Dissertations / Theses: 'Geochemical studies'

1

Das, Nachiketa. "Geochemical studies of Caithness flags." Thesis, University of Glasgow, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277227.

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Zeng, Yi-dong B. "Geochemical studies of microbial lipids." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235488.

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Mavrogenes, John Ashby. "Geochemical studies of earth materials." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/37460.

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Bray, Ian Stephen Johnson. "Geochemical methods for provenance studies of steatite." Thesis, University of Glasgow, 1994. http://theses.gla.ac.uk/2735/.

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The aim of archaeology is the reconstruction of past cultures and the processes behind cultures. Conclusive evidence of cultural contacts between distinct groups of peoples is of great importance. It has long been realised that the study of the raw materials utilised for artifacts that were then moved far from their place of origin is vital in identifying these contacts and this study is concerned with the investigation of one such material - steatite. Steatite is a soft talcose rock that is easily carved even with stone, bone or metal tools. It also has a low coefficient of thermal expansion. These physical properties have resulted in steatite being used as a raw material for the production of many domestic and decorative items throughout the world from prehistoric times until the present. However, the geological formation process has only occurred in a limited number of locations, and hence steatite sources have a relatively restricted geographical distribution. Thus steatite can be seen to fulfil a number of the basic requirements for provenancing, namely limited geographical distribution and extensive utilisation in the past. As a lithic material the physical production techniques do not affect the physical and chemical nature of the material, which may be a considerable problem with characterisation of other archaeological material, eg. ceramics, metal and glass. Thus by characterisation of source material, steatite artifacts of unknown provenance may be compared and their ultimate origin established. However, the formation of steatite is a complex process that often results in a source body that is inhomogeneous, making simple characterisation techniques inadequate. This study seeks to establish differences between source regions and between individual quarries. If a unique pattern in measurable properties can be established, by comparing artifacts to sources, their origin may be established.

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Jones, D. M. "Biodegradation of geochemical markers in pollution studies." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371787.

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Yendle, Peter W. "Chemometric studies of biochemical and geochemical systems." Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.232950.

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7

Elliot, Trevor. "Geochemical indicators of groundwater ageing." Thesis, University of Bath, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278513.

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Feltham, David John. "Trace element studies by proton microprobe analysis." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258766.

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9

Elvy, Shane Brett, University of Western Sydney, Faculty of Science and Technology, and School of Science. "Geochemical studies of base and noble metal compounds." THESIS_FST_SS_Elvy_S.xml, 1998. http://handle.uws.edu.au:8081/1959.7/821.

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The research in this study consisted of two strands. The first consists of noble metal geochemical studies and the second involves base metal supergene processes. The precious metal geochemistry carried out in the scope of this thesis involves palladium and tellurium geochemistry, surface chemistry studies of palladium-bismuth- and tellarium-bearing synthetic minerals, and electrochemical determinations of the inactivity of a variety of primary telluride minerals and alloys. Two new minerals have been found in deposits near Broken Hill, N.S.W. The second section of the research concerns itself with supergene processes in two copper-bearing orebodies. This was carried out by designing a method utilising solution equilibria to predict whether secondary mineral species are precipitating or dissolving in the supergene zones of the Girilambone, N.S.W. and North Mungana, Qld. orebodies. Results found could be used to develop new geochemical prospecting methods in the regions discussed.
Doctor of Philosophy (PhD)

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Elvy, Shane Brett. "Geochemical studies of base and noble metal compounds /." View thesis, 1998. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030821.172648/index.html.

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Thesis (Ph.D.) -- University of Western Sydney, Nepean, 1998.
CD-ROM (appendix) contains complete lists of the species distribution for each water sample; the constant correction spreadsheet; and, the possible stability constants for aqueous ionic species as well as the data ranges for both the Girilambone study and the North Mungana study. A thesis presented in accordance with the regulations governing the award of the degree of Doctor of Philosophy in the University of Western Sydney, Nepean, School of Science. Includes bibliographical references at end of each chapter.

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Pelling, Richard. "Integrated geophysical - geochemical studies of the oceanic crust." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315093.

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Lofts, Jeremy C. "Integrated geochemical-geophysical studies of sedimentary reservoir rocks." Thesis, University of Leicester, 1993. http://hdl.handle.net/2381/35058.

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Sisson, Thomas W. "Field, geochemical, and experimental studies of aluminous arc magmas." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/58230.

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Winterburn, Peter Alan. "Geochemical studies of peridotite xenoliths from southern African kimberlites." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/11595.

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Chabot, Nancy Lynne. "Geochemical studies of the cores of terrestrial planetary bodies." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289052.

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From the Earth to asteroids, numerous rocky bodies in our solar system are believed to have a metallic core at their center. However, due to the inaccessibility of these cores, fundamental issues, such as the composition of the cores or the processes of core formation and core evolution, are not well known. I have conducted both theoretical and experimental geochemical studies which have improved our understanding of the cores of terrestrial planetary bodies. The radioactive decay of K is an important planetary heat source, but the distribution of K in terrestrial planetary bodies has been debated. My experimental work, which examined the solubility of K in metal, shows no evidence for K to be an important heat source in metallic cores. The element pairs of Ag, Pd and Re, Os have been used to date core formation and core evolution events in our solar system. My experimental determination of the partitioning behavior of these important elements can be used to better understand their distribution in iron meteorites, our only samples of planetary cores. Simple fractional crystallization of a metallic core cannot explain the elemental trends observed within iron meteorite groups. I have developed a crystallization model which suggests slight inhomogeneities and mixing in the molten core were important during core evolution. As a metallic core crystallizes, liquid immiscibility may be encountered, which could significantly affect the subsequent evolution of the core. My experimental work suggests the role of liquid immiscibility during the crystallization of a metallic core is significantly smaller than the published phase diagram implies. These four topics, though each an independent project, together provide insight into the nature of the cores of terrestrial planetary bodies and the processes which affect those cores.

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Crane, Martin John. "Geochemical studies of selected base metal minerals from supergene zone /." View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030721.132607/index.html.

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Thesis (PhD) -- University of Western Sdyney, 2001.
"A thesis presented in accordance with the regulations governing the award of the degree of Doctor of Philosophy, University of Western Sydney" "November 2001" Bibliography: leaves 249 - 254.

