Canada is in the process of implementing a Deep Geologic Repository (DGR) to dispose of used nuclear waste. Adsorption behaviour of both Se(-II) and Tc(IV) onto granite, shale, limestone, illite, and MX-80 bentonite has been elucidated. Se(-II) adsorption onto granite and MX-80 bentonite displays a decrease in Rd with an increase in solution pH. Se(-II) adsorption onto granite decreases with an increase in solution ionic strength. Se(-II) adsorption onto MX-80 bentonite does not return evidence which supports an apparent effect due to the ionic strength. Tc(IV) adsorption onto shale, limestone, illite, and MX-80 bentonite remains constant as the solution pH increases. Ionic strength does not affect the magnitude of Tc(IV) adsorption across the adsorbents, however an increase in ionic strength accelerates Tc(IV) adsorption. Se(-II) surface complexation models are best simulated with the following surface complexes: ≡Feldspar_sSe-, ≡Biotite_sOH2HSe, ≡Albite_sSe-, ≡Montmorillonite_sSe-, and ≡Montmorillonite_sOH2HSe. Tc(IV) adsorption is best simulated with: ≡Biotite_sOTcO(OH), ≡Quartz_sOTcO(OH), (≡Feldspar_sOH)2TcO(OH)-, ≡Montmorillonite_sOTcO(OH), (≡Albite_sOH)2TcO(OH)-, ≡Illite_sOTcO(OH), and ≡Chlorite_sOTcO(OH). Se(-II) adsorption onto granite and MX-80 bentonite in CR-10 solution returns Rd values of (1.80 ± 0.10) m3∙kg-1 and (0.47 ± 0.38) m3∙kg-1, respectively. Tc(IV) adsorption onto granite and MX-80 bentonite in CR-10 solution returned Rd values of (1.47 ± 0.25) m3∙kg-1 and (2.19 ± 0.33) m3∙kg-1, respectively. Tc(IV) adsorption onto shale, limestone, illite, and MX-80 bentonite in SR-270-PW solution returned Rd values of (0.16 ± 0.10) m3∙kg-1, (0.44 ± 0.21) m3∙kg-1, (1.86 ± 0.44) m3∙kg-1, and (0.23 ± 0.10) m3∙kg-1, respectively. This thesis will further deepen the understanding of Se(-II) and Tc(IV) adsorption. / Thesis / Doctor of Philosophy (PhD) / Determining the adsorption of Se(-II) and Tc(IV) onto granite, shale, limestone, illite, and MX-80 bentonite is beneficial to choosing a location within Canada to locate a used nuclear fuel repository. This thesis aims to quantify the adsorption behaviour of Se(-II) and Tc(IV) in Ca-Na-Cl and Na-Ca-Cl solutions with respect to a varying solution ionic strength and pH. Quantification of the adsorption was accomplished with adsorption experiments used in conjunction with geochemical simulations. New simulated surfaces specific to granite, shale, and MX-80 bentonite have been developed to complete these simulations. A final achievement was quantifying the adsorption of Se(-II) and Tc(IV) in groundwater representative solutions specific to locations considered for the used nuclear fuel repository.

No description available.

The aim of the thesis has been to evaluate and understand the effect of caustic alkali solution of varying composition on the behaviour of expansive soil containing mixed layered minerals. Mixed layered minerals are formed of two or more kinds of inter grown layers, not physical mixtures. Illite - smectite is the most abundant and wide spread of the mixed layered clay minerals in sedimentary rocks and soils and also more common than either discrete illite or smectite. In geotechnical engineering much attention has not been paid to the behaviour of soils containing mixed layered minerals. Much less is known about the behaviour of these soils in polluted environment. Mixed layered minerals are more susceptible to environmental changes as the structural linkages between the layer minerals are weak compared to normal layered phyllosilicates. One important pollutant that can have considerable effect on the behaviour of soils is the caustic alkali contamination released from various industries. Recent studies have shown that the behaviour of even stable minerals is affected by alkali contamination. However, the effect of caustic alkali contamination on the behaviour of soils containing mixed layered minerals is not known and has been chosen for detailed study. Also to understand the mechanism of their interaction with alkali, it is necessary to study the effect of alkali solutions on the constituent clay minerals viz., montmorillonite and illite under similar conditions. To elucidate the mechanism of soil alkali interaction limited tests were conducted with simple electrolyte solution, as the alkali solution also acts as electrolyte apart from being alkaline. To confirm the mechanism of interaction, tests are also conducted on these soils with industrial spent liquor containing high caustic alkali and suspended alumina obtained from an alumina extraction plant treating bauxite with high alkali solutions at high temperatures. The results obtained in the laboratory are compared with the soil samples contaminated with leaking industrial Bayer's liquid in the field. Studies are also conducted to suggest remedial measures to control the adverse effects of alkali solutions on soil containing mixed layer minerals. The content of the thesis is broadly divide into 8 Chapters - viz., Introduction, Background and overview, Experimental program and procedures, Behaviour of soils containing mixed layer mineral illite - smectite (BCSI), Behaviour of montmorillonite and illite, Influence of Bayer's liquor and study on the field contaminated soils, Measures to control the influence of alkali contamination on BCSI and Summary and conclusions. The broad outline of these chapters is given in Chapter 1. A review of literature on the behaviour of soils containing different types of clay minerals with emphasis on mixed layer minerals has been presented in Chapter 2. The influence of different inorganic