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Rapien, Maria H. "Geochemical Evolution at White Island, New Zealand." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36832.
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White Island, New Zealand, is an active andesitic volcano that is located near the southern end of the Tonga-Kermadec Volcanic Arc at the convergent plate boundary where the Pacific Plate is being subducted beneath the Indian-Australian Plate. The plate tectonic setting, volcanic features and the petrology of White Island are thought to be characteristic of the environment associated with formation of porphyry copper deposits. White Island has only been active for about 10 Ka and, as such, is thought to be an ideal location to study early magmatic processes associated with formation of porphyry copper deposits. In this study, the geochemistry of the silicate melt at White Island has been characterized through detailed studies of silicate melt inclusions, phenocrysts, and matrix glass contained in recent ejecta (1977-1991). Most melt inclusions contained only glass, however, daughter minerals present in multiphase melt inclusions in the 1991 sample indicate a different P-T history compared to the other samples.
Samples studied are vesicular porphyritic andesitic dacites containing phenocrysts of plagioclase, orthopyroxene, and clinopyroxene. A glassy matrix containing crystallites surrounds the phenocrysts. Both mineral and silicate melt inclusions occur in all three phenocryst phases. Inclusions of plagioclase occur in pyroxenes and inclusions of orthopyroxene and clinopyroxene occur in plagioclase. Compositions of minerals are independent of mode of occurrence - that is, plagioclase (and orthopyroxene and clinopyroxene) compositions are the same regardless of whether they occur as phenocrysts or as inclusions in another mineral. Moreover, compositions of mineral inclusions and phenocrysts show no systematic variation within individual samples or in samples representing different eruptive events, indicating that the magma chamber is chemically homogenous over the time-space scale being sampled.
Various major, trace element and volatile compositional features of economic and non-economic (or barren) porphyry copper systems were compared to the White Island data. The Al2O3/(Na2O+K2O+CaO) ratio observed in economic porphyry copper deposits is always greater than or equal to 1.3, and glass in one phase melt inclusions, as well as glass in unhomogenized (1991) inclusions from White Island equal or exceed this value. The glass in the unhomogenized 1991 melt inclusions is corundum normative, with Si/(Si+Ca+Mg+Fet)>0.91, and K/(K+Ca+Mg+Fet)>0.36, all of which are characteristic of productive systems. Melt inclusions from White Island also show a positive Eu anomaly similar to that found in productive porphyry deposits, whereas non-productive systems show a negative Eu anomaly.
Copper concentrations (170-230 ppm) in melt inclusions from White Island are sufficiently high to generate an economic porphyry copper deposit based on theoretical models. High Cl/H2O ratios (0.15) in melt inclusions furthermore indicate that copper will be efficiently partitioned from the melt into the magmatic aqueous phase. The inferred pressure in the magma chamber at depth (1 kbar) is ideal for extracting copper from the melt, and mineral phases (pyrrhotite, biotite or amphibole) which could scavenge copper before it could be partitioned into the magmatic vapor phase are absent. Concentrations of S in the melt are also low, which would prevent pyrrhotite from crystallizing.
The tectonic setting and geochemical characteristics of the magma body at White Island are similar to features observed in economic porphyry systems elsewhere. These data suggest that development of economic porphyry copper mineralization at White Island is likely.<br>Master of Science
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Gleeson, Sarah Anne. "The geochemical evolution of mineralising brines, south Cornwall, U.K." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263363.
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Mohamed, Essam Abdelrahman. "Groundwater and surface water geochemical evolution : Liverpool area, UK." Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439482.
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The PhD thesis is focused on the hydrogeology and geochemistry of the surface and groundwater in Liverpool area. It provides a detailed understanding of the effect of the structural geology on the groundwater flow and the geographical variation in the groundwater geochemistry. Moreover, the studies have extended the research towards the geochemical evolution of the fresh and saline groundwaters and surface water. The main conclusions are that the major structural elements, especially the NNW-SSE major faults and a gentle NE-SW fold, have subdivided the aquifer into discreet six hydrogeological sub-basins. As a result of this, a single groundwater flow direction in the aquifer is not likely existed; multiple local flow directions are expected instead. The recharge of the aquifer sub-basins is mainly by vertical percolation while the lateral mixing between the different water types and the inland invasion of seawater are limited by the major faults. The aquifer has two major types of groundwaters. Fresh groundwater occupies one part, generally a few kilometres from the coast and saline groundwater in another part that has undergone seawater intrusion from the Mersey Estuary. The recharge of the fresh groundwater is mainly localised from surface waters (originally rainfall). The recent recharged groundwaters are expected in spatially restricted areas with low salinity and they broadly resemble surface waters except they are more acidic possibly due to C02 dissolution and dissociation, nitrification or sulphide oxidation. This immature groundwater evolved into the regionally dominant groundwaters through a combination of congruent dissolution of dolomite, cation exchange and sulphate mineral dissolution happening in the Sherwood Sandstone aquifer. Due to locally advanced stage of water rock interaction, the regionally dominant groundwater has evolved into higher salinity fresh groundwater at the southern end of a southward flowing compartment. Close to the urban heart of Liverpool the groundwater has undergone local pollution as reflected by the elevated salinity, Cl, S04 and N03 concentrations, The origin of the saline groundwater is mainly due to seawater intrusion based on the similarity in chemical composition between the saline groundwater and River Mersey water. This study has shown that highly saline groundwater has been expected in the Sherwood sandstone aquifer underneath Liverpool and close to the River Mersey. From the previous and present works the saline groundwater in this part of the aquifer mainly due to saline water intrusion from Mersey Estuary. This has been based on the geographic distribution and chemical affinity between the saline groundwater and Mersey Estuary water. The invaded Estuary water experienced a wide range of geochemical processes that deviates the composition of the water away from being a simple physical mixture between low salinity groundwater and seawater. During progressive invasion by seawater, it seems that cation exchange (Na-capture and Ca release) occurs first with a small amount of carbonate and even anhydrite cement dissolution. Next, cation exchange becomes relatively less important but bacterial sulphate reduction starts to occur. The final process during the later stages of saline invasion seems to be dolomitization of indigenous calcite accompanying more advanced bacterial sulphate reduction and with relatively minor cation exchange. The chemistry of the surface water has been studied in small river systems in the area (River Alt, Downholland Brook and River Alt). The main recharge of these surface waters is local rainfall. Dissolution of calcite and weathering of silicate minerals are the most common processes operating in a higher relief river basin floored by Sherwood Sandstone (Calder River regime), while the abundance of gypsum and calcite with silicate in the Downholland Brook and River Alt bed rocks explain the increase of the total dissolved salts and ionic composition of the former two streams waters. The continuous influx of atmospheric CO2 and H+ ions from the dissociation of H2C03 increases the ability of these waters dissolving minerals in contact especially carbonates and silicates. The concentration and lateral variation of the nitrate concentration in the surface and groundwaters have been studied trying to assess its possible source and fate. The results reveal that a significant part of nitrate in surface and groundwater is coming from the application of fertilizers in addition to urban waste water in the highly populated areas. Nitrification process in the soil zone transforms the N-compounds (eg. NH4) into nitrate. The direct drainage of soil water to the river course carries high nitrate to the river waters. The low nitrate concentration in the locally-recharged groundwater is mainly due to natural denitrification processes probably in the unsaturated and saturated zone however the high abstraction rate of the groundwater could be responsible for yielding water with high nitrate concentration.
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Greenwood, Joanna Catherine. "The secular geochemical evolution of the Trindade mantle plum." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439171.
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German, Laura Lynne. "The Geochemical Evolution of the Blood Falls Hypersaline System." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1438715896.
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Song, Suckhwan. "Geochemical evolution of Phanerozoic Lithospheric mantle beneath S.E. South Australia /." Title page, contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phs6983.pdf.
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Caracausi, Antonio. "Noble gases as geochemical tracers of Earth's dynamic and evolution." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0339.
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Dans mon projet, j'ai utilisé les gaz nobles (He, Ne, Ar, Kr et Xe) pour étudier les processus naturels se déroulant dans différents contextes géodynamiques (c.-à-d. subduction, collision continentale, rifting), montrant ainsi comment l'utilisation des gaz rares est fondamentale pour contraindre l'origine des substances volatiles et comment ils permettent une évaluation qualitative et quantitative des processus (interaction eau-gaz-roche) qui se produisent pendant la remontée des fluides de l'intérieur de la Terre vers l'atmosphère. Les résultats de mon projet peuvent être résumés en cinq thèmes principaux : 1) Aperçu de l’histoire du dégazage du manteau terrestre à partir d'analyses de haute précision des gaz rares du gaz magmatique ; 2) Systématique des gaz nobles et des isotopes du carbone sur le volcan Ciomadul, apparemment inactif (Roumanie): Preuve du dégazage volcanique ; 3) Fluides dérivés du manteau dans le bassin sédimentaire de Java oriental, Indonésie ; 4) Dégazage des volatiles du manteau dans un régime tectonique de compression hors du volcanisme: rôle de la délamination continentale ; 5) Dégazage continental de l'hélium dans un contexte tectonique actif (nord de l'Italie) : le rôle de la sismicité<br>In my project, I used the nobles gases (He, Ne, Ar, Kr and Xe) to investigate natural processes occurring in different geodynamical contexts (i.e., subduction, continental collision, rifting), showing how the use of the noble gases is fundamental to constrain the origin of volatiles, and to investigate the Earth interior. Furthermore, I also used these volatiles to recognize the processes (water-gas-rock interaction) that occur during the fluids up rise from the Earth’s interior to the atmosphere and quantitatively constrain the extents of these processes. The results of my project are summarized in five main topics: 1) Insights into the degassing history of Earth’s mantle from high precision noble gas analysis of magmatic gas 2) Noble Gas and Carbon Isotope Systematics at the Seemingly Inactive Ciomadul Volcano (Romania): Evidence for Volcanic Degassing 3) Mantle‐Derived Fluids in the East Java Sedimentary Basin, Indonesia 4) Outgassing of Mantle Volatiles in Compressional Tectonic Regime Away From Volcanism: The Role of Continental Delamination 5) Continental degassing of helium in an active tectonic setting (northern Italy): the role of seismicity
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Roche, Richard Louis. "Stratigraphic and geochemical evolution of the Glass Buttes complex, Oregon." PDXScholar, 1987. https://pdxscholar.library.pdx.edu/open_access_etds/3748.