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Abd-Alla, Mamdouh Ahmed. "Mineralogical and geochemical studies of tills in South-Western Scotland." Thesis, University of Glasgow, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278221.

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Shukla, Balvinder. "Petrological, geochemical and palaeontological studies of the Lough Neagh Group." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238998.

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Wagner, Thomas Paul. "Experimental and geochemical studies of terrestrial and lunar magmatic process." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/57843.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995.
Includes bibliographical references (p. 153-156).
by Thomas Paul Wagner.
Ph.D.

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Fotakis-Tsipouras, Constantine. "Geochemical exploration studies in the Lavrion (Laurium) area of Greece." Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/35027.

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Detailed geochemical studies of the dispersion patterns of selected elements (Cu, Pb, Zn, Ag, Mn, As, Fe, Ni, Co) were undertaken in the drainage sediments and soils in the Lavrion peninsula with the objective of demonstrating the application of geochemical techniques to the search for previously unknown mineral deposits. The study area comprises three geological units; the Anavissos, Kamareza and Plaka, each with its distinct stratigraphy and structural history. The Kamareza and Anavissos units are separated by the Legraina fault, while the overlying Plaka unit is separated from these underlying two units by an unconformity. Both geological and geochemical data indicate that karstic mixed sulphide mineralization is largely restricted in the Kamareza and Plaka units. An area of approximately 65 square kilometres was chosen for detailed stream sediment, soil, rock and bigeochemical studies. Digestion of 0.2 gms. Of minus 80-mesh material in 25% (HNO3 at 90°C) for 4 hours appeared to provide the optimum technique for dissolution of elements such as Cu, Pb, Zn, Mn, Fe and Ni. Analysis was performed by AAS for all these elements. Arsenic was also determined by the cold extraction method (James, 1957). The data obtained were treated by graphical, univariate and multivariate statistical techniques including histograms, bar-diagrams, graphs, frequency distribution analysis, moving averages, correlation coefficient, factor and regression analysis. Other properties including pH, conductivity, organic matter content and CaCO3, and both Fe-and Mn-oxide concentrations, were also investigated in order to establish their influence on the distribution patters of the various elements. It was demonstrated that within the study area mechanical dispersion dominates over chemical. In spite of contamination from extensive past mining activity, geochemical stream and soil surveys produce reliable distribution patterns in the Mediterranean environment of Lavrion. The occurrence of previously unknown mineralization was proven by trenching in target areas indicated by geochemical patterns. Biochemical surveys were also found to yield useful information, although they are time consuming and suffer from problems associated with the uneven distribution of plant species.

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Arno, Zachary. "Geochemical and Microbial Controls of Groundwater Quality in Northwestern Liberia." Thesis, University of Nevada, Reno, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10634173.

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Years of conflict, political instability, and national emergencies have left behind very little information on water resources in Liberia, West Africa. This research leverages major ion and trace element analysis, Escherichia coli (E. coli) field tests, and high-throughput sequencing of microbial 16S rRNA genes to address these gaps and develop a comprehensive snapshot of groundwater quality in the region surrounding Monrovia, the capital city. A novel protocol to collect and preserve microbial DNA from groundwater under tropical field conditions lacking a constant source of electricity was employed and yielded high quality DNA sequences of bacterial and archaeal phylogenetic marker genes.

Multivariate compositional data analysis methods were used to investigate geochemical processes impacting groundwater quality throughout the study area. Low conductivity, low pH groundwaters were found to dominate the system with the majority of geochemical variability in the water samples attributed to surficial inputs both natural and anthropogenic. The implicated low buffering capacity of the groundwater system suggests a high risk associated with mining operations in Liberia. From a public health perspective, nitrate contamination, attributed to widespread but localized infiltration of human and or animal waste/fertilizer(s), was identified as the most important chemical water quality issue. Sulfate was found to be indicative of urban water cycling processes.

Although nitrate, arsenic, and lead concentrations exceeded WHO guidelines in several wells, E. coli was identified in 39% of all groundwaters analyzed, suggesting fecal contamination as the most significant regional water quality risk to human health. Deeper wells had significantly (p < 0.05) lower probability of E. coli contamination, with no E. coli encountered in any well greater than 22 meters deep. Sequencing of 16S rRNA genes revealed highly variable microbial community compositions. Surficial inputs are suggested as the major drivers of microbial diversity and community composition. Groundwaters that tested positive for E. coli in the field were found to have significantly higher estimates of microbial alpha diversity (p < 0.05) than groundwaters that tested negative. Additionally, nitrate, silica, pH, and several other geochemical constituents were found to be strongly correlated with shifts in microbial community structure.

The identification of a wide diversity of pathogen-associated bacteria to the genus and species level suggests that microbial contamination is more widespread than indicated by the E. coli field test alone. Results highlight the vulnerability of aquifers in Liberia to contamination and call for an increased investment in the water supply infrastructure and enhanced monitoring of chemical and microbial constituents throughout the country. This work will help the government of Liberia establish baseline water-quality conditions and provides an initial set of water resource databases to improve water-quality monitoring capacity.

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Crane, Martin John, University of Western Sydney, of Science Technology and Environment College, and of Science Food and Horticulture School. "Geochemical studies of selected base metal minerals from the supergene zone." THESIS_CSTE_SFH_Crane_M.xml, 2001. http://handle.uws.edu.au:8081/1959.7/232.

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Acid leaching of different natural chrysocolla samples under ambient conditions demonstrated that the chemical and chrystallographic inhomogenity significantly affects the rate and that it is virtually impossible to use the mineral as a model for the kinetics of hydrometallurgical processing of copper ores.Dissolution experiments, stability diagrams,and X-ray powder diffraction studies are undertaken and studied in this research and results are given.It is found that a complete solid solution series exists in Nature with most tungstenian wulfenites and molybdenum stolzites containing a range of compositions. The first occurrence of a molybdenum stolzite from Broken Hill, Australia, which also contains small amounts of chromium is noted.Raman microprobe spectroscopy has proven to be a very quick and effective non-destructive method for semi-quantitative analysis of the wulfenite-stolzite and powellite-scheelite solid-solution series and in detecting very small amounts of substituted chromate in wulfenite, stolzite and anglesite
Doctor of Philosophy (PhD)

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23

Bowtell, Sophie Ann. "Geochronological and geochemical studies of Zermatt-Saas Fee Ophiolite, Western Alps." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305487.

