Dissertations / Theses on the topic 'Elemental geochemistry'

This study examines dust in the San Francisco Peaks located on the Colorado Plateau of northern Arizona, USA. Sample dusts were collected from potholes on Humphreys Peak (35^o20'22"N, 111^o41'42"W) in order to detect exogenous material and constrain dust sources. Bulk dust and local rock were characterized by Sr and Nd isotope fingerprints as well as elemental composition. Sr and Nd isotope ratios were analyzed by MC-ICP-MS; trace element concentrations were analyzed by Q-ICP-MS. Mineralogical analyses were also performed in an effort to characterize individual particles. Mineral grains were separated from bulk samples by conventional heavy mineral separations. The heavy fraction was imaged and characterized by SEM/EDX.

Both the isotopic and elemental bulk analyses indicated that the dust composition reflected not only a weathered local rock material but also exogenous material of continental crust origin. The dust was characterized by an average ⁸⁷Sr/⁸⁶Sr ratio of 0.7095 ± 0.0010 and an average ε _Nd of -7.13 ± 0.97. These signatures systematically and significantly deviate from the isotope fingerprints of the local rock, which exhibited an average ⁸⁷Sr/⁸⁶Sr ratio of 0.7037 ± 0.0002 and an average ε_Nd of -2.43 ± 0.43. The negative correlation between ε_Nd and ⁸⁷Sr/⁸⁶Sr is consistent with two component mixing of rock evolved from a mantle source and continental crust derived material.

Several geologically relevant trace elements were found to have significantly different average concentrations in the dust than in the local rock samples. Furthermore, the elemental abundances of most elements in the dust samples suggested a mixture of local rock and continental crust end members with the exception of Pb, which indicated an anthropogenic influence exhibiting enrichment factors between 1.65 and 7.44.

The mineral analysis provided further evidence of exogenous material and offered the opportunity for further constraint of the sources. Zircons were identified only in the dust and will be analyzed for U-Pb signatures in order to characterize the isotopic fingerprint of individual mineral grains, which will better distinguish external sources. Diatom skeletons were also found exclusively in the dust samples and offer a unique opportunity to more specifically implicate sources through a diatom assemblage.

Detailed major/trace element and high-precision Hf-Nd-Sr isotope data has been acquired for 86 samples of kimberlites from the recently discovered Lac de Gras kimberlite field in the Northwest Territories, Canada, plus 23 samples from other Canadian kimberlite occurrences. This constitutes the most comprehensive geochemical database available for kimberlites at the present time, and allows detailed comparisons to be made with the well-documented kimberlites of the Kaapvaal craton, southern Africa. Major and trace element data shows that some Lac de Gras kimberlites have interacted extensively with continental crust, whereas others are minimally contaminated with crust but have physically incorporated large quantities (˃30%) of lithospheric mantle peridotite. Fresh, minimally-contaminated kimberlites from Lac de Gras have both elemental and isotopic characteristics that are transitional relative to those typical of southern African Group I and II kimberlites. The Hf-Nd isotope variations of these samples also define a linear array that strongly suggests mixing of two or more components/reservoirs within the mantle. Isotopic mixing models and mass balance considerations constrain the most likely candidate components/reservoirs to be depleted sub-continental lithospheric mantle and a component with an isotopically-enriched, negative ΔɛHf signature that is derived from beneath the lithosphere. Such a component has previously been identified in southern African kimberlites, indicating that it is globally extensive within the mantle. Its resfriction to magmas generated at great depths, and its unusual Hf isotope signature also suggest that it may reside in isolation at some mantle boundary layer. Ancient oceanic crust, generated by melting in the presence of garnet and subsequently subducted and stored below the lithosphere, could evolve to negative ΔɛHf compositions. Melts of this material, variably recombined with the depleted, garnet- rich melting residua that constitute the lithosphere, can then account for the Hf-Nd kimberiite isotopic array. Trace element characteristics, such as K and Sr anomalies, are consistent with those of OIB-like magmas derived from within the convecting mantle.

Thesis (Ph. D.) University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 7, 2007) Includes bibliographical references.

O objetivo deste estudo foi aplicar técnicas de geoquímica de elementos maiores, menores e isótopos de Sr e Nd para identificar contaminação por fosfogesso em sedimentos fluviais da bacia hidrográfica Mogi/Piaçaguera. Para isto, foram analisados perfis de sedimento das margens dos rios Cubatão, Pereque, Mogi (montante, meio e jusante), Piaçaguera e Jurubatuba, inseridos no alto estuário santista, assim como solos, rochas e águas superficiais. Os métodos utilizados foram fluorescencia e difratometria de raios-x, microscopia ótica e analises isotópicas de Sr e Nd. Os resultados demonstraram fator de enriquecimento de Sr, Nd, Nb, La, F e Ce nos sedimentos superficiais do Rio Mogi jusante, comparado aos demais sedimentos fluviais analisados. As composições isotópicas dos sedimentos fluviais regionais foram dentro do padrão das rochas e solos da bacia hidrográfica. A exceção se deve aos sedimentos fluviais superficiais do Rio Mogi jusante que apresentaram assinaturas química e isotópica semelhantes do fosfogesso. O cálculo de proporção de mistura de composições isotópicas de Sr e Nd proveniente do fosfogesso indicou significativa discrêpancia para os dois métodos, de até 6% para Sr e 35% para Nd. Pelo contrário, diagramas 143Nd/144Nd e 87Sr/86Sr apresentaram proporções menores de 10%, coerentes com estudo da literatura que estimou de 13% a 18% a solubilização do fosfogesso em água. A normalização das composições isotópicas com a água do mar (e87Sr) dos resultados para extração parcial (ácido acético) indicou valores de e87Sr semelhantes para solos, sedimentos e águas superficiais da bacia hidrográfica, inclusive, levanta-se hipotese da influência da maré nos sedimentos do Rio Jurubatuba, com padrão isotópico semelhante da água do mar. Distintamente, confirmaram-se assinaturas isotópicas do fosfogesso nos sedimentos do Rio Mogi jusante. Em suma, isotopos de Sr e Nd demonstraram ser importantes ferramentas na identificação de plumas de contaminação antrópica, como também na identificação das prováveis fontes destas anomalias.
This objective of this study was applying geochemical techniques of major and minor elements, aswell as Sr. And Nd isotopes to identify contamination by phosphogypsum in fluvial sediments in the hydrografic basin of Mogi/Piaçaguera. Profiles of sediments from Cubatão, Pereque, Mogi (upstream,middle and downstream), Piaçaguera and Jurubatuba rivers margins, inserted in the high Santista stuary, as well as soils, rocks and superfial waters were analysed. The methods used were fluorescence and difratometria of X-rays, optical microscopy and isotopic analyses of Sr and ND. The results showed a factor of enrichment of Sr. Nd. NB, La, F and Ce in surface sediments of the Rio Mogi jusante, compared to other fluvial sediments analysed. The isotopic compositions of regional fluvial sediments were in accordance with rocks pattern and the hydrografic basin soils. The exception is due to surface fluvial sediments of the Rio Mogi jusante, which showed chemical and isotopic signatures similar to phosphogypsum. The calculation of proportion of isotopic composition mixtures of Sr. And Nd resulted from phosphogypsum indicated a significative discrepance for these two methods of up to 6% to Sr and 35% to Nd. On the contrary, 143Nd/144Nd and 87Sr/86Sr dyagrams presented minor proportions of 10% in coherence with the literature study, which estimated 13% to 18% the solubilization of phosphogypsum in water. The isotopic compositions normalization with sea water (e87Sr) of results for partial extraction (accectic acid) showed the value of e87Sr similar for soils, sediments and surface waters of the hydrografic basin. The hypotesis of the tidal influence in sediments of Rio Jurubatuba was arised, with a isotopic pattern similar to sea water. In a distinct way, the isotopic signatures of phosphogypsum in sediments of Rio Mogi jusante were confirmed. In summary,isotopes of Sr and Nd showed that are significant tools in the identification of plumas of antropic contamination, as well as in the identification of probable sources of these anomalies.

Understanding U-series isotopic disequilibria of partially melted crust is integral for determining the effect that crustal assimilation has on the U-series signature of magmas. In this work, U, Th and Ba (as a proxy for Ra) elemental abundances were gathered on the quenched glass in partially melted crustal xenoliths of granitic composition using microbeam techniques. The crustal xenoliths, which are found in basaltic lava, from Mirador Volcano in Chile, are old, and can be assumed to be at secular equilibrium, whereas melting occurred during eruption of Mirador in 1979. A comparison of the ratios Ba/Th and U/Th in the partial melts with those of the whole rock reveal how much fractionation has occurred during partial melting. Different ratios of U, Th and Ba compared to the whole rock substantiate fractionation via partial melting. Thus, assimilation of partial melts of crust can play a role in U-series isotopic disequilibria.

As rochas do Grupo Península Trinity e das unidadesequivalentes abrangem arenito, argilito e conglomerado, além de seus correspondentes metamórficos, e cuja formação é atribuída a correntes de turbidez. Afloram na parte norte da Península Antártica e arquipélagos adjacentes. Amostras de arenito, arcósio e conglomerado dessas unidades foram analisadas com intuito de traçar sua proveniência. A partir da análise petrográfica de arenito foi constatada a similaridade entre as rochas das formações do Grupo Península Trinity, Formação Grauvaca-Folhelho e Formação Miers Bluff. As rochas apresentam composição quartzo-feldspática, com baixa porcentagem de fragmentos líticos de composição plutônica, vulcânica e metamórfica. Diferenças composicionais ocorrem na Formação View Point, na qual também ocorre subarcóseo; e na Formação Miers Bluff, arcóseo lítico. As idades U-Pb de grãos detríticos de zircão para as rochas do Grupo Península Trinity da região de Botany Bay são concordantes e a mais jovem é 324 ± 8 Ma, ainda com quantidade expressiva de grãos com idades de 512 a 541Ma e 1001 a 1091Ma. Valores de ?Nd para rocha total, calculados para 220 Ma estão entre -5 e -8, indicando influência de fontes crustais recicladas ou de razoável residência crustal. A extensa gama de idades para a área-fonte indica reciclagem sedimentar de fonte diversa, com idades carboníferas, cambrianas e pré-cambrianas. O ?Hf calculado para as idades de U-Pb dos grãos de zircão detríticos mais jovens variade -1,2 a -5,7, também indicam extensa residência crustal. A amostra da Formação Legoupil, que complementa os dados de idades U-Pb em grãos detríticos de zircão para oGrupo Península Trinity, apresenta idade mais jovem de 265 ± 2, restringindo a idade máxima de sedimentação ao Permiano. Para as amostras da Formação Grauvaca-Folhelho as idades U-Pb em grãos detríticos de zircão apresentam duas concentrações bem definidas, permo-triássica e cambriana, com idade concordante mais jovem de 216 ± 2 Ma e mais antiga de 1,8 ± 0,13 Ga. Essas idades são condizentes com as dos grãos detríticos de zircão do Grupo Península Trinity. A partir dos dados de idades de grãos detríticos dezircão pode-se definir como a idade máxima para deposição para as formações Legoupil e Grauvaca-Folhelho sendo permo-triássica, assim como para as rochas do GrupoPenínsula Trinity em Botany Bay. Idades essas que levam a sugerir como fonte a Patagônia, no maciço Norte-patagônico, e Antártica Ocidental, na Terra de Mary Byrd. Estascondizem tanto em idade como em tipo de fonte, ígnea e metamórfica, com contribuição sedimentar.
The rocks of the Trinity Peninsula Group and equivalent units comprise sandstone, mudstone and conglomerate, as wel as their corresponding metamorphic rocks, whose formation is attributed to turbidity currents. They crop out in the northern Antarctic Peninsula and adjacent islands. Samples of sandstone, arkose and conglomerate of these units were analyzed in order to trace their provenance. From the petrographic analysis of sandstone was found similarity between the rocks of the Trinity Peninsula Group, Greywacke-Shale Formation and Miers Bluff Formation. The rocks have quartz-feldspathic composition, low percentage of lithic fragments of plutonic, volcanic and metamorphic rocks. Compositional differences occur in View Point Formation, which also occurs subarkose, and Miers Bluff Formation, lithic arcóseo. The U-Pb ages dates of detrital zircon grains in the rocks of the Trinity Peninsula Group region of Botany Bay are concordant and the youngest is 324 ± 8 Ma, but concentrations around 512-541Ma and 1001-1091Ma are common. Values of ?Nd calculated for 220 Ma are between -5 and -8, indicating influence of recycled crustal sources or with reasonable crustal residence. With extensive range of ages for the source area, indicating sediment recycling of diverse source areas, with ages spread from Carboniferous to Cambrian and Precambrian. The ?Hf calculated for dates U-Pb of younger detrital zircon ranges from -1.2 to -5.7, also indicate extensive crustal residence. The sample of Legoupil Formation, which complements the U-Pb dates for detrital zircon grains of the Trinity Peninsula Group, presents younger date of 265 ± 2, restricting the maximum age of the sedimentation asPermian. For samples of Greywacke-Shale Formation the U-Pb dates for detrital zircon grains exhibit two well-defined concentrations, permo-triassic and cambrian, with younger concordant date of 216 ± 2 Ma and older of 1.8 ± 0,13 Ga. These dates are consistent with those of detrital zircon grains from the Peninsula Group Trinity. From the data on detrital zircon grains can be defined as the maximum age for deposition for Legoupil and Greywacke-Shale formations being permo-triassic, as well as the rocks of the Trinity Peninsula Group in Botany Bay. Dates that suggest as a source area Patagonia, in Northern Patagonian massif and West Antarctica, in the Mary Byrd Land. These areas are consistent with both in age and rock types, igneous, metamorphic, and sedimentary, as the source area.