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Glass Buttes complex lies at the northern margin of the Basin and Range province in central Oregon and is cut by the northwest-trending Brothers fault zone. An older acrystalline volcanic sequence of high-silica rhyolites (>75% SiO2) forms a broad platform composed of domes and flows with minor pyroclastic deposits. The high-silica rhyolite sequence is divided on the basis of texture into 1) zoned flows and domes, 2) obsidian flows, 3) felsite flows, and 4) biotite-phyric flows and domes.
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Whattam, Scott A. "Evolution of the Northland ophiolite, New Zealand: geochemical, geochronological and palaeomagneticconstraints." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244890.
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Brownless, M. A. "Geochemical evolution, fluid-rock interaction and diagenesis of a carbonate-evaporite sequence." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317981.
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McGrath, Annette Gail. "Structural and geochemical evolution of an extensional metamorphic core complex, Paros, Greece." Thesis, University of Leicester, 1999. http://hdl.handle.net/2381/35066.
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Lower Miocene crustal extension on the island of Paros resulted in the generation of two low-lying, north-vergent extensional detachment faults that exhumed deep levels of the ductile, partially molten crust in the footwall, whilst simultaneously accumulating lower Miocene age (Aquitanian-Burdigalian) sedimentary basin deposits in the hangingwall. Continued progressive extension, during the regional D2a event, led to the development of two elongate migmatitic gneiss domes; the NW Paros Dome (NPD), and the Main Paros Dome, (MPD) in the footwall of each detachment fault. Voluminous partial melting of the footwall during the D2b event resulted in the profuse emplacement of hybrid, Hs - type granitoids into the lower plate of the NW Paros extensional detachment fault. It is proposed that a similar, deep-seated D2b pluton / migmatite dome exists beneath the core of the Main Paros Dome, over which the Eastern Paros Detachment Fault was additionally uplifted and warped. The granitoids are derived from the concomitant dehydration melting of a mixed gneiss-amphibolite source during decompression of the lower plate rocks. The hybrid nature of the granitoid suite is reflected in their major- and trace-element variations and isotopic characteristics. Rb/Sr whole rock dating yields an errorchron age of circa. 21 Ma for the granitoid suite, which is correlated to the M2b upper amphibolite facies thermal event in the Aegean. The NW Paros Detachment Fault and associated footwall dome are here described for the first time, and provide valuable insights into the deformational mechanisms of a developing gneiss dome. The Monasteri-Naoussa section of NW Paros is thought to expose the deepest levels of the lower plate on Paros, and essentially provides a "tectonic window" into the ductile mid-lower crust. It is accepted that continental extension in the Aegean was superimposed onto an overthickened crust related to an Eocene HPLT D1 compressional event. It is proposed that D1 tectonic stacking of the Attic-Cycladic litho-tectonic units is related to a process of continuous subduction-accretion, as opposed to pure continental collision. New structural data are presented regarding the mid Miocene NW-SE directed horizontal compression phase on Paros, related to a regional, dextral simple shear event (D3). The D3 compressional event is associated with ubiquitous brittle structures that cross-cut and deform the earlier, higher temperature ductile fabrics related to D2 crustal extension.
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Fassio, Joseph Michael. "Geochemical Evolution of Ferruginous Bauxite Deposits in Northwestern Oregon and Southwestern Washington." PDXScholar, 1990. https://pdxscholar.library.pdx.edu/open_access_etds/3821.
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Ferruginous bauxite deposits developed from flows of the Columbia River Basalt Group in northwestern Oregon and southwestern Washington. Samples of the iron pisolite and the gibbsite nodular zones from the upper portion of the weathering profile of drill core from Columbia County, Oregon and Cowlitz County, Washington, were analyzed by instrumental neutron activation. The mineralogy was determined using Xray diffraction and Mossbauer spectroscopy.
The gibbsite nodular zone is above the clay-rich saprolite or relic basalt zone. The nodules contain relic vesicles and well preserved relic plagioclase microlites. Gibbsite occurs with poorly crystalline goethite and hematite in the gibbsite nodular zone. Clays are absent in this part of the profile .
The iron pisolite zone is at the top of the profile above the gibbsite nodular zone. Both maghemite and goethite pisolites occur in the lower part of the zone while maghemite pisolites are dominant in the upper part of the pisolite zone.
The parent flow is the Frenchman Springs Member of the Wanapum Basalt for the Columbia County profile and the Pomona Member of the Saddle Mountains Basalt for the Cowlitz County profile.
Distribution of the major, minor and trace elements through the profile shows three distinct sympathetic patterns consisting of lanthanide elements and Na; As, Sbi Th, Hf, and Ta; and transition metals Fe, Ti, V, and Cr.
Ratios between the high-field strength elements Ta and Hf are nearly constant through the profile, and Hf appears to be the least mobile elements of the elements analyzed in the profile. Ratios of other elements were calculated against Hf, based on the assumption that it has remained largely immobile during weathering, to show element enrichment and depletion in the profile independent of mass-volume changes. Transition metals and Al show a progressive depletion through the upper gibbsite nodular and iron pisolite zone due to leaching in the profile. Lanthanide elements (except Ce), As, and Sb show an obvious enrichment in the iron pisolite zone relative to the gibbsite nodular zone.
Volume reduction during weathering was calculated based on the immobility of Hf. In the gibbsite nodular zone, the volume reduction calculated for bulk samples is greater than for gibbsite nodule separates suggesting that a greater volume reduction occurred the matrix material surrounding the nodules. Ratios between gibbsite nodules and parent basalt of the immobile elements Hf, Ta, Fe, Ti, Th and Cr suggest that the nodules, where the relic textures are preserved, have undergone volume reduction. Based on the immobility of Hf, the gibbsite nodules lost approximately 40% of the original volume. The volume factors based on the immobility of Hf show that the pisolite zone experienced a greater volume reduction than the gibbsite nodular zone.
Absolute gains and losses relative to the parent basalt show the following relative order of depletion: Na > La > Eu > Sm > Co > Mn > Ce > Sc > Ta > V > Cr > Lu > Th > Fe > Ga > Al. The lesser mobility of Ce and Lu relative to other lanthanide elements suggests fractionation of lanthanide elements in the bauxite profile. Aluminum is both enriched and depleted at different depths in the gibbsite nodular zone suggesting that Al is mobilized from the matrix and possibly the pisolite zone into Al enriched gibbsite nodules.
Volume reduction and destruction of relic textures in the pisolite zone is accompanied by small-scale mobilization of Th, Cr, Fe, Hf, Ga, Sc, and Ta during the formation of iron pisolites.
Formation of the iron pisolite zone above the gibbsite nodular zone may indicate a change in climate from a heavy year round to a seasonal rainfall pattern.
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Roberts, Martin Andrew. "The geochemical and volcanological evolution of the Mt. Meru region, northern Tanzania." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/251861.
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Anthony, Darlene. "Seasonal Effects on the Geochemical Evolution of the Logsdon River, Mammoth Cave, Kentucky." TopSCHOLAR®, 1998. http://digitalcommons.wku.edu/theses/331.
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The following research describes the collection and evaluation of geochemical data from the Logsdon River, an open-flow conduit that drains a portion of the Turnhole Spring drainage basin within the Mammoth Cave karst aquifer of south-central Kentucky. This spatial survey of nearly 10 km of continuous base-level conduit included seasonal sampling of carbon dioxide partial pressures (Pco2)> dissolved ions, and saturation indices for calcite (SIcal). The highest PC02 values are found at the upstream site, closest to the Sinkhole Plain recharge area, which creates under-saturated conditions. Rapid outgassing of C02 into the cave atmosphere creates oversaturated conditions for several thousand meters. This change in chemistry results in the accumulation of rimstone in these areas. A boost in PC02 roughly half-way through the flow path returns the water to slightly under-saturated conditions. The most likely source for additional C02 is in-cave organic decay, as the boost also occurs during winter, when microbial activity in the soil is at a minimum. A general decline in Ca2+ , Mg2+, and HC03 concentrations occurred over the distance through the Logsdon River conduit. This decline may reflect a diluting of water by localized inputs from the plateau and precipitation of travertine along the flow path. Although values for all parameters are greater in summer than winter, the trend in evolution is similar for both seasonal extremes. The nature of the transition from summer to winter conditions in the aquifer was investigated by way of an intensive study of the geochemistry at the Logsdon River monitoring well. The relationship between conductivity (spC) and pH was evaluated during both seasons in an attempt to predict the activity of hydrogen for any given water sample based on continuous spC measurements at the well. Data collected during the 1997-98 seasonal transition supported a single, nonlinear regression equation that may represent two distinct seasonal regimes.