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Snape, J. F. "Studies of the petrologic and geochemical diversity of the lunar regolith." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1381931/.

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This study comprises petrologic investigations of the lunar meteorite Northeast Africa (NEA) 001 and 16 fragments from the Apollo 12 soil 12003. These samples are examples of the variety of materials found in lunar feldspathic highland and mare regoliths, and provide insights into the petrogenesis of different lithologies and regolith mixing processes. They have been analysed by electron microprobe and laser ablation inductively coupled plasma mass spectrometry. NEA 001 is a feldspathic regolith breccia containing clasts of multiple lithologies including; feldspathic impact melt, ferroan noritic anorthosite, magnesian feldspathic clasts and low-Ti and very-low-Ti (VLT) basalts. Feldspathic impact lithologies in NEA 001 are more mafic than estimations for the composition of the upper feldspathic lunar crust, indicating that they have incorporated more mafic lower crustal material. The VLT basalt clasts have low incompatible trace elements (ITE) concentrations, and may represent products of primitive basaltic volcanism. The feldspathic nature of the sample, low-ITE concentrations, and the presence of magnesian feldspathic clasts suggest that the meteorite has been sourced from the Outer-Feldspathic Highlands Terrane, probably on the lunar farside. Apollo 12 landed in the eastern region of Oceanus Procellarum. Previous studies of Apollo 12 samples identified three major basaltic suites (olivine, ilmenite and pigeonite basalts) local to the region. Examples of all three of these have been identified within the 12003 soil collected near the Lunar Module. Two samples are identified as possibly representing a previously unrecognised basaltic suite. One sample is identified as a possible addition to the feldspathic suite; a potential fourth basaltic suite currently consisting of only one other sample. Three non-igneous samples are identified, including two breccias and one impactite. The petrologic analysis of these samples forms part of an ongoing basaltic diversity study which will also include radioisotope dating of these and other Apollo 12 soil samples.

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Chapman, Paul. "Geochemical and mineralogical studies of the weathering of Silurian argillaceous rocks." Thesis, Bangor University, 1986. https://research.bangor.ac.uk/portal/en/theses/geochemical-and-mineralogical-studies-of-the-weathering-of-silurian-argillaceous-rocks(6c031611-9af6-4a62-a663-d76c9cd5ad94).html.

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This work was carried out as part of the Natural Environment Research Council's geochemical cycling programme. Its aim was to identify the changes taking place in the constituent minerals as Silurian Gwestyn Shale weathers to a humic stagnopodsol soil at Plynlimon, mid Wales. Hand specimen appearance and chemical analyses show that the rock groups present at Plynlimon are not homogeneous. The chlorites in different rocks are also shown to have significantly different chemical compositions, and are seen to be physically intergrown with-mica. Another source of variation is that many of the soils are developed on glacial or periglacial deposits, rather than directly on rock.

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Kadem, Liftaa Selman. "Sedimentological, mineralogical and geochemical studies of Holocene coastal sediments, south western Scotland." Thesis, University of Glasgow, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287730.

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Wareham, Christopher Desmond. "Isotopic and geochemical studies of a Pliocene porphyry-mo system, Rico, Colorado." Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304968.

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The historic mining district of Rico in the southern Colorado Mineral Belt contains a Pliocene porphyry-Mo deposit and peripheral epithermal Pb-Zn-Ag deposits, and hot-springs. The porphyry-Mo mineralisation is confined almost exclusively to Precambrian greenstone. The epithermal mineralisation is hosted by a Palaeozoic and Mesozoic sequence dominated by carbonates, but containing evaporites. The system is geologically complex and focused on a resurgent dome which is cored by a horst of Precambrian strata, and cut by reactivated Precambrian basement shears. The shears have controlled the emplacement of the Laramide and Pliocene granitoids in area. The mineralisation is associated with more evolved members of the latter suite. Sr-Nd-Pb-O isotope and minor element data on the granitoid intrusions indicate that they are not simply differentiates of mantle magmas. However, Nd model ages indicate that they are not purely remelts of 1800Ma Precambrian crust. Realistically it is impossible to quantify the relative proportions of crust and mantle material involved in the genesis of the intrusions. Notwithstanding this, the Rico granitoids are isotopically distinct from those associated with Climax-type porphyry-Mo deposits in Colorado. Sr-Nd-Pb isotope and trace element data on a lamprophyre suite in the area suggest two episodes of mafic magmatism; a period whereby the source was predominantly subduction modified lithospheric mantle, and a period whereby the source was predominantly, OIB-type, asthenospheric mantle. δ-34S data and ore deposit paragenesis indicate that the sulphide S has an igneous origin and that the sulphate S was derived by mobilisation of Pennsylvanian evaporites. Modelling of the S isotopic data indicates a common S source for the epithermal and porphyry mineralisation. The sulphate and sulphide S reservoirs remained essentially decoupled during mineralisation. δ13C data are compatible with the hydrothermal C having been derived by the dissolution and re-precipitation of host sequence carbonate. Pb and Sr isotope analyses of ore and gangue minerals support the conclusions reached in the stable isotope study. The Sr isotope study indicates that the Sr isotopic composition of the hydrothermal fluids varies considerably. Pb isotope ratios measured on molybdenite, pyrite, and galena indicate that the mineralisation at Rico derived its Pb from source with a higher Th/U ratio than that involved in the genesis of Climax-type porphyry-Mo deposits. Sr and O isotope analyses of Laramide sills present throughout the Rico area indicate that the Sr isotopic composition of the hydrothermal fluids varied and that the Sr isotopic composition of altered sills is not solely a function of alteration temperature; the proportion of altered primary feldspar and the growth of Sr-rich secondary minerals is also important. REE data on these sills indicate that hydrothermal alteration mobilised and fractionated these elements, but that mobility is not simply a reflection of alteration temperature. [SO₄]^4- appears to have been an important REE complex in the near surface oxidising environment.

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Cundy, Andrew Brian. "Radionuclide and geochemical studies of recent sediments from the Solent estuarine system." Thesis, University of Southampton, 1994. https://eprints.soton.ac.uk/50591/.

