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Processus géodynamiques, systèmes pétroliers, problématiques environnementales, ou de la versatilité des isotopes du plomb comme outils de traçage / Lead isotopes, versatile tracers of geodynamic processes, petroleum systems, and environmental issuesFetter, Nadège 30 September 2019 (has links)
Le Pb est omniprésent dans les échantillons terrestres et sa relation avec ses ascendants radioactifs, l’U et le Th, en fait un marqueur de choix des processus géodynamiques.L’équipe lyonnaise de Janne Blichert-Toft et Francis Albarède a démontré, à travers une vaste compilation de données bibliographiques accompagnée de la production de nouvelles mesures, une correspondance entre la répartition des valeurs de composition isotopique du Pb dans la croûte continentale et la localisation de figures tectoniques majeures sur plusieurs continents (Bouchet et al., 2014 ; Blichert-Toft et al., 2016 ; Delile et al., 2014). L’existence de ces "provinces géochimiques" démontre l’intérêt des isotopes du Pb comme outil pour mieux comprendre comment l’histoire tectonique d’une région façonne la géochimie de ses continents. Un premier volet de ces travaux de thèse visait à compléter la base de données existante des compositions isotopiques du Pb dans la croûte continentale européenne, grâce à l’analyse de 104 échantillons de feldspaths potassiques issus de granites principalement originaires de Catalogne, de Corse, de Galice et de Kabylie, jusqu’ici restées en blanc sur les cartes précédemment établies. Les cartes ainsi obtenues, illustrant la répartition à travers l’Europe et le bassin méditerranéen des valeurs des "paramètres géochimiques" définis par Albarède et al. (2012), exprimant à partir des rapports isotopiques du Pb mesurés l’âge modèle de la roche et les fractionnements entre l’U, le Th et le Pb enregistrés en son sein, confirment le potentiel des isotopes du Pb comme traceurs robustes de l’héritage tectonique d’une région.Mais le cœur de cette thèse a été d’appliquer cet outil reliant chimie et histoire géodynamique que sont les isotopes du Pb à un type d’échantillon géologique pour lequel des analyses de haute précision de la compositions isotopique en Pb n’avaient jamais été entreprises jusqu’à maintenant : les pétroles bruts. Pour cela, il a fallu développer une méthode analytique novatrice permettant d’extraire le Pb de quelques millilitres de pétrole brut vers une solution aqueuse adaptée aux protocoles habituels de purification indispensables à des analyses isotopiques du Pb à haute précision par MC-ICP-MS (Fetter et al., 2019). Cette méthode a ensuite été appliquée à un total de 211 échantillons de pétrole brut issus de partout dans le monde. Des échantillons de roches mères d’hydrocarbures (schistes noirs) ont également été analysés afin de compléter les premières interprétations des résultats. Ce jeu de données unique met en évidence que le Pb contenu dans les pétroles bruts résultait du mélange d’au moins trois composantes d’âges modèles distincts : le pôle le plus radiogénique a été identifié comme associé aux roches mères des pétroles, tandis que les deux autres, d’âges modèles paléozoïque et protérozoïque, suggèrent des interactions conséquentes entre le pétrole et les roches encaissantes et sous-jacentes. Un nouveau modèle de migration du pétrole depuis sa roche mère a donc été proposé (Fetter et al., soumis), prenant en compte la forte implication des eaux circulant en profondeur dans les bassins sédimentaires en faisant intervenir un phénomène grandement négligé jusqu’à maintenant : la solubilité mutuelle de l’eau et du pétrole à haute température.La mise en évidence d’une dynamique complexe du Pb dans les pétroles bruts invalide une utilisation de ces derniers comme alternative aux feldspaths potassiques pour obtenir des données isotopiques en Pb fiables sur la croûte continentale européenne située sous les bassins sédimentaires. Cependant, elle ouvre de nouvelles portes quant à l’utilisation jusqu’ici inexplorée des isotopes du Pb comme traceurs de phénomènes de pollution associés à une prospection pétrolière peu responsable. / Lead is ubiquitous in terrestrial samples and its relationship to its radioactive ascendants, U and Th, makes it a prime