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Cox, David. "Surficial and geochemical evolution of periglacial soils : applications to mineral exploration in Yukon." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44758.
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Exploration geochemistry is a powerful tool when exploring for gold deposits in periglacial environments, such as west-central Yukon. However, this study identified two main challenges to using soils as indicators of bedrock mineralization: 1) the variability of sample material over the scale of hundreds of meters and 2) The dilution of metal concentration in soil caused by the addition of loess. Herein, a study into the distribution of surficial materials is presented, the outcome of which is the mapping of surficial units whereby the terrain is divided into domains based on topography, surficial material and surficial processes. Furthermore, a study into the distribution of metals, specifically gold, within a selection of domains concludes that there is considerable geochemical variation between domains and that no single optimum sample material occurs throughout west-central Yukon. Hence, a tailored sampling protocol, based on surficial mapping is recommended.
Results of scoping studies to the development of two methods to aid in exploration for gold deposits in west-central Yukon are presented: 1) a method for approximating the proportions of loess in a soil sample; proportion of loess in the Bdm horizon and Bm horizon from a selection of exposures from the Golden Saddle deposit were calculated. 2) A method for detecting bedrock alteration by the analysis of the mineralogy of surficial material; Well-crystalized illite, which forms specifically under hydrothermal conditions is identified in surficial material overlying the Golden Saddle deposit. This demonstrates that bedrock alteration minerals remain stable under surficial conditions. The two methods outlined above are demonstrated to be plausible and applicable to exploration in this area.
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Walker, Cherry L. "The volcanic history and geochemical evolution of the Hveragerði Region, S. W. Iceland." Thesis, Durham University, 1992. http://etheses.dur.ac.uk/5610/.
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The Hveragerði Region is situated at the Hengill Triple junction, SW Iceland, where there are three volcanic systems. The crust in the area is constructed from both fissure (elongate) and lava shield (conical) eruptive units. Hengill is the presently active spreading zone with the Hengill Central Volcano, whereas the Hveragerði region is inactive with the extinct Grensdalur Central Volcano. Recent geophysical research indicates the presence of high and low density volumes within the upper 5 km of the crust in this area. The location of the density anomalies coincides with surface geological features, such as Recent lava shields, and the extinct and active central volcanoes. A geological map of the Hveragerði Volcanic System has been constructed, and approximately 450 basaltic samples have been examined petrographically and analysed for whole- rock, volcanic glass and mineral chemical data from this region. Observations from these data, coupled with the geological and geophysical observations, suggest that the lava shields are fed straight from the base of the crust, whereas fissure eruptions originate from shallow crustal reservoirs The character of the crustal reservoir has been highly variable in the past 1 Ma, and has varied from a melt-dominated reservoir, to a crystal mush-dominated one. Each lava shield is compositionally distinct and is thought to preserve the mantle-melting signature. The compositional variation amongst the lava shields suggests that instantaneous melts are able to segregate from the mantle without complete mixing with accumulated melts from the entire length of the melting column. The depleted instantaneous melts from the crest and top of the melting column will either form picritic lava shields or they may interact with more fractionated crustal reservoirs and undergo quench crystallisation of megacrystic plagioclase (An 80-90). These crystals with associated pyroxene and olivine become flototion cumulates. There are episodes within the stratigraphy where off-axis lava shield and highly megacrystic fissure eruptions dominate, and such periods may represent periods of low magma supply. On the submerged mid-ocean ridges, linear and conical features are also observed, and these may be analogous to the fissure and lava shields, respectively. The basalt types reported here from the Hveragerdi region have also been reported off-shore, and they may therefore represent basalts derived from similar magmatic processes in a similar magmatic plumbing system. However, an initial observation of the relationship of 12 dredged basalts from 63˚ 10'N on the Reykjanes Ridge suggests that this is not the case at this locality.
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Hoostal, Matthew John. "Local Adaptation of Microbial Communities along Geochemical Spatial Gradients in Sediments of the Lake Erie Region." Bowling Green State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1375187243.
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Shannon, Andrew J. "Volcanic framework and geochemical evolution of the Archean Hope Bay Greenstone Belt, Nunavut, Canada." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/741.
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Part of the Slave Structural Province, the Hope Bay Greenstone Belt is a 82 km long north-striking sequence of supracrustal rocks dominated by mafic volcanic rocks with lesser felsic volcanic and sedimentary rocks. Mapping of two transects in the southern section and two transects in the northern section have contributed to a robust stratigraphic framework the belt. Three recently discovered Archean lode gold deposits in the Hope Bay Greenstone belt have associations with major structures and specific lithologies (Fe-Ti enriched basalts).
The Flake Lake and the Clover Transects are in the southern part of the belt and the Wolverine and Doris-Discovery Transects are in the northern part of the belt. This work subdivides the volcanic rocks into distinct suites based upon field, petrologic, geochemical, and geochronologic criteria. Some of the suites are stratigraphically continuous and can be correlated tens of kilometres along strike thereby linking the two parts of the Hope Bay Greenstone Belt.
U-Pb geochronology supports work by Hebel (1999) concluded that virtually all the supracrustal rocks in the Hope Bay Greenstone Belt were deposited over at least 53 m.y. (2716-2663 Ma), with the majority of the volcanism occurring after 2700 Ma.
A number of basalt groups are identified and include the normal basalt, the LREE-enriched basalt, the Ti-enriched basalt and the Ti-enriched Al-depleted basalt groups. They have chemical signatures that vary in trace elements particularly HFSE and REE’s, and can be easily be distinguished by geochemical screening. The felsic volcanic suites are also divided into three main groups, tholeiitic rhyolite, calc-alkaline dacite and calc-alkaline rhyolite groups. Nd and Hf isotope signatures are consistent with trace element signatures in identifying mafic and felsic volcanic groups, with the tholeiitic rhyolite showing highly variable signature.
The Hope Bay Greenstone Belt has been show to have a number of felsic and volcanic cycles. An early construction phase of the belt is made up of primarily mafic volcanics which is followed by felsic volcanism equalled mafic volcanism which lacks basalts enriched in Ti. The geodynamic environment that created the Hope Bay Greenstone Belt can be explained by plume influenced subduction zone.
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Veeger, Anne Isabella 1961. "Geochemical methods for evaluating the origin and evolution of ground water in volcanic rocks." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/191168.
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A broad-based geochemical approach, including chemical and isotopic analyses of ground water, chemical analysis of aquifer materials, and laboratory water-rock experiments, was used to evaluate the origin and chemical evolution of ground water on La Palma, a volcanic island in the Canary Archipelago. Stable isotopes of oxygen, hydrogen, carbon and sulfur were successfully used to delineate recharge zones and identify solute sources. Laboratory study of water-rock interactions established the source of solutes and the nature of the chemical reactions that control ground-water chemistry. Most ground water on La Palma originates in a recharge zone that encircles the island from 500 to 1800 meters above sea level. Dry fallout and seaspray are minor sources of solutes, however, evaporative concentration during recharge may produce elevated chloride levels in some portions of the island. Laboratory water-rock experiments and ground-water analyses indicate that incongruent dissolution of aluminosilicate minerals is the dominant process of solute acquisition. The geochemical evolution of most waters is controlled by the availability of dissolved carbon dioxide gas. However, oxidation of pyrite enhances the reactivity of ground water in some portions of the island. Waters in the early phases of chemical evolution appear to be in equilibrium with a kaolinite alteration product, whereas more mineralized waters have compositions consistent with smectite equilibrium. Zones or compartments of ground-water flow were delineated by classifying sampling sites into geochemically distinct groups. Eight distinct zones of ground-water flow were identified using these criteria, including superimposed but hydrologically separate flow paths.
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Zhao, Rujian. "Paragenetic and geochemical evolution of the Cregganbaum gold prospect, Co Mayo, Republic of Ireland." Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251921.
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Takazawa, Eiichi. "Geodynamic evolution of the Horoman peridotite, Japan : geochemical study of lithospheric and asthenospheric processes." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10667.
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Horning, Gregory (Gregory William). "Geophysical and geochemical constraints on the evolution of oceanic lithosphere from formation to subduction." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108908.