contaminants on the properties of soils in terms of their physical and chemical characteristics as well as their concentration has been summarized. The importance of changes in surface characteristics of soil particles and the changes in the thickness of diffuse double layer in altering the property of soils at low concentration of contaminants and changes in the mineralogy with high concentrated contaminants such as acids and alkalis has been highlighted. This forms the background information necessary to bring out the scope of the study. Four soils having different mineralogy have been used in this study. These soils are, black cotton soil containing predominantly mixed layer mineral illite - smectite mineral called rectorite, illite, montmorillonite (common smectite) and black cotton soil containing predominantly montmorillonite. The properties of the soils used are described in Chapter 3. Caustic alkali solutions of 1N, 4N concentration prepared in the laboratory and industrial alkali-spent liquor are used as contaminants. The spent Bayer's liquor had about 4N alkali concentration and 10% alumina in suspension. To simulate the effect of suspended alumina, two more caustic alkali solutions of 1N and 4N solutions containing 10% alumina by weight of solutions are also prepared. To isolate the effect of electrolyte solutions from that of alkali solution, two electrolyte solutions of 1N and 4N sodium chloride solutions are also used. Test procedures for conducting various tests such as pH, water adsorption characteristics, X-ray diffraction studies, SEM studies, thermal characteristics and geotechnical properties such as Atterberg limits, Oedometer tests and Shear Strength are given in this chapter. The test procedures are modified, wherever necessary, to bring out the effect of contaminants, particularly the effect of duration of interaction on the properties of soils. The source and properties of black cotton soil are presented in Chapter 4. Detailed x-diffraction studies have confirmed the presence of inter layered illite-smectite mineral viz., rectorite, which is uncommon in Indian expansive soils, and is classified as CH (Clay of high compressibility) as per ASTM soil classification. Effect of alkali and salt solutions of 1N and 4N concentration on all physico chemical and geotechnical properties are studied in this chapter. As it is known that presence of certain elements such as aluminium influence the soil alkali interaction, the effect of suspended alumina along with alkali solution has also been investigated. The effect of contaminating fluids such as 1N NaOH, 4N NaOH with and without alumina, 1N NaCl and 4N NaCl on the geotechnical properties of the soil has been studied. Mineralogical changes were observed by XRD and thermal studies in the soil treated with 4N NaOH solution and 4N NaOH + 10% alumina. The interlayer potassium of illite is released and potassium hydroxide is formed in soil treated with 4N NaOH. Swelling compounds such as sodium aluminium silicate hydroxide hydrate (SASH) has formed due to attack of 4N NaOH + 10% alumina on silica rather than on rectorite. Thus the studies clearly bring out that the rectorite present in the soil is dissociated only in the presence of strong alkali solutions of concentration of about 4N. The liquid limit of soil decreased with increase in the electrolyte concentration in the case of NaCl solutions. With 1N NaOH, the liquid limit of soil increased due to increase in the thickness of diffuse double layer due to increased pH. However, Proctor's maximum dry density increased and optimum moisture content decreased with 1N NaOH. With increase in the concentration of alkali solution to 4N, the rectorite dissociates into constituent minerals with the formation potassium hydroxide. The liquid limit of soil decreased probably due to the dominating influence of electrolyte nature of hydroxide solution over the effect of increased negative charge on clay particles due increase in the pH on the constituent minerals. Proctor's maximum dry density decreased and optimum moisture content increased with 4N NaOH. Sediment volume and oedometer free swell at seating/nominal surcharge load of 6.25 kPa of soil increased in 1N and 4N caustic alkali solutions, though by different mechanisms. The increase with 1N solution is essentially due to increased negative charges on clay mineral surface. However, the increase in swelling with 4N solution is associated with the dissociation of rectorite mineral and occurs in two distinct phases unlike in the case of 1N solution. While the first phase can be attributed to the effect of alkaline nature of the solution after reduction in its concentration due to reaction with rectorite and the consequent reduction in its electrolyte nature. The second phase is due to the swelling of the separated constituent minerals in the presence of excess of alkali and occurs after much delay. Consolidation behaviour of rectorite in 1N and 4N alkali solutions has been studied in two ways: 1). Loading without waiting for the second stage of swelling to occur, as in standard consolidation procedure and 2). Loading after completion of second stage of swelling which is occurring after considerable delay as explained earlier. Normally one would initiate loading after equilibrium is reached at the end of first stage of swelling and second stage of swelling is not suspected. As there is no second stage of swelling with 1N solutions, these two types of consolidation tests produced the same results. Abnormal rebound is observed during unloading with 4N solution in which loading cycle is initiated