tracer of geodynamic processes.The team of Janne Blichert-Toft and Francis Albarède, based in Lyon (France), has demonstrated on several continents, through large compilations of literature data supplemented by new measurements, a correspondence between the distribution of Pb isotopic compositions in the continental crust and major tectonic features (Bouchet et al., 2014 ; Blichert-Toft et al., 2016 ; Delile et al., 2014). The existence of these "geochemical provinces" has firmly established the potential of Pb isotopes as a tool for understanding how the tectonic history of a given region shaped its geochemistry. A first aspect of this PhD aimed at complementing the existing database of Pb isotopic compositions of the European continental crust through the analysis of 104 K-feldspar samples separated from granites originating mainly from Catalonia, Corsica, Galicia, and Kabylie, up until this PhD blank areas on the compiled map. The resulting updated maps showing the distribution throughout Europe and the circum-Mediterranean area of the "geochemical parameters" defined by Albarède et al. (2012), which derive a model age and fractionations between U, Th, and Pb from measured Pb isotopic ratios, confirm the potential of Pb isotopes as powerful tracers of the tectonic heritage of a given region.The core of this PhD, however, was to apply this tool connecting chemistry and geodynamic history to a type of geological sample so far never analyzed for high-precision Pb isotopic compositions: crude oil. To achieve this goal, a novel analytical method was developed which allows the extraction of Pb from a few milliliters of crude oil into an aqueous solution suitable for the standard Pb purification protocol essential for high-precision Pb isotope analysis by MC-ICPMS (Fetter et al., 2019). This method was then applied to a total of 211 crude oil samples from around the world. Hydrocarbon source rocks (black shales) also were analyzed. This unique data set reveals that Pb in crude oil results from the mixing of at least three endmembers of distinct model ages: the more radiogenic endmember is identified as the oil source rocks, while the other two components, of Paleozoic and Proterozoic ages, suggest considerable interactions between crude oil and the surrounding and underlying rocks. A new model was hence proposed for oil migration (Fetter et al., submitted), taking into account the key role of deep-seated waters circulating through the sedimentary basin by calling on a long-neglected phenomenon: mutual solubility of water and oil at high temperatures.Bringing to light the complex dynamics of Pb in crude oil invalidates the use of crude oil as an alternative to K-feldspars to obtain the Pb isotopic signature of the continental crust underlying sedimentary basins. However, it opens up new promising avenues for the yet unexplored use of Pb isotopes as tracers of irresponsible oil prospection related pollution.
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The Mineralogical Composition of House Dust in Ontario, CanadaWoldemichael, Michael Haile 01 February 2012 (has links)
Despite increasing concern about the presence of heavy metals, pesticides and other toxins in indoor environments, very little is known about the physical and chemical composition of ordinary household dust. This study represents the first systematic investigation of the mineralogical composition of indoor dust in residential housing in Canada.
Specimens of dust were obtained from homes in six geographically separate cities in the Province of Ontario: two located on the metamorphic and igneous rocks of the Precambrian Canadian Shield (Thunder Bay and Sudbury), the other four located on Palaeozoic limestone and shale dominated bedrock (Barrie, Burlington, Cambridge, and Hamilton). Forty samples of household vacuum dust were obtained. The coarse fraction (80 – 300 µm) of this dust was subjected to flotation (using water) to separate the organic components (e.g. insect fragments, dander), natural and synthetic materials (e.g. fibres, plastics) from the mineral residue. The mineral fraction was then analyzed using quantitative point counting, polarizing light microscopy, powder X-ray diffraction and scanning electron microscopy methods.