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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 104-115).<br>This thesis investigates the evolution of the oceanic lithosphere in a broad sense from formation to subduction, in a focused case at the ridge, and in a focused case proximal to subduction. In general, alteration of the oceanic lithosphere begins at the ridge through focused and diffuse hydrothermal flow, continues off axis through low temperature circulation, and may occur approaching subduction zones as bending related faulting provides fluid pathways. In Chapter 2 1 use a dataset of thousands of microearthquakes recorded at the Rainbow massif on the Mid-Atlantic Ridge to characterize the processes which are responsible for the long-term, high-temperature, hydrothermal discharge found hosted in this oceanic core complex. I find that the detachment fault responsible for the uplift of the massif is inactive and that the axial valleys show no evidence for faulting or active magma intrusion. I conclude that the continuous, low-magnitude seismicity located in diffuse pattern in a region with seismic velocities indicating ultramafic host rock suggests that serpentinization may play a role in microearthquake generation but the seismic network was not capable of providing robust focal mechanism solutions to constrain the source characteristics. In Chapter 3 I find that the Juan de Fuca plate, which represents the young/hot end-member of oceanic plates, is lightly hydrated at upper crustal levels except in regions affected by propagator wakes where hydration of lower crust and upper mantle is evident. I conclude that at the subduction zone the plate is nearly dry at upper mantle levels with the majority of water contained in the crust. Finally, in Chapter 4 I examine samples of cretaceous age serpentinite sampled just before subduction at the Puerto Rico Trench. I show that these upper mantle rocks were completely serpentinized under static conditions at the Mid-Atlantic Ridge. Further, they subsequently underwent 100 Ma of seafloor weathering wherein the alteration products of serpentinization themselves continue to be altered. I conclude that complete hydration of the upper mantle is not the end point in the evolution of oceanic lithosphere as it spreads from the axis to subduction.<br>by Gregory Horning.<br>Ph. D.
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CHAKRABORTY, SUVANKAR. "THE GEOCHEMICAL EVOLUTION OF ALKALINE MAGMAS FROM THE CRARY MOUNTAINS, MARIE BYRD LAND, ANTARCTICA." Bowling Green State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1174187928.
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Goff, Kathleen Roselle. "Geochemical analysis of weathering zones from Clear Creek watershed: implications for modeling Quaternary landscape evolution." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5481.
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Soil development on upland landscapes in east-central Iowa Peoria Loess deposits has been occurring for approximately the last 12,500 years. Weathering zone and pedogenic processes depend on environmental factors such as climate, precipitation, time, parent material, biota, and topography, among others. Analyzing the weathering zones of modern and paleosol profiles provides insight into current and paleo-environmental processes. This study employs several bulk geochemical analytic techniques (XRF, pXRF, LIBS, ICP-MS) to examine the weathering profiles formed in modern Peoria Loess deposits and underlying weathering profiles formed during the Farmdale Interstadial and the Sangamon Interglacial. Results indicate advanced weathering occurred in the paleosol sequences of the Farmdale and Sangamon compared to the modern weathering zone, based on depletion and enrichment of elemental concentrations. The interstadial/last interglacial paleosol weathering profiles exhibit increased depletion in CaO, MgO, Na2O, and K2O compared to the Holocene weathering profile formed in Peoria Loess. Enrichment of CaO and MgO in non-pedogenically altered Peoria Loess deposits is a possible indication of rapid loess accumulation, representing insufficient weathering of deposited material synchronous with deposition. Post-depositional weathering and hydrogeological mechanisms may also account for this mid-profile enrichment, providing for some complexity for interpretation. Regional comparison between three sediment cores - an agricultural field, a restored prairie and a pioneer cemetery - exhibit minor land-use influence on geochemical evolution with the agricultural field core exhibiting greater relative depletion in most oxides in the upper one meter, compared to the other sediment cores. However, slight regional heterogeneity in parent material, vegetation cover, and slope position may also account for geochemical variations. Therefore, it is difficult to conclude how the last 150 years of extensive land-use from human activity has impacted weathering and pedogenesis in this region. Additionally, this study validates using pXRF technology on Quaternary weathering profiles, and documents its technological shortcomings which provides essential information for drawing interpretations from these data.
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Weis, Dominique. "Geochemical evolution of the indian ocean mantle: dupal anomaly and role of the kerguelen plume." Doctoral thesis, Universite Libre de Bruxelles, 1992. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212956.
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Smithies, Robert Hugh. "The geochemical evolution of three alkaline complexes in the Kuboos-Bremen igneous province, southern Namibia." Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1005564.
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The Kuboos-Bremen Igneous Province comprises a linear zone of alkaline complexes that intrude Proterozoic and Pan-African rocks and trends in a northeast direction from the northwest of the Cape Province in South Africa into southern Namibia. Of the three most southerly complexes in Namibia. two comprise silicate rocks ranging from nepheline syenite to alkali-granite and are called the Grootpenseiland and Marinkas Kwela Complexes (GPC and MKC). The Marinkas Kwela Carbonatite Complex is the third and most northerly of the complexes. Isotopic age determinations on a number of rock types from both the silicate complexes yield ages around 520Ma and are consistent with published Pan-African ages for the Province. Each silicate complex shows a migrating locus of intrusion from Siundersaturated rocks in the southwest to Si-oversaturated rocks in the northeast. The complexes overlap in outcrop. The rocks are moderately to highly felsiC and none reflects primary magma compositions. The Si-undersaturated rocks from both complexes include side-wall cumulates formed from magmas that fractionated alkali-feldspar, clinopyroxene and amphibole. Foyaites also occur in the MKC and have a compositional range reflecting alkali-feldspar fractionation and, probably, some interaction with dolomite country rocks. Major and trace element data suggest that critically saturated alkali syenites occurring in both complexes evolved via protracted feldspar fractionation, and that critically saturated alkali-feldspar syenite occurring only in the GPC is a cumulate. The two rock types cannot be related genetically. Of the SI-oversaturated rocks in both complexes, those in the compositional range monzonite to granite were intruded before alkali-granites. Compositional diversity amongst the former reflects fractionation of feldspar and of mafic phases, but that process cannot genetically link the rocks to the alkali-granites. Isotopic compositions of Sr and Nd indicate that the silicate magmas were derived from an upper mantle source region characterised by low time-integrated Rb/Sr ratios and high time-Integrated Sm/Nd ratios, However, the evidence of Sr and 0 isotopic data is that the Si-oversaturated melts possibly interacted with a crustal component. presumably the Proterowlc rocks of the Namaqua Metamorphic Province. This interaction may explain the occurrence of apparently co-genetic rock series that evolved on opposite sides of the feldspar join in Petrogeny's Residua System. The Marinkas Kwela Carbonatite Complex was emplaced before the final intrusive phases of the MKC and exhibits unusually pronounced late-stage enrichment in manganese. The earliest intrusive rocks in the complex were nepheline syenites which were fenitised by later intrusions of sôvites. Although the commonly occurring magmatic sequence of sôvite-beforsite-ferrocarbonatite is observed at Marinkas Kwela, sôvites do not appear to have been parental to beforsites. Removal of apatite and early crystallisation of magnetite distinguish magnetite-rich beforsite from co-genetic apatite-rich beforsite. Two further magmatic sequences. the first from apatite-rich beforsite through ferrocarbonatite to Mn-rich ferrocarbonatite (high Fe/Mn) and the second from magnetite-rich beforsite to Mn-rich ferrocarbonatite (low Fe/Mn). reflect fractionation of dolomite and of dolomite+magnetite respectively.
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Mannan, A. (Abdul). "Stratigraphic evolution and geochemistry of the Neogene Surma Group, Surma Basin, Sylhet, Bangladesh." Doctoral thesis, University of Oulu, 2002. http://urn.fi/urn:isbn:9514267117.
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Abstract
The Surma basin is a part of the Bengal Basin situated in northeastern Bangladesh. The presence of eight gas fields and one oil field makes this an area that is interesting both economically and geologically. In spite of detailed geological and geophysical investigations, information available on palynostratigraphy and geochemistry for the area is scanty.
The aim of the present work was to investigate the palynological assemblages, mineralogy and geochemistry of the Surma Group (SG) sequences in Surma Basin, Bangladesh. Core samples (n = 188) were gathered from the wells following: Patharia well-5, Rashidpur well-1, Atgram well-IX, Habiganj well-1, Kailastila well-1 and Fenchuganj well-2. They were provided by BAPEX (Bangladesh Petroleum Exploration Company). X-ray Fluorescence (XRF), Atomic Absorption Spectrometry (AAS), Loss of Ignition (LOI), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used for geochemical and mineralogical study of shale samples. In the palynological study, the distributions of pollens and spores were determined. For data analysis, SPSS computer programme was used.
Palynological assemblages of the Surma Group of sedimentary sequence of Bangladesh include taxa range in age from the lower Miocene to the Upper Miocene which can be potentially used in dating and correlation. The Lower Miocene interval is correlated with the Simsang Palynological Zone IV of Meghalaya, India and the Bengal Palynological Zone (BPZ) V. The Upper Miocene is correlated with the Simsang Palynological Zone IV of Meghalaya, India and the BPZ Zone V of Bengal. They were deposited in two types of paleoenvironments ranging from the brackish type to shallow marine to brackish. The sequence contains reworked palynomorphs of BPZ IV and III namely Meyeripollies naharkotensis, Polypodiesporites Oligocenecus, Palmepollenities Eocencus and ornamented Tricolpate pollen of the Eocene-Oligocene age which are mainly encountered in the lower Miocene sediments indicative of increased tectonic activity in the area. Geochemical ratios (SiO2/ Al2O3, Cu/Zn, Maturity = K2O+ Al2O3/Na2O+MgO, Rb/K2O, K2O/Na2O, Cr/Rb, Zr/Rb, V/Rb, Th/U etc.) were useful for determining grain size, maturity, tectonics and environment of deposition. High Ba enrichment was detected in the Patharia well-5 and showed high surface water productivity and diagenetic mobilisation. Tectonic descrimination was achieved using SiO2 and K2O/Na2O ratio. XRD analysis revealed the minerals kaolinite, illite, chlorite, illite/smectite (I/S) and kaolinite/smectite (K/S) mixed layers. Kaolinite/Smectite here reported for the first time in Bangladesh. Clay mineral analyses provided evidence for diagenesis. Smectite diagenesis and dehydration have contributed to the generation of overpressure in the Bhuban Formation in the Patharia well -5.