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This study examines the geochemistry of salt marshes and intertidal sediments from the Solent estuarine system, southern England. Micro-, meso- and macro-scale studies have been carried out to assess the geochemical processes operating in these intertidal sediments and the use of radionuclides as tracers of sedimentary processes in the Solent area. Measurement of 210Pbxs, 137Cs and 60Co provides valuable information on sedimentary processes occurring in the Solent estuarine system. Subsurface maxima in activity are observed for 137Cs and 60Co (after normalisation to Al) which can be related to historical input, providing dated sediment horizons. This has enabled determination of Recent sediment accumulation rates and reconstruction of historical pollution records. Sediment accumulation rates obtained using 210PbXS/ l37Cs and 60Co in salt marsh environments provide an indication of the rate of Recent sea level rise, estimated as 4 mm y-1. This is in broad agreement with tide gauge data and when compared with longer term archaeological and radiochronological data may indicate an increase in the rate of mean sea level rise over the last 1000 years. Salt marsh areas with accumulation rates lower than 4 mm y 1 (from 137Cs and 60Co dating) are degenerating (undergoing die-back) indicating that they are failing to keep pace with the rising sea level. While local (intra-estuary) effects influence rates of sediment accumulation on a particular salt marsh the main control of sediment accretion over the whole Solent area is a rise in mean sea level. Dating of salt marsh sediment cores has allowed assessment of the historical record of anthropogenic pollutant input to the Solent (in particular for Pb and Cu). Pb isotope studies of salt marsh sediments from Southampton Water indicate increasing importance of anthropogenic Pb (from Precambrian ores) since the beginning of this century. A very prominent transient spike due to an anthropogenic Pb input is found in salt marsh sediments from the relatively unpolluted Beaulieu estuary. This may be related to military marshalling in the Beaulieu river before the Allied D-Day landings in 1944. Anthropogenic Cu is present in the Solent region mainly due to discharge from the Esso refinery at Fawley, Southampton Water. Analysis of Cu fluxes has shown that discharges peaked in ca.1970 and have significantly reduced since 1971 (due to effluent clean-up by the refinery). The reliable use of radionuclides as indicators of sediment accumulation depends on their chemical immobility (lack of redox migration). 60Co shows evidence for early diagenetic remobilisation at two salt marsh sites, and 2iopb m a v a i s o be mobile in some salt marsh areas. Remobilisation of 210Pb is apparently localised and may be aided by flooding/drainage cycles in the marsh. The use of these radionuclides as tracers of sediment accumulation in areas where significant early diagenetic remobilisation occurs is problematic. Where possible a number of chemically different radionuclides should be used to eliminate bias in calculated sediment accumulation rates due to redox mobilisation or diffusive processes. Detailed geochemical studies can assist in determining whether redox movement of radionuclides is occurring. A critical examination of the geochemical behaviour of both the stable counterparts of radionuclides and redox-sensitive elements is required if realistic sediment accumulation rates are to be obtained.

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Mello, Marcio Rocha. "Geochemical and molecular studies of the depositional environments of source rocks and their derived oils from the Brazilian marginal basins." Thesis, University of Bristol, 1988. http://hdl.handle.net/1983/a29755bf-1342-4601-8c5a-23849275f37c.

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A geochemical survey of Brazilian marginal basins using a wide selection of source rocks and oils, ranging from Lower Cretaceous to Tertiary in age, has been undertaken. The aims were to assess the palaeoenvironment of deposition of the source rocks, to correlate reservoired oils with their putative source rocks and to understand the effects of maturity on the composition and absolute concentrations of biological markers. The geochemical analyses included evaluation of organic ca~bon contents, Rock-Eval pyrolysis data, vitrinite reflectance measurements, determination of carbon isotope ratios, elemental and visual kerogen analysis, and molecular studies involving liquid and gas chromatography, qualitative and quantitative biological marker investigations using GC-MS, metastable GC-MS .and GC-MS/MS for saturated and aromatic hydrocarbons, and UV/vis spectrophotometry, probe MS and HPLC for metalloporphyrins. The metastable ion GC-MS data were evaluated using principal component analysis. Integration of the results with geological and paleontological data provides the recognition and differentiation of seven depositional regimes, namely lacustrine freshwater, lacustrine saline water, marine evaporitic, marine carbonate, marine deltaic with carbonate influence, open marine highly anoxic with a predominance of calcareous mUdstone lithology, and open marine anoxic, with predominance of siliciclastic lithology. The analyses of the oils reveal significant differences between groups which enable a correlation with putative source rocks laid down in five of the above depositional regimes: lacustrine freshwater; lacustrine saline water; marine evaporitic: marine carbonate and marine deltaic with carbonate influence. The quantitative approach used to determine the effect of thermal maturity on the composition and concentration of the biological markers shows that care must be taken in their use as maturity indicators, since source input and mineral matrix might play an important role. On the other hand, it also shows that the concentrations decrease considerably between the onset of petroleum generation and its peak. Thus, care must also be exercised when using biological marker concentration in palaeoenvironmental assessment The metalloporphyrins in a selection of organic rich sediments have also been examined. The results suggest that their distributions can be a useful auxiliary tool in the characterisation of depositional environments of petroleum source rocks. Finally, a combined geochemical and micropalaeontological study of Cenomanian to Maastrichtian pelitic sediments from the continental margin extends the occurrence of the recognised Cenomanian-Turonian and santonian "oceanic anoxic events". As an extension, the presence of such events in the Coniacian is reported. In contrast, the Campanian-Maastrichtian appears to be a time interval when deposition under oxygenated conditions produced sediments with low organic carbon contents and poor hydrocarbon source potential. In summary, biological marker characteristics of organicrich sediments can distinguish different types of depositional environments, assessment of from analysis allow oil-source rock correlations, and the the depositional environment of the source rocks only of the oils. Thus, this thesis provides a framework of biological marker characteristics which can be compared with samples from other parts of the world.

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Costa, Mafalda. "A geochemical approach to the study of archaeological glassy materials." Doctoral thesis, Universidade de Évora, 2021. http://hdl.handle.net/10174/29209.