without waiting for second stage of swelling to complete. It is interesting to note that while the liquid limit of soil decreased with increase in the concentration of alkali solution, the swelling increased. The testing procedure and period of interaction as well as the concentration of alkali solution during the test in these two tests are different. The effects of alkali solution are more severe in case of liquid limit because of thorough mixing and consequent effective reaction during testing. Similarly, the volume changes in soil that has already reacted with 4N alkali solution when exposed to further to alkali contamination are considerably less compared to uncontaminated soil exposed to fresh contamination. The shear strength of soil treated with 4N-alkali solution has increased particularly after long period of interaction. This indicates that the soil after mineralogical changes posses good strength. Chapter 5 presents the effect of alkali and salt solutions on the physico chemical and geotechnical properties of component minerals of mixed layered illite/smectite. For this study, commercially obtained montmorillonite (bentonite), naturally occurring black soil containing montmorillonite and commercially pure illite are used. It was observed that montmorillonite alkali reactions would not produce significant mineralogical changes where as illite is dissociated into smectite with the formation of potassium silicate by the interaction of released potassium with soluble silica. This confirms that the ultimate products of rectorite with alkali solutions would be smectite and compounds of potassium. In the absence of mineralogical alterations the liquid limit of montmorillonite decreases due to suppression of diffuse double layer thickness due to dominating influence of alkali solutions on this highly active clay. However a small increase in liquid limit is observed in illite with alkali solutions. Thus the net effect of alkali on rectorite is to decrease the liquid limit with increase in alkali concentration. While the free swell and oedometer swelling of montmorillonite generally decreases with increase in the alkali concentration, they increase in illite. However, in both the minerals the swelling occurs only in one phase. Thus the second phase of swelling that has been observed in rectorite can be attributed to delayed swelling of montmorillonite that has been released by the attack of alkali on rectorite. The behaviour of black soil containing mixed layer mineral contaminated in the field and laboratory by leaking Bayer's spent liquor in an alumina extraction plant has been studied in Chapter 6. The Atterberg limits of the samples treated with liquor are reduced and sediment volume increased. Similarly the swelling at seating load in consolidation test is higher in sample compacted with water and inundated with liquor. X-ray diffraction studies showed that the mineralogical changes are similar to those occurred with 4N caustic alkali solution. The mineralogical and micro structural changes in the soil samples that are contaminated by leaked spent liquor in the field are relatively more marked. Also the behavior of highly montmorillonite clay, bentonite, has been studied contaminated with liquor in the laboratory. The study on the effect of high concentrated alkali solutions on montmorillonite can be useful to study the effect of interaction on the dissociated montmorillonite. These studies are helpful to suggest some possible remedial measures to control the adverse effect of alkali on soils. Possible Remedial schemes that can be adopted before and after contamination of the soil to control the adverse effect of alkali solutions on the black cotton soil containing mixed layered mineral are listed and their effectiveness examined in Chapter 7. The suggested remedial measures include flushing with water to dilute the effect of alkali, neutralisation with dilute hydrochloric acid, stabilisation of soil with lime and calcium chloride and use of impervious membrane to separate the foundation soil from alkali solution. The effectiveness of different measures as well as the method of their application has been described. Efforts are made to understand the mechanism of remedial action. Consolidation tests conducted on soil contaminated with 4N alkali solution and inundated with water showed increased swelling due to dilution of the alkali concentration. Though the swelling of contaminated soil can be controlled by passing dilute hydrochloric acid (1N), the method is not advocated as it can lead to ground water contamination. Mixing the soil with solutions containing up to 5% by weight of calcium compound in water could not prevent the alkali induced heave in the long run when inundated with 4N alkali solution. This was due to dissolution of silica by the strong alkali solutions and formation of swelling compounds such as sodium aluminium silicate hydroxide hydrate (SASH). The formation of sodium aluminates occurred only when the alkali solution contained alumina or soil contained calcium compounds. There are no significant variations in the effects of calcium chloride or calcium hydroxide on contaminated soil. Replacing the foundation soil with soil thoroughly contaminated with 4N alkali solutions and controlling the migration of contaminants into the foundation soil using high-density polyethylene (HDPE) geosynthetic membranes can be an effective measure to control the heaving in alkali contaminated foundation soil containing interstratified illite – smectite. Summary and the major conclusions of the thesis are presented in Chapter 8.