Geochemical ratios of the present study from the Surma Basin is undoubtedly a powerful technique and can be applied to any sedimentary basin analysis to infer the palaeoenvironment, palaeoclimate and palaeotectonics.
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Pimentel, Marcio Martins. "Late Proterozoic crustal evolution of the Tocantins Province in central Brazil : an isotopic and geochemical study." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280038.
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Wong, Po-wan Kenny, and 王步雲. "Paleozoic tectonic evolution of the Chinese Altai Orogen: contraints from geochemical and geochronologic studies ofmafic rocks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44920878.
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Riter, Joyce Christine Alexis. "Geochemical and tectonic evolution of the Colorado Plateau mantle lithosphere : evidence from Grand Canyon mantle xenoliths /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Leaver, Julie. "The petrological and geochemical evolution of the Late Proterozoic Lithospheric mantle below Seiland Province northern Norway." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296735.
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Richer, Mathieu. "Volcanic framework, geochronology and geochemical evolution of the El Dorado gold district, El Salvador, Central America." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/32325.
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The Pliocene El Dorado epithermal Au-Ag vein system, located in northern El
Salvador, is hosted in Tertiary volcanic rocks that accumulated along the Caribbean plate
margin in response to the subduction of the Farallon/Cocos plate. The volcanic basement
rocks in the district form a >400-meters-thick sequence of basaltic to andesitic lava flows
and sedimentary rocks that were intruded by porphyritic basaltic to andesitic domes and
dikes during the late Miocene. These rocks petrologically correlate with the Eocene to
Miocene Morazan Formation of El Salvador. Mineralization in the district is constrained
between ~4.7 and 4.0 Ma, and likely occurred closer to the lower limit according to field
relationships and ⁴⁰Ar-³⁹Ar ages of bracketing volcanic rocks. The waning stage of
hydrothermal activity coincides with the onset of a period of extensive Pliocene felsic
volcanism (~4.0 to ~3.3 Ma) based on field relationships and ⁴⁰Ar-³⁹Ar geochronology of
hornblende-biotite-phyric dacitic to rhyolitic lava flows, domes and related pyroclastic
and sedimentary rocks. Pliocene and possibly younger post-mineral basaltic to andesitic
lava flows cap the volcanic sequence.
The sub-arc mantle source that generated primary magmas during the Miocene
and Pliocene is compositionally constrained between a depleted- and an enriched-MORB.
Selected trace element ratios (e.g., Ba/Th) suggest that subducted sediments and/or slabderived
fluids account for some of the geochemical variation in volcanic rocks at El
Dorado. The Sr, Nd and Pb initial (and measured) isotopic ratios of all volcanic rocks are
remarkably uniform, independent of age or rock type, likely indicating that the isotopic
composition of Tertiary magmas was buffered by the mantle, and possibly, by a constant
input of hemipelagic sediments during the Miocene and Pliocene. Short mixing trends in
Pb isotopes further suggest that Pliocene felsic magmas were generated from partial
melting of previously emplaced sub-arc igneous rocks, isotopically equivalent to the high
²⁰⁶Pb /²⁰⁴Pb volcanic basement rocks in the district, by introducing low ²⁰⁶Pb/²⁰⁴Pb
mantle-derived basaltic magmas in deep crustal hot zones (Annen et al., 2006).
The current exposures from north to south at El Dorado appear to represent an
oblique cross-section through the volcanic and hydrothermal system associated with the
low-sulfidation epithermal vein system. North and Central El Dorado, being dominated
by the mafic basement rocks, represent the deeper parts of the system. South El Dorado is
clearly the shallow level of the epithermal vein system, preserving the surface and
shallow sub-surface environments, including the sinters and contemporaneous to postmineral
felsic volcanic rocks. The distribution of volcanic facies along Titihuappa River,
a regional fault zone on the extreme south of the district, appears to define the
northwestern margin of the Pliocene Rio Titihuappa basin, potentially representing a
volcano-tectonic depression that formed during and/or shortly following vein formation.
The Miocene to Pliocene transition in Central America is marked by a trenchward
shift in subduction and associated magmatic activity (Weyl, 1980). The volcanic record
preserved at El Dorado suggests that the Pliocene magmatic event led to the formation of
compositionally evolved hydrous magmas that likely ponded in mid- to upper-crustal
magma chamber(s). These magma chambers potentially represented the critical heat
engine to the once active hydrothermal system and a possible source of precious metals.
Extensive felsic volcanism associated with the Pliocene magmatic system, possibly in
conjunction with caldera formation, may have suppressed the heat engine to
hydrothermal activity.
References
Annen, C, Blundy, J.D., and Sparks, S.J., 2006, The genesis of intermediate and silicic
magmas in deep crustal hot zones, Journal of Petrology, vol. 47, p. 505-539.
Weyl, R., 1980, Geology of Central America: Berlin-Stuttgart, Gebruder Borntraeger,
371 pp.<br>Science, Faculty of<br>Earth, Ocean and Atmospheric Sciences, Department of<br>Graduate
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Garnaut, Kelli. "Geochemical classification of the mafics in the Granites-Tanami Inlier and their implications for the regions evolution /." Title page, contents and abstract only, 1995. http://web4.library.adelaide.edu.au/theses/09S.B/09s.bg234.pdf.
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Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1996.<br>Australian National Grid reference The Granites Sheet (SF-52-3) 1:250 000. Includes bibliographical references.
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Harris, Nancy Ruth 1970. "Isotopic, geochemical, and geochronological constraints on the origin and evolution of Cenozoic volcanism, Baikal Rift Zone, Siberia." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/54432.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998.<br>Includes bibliographical references.<br>The Cenozoic Baikal Rift Zone, one of the world's major continental rifts, is expressed as an approximately 1800 km-long southwest-northeast oriented system situated along a suture between the Archean Siberian craton and younger Paleozoic fold belts. Oligocene to Recent age volcanic rocks and associated mantle xenoliths are distributed in three major regions of the rift zone: the Udokan volcanic field in the northeast, the Vitim volcanic field -200 km southeast of Lake Baikal, and a broad zone of volcanism to the southwest of Lake Baikal. This large-scale study investigates the geochemical evolution of the Baikal Rift Zone volcanism using major element, trace element, and isotopic (Sr, Nd, and Pb) geochemistry, as well as 40Ar/39Ar geochronology. In addition, a detailed isotopic study of megacrysts provides insight into the relationship between megacrysts and host lavas and the nature of the lithospheric mantle. Results of this study suggest that the source region for Baikal Rift Zone volcanic rocks is remarkably homogeneous considering the large region and time span over which these rocks erupted, and that crustal contamination has not been a significant controlling factor. The Tunka Basin, Oka Plateau, and Tuva volcanic fields in the western Baikal Rift Zone, and the Vitim volcanic field southeast of Lake Baikal, have a fairly restricted compositional range from basaltic andesite, alkaline basalt and hawaiite, to basanite and mugearite. In the Udokan volcanic field in the northeast, a more evolved series of rocks ranging to trachytic compositions erupted across the suture between the Archean craton and Paleozoic fold belts. Major and trace elements indicate that fractional crystallization of pyroxene, olivine, and plagioclase produced the observed range in compositions. The trace element and isotopic compositions of Baikal Rift Zone volcanic rocks are comparable to those observed in ocean island basalts. The Sr, Nd, and Pb isotope systematics can best be explained by mixing between the end-member mantle components DMM ( typical of the depleted source of MORB mantle) and EMI (enriched mantle type 1). Megacrysts of clinopyroxene, amphibole, garnet, biotite, and anorthoclase mirror the isotope systematics of the host volcanic rocks, and suggest that the megacrysts were derived from a melt closely related to their host rocks. Furthermore, megacrysts of clinopyroxene, as well as Cr-diopside from spinel lherzolites, have an unradiogenic Pb isotopic composition that may be representative of the EMI-like composition of the subcontinental lithospheric mantle.<br>by Nancy Ruth Harris.<br>Ph.D.
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Tice, Peter. "Petrology and Geochemical Evolution of the East Hill Suite of the Mont Saint-Hilaire Alkaline Plutonic Complex." ScholarWorks@UNO, 2010. http://scholarworks.uno.edu/td/1229.