Despite the great distances between the sampling localities and the distinct differences in bedrock geology, the mineral fraction of dust from all six cities is remarkably similar and dominated by quartz and feldspar, followed by lithic fragments, calcite, and amphibole. Some evidence of the influence of local geology can nevertheless be found. For example, a relatively higher proportion of sulphide minerals is observed in the two cities on the Canadian Shield where these minerals are clearly more abundant in the bedrock. Specimens from Sudbury, Canada’s largest mining centre located atop a nickel-sulphide mineral deposit, showed the highest sulphide contents. Quartz is the dominant mineral in all cities. All quartz grains have internal strain features and fluid inclusions that are indicative of a metamorphic-igneous provenance.
In all cities, sand is used on the streets as an abrasive for traction during the icy winter season. This sand is obtained in all cases from local glaciofluvial deposits that were ultimately derived principally from the rocks of the Canadian Shield in the last Pleistocene glaciations that affected all of Ontario. Thus, tracking in sand is the most plausible mechanism by which quartz was introduced into these homes since sampling was done, in all cases, in the winter season.
The results indicate that glacial deposits dominate the mineral composition of indoor dust in Ontario cities and that nature of the bedrock immediately underlying the sampling sites is relatively of minor importance.
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The Mineralogical Composition of House Dust in Ontario, CanadaWoldemichael, Michael Haile 01 February 2012 (has links)
Despite increasing concern about the presence of heavy metals, pesticides and other toxins in indoor environments, very little is known about the physical and chemical composition of ordinary household dust. This study represents the first systematic investigation of the mineralogical composition of indoor dust in residential housing in Canada.
Specimens of dust were obtained from homes in six geographically separate cities in the Province of Ontario: two located on the metamorphic and igneous rocks of the Precambrian Canadian Shield (Thunder Bay and Sudbury), the other four located on Palaeozoic limestone and shale dominated bedrock (Barrie, Burlington, Cambridge, and Hamilton). Forty samples of household vacuum dust were obtained. The coarse fraction (80 – 300 µm) of this dust was subjected to flotation (using water) to separate the organic components (e.g. insect fragments, dander), natural and synthetic materials (e.g. fibres, plastics) from the mineral residue. The mineral fraction was then analyzed using quantitative point counting, polarizing light microscopy, powder X-ray diffraction and scanning electron microscopy methods.
Despite the great distances between the sampling localities and the distinct differences in bedrock geology, the mineral fraction of dust from all six cities is remarkably similar and dominated by quartz and feldspar, followed by lithic fragments, calcite, and amphibole. Some evidence of the influence of local geology can nevertheless be found. For example, a relatively higher proportion of sulphide minerals is observed in the two cities on the Canadian Shield where these minerals are clearly more abundant in the bedrock. Specimens from Sudbury, Canada’s largest mining centre located atop a nickel-sulphide mineral deposit, showed the highest sulphide contents. Quartz is the dominant mineral in all cities. All quartz grains have internal strain features and fluid inclusions that are indicative of a metamorphic-igneous provenance.
In all cities, sand is used on the streets as an abrasive for traction during the icy winter season. This sand is obtained in all cases from local glaciofluvial deposits that were ultimately derived principally from the rocks of the Canadian Shield in the last Pleistocene glaciations that affected all of Ontario. Thus, tracking in sand is the most plausible mechanism by which quartz was introduced into these homes since sampling was done, in all cases, in the winter season.
The results indicate that glacial deposits dominate the mineral composition of indoor dust in Ontario cities and that nature of the bedrock immediately underlying the sampling sites is relatively of minor importance.
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The Mineralogical Composition of House Dust in Ontario, CanadaWoldemichael, Michael Haile 01 February 2012 (has links)
Despite increasing concern about the presence of heavy metals, pesticides and other toxins in indoor environments, very little is known about the physical and chemical composition of ordinary household dust. This study represents the first systematic investigation of the mineralogical composition of indoor dust in residential housing in Canada.