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In this dissertation, knowledge from social sciences and humanities was combined with that of natural sciences, especially Earth Sciences, to study man-made glass and faience artefacts from selected case studies from the Iron Age and Early Modern periods. The manufacture of man-made glassy materials relies on the exploitation of natural mineral resources. Moreover, since glassy objects inherit the chemical fingerprint of the geological provinces from which the raw materials used in their manufacture derive, geochemistry is essential in provenance studies. In fact, geochemistry can be used to pinpoint the geographical origin of an artefact, given the known proximity between primary or producing workshops and the favored silica source, but also to understand the raw material procurement strategies of glassy producing societies. While sand is not known to have been subjected to long-distance trade, the same cannot be said for other main components used in the production of man-made glassy objects, particularly the fluxing agents and (de)colorants or opacifiers. Earth Sciences, especially geochemistry, is, therefore, essential to reconstruct trade/exchange routes of both raw materials and finished glassy artefacts within or between different communities. Furthermore, the identification of the raw materials used in the production of man-made glassy artefacts, not only reveals how human societies adjust and interact with the environment but is essential to better comprehend the technological know-how required for their manipulation and use in the manufacture of these objects. Ultimately, this dissertation enabled the creation of new non-destructive and minimally invasive analytical methodologies that can be used to gain insights into glassy materials’ provenance and production technology, and to better comprehend the history and ethnography of the communities that produced, used, and trade or exchanged them; Resumo: Nesta dissertação, o conhecimento das ciências sociais e humanas foi combinado com o das ciências naturais, especialmente das Ciências da Terra, para estudar artefactos de vidro e faiança produzidos pelo homem, usando de estudos de caso da Idade do Ferro e da Idade Moderna. A produção de materiais vítreos depende da exploração de recursos minerais naturais. Como os objetos vítreos herdam a assinatura química das províncias geológicas das quais derivam as matérias-primas utilizadas na sua produção, a geoquímica é essencial nos estudos de proveniência. Na verdade, a geoquímica pode ser usada para localizar a origem geográfica de um artefacto, dada a proximidade conhecida entre oficinas primárias ou de produção e a fonte de sílica preferida, mas também para compreender as estratégias de aquisição de matérias-primas das sociedades produtoras de vidro. Embora se saiba que a areia não foi alvo de comércio de longa distância, o mesmo não pode ser dito para outros ingredientes usados na produção de objetos vítreos, particularmente os fundentes e os (des)colorantes ou opacificantes. As Ciências da Terra, especialmente a geoquímica, são, portanto, essenciais para reconstruir rotas de comércio ou troca, de matérias-primas e de artefactos vítreos, dentro ou entre diferentes comunidades. Além disso, a identificação das matérias-primas utilizadas na produção de artefactos vítreos produzidos pelo Homem, não só revela como as sociedades humanas interagem com o meio ambiente que as rodeia, mas é essencial para compreender melhor o know-how tecnológico necessário para sua manipulação e uso na produção desses objetos. Em última análise, esta dissertação permitiu a criação de novas metodologias analíticas, não destrutivas e minimamente invasivas, que podem ser usadas para obter informações sobre a proveniência e tecnologia de produção de materiais vítreos, e para compreender melhor a história e etnografia das comunidades que produziram, usaram e comercializaram estes objetos.

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Zhang, Xiping. "Geochemical exploration for polymetallic ores in volcano-sedimentary Rocks : studies in China and Finland /." Oulu : Oulun Yliopisto, 2000. http://herkules.oulu.fi/isbn9514257871.

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Gaab, Andreas S. "Isotope geochemical and geochronologic studies of basement units in the Central Western Carpathians (Slovakia)." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975961136.

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Hay, Susan Vivienne. "Some geochemical and isotopic studies of the Insch, Huntly and Belhavie intrusions, NE Scotland." Thesis, Royal Holloway, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271593.

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Diskin, Sorcha. "Isotopic and geochemical aids to provenance studies in the Westphalian of the British Isles." Thesis, Oxford Brookes University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271276.

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Lee, Kwok-Lin. "Petrological and geochemical studies of an abyssal periodotite from the Atlantis II fracture zone." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/54425.

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Aḥmad, Naz̲īr. "Palaeoenvironments, diagenesis, and geochemical studies of the Dungan Formation (Palaeocene), eastern Sulaiman Range, Pakistan." Thesis, University of Leicester, 1996. http://hdl.handle.net/2381/34934.

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The Sulaiman Range is located on the northwest margin of the Indian Plate. It forms the middle part of the Indus basin, and has been termed the Sulaiman sub-basin. The Indus basin is filled with a thick sequence of Mesozoic and Cenozoic sediments. The Dungan Formation is Palaeocene in age and comprises a 98 m thick predominantly carbonate sequence which extends about 200 km from north to south along the Sulaiman Range. The Formation is characterised by different microfacies. Petrographic studies revealed the following microfacies; peritidal carbonate, inner lagoon, oolitic, outer lagoon, rhodolith platform, nummulitic, larger foraminiferal, and planktonic foraminiferal. All these facies can be interpreted broadly within a homoclinal, windward carbonate ramp model. The cementation history has been investigated by petrography of stained thin sections, cathodoluminescence microscopy, XRD, electron microprobe, SEM (in back scattered mode), XRF, and carbon and oxygen stable isotope analysis to reveal trace element contents and their variation in the diagenetic cements. The diagenesis of the formation starts from the marine phreatic environment, characterised by micritization and peloidal cements. These cements are of high Mg-calcite, and low in Fe and Mn. They do not show luminescence. The active fresh water phreatic zone may involve leaching in the zone of solution, neomorphism, isopachous bladed cement around the oolites and foraminifera, syntaxial overgrowth cement on echinoderm fragments, and interlocking crystals of equant calcite that coarsen towards the pore centres (drusy cement). The neomorphic spars having irregular boundaries and are cloudy and patchy. They are also low in Fe and Mn, and non-luminescent. The isopachous bladed cements are low in Mg and high in Fe and Mn and show orange luminescence. The syntaxial overgrowth cements are low Mg-calcite. They show bright zoned luminescence, indicating different zones of Fe and Mn concentration. The drusy cement is also low Mg-calcite, and shows dull to orange luminescence indicating the high concentrations of Fe and Mn as compared to marine cement. The oxygen isotopic values of this cement type are low when compared to the whole rock. Vug and mould porosities are developed in the freshwater vadose zone, which are filled by sparry calcite cement. The shallow burial environment is marked by compaction of skeletal grains, stylolites and fractures. The fractures show two generations. The early fracture fills cements are non ferroan and show bright zoned luminescence. The later fracture fills cements are ferroan and non-luminescent. The oxygen isotope values of non-ferroan cement filling fractures are more negative when compared with that of ferroan cement filling fractures, which may be formed in shallow burial environments by formation water.