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The Mont Saint-Hilaire alkaline complex, Québec, is a Cretaceous rift-related intrusion comprising two gabbroic suites and the East Hill suite, an assemblage of several distinct nepheline syenites and evolved syenitic rocks. Whole-rock analysis of the East Hill suite reveals two fractionation trends, one which is described by the syenitic lithologies and one by the evolved syenites and syenoids. A lamprophyric unit stands on its own, geochemically, consistent with typical lamprophyre petrogenesis. Whole-rock geochemistry of the East Hill suite shows moderate silica content but highly alkaline rocks, enriched in Mn, Zn, Zr, Y, and Ce. Chlorine and sulfur are important and present in abundant secondary sodalite and pervasive microsulfides. Mineral geochemistry indicates decreasing oxygen fugacity with cooling, and phases such as titanite (present) and aenigmatite (absent) defined boundaries in fO2 – T space. Oxygen fugacity data combined with petrography and geothermometry defined an 2 fO – T curve for the East Hill suite magma, revealing that the oxygen fugacity ranged between approximately 10-10 bar at intrusion down to 10-25 bar subsolidus, and that, owing to non-linearity of oxygen buffers, the 2 fO – T path crossed below QFM early, went above QFM late in the crystallization history and then above HM with cooling. A similar procedure applied to sulfur fugacity generated a trend of initial increase from about 10-4 to 10-2 bar followed by decreasing sulfur fugacity with cooling down to approximately 10-8 bar. The oxygen trend implies that earlier suggestions that oxidation of iron drove the evolution of pyroxenes towards aegirine are incorrect. Textural evidence of abundant alteration and secondary mineralization suggests subsolidus action of alkaline fluids. Contrary to previous studies, most sodalite in the East Hill suite is not primary but is the product of reaction of nepheline with chloride-rich fluids after crystallization. Sodalite pseudomorphs continued to react with these fluids, whose chemistry changed with time to silica- then carbonate-rich, resulting in further reactions that led to natrolite and dawsonite deposition, accompanied by late-stage rhodochrosite. It is hypothesized that the silica- and carbonate-rich phase of these fluids caused the decomposition of a melilite groundmass in the lamprophyre to a natrolite-calcite assemblage.
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Mathia, Eliza Joanna. "Geological evaluation of Posidonia and Wealden organic-rich shales : geochemical and diagenetic controls on pore system evolution." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/2783.
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Free gas in shales occurs mainly in larger mesopores (width >6 nm) and macropores (width >50 nm) and is likely to be the first or even main contributor to gas production. Because evaluation of the storage capacity and final recovery of gas depends on distribution and connectivity of these pores, their correct quantification has become a focus point of advanced research. A major step for understanding pore systems in organic rich shales was made by recognition that under increasing thermal stress, decomposition of kerogen should progressively lead to development of organic porosity. Despite this, many questions concerning fate of organic porosity in organic rich rocks still remain unresolved. To date, several important attempts to link evolution of organic pores with maturation and organic matter content gave inconclusive and contradictory results. In this study, pore systems of the Lower Jurassic Posidonia and Lower Cretaceous Wealden shale, representing different mudrock types and covering a range of maturities, have been characterised. By integrating geochemical and petrophysical measurements, and with a detailed analysis of microscopic images we offered a unique approach for measuring porosity and pore characteristics on micrometre and centimetre scales with thorough understanding for a micrometer lithological variation. Key aims were to quantify the evolution of porosity associated with both organic matter and inorganic rock matrix as a function of maturity, and address the influence of mudrock heterogeneity on porosity change. Our experiments revealed a non-linear trend of porosity change with maturity in pores of all sizes, with an initial drop in the oil window as a result of mechanical compaction, chemical diagenesis, as well as pore-filling oil and bitumen. At comparable maturities, porosity and distribution of pores depend on the content of clays, organic matter, microfossils, silt grains and pore filling cement. In both Posidonia and Wealden, macropores (> 50 nm) account for merely up to 20% of total porosity physically measured, with the lowest percentage in the least mature samples. It was also demonstrated that gas sorption micropores are controlled by the amount of organic matter and clay minerals, and thus their microporous nature was confirmed. In terms of organic porosity development, we provided evidence that organic matter content and the path of its thermal decomposition control total porosities of the gas window shale. Importantly, neoformed intraorganic porosity is highly heterogeneous with 35% of organic particles containing visible pores (> 6 nm in diameter), and porosities of individual particles ranging from 0–50%. As a key result, we confirmed that porous zones in the gas window are associated with sites of bitumen retention and degradation. That indicates iii that the location of potential reservoirs of free gas should be linked to rigid zones, such as fossiliferous faecal pellets, or compaction shadows of mineral grains. Combined mercury injection and SEM data also showed that visible but potentially isolated macropores are connected, but only through throats below 20 nm. With the evolution of the porous network of bitumen saturating the shale matrix in the gas window, connectivity of the system changes from inorganic to organic dominated. The size of the pore throats, and the connectivity of the organic system in shales are likely key controls on the delivery of gas from pore to fracture and then to wellbore.
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Külahci, Doğan Gullu Deniz. "Chronological, magmatological and geochemical study of post-collisional basaltic volcanism in Central Anatolia and its spatio-temporal evolution." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22593/document.
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Cette thèse est consacrée à la caractérisation pétrologique et géochimique des basaltes quaternaires post-collisionnels d’Anatolie centrale (strato-volcans Erciyes et Hasandağ et volcanisme dispersé d'Obruk-Zengen et de Karapınar), en se focalisant sur l’évolution spatio-temporelle de ce magmatisme de la Cappadoce (Turquie). Par la géochronologie K-Ar, la coexistence de basaltes alcalins et calco-alcalins a été démontrée, parfois dans un même lieu et à la même époque. Par ailleurs, nos résultats montrent aussi que ces basaltes peuvent être très jeunes (quelques milliers d’années seulement). La minéralogie des basaltes quaternaires de la Cappadoce est la suivante : plagioclase, olivine, clinopyroxène, orthopyroxène et oxydes (magnétite, ilménite). Pourtant, seuls les basaltes de l’Erciyes contiennent de l’orthopyroxène, alors que ceux du Hasandağ et du volcanisme dispersé d’Obruk-Zengen et de Karapınar en sont dépourvus. Les phénocristaux de plagioclases présentent souvent des figures de déséquilibre, attribuées au processus de mélange magmatique : zonages complexes (normaux, inverses, oscillatoires), richesse en inclusions vitreuses, figures de résorption. Toutefois, la minéralogie observée est compatible avec un processus de cristallisation fractionnée dominant. Les géobaromètres utilisés montrent que l’origine des magmas de l’Erciyes est plus superficielle que celle des autres sites. Les résultats en géochimie confirment la dualité minéralogique observée entre l’Erciyes et les autres secteurs, ainsi que les caractères alcalins (néphéline normative) et calco-alcalins de basaltes parfois contemporains. Tous les basaltes étudiés sont enrichis en LREE et LILE. Les données isotopiques (Sr, Nd, Pb, O) montrent l’importance de la source lithosphérique enrichie. L’ensemble des données géochimiques montre aussi la signature d’autres sources et processus comme la contamination par la croûte continentale et l’héritage d’une ancienne subduction<br>This thesis revealed the petrological and geochemical characterization of post-collisional Quaternary basalts of Central Anatolia (Erciyes and Hasandağ stratovolcanoes, and dispersed volcanisms of Obruk-Zengen and Karapınar), focusing on the spatiotemporal evolution of the magmatism in Cappadocia (Turkey). K-Ar geochronology indicated the coexistence of alkaline and calc-alkaline basalts from the same location and age. Moreover, the results also show that these basalts may be very young (a few thousand years). The mineralogy of Quaternary basalts from the Cappadocia is as follows: plagioclase, olivine, clinopyroxene, orthopyroxene and oxides (magnetite, ilmenite). Orthopyroxene is observed only in basalts of Erciyes, while it is lacking in Hasandağ and dispersed volcanisms of Obruk-Zengen and Karapınar. The plagioclase phenocrysts often exhibit disequilibrium features attributed to magma mixing process: complex zoning (normal, inverse, oscillatory), concentric zones rich in melt inclusions, resorption features. However, the observed mineralogy is consistent with a dominant fractional crystallization process. The estimated geobarometer show that the origin of magmas of Erciyes is shallower than the other settings. The results in geochemistry confirm not only the mineralogical duality between Erciyes and the other settings but also the coexistence of alkaline (normative nepheline) and calc-alkaline characters of contemporary basalts. All studied basalts are enriched in LREE (Light Rare Earth Elements) and LILE (Large Ion Lithophile Elements). The isotopic data (Sr, Nd, Pb, O) indicate the importance of enriched lithospheric source. All geochemical data also display the signature of other sources and processes such as contamination by the continental crust and heritage of a former subduction
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Restrepo, Pedro Alonso. "Late Precambrian to Early Mesozoic tectonic evolution of the Colombian Andes, based on new geochronological geochemical and isotopic data." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187450.
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⁴⁰Ar/³⁹Ar and U/Pb geochronology of the basement rocks in the Colombian Andes confirm the presence of the Grenvillian age high metamorphic grade belt . The Grenvillian, or locally known as Nickerie-Orinoquiense orogenic belt, is exposed within basements uplifts along the Eastern Cordillera of Colombia and the Sierra Nevada of Santa Marta in the Caribbean coast. Rare Earth element geochemistry and petrology indicate that the Nickerie-Orinoquiense basement rock's protoliths are dominantly of continental affinity, now consisting mainly of metapsammites, metavolcanics and metaplutonic rocks metamorphosed to granulite facies PT conditions. Nd crustal residence ages and U/Pb zircon data indicate variable involvement of 'older' Late Archean - Early Proterozoic components and 'younger' ~ 1.1 Ga additions, which were tectonically mixed during the Nickerie-Orinoquian collisional metamorphic episode. Low metamorphic grade rocks that overlie the Nickerie-Orinoquian basement are exposed along the Eastern Cordillera of Colombia at the Quetame-Floresta-Santander massifs, Périja Range and Merida Andes. A U/Pb zircon age obtained from a synkinematic pluton structurally concordant with the low metamorphic grade belt from the Santander Massif, yielded a 477 ± 16 Ma, indicating a Mid-Ordovician regional greenschist to amphibolite facies metamorphic event for these rocks. The latter is referred-to as the 'Caparonensis Orogeny' in the Venezuelan Andes. Rare Earth Element geochemistry and petrologic data indicate that the low metamorphic grade belt consists of a thick supracrustal sequence i.e. metapelitic-metapsammitic sequence with minor crosscutting mafic dikes. Additional trace element discrimination plots indicate that the Caparonensis synkinematic plutons are of continental arc affinity. ⁴⁰Ar/ ³⁹Ar geochronology, petrology and field observations in Santander Massif, indicate a widespread regional metamorphic overprint took place in Late Triassic-Early Jurassic time. This event was the result of a thermal welt associated with back-arc extension and concomitant intrusion of a high volume of calk-alkalic plutons. Deposition of a thick molassic sequence (2000-4000 m) followed, flanking the uplifted region. The lower Paleozoic metamorphic rocks were elevated from greenschist to sillimanite (locally kyanite) PT metamorphic conditions and the Mid-Upper Paleozoic sedimentary cover was locally metamorphosed from greenschist to lower PT metamorphic conditions, as a function of relative distance to the plutonic centers at time of metamorphism.