This study utilizes new geochemical analyses of fluids (formation water and gas) collected predominately from Devonian organic-rich shales and reservoir sandstones from the northern Appalachian Basin margin to investigate basin scale hydrologic processes, water-rock reactions, microbial activity, and natural gas generation. Elemental and isotopic composition of co-produced formation waters and natural gas show that the majority of methane in Devonian organic-rich shales and reservoir sandstones is thermogenic in origin with localized accumulations of microbial gas. Microbial methanogenesis appears to be primarily limited by redox buffered conditions favoring microbial sulfate reduction. Thermal maturity (bioavailability) of shale organic matter and the paucity of formation waters may also explain the lack of extensive microbial methane accumulations. Iodine and strontium isotopes, coupled to elemental chemistry demonstrate basin scale fluid flow and clay mineral diagenesis. Evidence for this is based on anomalously high ¹²⁹I/I values sourced from uranium deposits (fissiogenic production of ¹²⁹I) at the structural front of the Appalachian Basin. Radiogenic ⁸⁷Sr/⁸⁶Sr (up to 0.7220), and depleted boron and potassium concentrations support smectite clay diagenesis at temperatures greater than 120 °C. The development of fissiogenic ¹²⁹I as a tracer of basin scale fluid flow is a novel application of iodine isotopes provided that the sources of cosmogenic and anthropogenic ¹²⁹I are reasonably well constrained. The anomalously high ¹²⁹I/I in Appalachian Basin brines may be alternatively explained by microbial fractionation based on a correlation with decreasing δ¹³C-DIC values and decreasing sulfate concentrations in the range of sulfate reduction. These results demonstrate that the microbial fractionation of iodine isotopes may be possible and an important consideration when interpreting ¹²⁹I/I, regardless of the source of ¹²⁹I. Results from this study have important implications for understanding the controls on and origins of natural gas production in sedimentary basins; tectonically and topographically driven basin scale fluid flow, including diagenetically induced waterrock reactions and mineral ore deposition related to orogenesis; and an improvement of the use of iodine isotopes for understanding large scale fluid flow, and possibly its use as a tracer of organic matter diagenesis and the distribution of radionuclides in the environment.

Orientador: Amauri Antonio Menegário
Banca: Verdiana Teixeira de Souza Martins
Banca: Juliana Aparecida Galhardi
Resumo: O metal tóxico de chumbo (Pb) pode ser prejudicial para a saúde humana em várias maneiras, mas também pode ser utilizado como um traçador da poluição ambiental, porque a abundância relativa dos seus quatro isótopos estáveis de massas 204, 206, 207 e 208 conhecidos varia de acordo com a fonte de emissão. Este estudo é focado nas concentrações de chumbo e nas razões isótopicas de material particulado das cidades brasileiras de Rio Claro (SP) e Goiânia (GO), a fim de determinar as principais fontes de poluição por Pb. Amostras de material particulado foram recolhidas em filtros de teflon limpos, durante a estações chuvosa e seca entre anos de 2014 e 2016 na UNESP - Campus de Rio Claro e no centro de Goiânia nas proximidades das estradas principais com um grande volume de tráfego. As concentrações de Pb e as razões isótopicas estáveis de 206Pb/207Pb e 208Pb/207Pb das amostras de material particulado foram analisadas por ICP-MS. Para aplicar esta técnica, foi necessário otimizar os parâmetros como o tempo de aquisição, tempo morto de detector e discriminação de massa, que afetam a exatidão da medida e precisão. Em Goiânia, as concentracões de Pb exibiram valores mais elevados na estação seca do que na estação chuvosa, enquanto as concentracões de Pb foram similares em ambas as campanhas de amostragem em Rio Claro. Trajetórias de volta do modelo HYSPLIT foram analisadas, a fim de investigarse associações entre os níveis de Pb e as direções das massas de ar. Entretanto, a comparação entre os valores das razões isótopicas 206Pb/207Pb e 208Pb/207Pb e os dados das fontes potenciais de Pb a partir de estudos prévios indicaram que a gasolina pode ser considerada como a principal fonte de Pb para o material particulado em Goiânia e Rio Claro. As razões... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The toxic metal lead (Pb) can be harmful to human health in various manners, but is also considered as a distinguished tracer of environmental pollution, since the relative abundance of its four stable isotopes with the atomic masses of 204, 206, 207 and 208 varies with the emission source. This study is focused on the lead concentrations and isotope ratios in the particulate matter of the Brazilian cities of Goiânia (GO) and Rio Claro (SP), in order to determine the main Pb pollution sources. Particulate matter samples were collected on clean Teflon filters during the rainy and dry season between 2014 and 2016 on the campus of the State University of São Paulo (UNESP) in Rio Claro city and in the centre of Goiânia city near main roads with a high traffic volume. The Pb concentrations as well as the 206Pb/207Pb and 208Pb/207Pb stable isotope ratios of the particulate matter samples were analysed by Inductively-Coupled Plasma Mass Spectrometry. To apply this analytical technique successfully, it was necessary to optimize parameters in case of acquisition time, detector dead time and mass discrimination, which affect the measurement accuracy and precision. Results showed that lead concentrations in Goiânia were different between rainy and dry season. In Goiânia, Pb concentrations showed higher values in dry season than in rainy season, while Pb concentrations were more similar in both sampling periods in Rio Claro. Back trajectories were analysed with the HYSPLIT model to investigate associations between Pb concentration levels and the direction of incoming air masses. However, the comparison of the obtained 206Pb/207Pb and 208Pb/207Pb isotope ratios data with data of potential Pb sources from previous studies indicated that gasoline may be considered as main Pb sources in the particulate matter of Goiânia and Rio Claro. Pb... (Complete abstract electronic acess below)
Mestre

L’accroissement de l’urbanisation et le développement industriel modifient la composition des géosphères de la Terre, en augmentant le nombre de problèmes géoécologiques et en affectant négativement la santé humaine. Actuellement, plus d'attention est accordée à la surveillance de l'état des composants de l’environnement naturel urbain. En Russie, les méthodes biogéochimiques (par ex., l'application de feuilles des arbres comme un récepteur naturel de la pollution) sont largement utilisées pour caractériser les problèmes géoécologiques des territoires dans des conditions d’intensité d’activités industrielles. Dans les pays occidentaux, les méthodes permettant d'estimer l'impact des facteurs ambiants sur la géosphère et la santé humaine sont répandues, parmi lesquelles l'évaluation des impacts du cycle de vie (ÉICV). Cependant, ces méthodes ne sont toujours pas appliquées en combinaison. L’utilisation d’indicateurs efficaces reflétant l'intensité de l'impact anthropique sur les écosystèmes; d’une cartographie de la distribution des polluants, ainsi que l'utilisation a posteriori de ces résultats dans l'évaluation des impacts sur l'environnement et la prédiction de leurs effets négatifs des entreprises industrielles (toxicité humaine et l'écotoxicité) sont pertinents pour l'évaluation complète des écosystèmes urbains. Cette méthode intégrée a été proposée et mise en œuvre sur le territoire d’Ust-Kamenogorsk, l'une des villes ayant subie des transformations technogéniques significatives au Kazakhstan avec un ensemble spécifique d’entreprises
With widespread urbanization and industrial development, the composition of the Earth's geosphere shells has changed, increasing the number of geoecological problems of territories and negatively affecting human health. Currently, more attention is being paid to monitoring the state of the components of urban natural environments. In Russia, biogeochemical methods (e.g. applying tree leaves as a kind of natural receptor of pollution) are widely used to characterize the geoecological problems of the territories under the pressure of intensive industrial activities. In Western countries, methods allowing us to estimate the impact of ambient factors on ecosystems and human health have become widespread; life cycle impact assessment is among them. However, these methods still have not been applied in combination. Therefore, the implementation of a comprehensive assessment of urban ecosystems using indicators reflecting the intensity of anthropogenic impact on ecosystems, following mapping of pollutant distributions, as well as the subsequent use of the results in the evaluation of the industrial enterprises' impact on the environment and in the prediction of the negative effects of pollution (human toxicity and ecotoxicity) are relevant. Such integrated method combining two methodologies was suggested and implemented in the territory of Ust-Kamenogorsk city, one of the significantly technogenic transformed cities in Kazakhstan with a specific set of enterprises

In the Pilgangoora Belt of the Pilbara Craton, Australia, the 3517 Ma Coonterunah Group and 3484-3468 Ma Carlindi granitoids underlie the 3458 Ma Warrawoona Group beneath an erosional unconformity, thus providing evidence for ancient emergent continental crust. The basalts either side of the unconformity are remarkably similar, with N-MORB-normalised enrichment factors for LILE, Th, U and LREE greater than those for Ta, Nb, P, Zr, Ti, Y and M-HREE, and initial e(Nd, Hf) compositions which systematically vary with Sm/Nd, Nb/U and Nb/La ratios. Geological and geochemical evidence shows that the Warrawoona Group was erupted onto continental basement, and that these basalts assimilated small amounts of Carlindi granitoid. As the Coonterunah basalts have similar compositions, they probably formed likewise, although they were deposited >60 myr before. Indeed, such a model may be applicable to most other early Pilbara greenstone successions, and so an older continental basement was probably critical for early Pilbara evolution. The geochemical, geological and geophysical characteristics of the Pilbara greenstone successions can be best explained as flood basalt successions deposited onto thin, submerged continental basement. This magmatism was induced by thermal upwelling in the mantle, although the basalts themselves do not have compositions which reflect derivation from an anomalously hot mantle. The Carlindi granitoids probably formed by fusion of young garnet-hornblende-rich sialic crust induced by basaltic volcanism. Early Archaean rocks have Nd-Hf isotope compositions which indicate that the young mantle had differentiated into distinct isotopic domains before 4.0 Ga. Such ancient depletion was associated with an increase of mantle Nb/U ratios to modern values, and hence this event probably reflects the extraction of an amount of continental crust equivalent to its modern mass from the primitive mantle before 3.5 Ga. Thus, a steady-state model of crustal growth is favoured whereby post ~4.0 Ga continental additions have been balanced by recycling back into the mantle, with no net global flux of continental crust at modern subduction zones. It is also proposed that the decoupling of initial e(Nd) and e(Hf) from its typical covariant behaviour was related to the formation of continental crust, perhaps by widespread formation of TTG magmas.