Master of Science / Department of Geology / Matthew Totten / The Woodford shale is recognized as an abundant source rock across Oklahoma and much of the midcontinent (Lambert, 1990), and up to 8% of the world’s hydrocarbon reserves are estimated to have been sourced by the Woodford and its equivalents (Fritz et al, 1991). The Woodford shale is far more complex than other Devonian black shales found in North America due to the presence of alternating bands of chert-like amorphous silica and silica-rich shale. Analysis of chert and its possible role in gas generation and storage in shales has been largely overlooked. The goal of this study is to determine if chert size, amounts, or polycrystallinity can be indicators of thermal maturity within the Woodford shale. Handheld XRF analysis was conducted on the whole rock samples, and a mudrock specific sodium bisulfate fusion was used to separate the non-clay fraction. SEM was performed on the resulting separates to study and observe changes in chert fabric, grain-size, and amount. No correlations were observed to indicate that chert is an indicator of thermal maturity within the Woodford shale. Increase in chert growth and amount was also not detected within the size fractions as thermal maturity increases. Handheld XRF proved to be a good proxy for quick, onsite analysis of silica concentrations, as well as the amount of organic matter within drill core. This could be beneficial as hydraulic fracking produces best results in areas of higher silica content, and the wells with the highest organic matter have the highest potential for petroleum accumulations.

Manguezais são ecossistemas de transição entre ambientes continental e marinho. Estão amplamente distribuídos ao longo da costa brasileira, sob grande variabilidade de condições climáticas, oceanográficas, geológicas e geomorfológicas. A mineralogia dos solos reflete e interfere nos processos de formação de solos e no comportamento biogeoquímico de nutrientes e potenciais substâncias poluentes, orgânicas e inorgânicas. O presente estudo avaliou a composição mineralógica dos solos de oito manguezais, do litoral sul ao norte do país, por meio de DRX, infravermelho e MET, das frações finas (silte, argila total e argila fina). A assembléia mineralógica da fração argila é composta, predominantemente, por caulinita, esmectita, ilitas férricas e traços de quartzo e gibbsita. Na argila fina, observou-se a presença de grandes quantidades de caulinita e esmectitas, provavelmente férricas, associadas a algum mineral 2:1 HE além de ilita de baixa cristalinidade interestratificada com minerais expansivos. Dados de semi-quantificação e características cristalográficas de caulinitas e ilitas revelam que a geologia das áreas continentais adjacentes aos manguezais influencia diretamente a assembléia mineralógica dos solos desses ambientes. Sob esse olhar, três padrões de manguezais foram identificados ao longo da costa: manguezais influenciados diretamente por sedimentos derivados de solos desenvolvidos sobre materiais geológicos do escudo cristalino pré-cambriano, com caulinitas pouco cristalinas, ilitas originadas das micas presentes nas rochas correspondentes e esmectitas autigênicas; manguezais próximos a áreas dos tabuleiros terciários do grupo Barreiras, com caulinitas mais cristalinas e menores teores de minerais 2:1; e aqueles sob influência de materiais advindos do clima semi-árido nordestino (menos alterados), com grande quantidade de minerais 2:1 neoformados e herdados dos solos dessas áreas adjacentes, o que pode ser apoiado pelas maiores quantidades de ilitas, com cristalinidade menor. Estudos mais específicos acerca da composição química dos minerais e de seus mecanismos geoquímicos de formação devem ser realizados futuramente, para melhor entendimento dos processos propostos e sua relação com a dinâmica biogeoquímica de importantes elementos nesses ambientes, especialmente do Fe presente nos filossilicatos. / Mangroves are transitional ecosytems between continental and marine environments. Its widely distributed along Brazilian coast under great variability of climatic, oceanographic, geological and geomorphological conditions. Its soil mineralogy has a relevant role in the pedogenic processes and biogeochemical behavior of nutrients and potential inorganic and organic pollutants substances. The present study evaluated the mineralogical composition of fine fractions (silt, clay and fine clay) of eight Brazilian mangrove soils of south to north coast using XRD, infrared spectrometry and TEM analyses. The mineralogical assemblage of clay fraction consists on