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Scherer, Hannah Howell. "Field, geochronologic, and geochemical constraints on the early mesozoic paleogeographic and tectonic evolution of the central Klamath Mountains, California /." May be available electronically:, 2006. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Mamberti, Marc. "Origin and evolution of two distinct Cretaceous oceanic plateaus accreted in Western Ecuador (South America) : Petrological, geochemical and isotopic evidence." Phd thesis, Université Joseph Fourier (Grenoble), 2001. http://tel.archives-ouvertes.fr/tel-00688387.
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La géologie de l'Equateur se distingue de celle du reste des Cordillères andines par la présence de terrains océaniques qui s'accrètent successivement à la marge depuis la fin du Crétacé jusqu'au Paléocène. Ces terrains exotiques sont constitués de fragments de deux plateaux océaniques du Crétacé inférieur (123 Ma) et supérieur (90 Ma) et de plusieurs arcs insulaires (100 à 40 Ma). Dans la Cordillère occidentale, le plateau crétacé inférieur et les terrains océaniques du crétacé supérieur (plateau et arcs insulaires) s'accrètent respectivement à 85-80 Ma et 70-65 Ma. Le plateau océanique daté à 123 Ma est constitué: (i) de cumulats basiques et ultrabasiques (série de San Juan) et (ii) de basaltes en coussins et de dolérites massives recoupés par des petites intrusions de gabbro sub-doléritique. Les cumulats forment une série continue depuis des dunites et wehrlites jusqu'à des gabbros à clinopyroxène. Basaltes, dolérites et gabbros présentent tous les caractères de basalte de plateau océanique (OPB; MgO = 7%; spectres de terres rares plats, pas d'anomalie négative en Nb et Ta). Les compositions isotopiques (Nd et Pb) des cumulats et de l'ensemble basalte-dolérite sont identiques et démontrent que toutes ces roches dérivent d' une source mantellique enrichie. Les picrites et les basaltes enrichis ou non en MgO, associés à des dolérites et des gabbros, représentent des témoins accrétés du plateau océanique crétacé supérieur caraïbe. Les picrites (MgO -20 %) sont appauvries en terres rares légères, peu radiogéniques en Pb et caractérisées par des eNd élevés (+8 à +10). Les basaltes riches en MgO (9-10%) sont enrichis en terres rares légères. La géochimie en éléments traces des basaltes pauvres en MgO est identique à celle d'OPB. Par contre, les rapports isotopiques du Pb des basaltes, riches en MgO ou non, sont très élevés indiquant que toutes ces laves dérivent d'une source enrichie de type HIMU, caractère commun à tous les basaltes du plateau caraïbe .
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Stechern, André [Verfasser]. "Decoding magma plumbing and geochemical evolution of active volcanoes of the Central Andes (North Chile) with petrological methods / André Stechern." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1074968824/34.
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Barnes, Elspeth M. "The rare element Little Nahanni Pegmatite Group, NWT : studies of emplacement, and magmatic evolution from geochemical and Li isotopic evidence." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27027.
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Rare element pegmatites represent some of the last stages of igneous differentiation and are influential in element redistribution in the upper crust, leading to significant enrichment/depletion of various trace elements. Research into the processes that form these intrusions increases our understanding of the geochemical evolution of silicate earth and improves the potential for successful pegmatite exploration.
This study focussed on the dikes comprising the rare element Little Nahanni Pegmatite Group (LNPG), Mackenzie Mountains, northern Canadian Cordillera. These peraluminous dikes have high concentrations of several rare elements, e.g., Li (up to 14,000 ppm), Cs (up to 500 ppm), Ta (up to 190 ppm), and Rb (up to 7,500 ppm). Orientation of the dikes was influenced during emplacement (2-3 kbar, ~400-500 °C) at ~90 Ma (apatite, U-Pb) by pre-existing foliation in the strongly deformed, stratified host rock of the Fork anticlinorium (axial planar cleavage and bedding).
Differences in ⁴⁰Ar/³⁹Ar dates on pegmatite minerals (muscovite 77.1±3.6 and ~80 Ma and lepidolite 65.8±0.8 Ma) indicate the presence of an elevated paleogeothermal gradient (~60°C/km). Structural and contact metamorphic evidence identify a local heat source within the anticlinorium that may have been the source chamber for the dikes.
Whole rock trace element concentrations and ratios, mineralogical and textural variations, and fractionation of Li isotopic ratios (δ7Li = -0.94‰ to +11.36‰) record a range of magmatic fractionation. Approximately 85% of the dikes are spodumene-rich, with discontinuous REEN patterns and low degrees of Li isotope fractionation, the remaining ~15% show greater magmatic fractionation, with little spodumene, and have flat or listric REEN patterns and strongly fractionated Li isotopic ratios. The replication of the REEN patterns by P and F saturation (mineral precipitation and fluid separation), illustrates the influence of flux components on the composition of late stage melts.
The Li isotope composition of rapidly crystallized, co-precipitated mineral assemblages appears to show the retention of a kinetic isotopic fractionation signature; providing a potential method to assess the chemical equilibrium of the system.
This integrated study advances our understanding of rare element pegmatite formation in several aspects, in particular the role of fluxes in their geochemical evolution.
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Simpson, Clayton A. "Constraints on proterozoic crustal evolution from an isotopic and geochemical study of clastic sediments of the Gawler Craton, South Australia /." Title page, contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09SB/09sbs613.pdf.
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Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1995.<br>Map sheets: Lincoln (SI 53-11) 1:250 000 Tumby Bay (SI 53-6129) 1:100 000. Includes bibliographical references.
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Anderson, Eric Douglas. "PETROLOGIC, GEOCHEMICAL, AND GEOCHRONOLOGIC CONSTRAINTS ON THE TECTONIC EVOLUTION OF THE SOUTHERN APPALACHIAN OROGEN, BLUE RIDGE PROVINCE OF WESTERN NORTH CAROLINA." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/820.
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The Blue Ridge Province of western North Carolina contains a wide variety of metamorphosed igneous and sedimentary rocks that record the tectonic effects of Precambrian and Paleozoic orogenic cycles. Tectonic interpretations of the events that led to the present configuration are varied and often conflicting. This investigation examines metamorphosed mafic rocks that are widely interpreted to have formed during the closure of ocean basins. Metabasites, and specifically eclogites, have a tendency to mark tectonic sutures and frequently preserve pressure (P), temperature (T), and age data (t) that can be gleaned from mineral equilibria and U-Pb isotopic compositions. As such, the examination of the metabasites is considered the key to understanding the orogenic history of the southern Blue Ridge where these metabasites occur. Chapter 2 is an investigation of the retrograde reactions related to the decompression of sodic pyroxenes that react to form diopside-plagioclase-hornblende-quartz symplectites as stability fields are overstepped during isothermal decompression. In Chapter 3 metabasites from the central and eastern Blue Ridge are re-examined and P-T pathways of these lithologies are determined. The argument is made that the Taconic orogeny of the Blue Ridge is the result of a continent-continent collision event that culminated in a mega-mélange that coincides with the Cullowhee terrane and the eastern Blue Ridge mélange of western North Carolina. Chapter 4 contains the results of a geochronological investigation of the Precambrian basement complex of the eastern Great Smoky Mountains. Chapter 5 is a whole rock geochemical study of the same basement complex. In Chapter 6, a potential lithologic correlation between the southern Blue Ridge basement and the Arequipa- Antofalla block of Peru is discussed. The geologic history of western South America from the Mesoproterozoic through Cambrian is summarized, a potential isotope-based lithologic correlation is proposed, and the early tectonic history of the central Blue Ridge is discussed. Chapter 7 contains brief summaries of Chapters 1-6.
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Bouilhol, Pierre. "Structural, petrological and geochemical constraints on transfer and evolution of arc magmas in the mafic-ultramafic Sapat Complex (Kohistan; Northern Pakistan) /." Zürich : Eidgenössische Technische Hochschule, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18081.
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Gupta, K. D. "Tectono-stratigraphic evolution of deep-marine clastic systems in the Eocene Ainsa and Jaca basins, Spanish Pyrenees : petrographic and geochemical constraints." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1445277/.