Ce travail est axé sur l’étude d’un profil de sol et des solutions de sol prélevés sur une parcelle expérimentale couvertes d’épicéas. Tous ces échantillons proviennent du Bassin Versant du Strengbach (Observatoire HydroGéochimique de l’Environnement – OHGE), ont été échantillonnés à différentes profondeurs (5, 10, 30 et 60 cm) et durant la période comprise entre 2009 et 2013.Les caractérisations des extraits des sols par spectroscopie Infra-Rouge ont permis de mettre en évidence les modifications des groupements fonctionnels organiques avec la profondeur et que ces modifications ont une forte incidence sur le comportement des cations (majeurs et traces) dans le sol. Des expérimentations d’ultra-filtration ont permis d’identifier les flux colloïdaux et dissous du carbone organique ainsi que ceux des éléments majeurs et traces présents dans les solutions de sol. L’utilisation conjointe des traceurs isotopiques (87Sr/86Sr et δ44/40Ca) et chimiques (Terres Rares) ont mis en évidence des processus ayant lieu aux interfaces eau-sol-plante, comme le prélèvement racinaire ou l’altération des sols
This work is focused on the study of a profile of soil and soil solutions collected on an experimental plot covered with spruce. All these samples come from the watershed of the Strengbach (environment - OHGE Hydrogeochimique Observatory), were sampled at different depths (5, 10, 30 and 60 cm) and during the period between 2009 and 2013. Characterizations of soil extracts by infrared spectroscopy allowed to highlight changes in the organic functional groups with depth and that these changes have a significant impact on the behaviour of the cations (major and trace) in the soil. Ultrafiltration experiments helped to identify flows of colloidal and dissolved organic carbon as well as those of the major and trace-element present in soil solutions. The joint use of isotope tracers (87Sr / 86Sr and δ44 / 40 Ca) and chemical (Rare Earth Elements) have highlighted processes taking place at the water-soil-plant interface, as the uptake by root or soil alteration

The present status of the environment, including environmental problems such as heavy metal accumulation in aquatic and terrestrial ecosystems, is in part the consequence of long-term changes. Cores from peatlands and other natural archives provide us with the potential to study aspects of the atmospheric cycling of elements, such as metal pollutants, on timescales much longer than the decade or two available to us with atmospheric deposition monitoring programs. The past decade especially has seen a rapid increase in interest in the biogeochemical record preserved in peat, particularly as it relates to environmental changes (e.g. climate and pollution). Importantly, recent studies have shown that carbon dynamics, i.e., organic matter decomposition, may influence the record of atmospherically derived elements such as halogens and mercury. Other studies have shown that under certain conditions some downward movement of atmospherically deposited elements may also occur, which adds complexity to establishing reliable chronologies as well as inherent problems of estimating accurate accumulation rates of peat and past metal deposition. Thus, we still lack a complete understanding of the basic biogeochemical processes and their effects on trace element distributions. While many studies have validated the general temporal patterns of peat records, there has been a limited critical examination of accumulation records in quantitative terms. To be certain that we extract not only a qualitative record from peat, it is important that we establish a quantitative link between the archive and the few to several decades of data that are available from contemporary monitoring and research. The main objective of this doctoral thesis was to focus on improving the link between the long-term paleorecord and the contemporary monitoring data available from biomonitoring and direct deposition observations. The main research questions have therefore been: Are peat archives an absolute or relative record? And how are geochemical signals, including dating, incorporated in the peat archive? What temporal resolution is realistic to interpret by using peat cores?

In the Pilgangoora Belt of the Pilbara Craton, Australia, the 3517 Ma Coonterunah Group and 3484-3468 Ma Carlindi granitoids underlie the 3458 Ma Warrawoona Group beneath an erosional unconformity, thus providing evidence for ancient emergent continental crust. The basalts either side of the unconformity are remarkably similar, with N-MORB-normalised enrichment factors for LILE, Th, U and LREE greater than those for Ta, Nb, P, Zr, Ti, Y and M-HREE, and initial e(Nd, Hf) compositions which systematically vary with Sm/Nd, Nb/U and Nb/La ratios. Geological and geochemical evidence shows that the Warrawoona Group was erupted onto continental basement, and that these basalts assimilated small amounts of Carlindi granitoid. As the Coonterunah basalts have similar compositions, they probably formed likewise, although they were deposited >60 myr before. Indeed, such a model may be applicable to most other early Pilbara greenstone successions, and so an older continental basement was probably critical for early Pilbara evolution. The geochemical, geological and geophysical characteristics of the Pilbara greenstone successions can be best explained as flood basalt successions deposited onto thin, submerged continental basement. This magmatism was induced by thermal upwelling in the mantle, although the basalts themselves do not have compositions which reflect derivation from an anomalously hot mantle. The Carlindi granitoids probably formed by fusion of young garnet-hornblende-rich sialic crust induced by basaltic volcanism. Early Archaean rocks have Nd-Hf isotope compositions which indicate that the young mantle had differentiated into distinct isotopic domains before 4.0 Ga. Such ancient depletion was associated with an increase of mantle Nb/U ratios to modern values, and hence this event probably reflects the extraction of an amount of continental crust equivalent to its modern mass from the primitive mantle before 3.5 Ga. Thus, a steady-state model of crustal growth is favoured whereby post ~4.0 Ga continental additions have been balanced by recycling back into the mantle, with no net global flux of continental crust at modern subduction zones. It is also proposed that the decoupling of initial e(Nd) and e(Hf) from its typical covariant behaviour was related to the formation of continental crust, perhaps by widespread formation of TTG magmas.

The elemental analysis of soil is useful in forensic and environmental sciences. Methods were developed and optimized for two laser-based multi-element analysis techniques: laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and laser-induced breakdown spectroscopy (LIBS). This work represents the first use of a 266 nm laser for forensic soil analysis by LIBS. Sample preparation methods were developed and optimized for a variety of sample types, including pellets for large bulk soil specimens (470 mg) and sediment-laden filters (47 mg), and tape-mounting for small transfer evidence specimens (10 mg). Analytical performance for sediment filter pellets and tape-mounted soils was similar to that achieved with bulk pellets. An inter-laboratory comparison exercise was designed to evaluate the performance of the LA-ICP-MS and LIBS methods, as well as for micro X-ray fluorescence (μXRF), across multiple laboratories. Limits of detection (LODs) were 0.01-23 ppm for LA-ICP-MS, 0.25-574 ppm for LIBS, 16-4400 ppm for µXRF, and well below the levels normally seen in soils. Good intra-laboratory precision (≤ 6 % relative standard deviation (RSD) for LA-ICP-MS; ≤ 8 % for µXRF; ≤ 17 % for LIBS) and inter-laboratory precision (≤ 19 % for LA-ICP-MS; ≤ 25 % for µXRF) were achieved for most elements, which is encouraging for a first inter-laboratory exercise. While LIBS generally has higher LODs and RSDs than LA-ICP-MS, both were capable of generating good quality multi-element data sufficient for discrimination purposes. Multivariate methods using principal components analysis (PCA) and linear discriminant analysis (LDA) were developed for discriminations of soils from different sources. Specimens from different sites that were indistinguishable by color alone were discriminated by elemental analysis. Correct classification rates of 94.5 % or better were achieved in a simulated forensic discrimination of three similar sites for both LIBS and LA-ICP-MS. Results for tape-mounted specimens were nearly identical to those achieved with pellets. Methods were tested on soils from USA, Canada and Tanzania. Within-site heterogeneity was site-specific. Elemental differences were greatest for specimens separated by large distances, even within the same lithology. Elemental profiles can be used to discriminate soils from different locations and narrow down locations even when mineralogy is similar.

Silicate melt inclusions (MI) are small samples of melt that are trapped during crystal growth at magmatic pressures and temperatures. The MI represent a sample of the melt that was isolated from the magma during host crystal growth. Thus, MI provide a valuable tool for constraining the magmatic history of igneous systems because they provide an unambiguous method to directly determine compositions of melts from which the host crystal grew. As such, coupled petrographic examination and geochemical analyses of MI and host crystals can reveal information about crystal/melt processes in igneous systems that are difficult (or impossible) to assess through conventional methods. Many studies have used MI to monitor large scale petrogenetic processes such as partial melting and fractional crystallization. The research presented below focuses on using MI to constrain processes that operate at the crystal/melt interface because MI are samples of melt that resided adjacent to the host crystal prior to entrapment as an inclusion. Chapter one addresses challenges associated with preparing small crystals containing MI for geochemical analysis. In chapter two trace element analyses of MI and the immediately adjacent host zircon crystals are used to determine zircon/melt partition coefficients. In chapter 3 the significance of boundary layer development adjacent to growing crystals is evaluated by comparing the trace element compositions of MI host crystals that have significantly different trace element mineral/melt partitioning behavior.
Ph. D.

Les spéléothèmes (concrétions carbonatées se formant dans les zones karstiques) sont des archives paleo-climatiques reconnues, dont l'intérêt majeur est de pouvoir être datées précisément par la méthode Uranium-Thorium. En revanche, les traceurs traditionnellement utilisés pour reconstruire les climats passés à partir de ces objets géologiques ne sont pas directement quantifiables en termes de paramètres climatiques comme la température moyenne, ou la quantité de précipitation. Les variations des concentrations en éléments traces contenus dans les spéléothèmes ont pu être relié dans certains sites aux changements climatiques passés, mais des doutes existent sur la robustesse de leur signal au sein d'une même grotte et entre différents sites.Nous nous sommes appliqués à déterminer les variations au cours des 50 000 dernières années de plusieurs catégories d'éléments (alcalino-terreux, uranium, et terres rares) dans des stalagmites de deux grottes situées dans le sud de la France (les grottes de Villars en Dordogne et de Chauvet en Ardèche), par spectrométrie ICP-MS. Les spéléothèmes sélectionnés ont déjà été datés et ont enregistré les variations paleo-environnementales à travers les isotopes stables de la calcite. Trois périodes d'étude caractérisées par des changements particuliers sont étudiées: le stade isotopique 3 de la dernière période glaciaire (~50-30 ka), la dernière déglaciation (~20-10 ka) et la fin de l'Holocène (~2-0 ka).Le signal des variations des alcalino-terreux à Villars pendant le stade isotopique 3 est significatif et robuste. La variabilité du strontium notamment, qui provient de processus hydrologiques intra-karst, suit les événements climatiques rapides enregistrés dans l'hémisphère Nord. D'autre part, le comportement de nombreux éléments traces pendant la déglaciation est similaire entre les grottes de Villars et de Chauvet. Enfin, des changements du couvert végétal sont probablement à l'origine des changements synchrones enregistrés par les éléments traces et les isotopes stables de la calcite au cours des deux derniers millénaires à Villars.Par ailleurs, l'étude des coefficients de partition des alcalino-terreux, de l'uranium et des terres rares dans des conditions variées montre l'importante de la variabilité inter-site de leur partitionnement.