Specimens of dust were obtained from homes in six geographically separate cities in the Province of Ontario: two located on the metamorphic and igneous rocks of the Precambrian Canadian Shield (Thunder Bay and Sudbury), the other four located on Palaeozoic limestone and shale dominated bedrock (Barrie, Burlington, Cambridge, and Hamilton). Forty samples of household vacuum dust were obtained. The coarse fraction (80 – 300 µm) of this dust was subjected to flotation (using water) to separate the organic components (e.g. insect fragments, dander), natural and synthetic materials (e.g. fibres, plastics) from the mineral residue. The mineral fraction was then analyzed using quantitative point counting, polarizing light microscopy, powder X-ray diffraction and scanning electron microscopy methods.
Despite the great distances between the sampling localities and the distinct differences in bedrock geology, the mineral fraction of dust from all six cities is remarkably similar and dominated by quartz and feldspar, followed by lithic fragments, calcite, and amphibole. Some evidence of the influence of local geology can nevertheless be found. For example, a relatively higher proportion of sulphide minerals is observed in the two cities on the Canadian Shield where these minerals are clearly more abundant in the bedrock. Specimens from Sudbury, Canada’s largest mining centre located atop a nickel-sulphide mineral deposit, showed the highest sulphide contents. Quartz is the dominant mineral in all cities. All quartz grains have internal strain features and fluid inclusions that are indicative of a metamorphic-igneous provenance.
In all cities, sand is used on the streets as an abrasive for traction during the icy winter season. This sand is obtained in all cases from local glaciofluvial deposits that were ultimately derived principally from the rocks of the Canadian Shield in the last Pleistocene glaciations that affected all of Ontario. Thus, tracking in sand is the most plausible mechanism by which quartz was introduced into these homes since sampling was done, in all cases, in the winter season.
The results indicate that glacial deposits dominate the mineral composition of indoor dust in Ontario cities and that nature of the bedrock immediately underlying the sampling sites is relatively of minor importance.
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The Mineralogical Composition of House Dust in Ontario, CanadaWoldemichael, Michael Haile January 2012 (has links)
Despite increasing concern about the presence of heavy metals, pesticides and other toxins in indoor environments, very little is known about the physical and chemical composition of ordinary household dust. This study represents the first systematic investigation of the mineralogical composition of indoor dust in residential housing in Canada.
Specimens of dust were obtained from homes in six geographically separate cities in the Province of Ontario: two located on the metamorphic and igneous rocks of the Precambrian Canadian Shield (Thunder Bay and Sudbury), the other four located on Palaeozoic limestone and shale dominated bedrock (Barrie, Burlington, Cambridge, and Hamilton). Forty samples of household vacuum dust were obtained. The coarse fraction (80 – 300 µm) of this dust was subjected to flotation (using water) to separate the organic components (e.g. insect fragments, dander), natural and synthetic materials (e.g. fibres, plastics) from the mineral residue. The mineral fraction was then analyzed using quantitative point counting, polarizing light microscopy, powder X-ray diffraction and scanning electron microscopy methods.
Despite the great distances between the sampling localities and the distinct differences in bedrock geology, the mineral fraction of dust from all six cities is remarkably similar and dominated by quartz and feldspar, followed by lithic fragments, calcite, and amphibole. Some evidence of the influence of local geology can nevertheless be found. For example, a relatively higher proportion of sulphide minerals is observed in the two cities on the Canadian Shield where these minerals are clearly more abundant in the bedrock. Specimens from Sudbury, Canada’s largest mining centre located atop a nickel-sulphide mineral deposit, showed the highest sulphide contents. Quartz is the dominant mineral in all cities. All quartz grains have internal strain features and fluid inclusions that are indicative of a metamorphic-igneous provenance.
In all cities, sand is used on the streets as an abrasive for traction during the icy winter season. This sand is obtained in all cases from local glaciofluvial deposits that were ultimately derived principally from the rocks of the Canadian Shield in the last Pleistocene glaciations that affected all of Ontario. Thus, tracking in sand is the most plausible mechanism by which quartz was introduced into these homes since sampling was done, in all cases, in the winter season.
The results indicate that glacial deposits dominate the mineral composition of indoor dust in Ontario cities and that nature of the bedrock immediately underlying the sampling sites is relatively of minor importance.
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