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The Early-Middle Eocene deep-marine siliciclastic systems of the Ainsa and Jaca foreland basins, Spanish Pyrenees, have been used to develop and support generic models for deep-marine deposits, from process-based to system-based perspectives, and these ideas have been applied globally by academics and industry alike. Despite the considerable amount of research into many aspects of sedimentology of the Ainsa and Jaca basins, the widely-adopted stratigraphic correlation of sandstone systems in the Ainsa and Jaca basins is very poorly-constrained, although the stratigraphy and accurate correlation of sandstone bodies along the basin are paramount to any depositional models that arise from any studies in the Ainsa and Jaca basins. This study used petrography, geochronology, major and trace element geochemistry to better constrain and understand the evolution of the basinal sediments and fingerprint the sandstone bodies within the Ainsa-Jaca basin as a means of correlation. An additional pilot study was carried out on carbon and oxygen isotopic signatures of larger foraminifera from the outcrops. Three discrete sediment sources are recognised for the deep-marine Early to Mid-Eocene sandstone bodies in the Ainsa and Jaca basins. The arenite composition in the Ainsa and Jaca basins is interpreted to be mainly controlled by synsedimentary tectonic processes that led to changes in sediment sources during basin evolution. Comprehensive petrography data shows that each system of the Ainsa and Jaca basins has a characteristic petrofacies. Three main petrofacies are recognised and on the basis of these petrofacies, a revised correlation of the sandy systems is proposed between the more proximal Ainsa basin, and the more distal Jaca basin sediments, now separated by the Boltana anticline, across which it is impossible to actually trace out individual beds or sandstone packages between both basins. The new correlation scheme, along with the newly identified sediment provenances, changes the current (published) understanding of the Ainsa and Jaca basins evolution and palaeogeography.
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Foulkes, Susan Elizabeth. "New geochemical constraints on the genesis of the Gamsberg zinc deposit, Namaqualand Metamorphic Province, South Africa." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1012084.
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The base metal massive sulfide deposits of the Aggeneys-Gamsberg (A-G) District are hosted within the Mesoproterozoic Bushmanland Group of the Namaqua-Natal Metamorphic Complex in the Northern Cape Province of South Africa. The district displays an apparent eastward trend in the economic concentration of base metals (+ barite) from relatively Cu-Pb-rich, Ba-poor mineralisation at Black Mountain to Zn- and Ba-rich ores at Gamsberg. Base metal sulfides at Gamsberg are restricted to the so called Gams (Iron) Formation which comprises a sulfidic mineralized unit (“B”) enveloped within a sequence of meta-sedimentary units (“A” and “C”). The aim of the study was to shed further light on the genesis and chemical evolution of the sulfide mineralisation at Gamsberg in the context of the entire A-G District, by interrogating further the apparent district-wide trend in base metal distribution. The Gams Iron Formation was sampled and studied from one key drill core intersection (“G1”) which intersects the largest part of it as described elsewhere; a small number of additional samples from a second drill core (“G2”) complemented the main sample suite. Minerals that make up the silicate assemblages across the studied section include quartz, garnet, pyroxene, pyroxenoid, phyllosilicates, carbonates, amphiboles, oxides (chiefly magnetite) and graphite. In a stratigraphic context, the mineralogical variations conform directly to those documented in the relevant literature from the Gamsberg locality. These are coupled, where possible, with mineral-chemical profiles of selected silicate species which replicate those of bulk-rock compositions, particularly with respect to Mn, Fe and Ca in the upper C Unit of the studied section. These signals collectively track the characteristic transition from a terrigenous, siliciclastic sediment-dominated footwall to an exhalative sediment-dominated hanging wall to the sulfide mineralisation as also seen in similar deposits elsewhere, particularly with respect to the characteristic Mn-rich signature increasingly observed in the hanging wall C Unit. The foregoing suggests that the examined section faithfully records the interpreted primary stratigraphy of the deposits, despite the complex structural and metamorphic overprint that characterises the region. This facilitates a stratigraphic analytical approach on the sulfidic Unit B, through a combination of mineral-chemical and stable isotope analyses. Dominant sulfides in Unit B are sphalerite and pyrite, with lesser pyrrhotite and minor galena. Sphalerite shows high and generally invariant contents of Fe (mean 12.18wt%, as FeS) whereas Zn anti-correlates with Mn (mean 5.58wt%, as MnS). Isotopic analyses for S, Fe and Zn in hand-picked sphalerite and pyrite separates were used with a view to providing new evidence for chemical and isotopic variation within the sulfide ore-body in a vertical (i.e. stratigraphic) sense, discuss the implications thereof, and ultimately interpret the new data in light of similar existing data from the A-G District and elsewhere. The δ³⁴S data for pyrite (plus a single pyrrhotite grain) and sphalerite from both cores G1 and G2 show comparable compositional ranges between 22.9 and 30.4‰ and between 27 and 30.1‰ respectively. The δ⁵⁶Fe data for pyrite show a range between -1.85 and 0.19‰, whereas seven sphalerite separates have a very narrow range of δ⁶⁶Zn from 0.06 to 0.20‰. The atypically high sulfur isotope data reported in this study are interpreted to reflect sedimentary deposition of primary sulfide ore at Gamsberg from an isotopically highly evolved seawater sulfate source through large-scale Rayleigh fractionation processes. Thermogenic sulfate reduction is proposed to have been the main reductive mechanism from seawater sulfate to sulfide, given the absence of very low δ³⁴S data for sulfides anywhere in the A-G District. By contrast, the δ⁶⁶Zn values for sphalerite are for all intents and purposes invariant and very close to 0‰, and therefore suggest little Zn isotope fractionation from an original exhalative fluid source. On this evidence alone, Zn isotopes therefore appear to hold little promise as a proxy of the chemical and isotopic evolution of SEDEX deposits in space and time, although this can only be verified through further application in the broader A-G District and similar deposits elsewhere. The apparent decoupling of Zn and S isotopes in the Gamsberg sulfide deposit, however, points towards diverse sources of these two components, i.e. ascending metalliferous brines versus seawater respectively. Finally, pyrite δ⁵⁶Fe data do show a stratigraphic trend of generally declining values up-section, which are interpreted to reflect the influence of broadly coeval precipitation of isotopically heavy Fe-oxides on a broader-scale – now preserved as abundant magnetite through metamorphism. Further work on the iron isotope composition of silicate-and oxide-hosted Fe on a local-to-district scale will assist in testing this interpretation.
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Zhang, Chao [Verfasser]. "Petrological, mineralogical and geochemical investigations of late Mesozoic magmatism in Eastern China : implications for tectonic evolution and crust-mantle interaction / Chao Zhang." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2012. http://d-nb.info/1024681157/34.
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Moore, Nicole E. DeBari Susan M. "Origin and geochemical evolution of mafic magmas from Mount Baker in the northern Cascade arc, Washington : probes into mantle and crustal processes /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=345&CISOBOX=1&REC=14.
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Ward, Emily Geraghty. "DEVELOPMENT OF THE ROCKY MOUNTAIN FORELAND BASIN: COMBINED STRUCTURAL, MINERALOGICAL, AND GEOCHEMICAL ANALYSIS OF BASIN EVOLUTION, ROCKY MOUNTAIN THRUST FRONT, NORTHWEST MONTANA." The University of Montana, 2007. http://etd.lib.umt.edu/theses/available/etd-09262007-094800/.
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The sub-Middle Jurassic unconformity exhumed at Swift Reservoir, in the Rocky Mountain thrust belt of Montana, exposes structures that call for a re-evaluation of the deformation history at this locale. The unconformity separates Late Mississippian Madison Group carbonate (~340 Ma) from the transgressive basal sandstone of the Middle Jurassic (Bajocian-Bathonian) Sawtooth Formation (~170 Ma). Fieldwork established that northwest-trending, karst-widened fractures (grikes) are filled with cherty, phosphatic sandstone and conglomerate of the Sawtooth Formation and penetrate the Madison Group for 4 meters below the unconformity. Clam borings, filled with Sawtooth sandstone, pierce the unconformity surface, some of the fracture walls, and also perforate rounded clasts of Mississippian limestone that lie on the unconformity surface within basal Sawtooth conglomerate. Following deposition of the overlying foreland basin clastic-wedge, the grikes were stylolitized by layer-parallel shortening and buckled over fault-propagation anticlinal crests in the Late Cretaceous-Paleocene fold-and-thrust belt. The model proposes that the grikes record uplift and erosion followed by subsidence as the Rocky Mountain foreland experienced elastic flexure in response to tectonic loading at the plate boundary farther to the west during Early Jurassic; the forebulge opened strike-parallel fractures in the Madison Group that were karstified. The grike system contributes to the secondary porosity and permeability of the upper Madison Group; a major petroleum reservoir in the region. Grikes acted as fluid pathways during basin evolution as seen from the clay mineral assemblage and fluid inclusions contained within the grike fill. Mixed-layer illite-smectite (I/S) indicates that the grikes did not exceed 210∞ C (complete smectite-illite transition). The illite likely resulted from superstaturated fluids flushing through the foreland at the onset Laramide orogeny and may have been coincident with hydrocarbon migration. Hydrocarbon inclusions contained within the grike cements were trapped at temperatures ranging from 110∞-170∞ C; correlative with the clay temperature calculations. Recognition of the fractures as pre-middle Jurassic revises previous models, which related them to Cretaceous fracturing over the crests of fault-propagation folds, substantially changing the understanding of the hydrocarbon system.