Rare earth elements (REE) are known as the lanthanide series (La-Lu) plus yttrium (Y) and scandium (Sc). REE are essential materials for modern industries and especially for green technologies (wind turbines, batteries, lasers, catalysts, etc.). However, despite their high global demand, their supply is limited such that the EU has cataloged it as critical raw materials. In order to ensure the supply of REE in the future, the search for alternative sources of these elements worldwide has been promoted in recent years. Acid mine drainage (AMD) produced by the Fe-sulphide weathering can effectively leach Fe, Al, SO4, and REE from the host rock. This can lead to high concentrations of these liberated species in the affected waters. Thus, the REE concentrations in AMD can be between two and three orders of magnitude higher than natural waters, as such it can be considered as a complementary source of REE recovery. The increase of pH in AMD by mixing neutral waters results in the precipitation of iron oxy-hydroxysulfate (schwertmannite) from pH 3-3.5, and aluminum (basaluminite) from pH 4-4.5 in the river channels. This process may be accompanied by REE scavenging. Due to its acidity and high metal load, acid mine drainage presents a major environmental problem worldwide, therefore, different treatment systems have been developed to minimize its impact. Disperse Alkaline Substrate (DAS) passive remediation system neutralizes AMD by dissolving calcite, and allowing the sequential precipitation of schwertmannite and basaluminite in separated layers, where REE are preferably retained in the basaluminite-enriched waste. Despite this, there are still no studies describing the adsorption of REE on both basaluminite and schwertmannite in these environments. The REE scavenging mechanism is studied by adsorption on synthetic minerals of basaluminite and schwertmannite as a result of variation to the both the pH and sulfate concentration. A thermodynamic adsorption model is proposed based on experimental results in order to predict and explain the REE mobility in AMD mixtures with neutral waters and in a passive treatment system. Basaluminite and schwertmannite have a nanocrystalline character. Further, schwertmannite has been observed to transform into goethite on weekly timescales, resulting in sulfate release. However, there is a gap of knowledge about basaluminite stability at variable sulfate concentration and pH and its possible transformation to other more crystalline Al-minerals. In this study, basaluminite local order at different pH values and dissolved sulfate concentrations was characterized. Results demonstrate that basaluminite can transform to nanoboehmite in weeks under circumneutral pH. However, the presence of sulfate can inhibit this transformation. Separate adsorption experiments on both basaluminite and schwertmannite were performed with two different concentrations of SO4 while varying the pH (3-7). Results show that the adsorption is strongly dependent on pH, and to a lesser extent on sulfate concentration. Lanthanide and yttrium adsorption is most effective near pH 5 and higher, while that of scandium begins around pH 4. Due to the high concentrations of sulfate in acidic waters, the predominant aqueous REE species are sulfate complexes (MSO4+). Notably, Sc(OH)2+ represents a significant proportion of aqueous Sc. , A surface complexation model is proposed in which predominant aqueous species (Mz+) adsorb on the mineral surface, XOH, following the reaction: The adsorption of the lanthanides and yttrium occurs through the exchange of one and two protons from the basaluminite and schwertmannite surface, respectively, with the aqueous sulfate complexes. The sorbed species form monodentate surface complexes with the aluminum mineral and bidentate with the iron mineral. In the case of Sc, the aqueous species ScSO4+ and Sc(OH)2+ form bidentate surface complexes with both minerals. EXAFS analysis of the YSO4+ complex adsorbed on the basaluminite surface suggests the formation of a monodentate inner sphere complex, in agreement with the proposed thermodynamic model. Once the surface complexation model was validated, it was used to asses and predict the REE mobility in passive remediation systems and acidic water mixing zones with alkaline inputs from the field. The REE are preferentially retained in basaluminite-rich waste during passive remediation due to its sorption capacity between pH 5-6. In contrast, schwertmannite waste contains very little REE because the formation of this mineral occurs at pH lower than 4, which prevents REE adsorption. Further, Sc may be scavenged during schwertmannite precipitation as a result of this low pH The model correctly predicts the absence of REE in schwertmannite precipitates and the enrichment of the heavy and intermediate REE with respect to the light REE in basaluminite precipitates collected in the water mixing zones. However, there is a systematic overestimation of the fractionation of rare earths in basaluminite precipitate. This inaccuracy is mainly due to the fact that the mineral precipitation and adsorption are not synchronous process, while basaluminite precipitates from pH 4, REE adsorption occurs at higher pH values, between 5 and 7, when the water mixture reaches these values and a fraction of the particles have been dispersed.
Las tierras raras (en inglés rare earth elements, REE) son conocidas como el conjunto de la serie de los lantánidos (La-Lu), itrio (Y) y escandio(Sc). Las tierras raras son materiales indispensables para las industrias modernas y en especial para las tecnologías verdes (aerogeneradores, baterías, láseres, catalizadores, etc.). Sin embargo a pesar de su gran demanda mundial, su abastecimiento es limitado, por lo que han sido catalogadas por la UE como materias primas críticas (Critical Raw Materials). Con el objetivo de asegurar el abastecimiento de REE en el futuro, en los últimos años se ha promovido la búsqueda de fuentes alternativas de estos elementos en todo el mundo. El drenaje ácido de mina (en inglés acid mine drainage, AMD) producido por la meteorización de sulfuros de Fe, tiene un alto poder de lixiviación de las rocas, por lo que las aguas afectadas adquieren elevadas concentraciones en disolución de Fe, Al, SO4 y otros metales, como las REE. Así, las concentraciones de REE en AMD son entre dos y tres órdenes de magnitud superiores al resto de las aguas naturales y pueden suponer una fuente complementaria de recuperación de REE. El aumento de pH del AMD por mezcla con aguas neutras da lugar a la precipitación en los cauces de los ríos de oxy-hidroxisulfatos de hierro (schwertmannita), a partir de pH 3-3.5, y de aluminio (basaluminita), a partir de pH 4-4.5; acompañado de la eliminación de las tierras raras. Debido a su acidez y carga metálica, el drenaje ácido de mina presenta un problema medioambiental de primera magnitud, por lo que se han desarrollado diferentes sistemas de tratamiento para minimizar su impacto. El sistema de tratamiento pasivo Disperse Alkaline Substrate (DAS) produce la neutralización de las aguas ácidas por la disolución de la calcita presente en el sistema, permitiendo la precipitación secuencial, de schwertmannita y basaluminita. Las tierras raras quedan retenidas preferentemente en el residuo enriquecido en basaluminita. A pesar de ello, aún no existen estudios que describan la adsorción de tierras raras tanto en basaluminita como schwertmannita en estos ambientes. En esta tesis se estudia el mecanismo de retención de las tierras raras mediante adsorción en minerales sintéticos de basaluminita y schwertmannita, en función del pH y del contenido de sulfato disuelto. Con los resultados experimentales obtenidos, se propone un modelo termodinámico de adsorción para predecir y explicar la movilidad de las tierras raras observada en mezclas de AMD con aguas neutras y en un sistema de tratamiento pasivo. La basaluminita y la schwertmannita presentan un carácter nanocristalino. Es conocido que la schwertmannita se transforma en goethita en semanas, liberando sulfato. Sin embargo, nada se sabe de la basaluminita y su posible transformación a otros minerales de Al más cristalinos. De este modo, la caracterización del orden local de la basaluminita a diferentes valores de pH y sulfato se expone en primer lugar. Dependiendo del pH y el sulfato en disolución, la basaluminita se transforma en diferentes grados a nanoboehmita en semanas, pero tiende a estabilizarse con la presencia de sulfato en solución. Los experimentos de adsorción en basaluminita y schwertmannita con diferentes concentraciones de SO4 realizados para cada mineral y en rangos de 3-7 de pH han demostrado que la adsorción es fuertemente dependiente del pH, y en menor medida del sulfato. La adsorción de los lantánidos y del itrio es efectiva a pH 5, mientras que la del escandio comienza a pH 4. Debido a las altas concentraciones de sulfato en aguas ácidas, las especies acuosas predominantes de las tierras raras son los complejos con sulfato, MSO4+. Además del complejo sulfato, el Sc presenta importantes proporciones de Sc(OH)2+ en solución. En función de la dependencia del pH y de la importancia de la especiación acuosa, se propone un modelo de complejación superficial donde la especie acuosa predominante (Mz+) se adsorbe a la superficie libre el mineral, XOH, cumpliendo la siguiente reacción: La adsorción de los lantánidos y del itrio se produce a través del intercambio de uno o dos protones de la superficie de la basaluminita o de la schwertmannita, respectivamente, con los complejos sulfato acuoso, formando complejos superficiales monodentados con el mineral de aluminio y bidentados con el de hierro. En el caso del Sc, las especies acuosas ScSO4+ y Sc(OH)2+ forman complejos superficiales bidentados con ambos minerales. Complementando el modelo propuesto, el análisis de EXAFS del complejo YSO4+ adsorbido en la superficie basaluminita sugiere la formación de un complejo monodentado de esfera interna, coincidiendo con el modelo termodinámico propuesto. El modelo de complejación superficial, una vez validado, ha permitido evaluar y predecir la movilidad de REE en los sistemas de tratamiento pasivos y en zonas de mezcla de aguas ácidas con aportes alcalinos estudiados en el campo. La preferente retención de las tierras raras en la zona de la basaluminita precipitada en los sistemas de tratamiento pasivo ocurre por adsorción de las mismas a pH entre 5-6. La ausencia de tierras raras en la zona de schwertmannita se debe al bajo pH de su formación, inferior a 4, que impide la adsorción de las mismas. Sin embargo, debido a su menor pH de adsorción, una fracción de Sc puede quedar retenida en la schwertmannita. El modelo también predice correctamente la ausencia de REE en los precipitados de schwertmannita y el enriquecimiento de las tierras raras pesadas e intermedias respecto a las ligeras en los precipitados de basaluminita recogidos en el campo en las zonas de mezcla de aguas. Sin embargo, se ha observado una sistemática sobreestimación del fraccionamiento de las tierras raras en los precipitados de basaluminita. Este hecho se debe principalmente a que la precipitación del mineral no ocurre de forma síncrona con la adsorción, precipitando la basaluminita a partir de pH 4 y adsorbiendo tierras raras a pH más altos, entre 5 y 7, cuando las partículas sólidas han sido parcialmente dispersadas.

Isotopic and trace element analyses are essential to our understanding ore-forming processes, but traditionally these techniques have required bulk digestion of rocks and minerals. Recent advances in in situ microanalytical techniques permit us to analyse samples on a mineral-by mineral basis and probe the chemistry of individual growth bands in minerals, providing a near-continuous record in any zoned mineral. This thesis is composed of five studies using the in situ geochemistry of 'gangue' (non-ore) minerals to elucidate cryptic ore-forming processes that are obscured using conventional analyses. The first half of this thesis presents coupled isotopic and trace element analyses in quartz and pyrite from magmatic-hydrothermal Cu-Au deposits. These studies revealed complex chemical zonation, providing a detailed record of cryptic fluid chemistry and depositional processes. A distinct isotopic signature and residual metastable silica hydrates in quartz microcrystals from the El Indio deposit, Chile provided the first evidence for silica maturation in a high-temperature environment and the first evidence for non-equilibrium isotope fractionation in quartz. The second half of this thesis focuses on the trace element chemistry of minerals from the Bellevue Core, a ~3 km drillcore intersecting the upper half of the Bushveld Complex, South Africa - the largest known repository of platinum-group elements (PGEs). These studies revealed a prospective PGE horizon and provide the first evidence for extensive equilibration of plagioclase in cumulate rocks.