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Hagen, Erik Harold. "Geochemical studies of Neogene Till in the Transantarctic Mountains: evidence for an extraterrestrial component." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406893208.

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McCoyd, Richard James. "Isotopic and geochemical studies of the epithermal-mesothermal Pb-Zn deposits of S.E. Bulgaria." Thesis, University of Aberdeen, 1995. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU551163.

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The study was based upon five Pb-Zn districts located in S.E. Bulgaria, these were Madan, Madjarovo, Laki, Zvezdel and Spaheivo districts with most of the work concentrating on Madan and Madjarovo. The Madan district consists of approximately twenty vein and replacement deposits hosted within amphibolite grade metamorphic rocks. The Madjarovo district comprises approximately forty five veins which are predominantly hosted within an eroded strato-volcano but with some of the veins passing down into the underlying metamorphic basement. The deposits of the Laki district are also hosted within the metamorphic basement and can be considered as an analogue to Madan, while Zvezdel and Spaheivo are volcanic-hosted and similar to Madjarovo. Fluid inclusion micro-thermometry shows that the mineralization in Madan, Madjarovo and Laki was deposited by fluids with a salinity of 3-5 eq. wt. %. NaCl and at temperatures of between 240°C and 300°C. In Madan and Laki the associated alteration is dominated by sericite while in Madjarovo both sericite and adularia are present, such an assemblage suggests neutral to slightly alkaline conditions. In addition a zone of sericitic - advanced argillic alteration is present at Madjarovo, this contains a range of minerals including kaolinite and alunite and is believed to have formed in a strongly acidic environment. The trace element geochemistry of the differing alteration types at Madjarovo also suggests that the alteration was produced by two separate fluids. A range of stable isotope analyses were undertaken to attempt to identify the source of the fluids and other constituents. The δ³⁴S sulphide values from the mineralization and alteration ranges between -1‰ and +7‰ for all districts except Spaheivo which has values of -5‰ to -7‰. Whole rock sulphur data from the metamorphic basement varies from - 7‰ to +5‰ and so is a viable source alongside igneous sulphur. The δ¹³C calcite in the metamorphic-hosted districts ranges from -4‰ to +2‰. This indicates that the carbon was predominantly derived from marble horizons within the basement which have a similar range of values. This contrasts with the delta δ¹³C calcite in the volcanic-hosted districts which is typically more depleted and suggests a different or additional source of carbon.

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Theander, Astrid. "Mapping of contaminant dispersion from a polluted mining area by geochemical and geophysical methods, Rävlidmyran,northern Sweden : Use of geochemical and geophysical studies to investigate contaminants." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-73634.

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After open pit mining, the pit can either be backfilled or be filled with groundwater andbecome a pit lake. These lakes tend to be acidic and contains high concentrations ofmetals, which increases the environmental risks in the area. One of these pit lakes isRävlidmyran in the Skellefte ore district. This problem and this pit lake have created thepurpose of this thesis, which is to compare the different water types connected to an openpit, i.e. groundwater, surface water and the actual pit lake water, and to connect the waterwith geophysical readings. The purpose is also to compare ratios between elements to beable to gain more geochemical information.To gain information about the groundwater, several groundwater pipes have since a longtime back been installed in the area. The groundwater has thereafter regularly beensampled and analysed. The surface water has also been sampled regularly in differentspots. In the pit lake, a depth profile has been created by water sampling at differentdepths in the pit lake. The geophysical measurements used in this thesis are resistivityand induced potential measurements, and measurements were done with the slingrammethod.The water sampling indicated that all three types of water contained elevatedconcentrations of metals. The ratio between (Cu+Zn+Pb)/Na indicated that the pit lakehad the highest value. The measurement also indicated that the highest concentration ofdissolved metals is found under the chemocline in the pit lake, compared with other watertypes. Also, the ratio Fe/S were the highest under the chemocline in the pit lake, whichindicates e.g. dissolution of pyrite. When it comes to the ratio representing e.g. dissolutionof gypsum (Ca/S) it was below 1 all the time, except for in two groundwater pipes. The(Ca+Mg)/Na–ratio had the highest values in the pit lake and that indicates dissolution ofe.g. carbonates. This is not very surprising since the pit lake has been and are limedregularly.The geophysical investigations indicated increased electrical conductivity in a waste rockheap northwest of the pit lake, where the sampling indicated elevated copperconcentrations. The readings also show that the groundwater flow direction is againstLake Hornträsket north of the pit lake. They also indicated potential flow paths for thegroundwater. These can contain elevated concentrations of ore elements, which can beconfirmed by a sampling of the groundwater in that area. From the geophysical data, it isalso possible to see that one of the profiles are located along a possible groundwaterplume, based on a low resistivity area and the shape of the potential plume.
Efter brytning ur ett dagbrott, så kan dagbrotten ur efterbehandlingssyfte till exempel bliåterfyllt med antingen gråberg eller med vatten. Ifall dagbrottet blir återfyllt med vattenoch en dagbrottssjö skapas, så tenderar denna sjö att vara försurad och innehålla förhöjdahalter av metaller. Detta ökar de lokala belastningarna på miljön i området. En av dessadagbrottssjöar är Rävlidmyran som ligger i Skelleftefältet. Denna dagbrottssjö och dessbieffekter har skapat syftet med detta examensarbete, vilket är att jämföra olikavattentyper kopplade till Rävlidmyran (grundvatten, ytvatten och vatten i dagbrottssjön)samt att jämföra geokemin med geofysiska mätningar. Syftet är också att jämföramolkvoter mellan relevanta element för att i sin tur få mer geokemisk information.För att få fram mer information om grundvatten så har flertalet grundvattenrörinstallerats i området sen flera år tillbaka. Därefter har grundvattnet provtagits ochanalyserats regelbundet. Ytvattnet i området har också provtagits. I dagbrottssjön har enprofil tagits fram genom att ta vattenprover på olika djup i sjön. De geofysiskamätningarna som gjorts är resistivitet och inducerad potential mätningar, samtmätningar som utförts med slingram-metoden.Vattenprovtagningarna indikerade att alla tre vattentyper innehåller förhöjda halter avmetaller. Molkvoten (Cu+Zn+Pb)/Na visade att kvoten var högst under kemoklinen idagbrottssjön i jämförelse med de andra två vattentyperna. De kemiska analyserna avvattenproverna av de olika vattentyperna pekade också på att vattnet under kemoklineni dagbrottssjön innehöll en större mängd lösta joner. Kvoten Fe/S var också högst i dettavatten. När det kommer till molkvoten som bland annat representerar gipsutfällning ochgipsupplösning – Ca/S – så var det under 1 i hela området, med undantag för tvågrundvattenrör. Kvoten (Ca+Mg)/Na var högst i dagbrottssjön och det indikerarupplösning av exempelvis karbonater. Detta är inte helt oväntat, då dagbrottssjön kalkatsregelbundet sedan en lång tid tillbaka.De geofysiska utredningarna indikerade på förhöjd elektrisk konduktivitet i ettgråbergsupplag nordväst om dagbrottssjön, där vattenanalyserna påvisade en förhöjdkoncentration av koppar. Mätningarna visade även att grundvattnets riktning var motsjön Hornträsket, som är lokaliserad norr om dagbrottssjön. De indikerade ävenpotentiella flödesvägar för grundvatten. Dessa flödesvägar kan innehålla förhöjda halterav metaller, vilket kan bekräftas med hjälp av provtagningar av grundvatten i området.Från de geofysiska mätningarna är det också möjligt att se att en av profilerna är placeradlängs med en möjlig grundvattenplym, baserat på en låg resistivitet och den potentiellaplymens form.

