine pour le chlore. Cependant, le même type II est également observé à grande distance de la mer où une contribution marine est difficilement envisageable. D’autre part, les compositions relatives en Cl/B and Cl/Li des sources de type II ne semblent pas compatibles avec une origine marine. Aucune composition de fluide « mature » de type neutre chlorure n’a été observée, l’origine des fluides de type II pourrait cependant résulter d’un mélange entre des eaux enrichies en HCO3- et des eaux neutres chlorures.
Doctorat en Sciences
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Abstract:

Rocks provide insight into ancient times before complex animals existed. The oldest sedimentary rocks in Grand Canyon (the Bass Formation) allow us to glimpse into what things might have been like over a billion years ago. These rocks record the time known as the Mesoproterozoic Era (1.6 to 1.0 billion years ago), otherwise known as the ‘boring billion’. These rocks are thought to be the right age to indicate the end of an oddly stable world when continents were quiet and life was calm, yet they predate younger rocks that record extreme events. The Bass Formation, some of the only rock of this age in the world, contains evidence for life and the carbon cycle, and yields information about Earth’s environments 1.2 billion years ago.The carbon cycle can be studied using carbonate rocks. Assuming that the rock has the same chemistry as the water it formed in, we can measure the relative abundance of carbon isotopes to see a ‘fingerprint’ of the system during the time the rock was deposited. During the boring billion, it is thought that very little variation occurs in this fingerprint. However, as more studies are completed, we see a modest variation in units around the age of the Bass Formation. The fingerprint results from this study can be added to the growing collection of Mesoproterozoic studies and help to further our knowledge about the world from this not-so-boring period of time.