The globally-deposited clay layer marking the Cretaceous-Tertiary boundary has been studied to determine the mineralogical carrier phases for the anomalously concentrated platinum-group elements, the affinity of these elements for organic complexes in low temperature environments, the degree of terrestrial input to the boundary clay and the usefulness of platinum-group elemental ratios in projectile identification. Grain size separates from marine and terrestrial Cretaceous-Tertiary boundary sites were analyzed for platinum-group elements (Pt, Pd, Ru, Ir, Rh) and gold using sensitive induced coupled plasma mass spectrometry. Detection limits on a five gram sample are 0.05 ppb (Rh, Ru, Ir), 0.1 ppb (Pt, Pd) and 0.2 ppb (Au). Platinum-group elements are concentrated in clay minerals (smectite and illite-smectite clay) formed by the alteration of the original microtektite host. There is also an ubiquitous organic carrier. Ruthenium and Ir were found to be the least susceptible to be fixed in organics. This fact, combined with the geochemical coherence of Ru and Ir makes them more suitable than the other platinum-group elements for estimating the terrestrial platinum-group element input to the boundary clay and for identifying the projectile. The Ru/Ir ratio of marine sections (1.77 $\pm$ 0.53) is statistically different from that of the terrestrial sites (0.92 $\pm$ 0.28), and each represents a relatively coherent group. The marine Ru/Ir ratios are chondritic (1.48 $\pm$ 0.09), but the terrestrial ratios are not. Fractionation of Ru and Ir during condensation from the ejecta cloud may account for the broad differences between marine and terrestrial sites. Post-sedimentary alteration, remobilization or terrestrial PGE input may be responsible for the Ru/Ir ratio variations within the groups of marine and terrestrial sites studied. Modelling indicates that the marine ratios could also be attained if $\approx$15% of the boundary metals were contributed by Deccan Trap emissions. However, volcanic emissions could not have been the principal source of platinum-group elements in the boundary clay because mantle PGE ratios and abundances are inconsistent with those measured in the clay. The Ru/Ir values for pristine Tertiary mantle xenoliths (2.6 $\pm$ 0.48), picrites (4.1 $\pm$ 1.8) and for the Deccan Trap basalt (3.42 $\pm$ 1.96) are all statistically distinct from those measured in the Cretaceous-Tertiary boundary clay. Several Canadian impact craters, believed to have been formed by the impact of chondritic projectiles, were analyzed for platinum-group elements in order to test if the interelement ratios identify the chondrite (i.e., the nature of the impactor). However, the dearth of literature data for various types of meteorites, the overall similarity in their platinum-group element ratios, the unknown fractionation effect upon meteorite volatilization and condensation, and the post-depositional alteration and remobilization of platinum-group elements all hamper application of the technique. Consequently, platinum-group elements cannot be readily utilized for identifying impactors beyond broad groups of meteorites (e.g., chondrite vs. iron). Nevertheless, they can often be used as supporting geochemical evidence, along with other elements (e.g., with Ni, Cr, Co abundance and ratios). This is the case at the K-T boundary, where Ru/Ir ratios, mineralogical and geochemical evidence all support a chondritic nature for the impactor.

This thesis consists of three main chapters preceded by an introduction that discusses the importance of diffusion in minerals to constrain the geochemistry of various magmatic processes. The first chapter deals with the experimental technique and measurement of tracer element diffusion data in garnet and clinopyroxene. Self-diffusion coefficients of selected REE have been measured as a function of temperature (770°C-1050°) at 1 bar and oxygen fugacity (fO₂) corresponding to that defined by the iron-wustite buffer. The experimental results indicate small variations of diffusivity for REE in both garnet and clinopyroxene and an activation energy which is similar to the activation energy for diffusion of major components. In the second chapter the atomistic mechanism of Nd diffusion in garnet is investigated by molecular dynamics (MD) simulation. An optimization procedure based on genetic algorithm provides the semi-empirical coefficients that are used to reproduce the repulsive forces between atoms. Results from MD simulations at high pressure and temperature show that Schottky defect is the most favorable mechanism for vacancy formation in the intrinsic region. The preferred reaction to incorporate neodymium in the dodecahedral site involves transferring an iron atom to the octahedral site after removing the aluminum atom from the lattice site. A model of diffusion in the extrinsic region with a prescribed vacancy defect fraction in the garnet (10⁻⁴) also provides an acceptable result. The third chapter considers some of the potential applications of the REE diffusion data in garnet and clinopyroxene to magmatic processes. REE patterns obtained from the solution of a moving boundary problem shows that incompatible elements are more sensitive to disequilibration controlled by diffusion. Melt generated by disequilibrium melting is less enriched in incompatible elements than melt produced by an equilibrium melting process. Solution of a multiphase flow model, including the chemical transport equations with diffusion in a solid phase, permits a more realistic investigation of the disequilibrium melting process. During the ridge evolution the model predicts negligible effect of solid state diffusion on the geochemical evolution of the partial melt and the residual solid.

Summary in English.
Bibliography: leaves 70-75.
Recent research on the platinum-group elements (PGE) has shown increased concentrations in environmental samples, probably as a result of the widespread use of PGE (Pt, Pd and Rh in particular) as catalysts in the chemical and car industry. Most of the recent research on PGE focuses on the analysis of concentrations in environmental samples exposed to anthropogenic sources of PGE, but there are very few studies that have investigated sorption behaviour of PGE in soils.

The work described in this thesis is primarily concerned with (i) the development of analytical methods for the determination of inorganic elements in peat, (ii) the production and analysis of a certified peat reference material, and (iii) the application of methods and procedures to the generation and interpretation of elemental profiles in cores from the largest ombrotrophic peat bog in Scotland. The effects of sample preparation on the determination of inorganic elements in peak samples were thoroughly investigated. The analytical methods and quality assurance procedures developed using the certified reference material were applied to the analysis of two Flanders Moss peat cores that had been collected by different coring techniques. An offset between the elemental profiles of the two cores was attributed to loss of surface material in the case of one, confirmed by stable (²⁰⁶Pb/²⁰⁷Pb) and radioactive (²¹⁰Pb) isotopic analysis. The depth profiles of the various elements were interpreted in terms of influences such as nutrient uptake and recycling, anthropogenic inputs from industry, energy generation and transport, soil dust, and post-depositional remobilisation and redistribution. For Pb, for which a record for atmospheric deposition was retained, the relative contributions of different sources (e.g. smelting, coal combustion, car-exhaust emissions) during the industrial era were assessed using Pb concentration and ²⁰⁶Pb/²⁰⁷Pb ratio variations in ²¹⁰Pb-dated peat. The importance of atmospheric Pb deposition prior to the introduction of leaded petrol was confirmed and, in the more distant past, a small Pb peak at a depth of ~1 m was tentatively attributed to Pb mining and smelting activities during the period of the Roman Empire.

The aim of this study was to. examine the relationship between organic maturity and trace element geochemistry of organic rich mudstones, to assess their behaviour as sources or sinks of metals during diagenesis, and their role in mineral deposit genesis. The suite studied consisted of 193 samples from the Draupne, Heather, and Kimmeridge Clay Formations from the Norwegian North Sea and onshore UK. All three formations had above average contents of C and S, and the Draupne and Heather Formations had a low carbonate content. The Draupne Formation was particularly enriched in a number of trace elements but only Cr, Mo, Nb, and U were enriched in all three formations. After transformation of the data to avoid difficulties in interpretation, correlation analysis allowed the trace elements to be divided into three groups on the basis of their mineralogical residences. The use of a battery of geochemical and mineralogical indices demonstrated that variation in sedimentological and environmental factors were significant within the formations studied, and that the relationship between organic maturity and trace element content could not be investigated in isolation. The technique of path analysis was used to assess the strength and nature of this relationship relative to the variation due to other causes. Pb and Zn were found to increase with increasing maturity in both the Draupne and Heather Formations, and Mo was found to decrease. U was seen to decrease, and Cd to increase, in the Draupne Formation only, where they were especially abundant. It is believed that Pb and Zn were supplied by migrating basinal brines which may have acted to remove Mo and U. Other processes which may have mobilised these elements are the in situ generation of organic acids and hydrocarbons.

This study documents the magmatic, hydrothermal and supergene mineralogy and geochemistry of phosphorus and rare earth elements in carbonatite complexes using examples from Tundulu (Malawi), Sokli (Finland), Siilinjarvi (Finland) and Kaluwe (Zambia). In carbonatites, phosphorus averages 1-2% P20S and forms the minerals fluorapatite and monazite. Hydrothermal and supergene processes enrich fluorapatite in Na and REEs through vitusite-type exchanges which lead to formation of vitusite, belovite and britholite; and in CO2 through anti-francolite substitutions. The highest rare earth element contents are found in late-stage ankerite carbonatites or similar rocks of low temperature origin (T < S(XtC) and in hydrothermally altered rocks, where they occur mainly as fluorocarbonates or carbonates. Such minerals are consistent with the REEs having been transported in form of mixed fluoride-carbonate complexes. The mineral paragenesis in hydrothermal veins suggests that different fluorocarbonates precipitated depending on the activity of Ca supplied to the fluid by the wall rocks. The various minerals are modelled to form by simple combinations of calcite (CaCO:v and bastnaesite (REEC03F) molecules. A secondary characteristic feature of these reactions is that extreme heavy rare earth enrichment occurs if the wall rocks are apatite-rich. Petrogenetic modelling using REEs suggests that carbonatites are unlikely to be derived from carbonated silicate magmas by fractional crystallisation or liquid immiscibility. These findings are supported by ex solution temperatures of about 9S0·C recorded using the calcitedolomite geothermometer for quenched lapilli from the Kaluwe carbonatite.

Rare Earth Element (REE) determination in samples of coal and fly ash was undertaken by gradient high performance ion chromatography (HPIC). Ion chromatographic analysis requires that samples be in solution and that the matrix transition metals be removed. Coal samples, weighing 0.20g, were successfully dissolved in sealed pressure vessels in a microwave oven. Standard ashing procedures, followed by acid dissolution, were carried out to allow comparison with the microwave digestion technique. A lithium metaborate/tetraborate fusion and acid dissolution technique was used for the dissolution of fly ash. For the technique of REE determination the sample matrix was removed by off-line cation exchange. In an initial stage of the HPIC analysis the transition metals were removed by anion exchange using pyridine-2,6 dicarboxylic acid. The REE were then analysed using gradient elution of oxalic and diglycolic acid. Typically a 100μ1 volume of sample solution was employed for REE determination, but in the case of low ash (low REE) coal samples, prepared by microwave digestion, on-line concentration of 3-5 ml of sample, was necessary. The separated REE were reacted with 4-(2-pyridylazo)-resorcinol (PAR) and detected photometrically using a visible light detector at a wavelength of 520nm. Reproducibility for each REE was typically better than 5%CoV. Results from the analysis of coal and fly ash international standard reference materials were in acceptable agreement with values from alternative analytical procedures. Smooth, coherent trends obtained when the data were plotted on chondrite and "shale composite" normalised diagrams provided some support for the accuracy of the technique. The application of HPIC to the determination of REE in coals was demonstrated by the analysis of a new international reference coal sample, USGS CLB-1. Differences in REE concentrations between coal samples prepared by microwave digestion and ashing were observed. The HPIC analytical technique was also applied to the determination of REE in fly ash. The REE concentrations of fly ash from sequential electrostatic precipitators, from Lethabo and Kendal power stations, were determined to elucidate the behaviour of REE after the combustion of coal. REE concentrations increased through the sequential precipitators.