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40

Thomas, Mark W. "Geochemical Modeling of CO2 Sequestration in Dolomitic Limestone Aquifers." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3708.

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Geologic sequestration of carbon dioxide (CO 2) in a deep, saline aquifer is being proposed for a power-generating facility in Florida as a method to mitigate contribution to global climate change from greenhouse gas (GHG) emissions. The proposed repository is a brine-saturated, dolomitic-limestone aquifer with anhydrite inclusions contained within the Cedar Keys/Lawson formations of Central Florida. Thermodynamic modeling is used to investigate the geochemical equilibrium reactions for the minerals calcite, dolomite, and gypsum with 28 aqueous species for the purpose of determining the sensitivity of mineral precipitation and dissolution to the temperature and pressure of the aquifer and the salinity and initial pH of the brine. The use of different theories for estimating CO2 fugacity, solubility in brine, and chemical activity is demonstrated to have insignificant effects on the predicted results. Nine different combinations of thermodynamic models predict that the geochemical response to CO2 injection is calcite and dolomite dissolution and gypsum precipitation, with good agreement among the quantities estimated. In all cases, CO2 storage through solubility trapping is demonstrated to be a likely process, while storage through mineral trapping is predicted to not occur. Over the range of values examined, it is found that net mineral dissolution and precipitation is relatively sensitive to temperature and salinity, insensitive to CO2 injection pressure and initial pH, and significant changes to porosity will not occur.

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Smith, Jennifer Mae. "Geochemical signatures in the coral Montastraea modern and mid-Holocene perspectives /." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001593.

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Mavromatis, Vasileios [Verfasser]. "Mineralogical and isotope geochemical investigations of high Mg-calcites : laboratory and field studies / Vasileios Mavromatis." Kiel : Universitätsbibliothek Kiel, 2010. http://d-nb.info/1020002840/34.

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Dolgopolova, Alla V. "Geochemical and isotope studies of element dispersal in the environment during mining and ore processing." Thesis, Imperial College London, 2005. http://hdl.handle.net/10044/1/11999.

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44

Geng, Hongyan, and 耿红燕. "Geochemical and geochronological studies of carboniferous magmatism inthe West Junggar: ridge subduction in thelate paleozoic?" Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45983999.

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Mercone, Domenico Carlo. "High-resolution geochemical studies on the most recently-accumulated sapropel S1 in the eastern Mediterranean." Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/42140/.

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The sediments of the eastern Mediterranean Sea contain Corg-rich layers, termed sapropels, interbedded with Corg-poor sediments which form by far the greater part of the sedimentary record. This research presents a high-resolution geochemical investigation on slowly- and rapidly-accumulated SI units. Mn, Fe, I and Se profiles in slowly-accumulated SI units (5-10 cm.kyr"1) have shown that these sapropels are affected by post-depositional oxidation following their formation which produces a much thinner sapropel than was originally deposited. In the slowly-accumulated examples investigated, up to 11.5 cm of the original sapropel has been lost through oxidation in as little as 6 kyr. Downward progression of the redox front causes the remobilisation and re-arrangement of redox-sensitive elements (As, Fe, I, Mn, Mo, Se, U and V) around the oxic/post-oxic boundary. Concentration-depth profiles of the redox-sensitive elements in SI have shown that these elements are immobilised in oxic and post-oxic conditions or both. It is noted that I and Se form well-defined peaks at the top of SI, and it is suggested that these two elements may be reliable markers for defining the location of an active oxidation front in the absence of pore water measurements. During this research, it was discovered that Hg behaves similarly to I and Se at the oxic/postoxic boundary, forming a well-defined peak in post-oxic conditions. In turbidite and sapropel examples, Hg is always closely associated with Se and it is suggested that Hg and Se become immobilised through the formation of the selenide mineral tiemannite (HgSe). The presence and persistence of Hg peaks in both recent and ancient sediments (up to 4 Ma) implies that Hg may be a useful diagnostic tool for defining the locations of both active and relict oxidation fronts. Investigation of two rapidly-accumulated Sis from the Adriatic (MD 90-917) and Aegean Seas (LC21) has shown that these cores have suffered negligible post-depositional oxidation due to rapid accumulation rates. The validity of the Ba/Al ratio as a more reliable and persistent productivity index has been confirmed in both LC21 and MD 90-917 where Ba/Al is directly related to Corg content over the entire visual SI units. In both cores SI appears as a doublet. This doublet is centred on 7.5 kyr BP and geochemical and micropalaeontological evidence indicates that this "saddle" is best interpreted as an episode of improved reventilation and increased deep-water O2 concentrations. A number of redox-sensitive elements are enriched (Cr, Mo, Ni, S, Se, U, V and Zn) in LC21 and MD 90-917, and exhibit double peaks in their concentrationdepth profiles. The principal routes by which SI develops high authigenie levels of redox-sensitive elements are: (i) pre-concentration in the water column by biological uptake followed by deposition at the sedimentwater interface and/or (ii) diffusion from seawater through pore waters into sediments followed by reduction and immobilisation under more reducing conditions. Under more reducing conditions, redox-sensitive elements are immobilised through associations with Corg, pyrite, sulphides or form insoluble solid phases (e.g. U is precipitated and immobilised as UO2(S)). Palaeoproductivity estimates based on Ba/Al weight ratios indicate that productivity was up to 5 times higher during SI formation compared with the present. It is suggested that high productivity was initiated by the formation of a deep chlorophyll maximum formed in response to an increased input of freshwater into the eastern Mediterranean. During SI formation, the flux of Corg greatly exceeded the supply of dissolved O2 to the bottom waters and so it is inferred that deposition of SI occurred under anoxic conditions. Interpretations of geochemical parameters such as S/C criteria, I/Corg and V/(V+Ni) ratios and framboidal pyrite sizes all indicate that bottom waters were anoxic-non sulphidic rather than anoxic-sulphidic during SI formation. The geochemical interpretation is in agreement with the benthic foraminiferal data, which show that the two S1 layers have an abundance of low-oxygen tolerant species. It is unclear whether anoxic conditions are induced by increased productivity alone or through a combination of increased productivity and reduction in deep-water formation. Evidence presented indicates that productivity and preservation are both necessary prerequisites for SI deposition. SI initiation and cessation was investigated by AMS 14C dating based upon the Ba/Al ratio criterion. AMS 14C ages for slowly-accumulated sapropels indicate that SI formation started at 10 kyr BP and ended by 5.3 kyr BP. For the rapidly-accumulated cores, the onset and termination of SI is more variable although SI was underway by 9.5kyr BP and complete by 6.0 kyr B.P. The offset in ages is attributed to bioturbation mixing artefacts affecting the Ba/Al signal in the slower-accumulated cores. Since rapidly-accumulated cores are not significantly affected by bioturbation, the best estimate for the duration of SI is 9.5-6.0 kyr B.P.