kaolinite, smectite, ferric illite and traces of quartz and gibbsite. In fine clay fraction it can be observed great amounts of kaolinite and smectites, probably ferric, associated with 2:1 hydroxy interlayered minerals beyond poorly crystalline illite-smectite interstratified minerals. Semi-quantification data and kaolinite/illite crystallographic characteristics reveal the importance of geological materials of continental adjacent areas for mineralogical composition of mangrove soils. Thus three different patterns were identified along the coast: mangrove influenced directly by sediments derived from soils developed on geological materials of Pre-Cambrian basement rocks, with poorly crystalline kaolinites, illite transformed from diagenetic mica present in Pre-Cambrian and authigenic smectites; mangroves next to Tertiary Barreiras Group sediments, with better crystalline kaolinites and less amounts of 2:1 phyllosilicates; and mangroves under influence of sediments that come from soils developed under northeastern semi-arid climate (less weathered), evidenced by great amounts of inherited and neoformed 2:1 phyllosilicates and poorly-crystalline illite. More specific studies about clay minerals chemical composition and its geochemical formation mechanisms should be performed in future, for better understanding of proposed processes and its relation with the biogeochemical dynamics of certain elements in this environment, specially the iron present in phyllosilicates.

Manguezais são ecossistemas de transição entre ambientes continental e marinho. Estão amplamente distribuídos ao longo da costa brasileira, sob grande variabilidade de condições climáticas, oceanográficas, geológicas e geomorfológicas. A mineralogia dos solos reflete e interfere nos processos de formação de solos e no comportamento biogeoquímico de nutrientes e potenciais substâncias poluentes, orgânicas e inorgânicas. O presente estudo avaliou a composição mineralógica dos solos de oito manguezais, do litoral sul ao norte do país, por meio de DRX, infravermelho e MET, das frações finas (silte, argila total e argila fina). A assembléia mineralógica da fração argila é composta, predominantemente, por caulinita, esmectita, ilitas férricas e traços de quartzo e gibbsita. Na argila fina, observou-se a presença de grandes quantidades de caulinita e esmectitas, provavelmente férricas, associadas a algum mineral 2:1 HE além de ilita de baixa cristalinidade interestratificada com minerais expansivos. Dados de semi-quantificação e características cristalográficas de caulinitas e ilitas revelam que a geologia das áreas continentais adjacentes aos manguezais influencia diretamente a assembléia mineralógica dos solos desses ambientes. Sob esse olhar, três padrões de manguezais foram identificados ao longo da costa: manguezais influenciados diretamente por sedimentos derivados de solos desenvolvidos sobre materiais geológicos do escudo cristalino pré-cambriano, com caulinitas pouco cristalinas, ilitas originadas das micas presentes nas rochas correspondentes e esmectitas autigênicas; manguezais próximos a áreas dos tabuleiros terciários do grupo Barreiras, com caulinitas mais cristalinas e menores teores de minerais 2:1; e aqueles sob influência de materiais advindos do clima semi-árido nordestino (menos alterados), com grande quantidade de minerais 2:1 neoformados e herdados dos solos dessas áreas adjacentes, o que pode ser apoiado pelas maiores quantidades de ilitas, com cristalinidade menor. Estudos mais específicos acerca da composição química dos minerais e de seus mecanismos geoquímicos de formação devem ser realizados futuramente, para melhor entendimento dos processos propostos e sua relação com a dinâmica biogeoquímica de importantes elementos nesses ambientes, especialmente do Fe presente nos filossilicatos. / Mangroves are transitional ecosytems between continental and marine environments. Its widely distributed along Brazilian coast under great variability of climatic, oceanographic, geological and geomorphological conditions. Its soil mineralogy has a relevant role in the pedogenic processes and biogeochemical behavior of nutrients and potential inorganic and organic pollutants substances. The present study evaluated the mineralogical composition of fine fractions (silt, clay and fine clay) of eight Brazilian mangrove soils of south to north coast using XRD, infrared spectrometry and TEM analyses. The mineralogical assemblage of clay fraction consists on kaolinite, smectite, ferric illite and traces of quartz and gibbsite. In fine clay fraction it can be observed great amounts of kaolinite and smectites, probably