Thesis (M.S. in geology)--Washington State University, May 2010.
Title from PDF title page (viewed on May 21, 2010). "School of Earth and Environmental Sciences." Includes bibliographical references.

The increasing load of toxic elements entering the ecosystems, as a consequence of anthropogenic processes, has grown public awareness in the last decades, resulting in a great number of studies focusing on pollution sources, transport, distribution, interactions with living organisms and remediation. Physical/chemical processes that drive the uptake, assimilation, compartmentation and translocation of heavy metals in biota has received a great deal of attention recently, since elemental concentrations and isotopic composition in biological matrices can be used as  probes of both natural and anthropogenic sources. Further they can help to evaluate fate of contaminants and to assess bioavailability of such elements in nature. While poorly defined isotopic pools, multiple sources and fractionating processes add complexity to source identification studies, tracing is hindered mainly by poorly known or unidentified fractionating factors. High precision isotope ratio measurements have found increasing application in various branches of science, from classical isotope geochronology to complex multi-tracer experiments in environmental studies. Instrumental development and refining separation schemes have allowed higher quality data to be obtained and played a major role in the recent progress of the field. The use of modern techniques such as inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for trace and ultra-trace element concentrations and isotope ratio measurements have given new opportunities.  However, sources of errors must be accurately evaluated and avoided at every procedural step. Moreover, even with the utilization of sound analytical measurement protocols, source and process tracing in natural systems can be complicated further by spatial and temporal variability. The work described in the present thesis has been focused primarily on analytical method development, optimization and evaluation (including sample preparation, matrix separation, instrumental analysis and data evaluation stages) for isotopic and multi-elemental analyses in environmental samples at trace and ultra-trace levels. Special attention was paid to evaluate strengths and limitations of the methods as applied to complex natural environments, aiming at correct interpretation of isotopic results in environmental forensics. The analytical protocols covered several isotope systems of both stable (Cd, B, Cr, Cu, Fe, Tl and Zn) and radiogenic (Os, Pb and Sr) elements. Paper I was dedicated to the optimization and testing of a rapid and high sample throughput method for Os concentrations and isotope measurements by ICP-SFMS. If microwave (MW) digestion followed by sample introduction to ICP-SFMS by traditional solution nebulization (SN) offered unparalleled throughput important for processing large number of samples, high-pressure ashing (HPA) combined with gas-phase introduction (GPI) proved to be advantageous for samples with low (below 500 pg) analyte content. The method was applied to a large scale bio-monitoring case, confirming accumulation of anthropogenic Os in animals from an area affected by emissions from a stainless steel foundry. The method for Cr concentrations and isotope ratios in different environmental matrices was optimized in Paper II. A coupling between a high pressure/temperature acid digestion and a one pass, single column matrix separation allowed the analysis of chromites, soils, and biological matrices (first Cr isotope study in lichens and mosses) by ICP-SFMS and MC-ICP-MS. With an overall reproducibility of 0.11‰ (2σ), the results suggested a uniform isotope composition in soil depth profiles. On the other hand a strong negative correlation found between δ53Cr and Cr concentrations in lichens and mosses indicates that airborne Cr from local anthropogenic source(s) is depleted in heavy isotopes, therefore highlighting the possibility of utilization of Cr isotopes to trace local airborne pollution source from steel foundries.   Paper III describes development of high-precision Cd isotope ratio measurement by MC-ICP-MS in a variety of environmental matrices. Several digestion methods (HPA, MW, ultrawave and ashing) were tested for sample preparation, followed by analyte separation from matrix using ion-exchange chromatography. The reproducibility of the method (2σ for δ114Cd/110Cd) was found to be better than 0.1‰. The method was applied to a large number of birch leaves (n>80) collected at different locations and growth stages. Cd in birch leaves is enriched in heavier isotopes relative to the NIST SRM 3108 Cd standard with a mean δ114Cd/110Cd of 0.7‰. The fractionation is assumed to stem from sample uptake through the root system and element translocation in the plant and it exhibits profound between-tree as well as seasonal variations. The latter were compared with seasonal isotopic variations for other isotopic systems (Zn, Os, Pb) in the same trees to aid a better understanding of underlying processes. In Paper IV the number of isotope systems studied was extended to include B, Cd, Cu, Fe, Pb, Sr, Tl and Zn. The analytical procedure utilized a high pressure acid digestion (UltraCLAVE), which provides complete oxidation of the organic material in biological samples, and a two-column ion-exchange separation which represents further development of the separation scheme described in Paper III. Such sample preparation ensures low blank levels, efficient separation of matrix elements, sufficiently high analyte recoveries and reasonably high sample throughput. The method was applied to a large number of biological samples (n>240) and the data obtained represent the first combined characterization of variability in isotopic composition for eight elements in leaves, needles, lichens and mushrooms collected from a geographically confined area. To further explore the reason of variability observed, soil profiles from the same area were analyzed for both concentrations and isotopic compositions of B, Cd, Cr, Cu, Fe, Pb, Sr, Tl and Zn in Paper V. Results of this study suggest that the observed high variability can be dependent on operationally-defined fractions (assessed by applying a modified SEP to process soil samples) and on the typology of the individual matrix analyzed (assessed through the coupling of soil profile results to those obtained for other matrices: lysimetric waters, mushrooms, litter, needles, leaves and lichens). The method development conducted in this work highlights the importance of considering all possible sources of biases/errors as well as possibility to use overlapping sample preparation schemes for multi-isotope studies. The results obtained for different environmental matrices represent a starting point for discussing the role of natural isotopic variability in isotope applications and forensics, and the importance of in-depth knowledge of the multiple parameters affecting the variability observed.

Large scale mapping in Prosser Township has revealed an entirely felsic subaqueous volcanic sequence containing both pyroclastic and effusive high silica rhyolites which are exceptionally well preserved. The eruption sequence alternates between thin coulees and tuffaceous units, all of which are covered by two distinct units, a pumice- and spatter-rich tuff breccia and a quartz porphyritic rhyolite. Aphyric coulees are well preserved, having flow banding, perlite, and hyaloclastite, which are indicative of a glassy protolith. In the coulee interior there is no evidence of sea-floor clay alteration; the former glass has been isochemically recrystallized to an inter-grown mixture of quartz and plagioclase during metamorphism. These formerly glassy rhyolites formed thin flows by normal effusive eruption without the intervention of high temperatures or volatile depolymerising agents. The crystal-poor rocks were not erupted near their liquidus temperatures (ca. 980°C) as suggested by earlier work using zircon saturation thermometry, but instead the Ti-in-zircon thermometer demonstrates they were erupted around 830°C. Detailed petrography has allowed the robust determination of a protolith composition which is used to assess mobility of the rare earth and high field strength elements. The rare earth elements are shown to be considerably mobile, approximately by a factor of three within a single, 6 m thick coulee. In contrast the HFSE, with the exception of Pb and Y, have only been mobilized up to 10%, largely as a result of sericitization and chloritization. The Nb/Zr vs. Al2O3/TiO2 diagram reliably discriminates between aphyric and quartz porphyritic rhyolite units which respectively correlate with the Lower and Upper members of the nearby Kidd Creek deposit. Furthermore the Hf-Th-Ta diagram shows a clear magmatic evolutionary trend towards the Hf apex. This is consistent with observed zircon abundances within the aphyric rhyolite coulees. The volcanological, textural and lithogeochemical work allows for the correlation of the Prosser Township rocks to the adjacent Kidd Creek mine stratigraphic sequence. However, the Middle member at the mine, a volcanoclastic unit which separates aphyric and quartz porphyritic lavas, is found as a pyroclastic pumice- and spatter-rich tuff breccia at Prosser Township that has not been previously described in the area. As such it may provide a suitable host rock for hydrothermal massive sulphide mineralization.

In the Mojave Pegmatite district, located in northwestern AZ, numerous pegmatites intrude syn- to post-collisional Paleoproterozoic granitic rocks. The slightly older Cerbat plutons are associated with the suturing of the Mojave and Yavapai terranes whereas Aquarius granites were emplaced during the Yavapai Orogeny as the sutured terranes docked with North America. A detailed study of 5 pegmatites shows that they are zoned with composite cores and contain REE minerals characteristic of NYF pegmatites. However, they exhibit characteristics atypical for NYF pegmatites including F depletion, white microcline, an absence of columbite and, in the Rare Metals pegmatite, have muscovite and beryl. With the exception of the Kingman pegmatite, they exhibit normal LREE-HREE distributions. The Kingman pegmatite is extremely LREE enriched, HREE depleted and exhibits an unusual Nd enrichment which, in some cases, is sufficiently high that allanite is Nd dominant, thus a new mineral species, allanite-Nd.

A novel and simple "constant-addition" technique was used to study calcite precipitation kinetics and the partitioning of REE between calcite overgrowths and their parent seawater solutions under steady state conditions.
As a consequence of solute interactions in solution and at the growing mineral surface, the calcite precipitation mechanism in seawater is complex. It is dominated by the following reversible overall reaction: $ rm Ca sp{2+}+CO sbsp{3}{2-} rightleftharpoons CaCO sb3.$ A kinetic expression is proposed which describes the precipitation rate according to this reaction. A partial reaction order of 3 with respect to CO$ sb3 sp{2-}$ is obtained.
REE have a strong affinity for calcite and substitute for Ca$ sp{2+}$. REE partition coefficients in calcite overgrowths were calculated from their concentrations in the overgrowths and their parent solutions using a non-thermodynamic homogeneous model. The concentrations were determined by chelation and gradient ion chromatography (CGIC) using a revised procedure. REE partition coefficients decrease gradually with increasing REE atomic number. They are sensitive to changes in (REE): (Ca$ sp{2+}$) and the presence of O$ sb2$ in solution, but unaffected by the precipitation rate, $ rm lbrack CO sb3 sp{2-} rbrack$ or Pco$ sb2$ of the solution. The partitioning behaviour of REE is negatively correlated to the solubility of their respective carbonates and influenced by speciation, adsorption, and subsequent surface reactions (e.g., dehydration).