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Garcia, Susana. "Experimental and simulation studies of iron oxides for geochemical fixation of CO2-SO2 gas mixtures." Thesis, University of Nottingham, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523076.

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Lazareva, Olesya. "Detailed geochemical and mineralogical analyses of naturally occurring arsenic in the Hawthorn Group." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000521.

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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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Viskupic, Karen M. (Karen Marie) 1975. "Crustal melting in the Himalayan orogen : field, geochemical and geochronological studies in the Everest region, Nepal." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/59101.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003.
Includes bibliographical references.
A combination of field studies and geochemical techniques were used to investigate the timing and processes involved in leucogranite generation in the Everest region of the Himalayan orogen. Geochemical investigations focused on samples from three outcrops at different structural levels in the Himalayan metamorphic core where in situ crustal melting and multiple generations of leucogranite intrusions were observed. Accessory phase thermochronological and U-Pb geochronological studies were combined to determine the timing of anatexis in a migmatite at the structurally lowest outcrop. Quantitative measurement of REE and Y in monazites and xenotimes, that were later dissolved and dated by U-Pb IDTIMS, revealed monazite growth at temperatures appropriate for crustal melting (>650⁰C) between 25.4 and 24.8 Ma, suggesting that anatexis was ongoing at that time. Further constraints were placed on the timing of crustal melting, granite crystallization and cooling with a detailed U-Pb IDTIMS and 40Ar/39Ar study of leucogranite dikes, sills, and the metamorphic rocks they intrude. Backscattered electron imaging of accessory minerals provided important insights into the petrogenesis of monazite, xenotime and zircon, and guided efforts to isolate accessory phase growth domains. In two granitic sills, extensive accessory phase crystallization between ca. 26 and ca. 23 Ma was interpreted to be the result of episodic to semi-continuous melt generation and crystallization at least between those times. These melt products were later entrained in melts that crystallized as syntectonic sills at 21-22 Ma. Younger crosscutting dikes crystallized between 17.5 and 18.3 Ma.
(cont.) The range in accessory phase dates from these dikes and sills that represent magmatic crystallization ages spans from 26.2 to 17.5 Ma, providing evidence for melt generation in one region over roughly 9 million years. Neodymium isotopic signatures of the same monazite and xenotime grains dated by U-Pb IDTIMS were used to investigate melting processes and granite source-rock characteristics. The dominant control of monazite on the Nd isotopic composition of its host rock was clearly demonstrated. Some Nd isotopic heterogeneities recorded in monazite and in xenotime support a model for melt generation where accessory phases grow from locally derived sources in an isotopically heterogeneous melt.
by Karen M. Viskupic.
Ph.D.

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Jorquera, Zuniga Carmina Olivia. "Geochemical baselines based on stream waters : applications to environmental studies, Central Chile as a case study." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/28149.

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Increasing environmental regulation has resulted in mining companies monitoring levels of toxic trace elements in the environment. However, little research has been done to identify the sources of such elements as natural or manmade. Whilst the mining industry has traditionally used hydrogeochemical baselines for exploration, this study has evaluated the use of such baselines for environmental assessments of drainage systems, particularly the identification and quantification of natural and anthropogenic sources. The results are discussed in the context of water quality regulation and guideline values. The research generated the first systematic regional geochemical baseline of Central Chile including the classic Andean copper mineral province and the Andina-Los Bronces mining district. The study area included three major catchments flowing from the Andean Cordillera into inhabited valleys, with the potential for contamination from agriculture and the urban environment. Waters were sampled at a density of 1 per 100 sq. km. over 20000 sq. km. in five seasons over three years. Multi-element chemistry and stable isotopes were determined. The geochemical baseline was prepared using high quality geochemical data. The distribution patterns of the anomalously high geochemistry showed strong relationships with bedrock geology, including the presence of evaporites, sulphide mineralisation and hydrothermally altered rocks (differentiated using isotopes in sulphate). High concentrations of nitrate and phosphate were identified in agricultural areas reflecting pollution from fertilisers and sewage (distinguished using isotopes in nitrate). Areas affected by fertilisers and sewage were significantly greater than those affected by mining. Waters draining unmined Cu-mineralisation had much higher Cu and Ni levels and lower pH than Cu-mine area waters. Most regional geochemistry was below international guidelines and Chilean regulatory levels and where elevated it reflected natural sources and seasonal variations. The study demonstrates that geochemical baselines have considerable potential for distinguishing between natural and anthropogenic pollutant sources in environmental assessments.

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Dissertations / Theses on the topic 'Geochemical studies'

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