Pyrrhotite and pyrite commonly contain minor quantities of cobalt, nickel, arsenic and other trace elements, which reflect major effects of source lithology and fluid chemistry, and subordinate effects relating to local processes. Electron probe micro-analyses (EPMA) of silicates from a suite of fifteen metasomatic Fe-oxide and affiliated ore samples show enrichments of chlorine in biopyriboles associated with Co-bearing iron sulfides and arsenides. Biotite from several localities contains from 1.5 to over 5.5 wt.% Cl. Amphiboles from several localities are also Cl-enriched, with up to 2.7 wt.% Cl. Amphibole from the Osborne Au-Cu deposit in Queensland also contains up to 1.5 wt.% scandium. Otherwise, mild enrichments of both scandium and vanadium are widespread in the silicates from many of these samples, particularly in epidote (up to 550 ppm Sc and up to 1860 ppm V), amphibole (to 260 ppm Sc) and diopside (to 0.57 wt.% V from one locality). A more extensive study was undertaken to determine the trace element distribution in iron sulfides. Over 1100 EPMA and 150 SIMS analyses of pyrite, pyrrhotite, and other sulfides were collected, representing over 100 localities and a dozen major ore-forming environments. These results were combined with data from the literature to assess overall Co, Ni, As, Se, Pd and Au distributions in iron sulfides across a range of geologic processes and lithologies. Iron sulfides from mafic-hosted magmatic oxide and sulfide systems are enriched in Co and Ni. In contrast to magmatic systems, iron sulfides from hydrothermal systems dominated by magmatic-derived aqueous fluids tend to be low in overall trace elements, regardless of the host lithology. Iron sulfides from hydrothermal systems dominated by external fluids show a wide variation in trace element content. In deposit types formed by dilute fluids (e.g. epithermal Au), Co and Ni tend to be low in pyrite whereas As may be quite high. Where high salinity fluids are implicated (as in metasomatic Fe-oxide systems), As and Ni contents in pyrite are variable but Co is typically enriched. Iron sulfide compositions also reflect source lithologies. Among diverse volcanogenic massive sulfide (VMS) deposits, pyrite from the more mafic Cyprus and Besshi types show notable enrichments of Co whereas Kuroko deposits rarely show any enrichment. Hence, source lithology and fluid chemistry play major roles in the minor element make-up of the iron sulfides across a range of deposit types. A parallel investigation was undertaken to assess the role of thermodynamics on the trace elements contents of iron sulfides. From a synthesis and evaluation of published experimental results, phase relationships in the Co-S-O-(Si) system were calculated and contrasted to the equivalent Fe system. The boundaries between the sulfides and oxides in the Co-S-O system are shifted to higher oxygen fugacities relative to the phase boundaries in the Fe-S-O system. In addition to the Fe-Co-S-O-(Si) system, phase relations in the Fe-(Ni,Co)-As-S system have been evaluated. Arsenic is implicated in a coupled substitution mechanism [CoAs]₁[FeS]₋₁ observed in some pyrite. The observed substitution behavior may be a reflection of the limiting assemblages present.

Bibliography: pages 94-99.
This thesis describes work performed to establish and demonstrate a quantitative trace element microanalysis technique for geological material using protons accelerated by the Van de Graaff Accelerator at the National Accelerator Centre (NAC) in Faure near Cape Town. The method relies on the analysis of Proton Induced X-ray Emission (PIXE) spectra, interpreted with the help of the GeoPIXE software package. The use of the Si(Li) energy dispersive detector provides simultaneous multi-element detection at the parts-per-million (ppm) level, and a scanning beam facility permits trace element distributions to be studied at these levels. The calibration of the detector efficiency and the thicknesses of selectable X-ray attenuating filters was performed using pure elemental samples. This involved the accurate determination of the target to detector distance, the thickness of the active volume of the Si(Li) detector crystal, the thicknesses of all the absorbing layers between the sample and the detector crystal, and the assessment of the effects of incomplete charge collection in the detector.

The Neoproterozoic was a time of major change in Earth’s surficial history, including a major rise in atmospheric oxygen, the first appearance of complex metazoan life, and a series of worldwide glaciations. A particular interesting element of these so called “snowball Earth” glacial deposits is the presence of iron formation, a distinctive Precambrian rock type that is largely absent from the post-Paleoproterozoic record. Despite being relatively poorly studied with respect to their geochemistry and sedimentology, Neoproterozoic iron formations are used to support many models for the record of oxygen concentrations of the Earth. The classical example of Neoproterozoic iron formation is the Rapitan iron formation of northwestern Canada. This hematite-jasper iron formation is associated with glaciogenic turbidites and diamictites. Despite being the archetype, the Rapitan iron formation has not been studied in the context of recent ideas about the Neoproterozoic. In this thesis, the stratigraphy, geochemistry, and basin architecture of the Rapitan iron formation are reassessed. Using the REE+Y and the redox-sensitive elements Mo and U, it is shown that the Rapitan iron formation was deposited in a partially restricted basin from biogenically reduced iron under variable redox conditions. Elemental Re and Mo isotopes further show that although oxic and ferruginous conditions predominated during deposition of the iron formation, a transition towards a sulfidic water column locally terminated deposition. Finally, regional stratigraphy and geochemistry show that the iron formation was preferentially deposited in deep, newly formed basins that were protected from significant siliciclastic sedimentation. These basins were delimited by inferred crustal-scale faults trending roughly perpendicular to the axis of the rift basin, and allowed significant changes in thickness and sedimentological character over short distances along strike. These factors help build an overall geotectonic regime under which Neoproterozoic iron formations were deposited: young, deep rift basins that had undergone marine incursion, and were intermittently sealed by an ice shelf, allowing for the generation of an anoxic, iron-rich water column. The absence of the Eu anomaly and the heavy Mo isotopic signature indicate that the open ocean was fully oxygenated at the time of Rapitan iron formation deposition, as opposed to ferruginous as previously suggested.

The Dumper Dew is a newly discovered pegmatite located on the eastfacing slope of Uncle Tom Mountain in Oxford County, Maine. It is a geochemically evolved LCT-type pegmatite petrogenetically linked to the middle Paleozoic Sebago batholith. Shallow emplacement of the Dumper Dew is evidenced by abundant miarolitic cavities found in the pegmatite. The sheet-like structure of the pegmatite coupled with its intrusion in lowmetamorphic grade country rock suggests rapid crystallization. Northern portions of the wall zone and intermediate zones have undergone hydrothermal alteration by the migration of late-stage fluids. The pegmatite hosts a diverse assemblage of rare-element mineral phases due to its high degree of geochemical fractionation. Trends of geochemical fractionation of individual mineral phases such as K-feldspar, muscovite, garnet, apatite, beryl, spodumene, triphylite-lithiophilite, tourmaline, cassiterite, and columbite-tantalite were attained via instrumentation assay. These trends illustrate an enhanced degree of magmatic differentiation relative to other pegmatites in the area.

The Western Gneiss Region (WGR) in Norway is home to some of the world’s most spectacular exposures of high pressure (HP) and ultrahigh pressure (UHP) eclogites. Despite extensive petrological studies into their pressure, temperature and time (PTt) histories, relatively few have reported on their trace element compositions. Such data can be used to supplement our understanding of the provenance and history of Norwegian eclogites, as well as to further our understanding of trace element fluxes during HP to UHP metamorphism in subduction zone settings. In order to address this shortfall in data availability, the first step was to investigate and apply the best dissolution techniques for preparing eclogite samples for chemical analysis. Eclogites commonly contain up to a few weight percent rutile (TiO2), which is known to be an important host for a variety of major and trace elements (e.g. Ti, Nb and Ta). However, typical rock digestion procedures are incapable of dissolving rutile, and thus may lead to inaccurate measurements. It was found that that total dissolution of rutile can be achieved by dissolving samples in sealed pressure vessels at increased pressures and temperatures, ultimately leading to greatly increased data accuracy for analyses of any rutile-bearing lithology. The solutions were analysed by standard ICP-MS techniques and the results compared to analyses of powders by XRF spectrometry. Our high-accuracy and high-precision data were subjected to immobile trace element discriminant analyses that suggested eclogites belonged to three broad geochemical groups: eclogites with mid ocean ridge Basalt (MORB)-like composition; eclogites with arc-like composition; and eclogites with geochemical signatures significantly perturbed by metamorphism. The geochemistry of eclogites in the first two groups are shown to likely reflect protolith composition, and as such we used model protolith compositions to calculate estimated element mobilities (EMMs) for those elements considered relatively mobile during metamorphism. It was not possible to determine protoliths for eclogites in the third category using trace elements alone. Finally, the trace element geochemistry of a large number of separated eclogite-hosted rutiles was studied. The data collected were used to demonstrate that rutile contains significant amounts of the whole-rock’s high field strength element (HFSE) budget, and may exert significant control on the HFSE composition of passing hydrothermal fluids. Furthermore, Zr-in-rutile thermometry (ZRT) was applied to separated rutiles. This temperature information was used to better our understanding of the thermal history of the WGR, as well as to create a map of eclogite temperatures in the Nordfjord-Statlandet area. This high-resolution thermal map of arguably the most important area of the WGR, supports current interpretations that during the Caledonian Orogeny the leading edge of the Baltica plate was consumed in a northwest to north-northwest-dipping subduction zone under Laurentia. Furthermore, isotherms on this map mimic several major fold hinges in the region rather well, thus providing support to the hypothesis that such structures were most likely formed during the collapse of the Scandinavian Caledonian Orogen after the peak metamorphism of most eclogites.

Despite an increased interest in exploitation of hydrocarbon source rock resource plays, there remains an incomplete understanding of organic and inorganic component interaction within source rocks. Few studies have been conducted concerning the associations between organic and inorganic geochemistry for the purposes of understanding kerogen type, thermal maturity influence, and paleoredox setting. This investigation’s goal was evaluating these relationships with samples from the Eagle Ford Formation using organic data, obtained by Rock-Eval pyrolysis and oxidation, and inorganic data, obtained using high-temperature and pressure leaching experiments. The study additionally tested various parameters for whole rock batch leaching, including time, temperature of leaching, and use of acids. The most successful leaching technique was applied to samples that (1) had first been subjected to Rock-Eval pyrolysis, at three different maximum temperatures (450°C, 550°C, and 650°C), as well as (2) samples that had not been subjected to pyrolysis. As different kerogen fractions were destroyed at these different temperatures, variances in elemental concentrations leached from these samples could be attributed, at least partially, to these fractions. Using this approach, the lower molecular weight kerogen fraction contained most of the elements likely attributable to carbonates and sulfides associated with the kerogen (e.g., Ca, Mg, Mn, Mo, P, S, Sr, Zn). The higher molecular weight portion contained more elements probably attributable to clays, quartz, and other clastic minerals (e.g., Al, Fe, K, Si). An evaluation of the overall element chemistry of the rock paired with Rock-Eval parameters showed (1) major/trace elements varied according to amount and type of organic carbon in the Eagle Ford samples, (2) relative abundances of certain major/trace elements were useful proxies for bulk mineralogy and depositional environment, and (3) relationships between certain clay-related major and trace elements and T_max values suggesting clays and trace elements acted to catalyze the cracking of the kerogen.

Ni laterites are considered worthy targets for critical metals (CM) exploration as rare earth elements (REE), Sc and platinum group elements (PGE) can be concentrated during weathering as a result of residual and secondary enrichment. In this investigation geochemical and mineralogical data of CM from two different nickel laterite types (i) from the Moa Bay mining area in Cuba (oxide type) and (ii) from the Falcondo mining area in the Dominican Republic (hydrous Mg silicate type) are presented. Emphasis is given on examining their potential to accumulate CM and on processes involved. Results show that CM are concentrated towards the surface in specific zones: (i) REE in clay minerals rich horizons and within zones composed of secondary Mn oxide(s) (ii) Sc within zones rich in secondary Fe and Mn bearing oxide(s) and (iii) PGE in zones with high concentrations of residual chromian spinel and secondary Fe and Mn bearing oxide(s) at upper levels of the Ni laterite profiles. Concentration factors involve (i) residual enrichment by intense weathering (ii) mobilization of CM during changing Eh and pH conditions with subsequent reprecipitation at favourable geochemical barriers (iii) interactions between biosphere and limonitic soils at highest levels of the profile (critical zone) with involved neoformation processes. Total contents of CM in both Ni laterite types are low when compared with conventional CM ore deposits but are of economic significance as CM have to be seen as cost inexpensive by-products during the Ni (+Co) production. Innovative extraction methods currently under development are believed to boost the significance of Ni laterites as future unconventional CM ore deposits. Two Ni laterite profiles from the Falcondo mining area have been compared for their platinum group element (PGE) geochemistry and mineralogy. One profile (Loma Peguera) is characterized by PGE-enriched (up to 3.5 ppm total PGE) chromitite bodies incorporated within the saprolite, whereas the second profile is chromitite-free (Loma Caribe). Total PGE contents of both profiles slightly increase from parent rocks (36 and 30 ppb, respectively) to saprolite (-50 ppb) and reach highest levels within the limonite zone (640 and 264 ppb, respectively). Chondrite-normalized PGE patterns of saprolite and limonite reveal rather flat shapes with positive peaks of Ru and Pd. Three types of platinum group minerals (PGM) were found by using an innovative hydroseparation technique: (i) primary PGM inclusions in fresh Cr-spinel (laurite and bowieite), (ii) secondary PGM (e.g., Ru-Fe-Os-Ir compounds) from weathering of preexisting PGM (e.g., serpentinization and/or laterization), and (iii) PGM precipitated after PGE mobilization within the laterite (neoformation). Results provide evidence that (i) PGM occurrence and PGE enrichment in the laterite profiles is independent of chromitite incorporation; (ii) PGE enrichment is residual on the profile scale; and (iii) PGE are mobile on a local scale leading to in situ growth of PGM within limonite, probably by bioreduction and/or electrochemical metal accretion. Free grains of PGM with delicate morphologies were discovered in limonite hosted chromitite samples (“floating chromitites”) from highest levels in the Falcondo Ni laterite deposit (Dominican Republic). Textural and chemical evidence obtained via SEM and EMP analysis points to a multistage formation: (i) primary PGM formation at magmatic stage; (ii) transformation to highly porous secondary Os-Ru PGM during serpentinization; (iii) neoformation of Ir-Fe-Ni-(Pt) mineral phases during early stages of lateritization; (iv) neoformation of Pt-(Ir) mineral phases within the critical zone of the profile resulting in nugget shaped accumulation of rounded particulates during late stages of lateritization. The observation of accumulations of most likely biogenic mediated in situ growth of Pt rich nanoparticles in supergene environments could help to explain (i) why Pt bearing nuggets are the most abundant PGM found in surface environments, (ii) why Pt nuggets from placer deposits generally surpass the grain sizes of Pt grains found in parent rocks by several orders of magnitude (few micrometers vs. several millimeters) and (iii) how anthropogenic PGE contamination may affect our biosphere. Osmium chromitite, saprolite and limonite (Falcondo mining area), suggest that serpentinization of the Loma Caribe peridotite has not significantly affected the Re-Os system in Os-rich PGM. This is noted by the fact, that primary PGM formed at magmatic stage and secondary Ru-Os-Mg- isotope characteristics from primary and secondary PGM, separated from Si PGM formed due desulphurization of primary PGM with significant incorporation of Mg silicates, have almost identical Os isotope characteristics, typical of the mantle. However, the Re-Os system can be significantly disturbed during stages of lateritization when porous secondary PGM react with Fe-rich fluids, thus forming hexaferrum and magnetite in the 187 188 interstices of secondary PGM. Here presented data indicate that more radiogenic ratios in higher levels of the weathering profile are linked to steady mobilization of PGE within secondary PGM resulting in subsequent loss of Os counterbalanced by the incorporation of Fe. Os/ Os In this investigation presented data clearly states that PGE are neither noble nor inert in surface environments, at least in those related to tropical Ni laterites from the Northern Caribbean.

Several scenarios set forth to explain the siderophile element abundance patterns in the mantles of the Earth and the Moon involve the segregation of Ni-rich metal to the cores of those bodies under oxidizing conditions. To test these models, the partition coefficients of Ni, Co, Mo, W, P, and Ga between basaltic liquid, Ni-rich metal, and Ni-rich sulfide were experimentally determined under a wide range of oxygen fugacities. The partition coefficients are then used in mass balance calculations to test these scenarios involving oxidizing conditions during the formation of both the Earth's and the Moon's cores. The results show that the siderophile element pattern in the Earth's mantle is consistent with a late stage segregation of a small fraction of metal that consists of approximately 70% Ni at low degrees of partial melding of the silicates. This result is not consistent with the early Earth being substantially molten as the result of a giant impact to form the Moon. The results for the Moon show that the siderophile element pattern in the lunar mantle is consistent with the segregation of a small Ni-rich core at high degrees of melting of the silicates if some elements are initially depleted by some other process--presumably volatility during a giant impact. The high degree of partial melting of silicates is consistent with the postulated magma ocean on the Moon.

A funnel-shaped alteration pipe in Archean tholeiitic to transitional rhyolite and andesite underlying massive Zn-Cu sulphide ore at the Norbec mine in northwestern Quebec was outlined from drill core samples. Geochemical parameters, including mass changes and mobile element ratios were used with normative alteration mineralogy and thin section petrography to determine the extent of the alteration. The alteration was initially characterised by a peripheral zone of sericite-chlorite-quartz and a central chlorite-quartz zone. Isochemical metamorphism of the alteration pipe within the contact aureole of the Lac Dufault stock has converted these assemblages to cordierite-anthophyllite-biotite bearing rocks.
Bulk oxygen isotope data for the altered rhyolite suggest that the Norbec deposit formed at temperatures between 200$ sp circ$C and 300$ sp circ$C, with highest temperatures in the central chloritic zone of the alteration pipe. Calculations using SiO$ sb2$, K and Fe solubilities in typical sea-floor hydrothermal fluids suggest that water/rock ratios of 250 to 900 were necessary to introduce the added mobile elements to the alteration pipe.

It is well known that the release of long-lived radionuclides to the water path is probably the most relevant radiological risk originating from an underground repository. Transuranic elements (ie. all elements with an atomic number greater than 92 (U)) do not have any non-radioactive isotopes and are very rare in natural materials. The long term geochemical behaviour of these elements must thus be derived from chemical analogues such as the rare earth elements (REE), Th and U. Steenkampskraal monazite mine, situated 350 km north of Cape Town, has been found to be an excellent locality for the study of these elements, due to the high concentration of these elements in the ore as well as the ideal geology, which consists of low permeability rocks with groundwater flow governed by fractures. The ore body consists of a monazite [(REE, Th, U)P04], apatite [Ca₃P0₄)₂], chalcopyrite [CuFeS] and magnetite [FeP₄] veindeposit. Water was sampled from six boreholes in the vicinity of the mine and five wi.ndpumps on the surrounding farm Nabeep and Brandewynskraal. Surface water samples were taken from the slimes dam, an ephemeral stream on the western side of the mine, as well as from the surface of a road shortly after rain, below the tailings. Four water samples were taken from within the underground mine workings (Mainshaft, Main shaft extension, Sump on level 3 and Inclined shaft). Colloids were sampled from three of the boreholes and a precipitate was taken from the surface of the main shaft water. Soils were sampled along two transects away from the mine on the eastern and western side of the ore body. Due to the topography of the area, surface contamination could only occur on these two sides. Stable isotopes of oxygen (8 180) and hydrogen ((8 180) indicated the presence of two distinct groups of waters within the vicinity of the mine. One group is composed of unevaporated waters and includes all borehole sand the water sampled in the inclined shaft. The water moving through the inclined shaft is in contact with the ground water. A second group of highly evaporated waters was present in the slin1es dam samples as well as the underground water samples not directly in contact with groundwater. Groundwater contamination by REE-bearing phosphate minerals has resulted in measurable concentrations of U, Th and REE in all mine waters and boreholes in the near vicinity of the mine. The chondritenormalized REE patterns of the water samples are sin1ilar to those displayed by monazite, with a distinctive Eu depletion and an obvious enrichment in LREE with respect to HREE. Monazite-normalized REE patterns for the selected borehole waters show a marked fractionation between LREE and HREE, with the HREE strongly enriched in the aqueous phase. Heavy REE have been shown to have a greater tendency for complexatioi1 and a greater affinity for mineral surfaces. In the present study, the three boreholes in which colloids were found had high concentrations of U, Th and REE. It is likely that colloidal transport of these elements is the dominant mechanism of transport.

La Nouvelle-Calédonie, île située au Sud-Ouest de l’Océan Pacifique et actuel 6e producteur mondial de nickel, est confrontée à une pollution sédimentaire sans précédent de ses cours d’eau. En effet, l’exploitation minière débutée dès les années 1880 a fortement amplifié les processus d’érosion des sols et de transport sédimentaire. Une hyper-sédimentation des hydro-systèmes calédoniens a notamment été constatée suite au déploiement de l’activité minière sur l’archipel. Bien que ce phénomène constitue un facteur aggravant les problèmes d’inondation caractéristiques de ces régions tropicales, les contributions sédimentaires générées par l’exploitation minière restent encore inconnues à ce jour et sont pourtant importantes pour guider la mise en œuvre de mesures visant à réduire ces apports sédimentaires.À cette fin, une étude de traçage sédimentaire qualifiée de fingerprinting a été menée sur un bassin « pilote » : le bassin versant de Thio (397 km²), considéré comme le « berceau » de l’activité minière en Nouvelle-Calédonie. Différents marqueurs tels que les radionucléides, la géochimie élémentaire ou la « couleur » ont été testés pour quantifier les contributions des sources minières aux apports sédimentaires générés par deux crues cycloniques récentes (dépression tropicale en 2015, cyclone Cook en 2017). Une carotte sédimentaire a également été prélevée dans la plaine inondable de la rivière Thio afin de reconstruire l’évolution temporelle des contributions des sources minières. Les résultats de cette étude montrent que les contributions des sources minières dominent, avec une contribution moyenne comprise entre 65-68% pour la crue de 2015 et entre 83-88% pour celle de 2017. L’impact de la variabilité spatiale des précipitations a notamment été mis en évidence pour expliquer les variations des contributions de ces sources. Les variations temporelles des contributions des sources minières déduites de l’analyse de la carotte sédimentaire ont, quant à elles, pu être associées aux différentes périodes historiques de l’exploitation minière sur le bassin versant de Thio (pré-mécanisation, mécanisation, post-mécanisation de l’activité minière). Les contributions des sources minières restent, là encore, dominantes avec une contribution moyenne le long du profil sédimentaire de 74%. La méthode de traçage validée a ensuite été testée sur quatre autres bassins versants de Nouvelle-Calédonie afin d’évaluer la transposabilité de cette approche
New Caledonia, an island located in the south-western Pacific Ocean and currently the world's sixth largest producer of nickel, is facing unprecedented sedimentary pollution of its river systems. Indeed, nickel mining that started in the 1880s accelerated soil erosion and sediment transport processes. Hyper-sedimentation of the Caledonian hydro-systems has been observed after the deployment of mining activities on the archipelago. Although this phenomenon exacerbates the flooding problems experienced in these tropical regions, the sediment contributions generated by nickel mining remain unknown and are nevertheless required to guide the implementation of control measures to reduce these sediment inputs.To this end, a sediment fingerprinting study was carried out in a "pilot" catchment: the Thio River catchment (397 km²), considered as one of the first areas exploited for nickel mining in New Caledonia. Different tracers such as radionuclides, elemental geochemistry or "colour" properties were tested to trace and quantify the mining source contributions to the sediment inputs generated during two recent cyclonic flood events (tropical depression in 2015, cyclone Cook in 2017). A sediment core was also collected in the floodplain of the Thio River catchment to reconstruct the temporal evolution of these mining source contributions. The results of this study show that mining sources dominated sediment inputs with an average contribution ranging from 65-68% for the 2015 flood event to 83-88% for the 2017 flood event. The impact of the spatial variability of precipitation was highlighted to explain the variations in the contributions of these sources across the catchment. The temporal variations in the contributions of the mining sources deduced from the analysis of the sediment core were interpreted at the light of the mining history in the Thio River catchment (pre-mechanization, mechanization, post-mechanization of mining activity). The contributions of mining sources were again dominant with an average contribution along the sedimentary profile of 74 %. Once validated, this tracing method has been tested in four other catchments of New Caledonia in order to evaluate the validity of the approach in other contexts