ferric, associated with 2:1 hydroxy interlayered minerals beyond poorly crystalline illite-smectite interstratified minerals. Semi-quantification data and kaolinite/illite crystallographic characteristics reveal the importance of geological materials of continental adjacent areas for mineralogical composition of mangrove soils. Thus three different patterns were identified along the coast: mangrove influenced directly by sediments derived from soils developed on geological materials of Pre-Cambrian basement rocks, with poorly crystalline kaolinites, illite transformed from diagenetic mica present in Pre-Cambrian and authigenic smectites; mangroves next to Tertiary Barreiras Group sediments, with better crystalline kaolinites and less amounts of 2:1 phyllosilicates; and mangroves under influence of sediments that come from soils developed under northeastern semi-arid climate (less weathered), evidenced by great amounts of inherited and neoformed 2:1 phyllosilicates and poorly-crystalline illite. More specific studies about clay minerals chemical composition and its geochemical formation mechanisms should be performed in future, for better understanding of proposed processes and its relation with the biogeochemical dynamics of certain elements in this environment, specially the iron present in phyllosilicates.

Ce travail tente de caractériser les modifications structurales affectant les minéraux argileux lors de leur diagenèse d'enfouissement. Ces évolutions structurales ont été décrites dans la littérature comme résultant d'une transformation illite-smectite, par l'intermédiaire d'édifices interstratifiés dont la teneur en feuillets illitiques augmente avec la profondeur d'enfouissement. Historiquement, la diffraction des rayons a été l'outil privilégié pour mettre en évidence ces évolutions structurales du fait des modifications induites sur les profils de raies caractéristiques de ces interstratifiés. Afin de permettre une identification objective des interstratifiés, souvent présents en mélanges complexes de phases aux caractéristiques proches, une méthode de traitement numérique (décomposition) des diffractogrammes de rayons X a été développée afin d'en isoler les différentes contributions élémentaires. L'identification minéralogique est ensuite réalisée par comparaison des paramètres (position, largeur à mi-hauteur) déterminés pour chacune de ces contributions avec les valeurs obtenus sur des diffractogrammes calculés sur la base de modèles structuraux. Ces modèles intègrent la teneur en illite (smectite) des interstratifiés, l'état d'hydratation des smectites, la taille des domaines cohérents de diffraction, ainsi que des paramètres permettant de décrire l'ordre partiel ou la ségrégation. Cette méthodologie a enfin été appliquée sur des échantillons provenant de plusieurs puits forés dans le bassin de Paris et décrivant une section E-W, ainsi que sur des échantillons provenant des séries de référence du Gulf Coast. En s'appuyant sur l'analyse morphologique et chimique des particules argileuses de ces séries réalisée par Didier Champion, les résultats obtenus permettent de proposer des mécanismes réactionnels pour la transformation minéralogique observée. En particulier, la diminution de la teneur en smectite des interstratifiés correspond à la croissance de feuillets illitiques autour des particules pré-existantes par un processus analogue au mûrissement d'Ostwald. La chimie du pôle illite est fixe et présente une charge de ~0.9 par O10(OH)2.

A l'Est du Bassin de Paris, la superposition de roches sédimentaires aux propriétés hydrauliques, thermiques et mécaniques contrastées forme un système géologique compartimenté. Les séries aquifères du Jurassique moyen et supérieur et du Trias (faciès Buntsandstein) sont séparées par des niveaux aquitards constitués d'évaporites et d'argiles, parmi lesquelles la succession callovo-oxfordienne épaisse de 150 m, sélectionnée par l'agence nationale pour la gestion des déchets radioactifs (Andra). Retracer l'histoire thermique des séries sédimentaires mésozoïques et lier cette histoire aux processus d'interactions fluides-roches ayant modifié les propriétés pétrophysiques des formations perméables constitue la problématique centrale de ce travail de thèse. Ce mémoire présente, dans une première partie, une synthèse de l'évolution thermique des séries mésozoïques, s'appuyant sur des données géothermométriques (réflectance de la vitrinite, isomérisation des biomarqueurs moléculaires, inclusions fluides) et sur la modélisation numérique du bassin. Dans une seconde partie, les propriétés physico-chimiques des paléo-fluides ayant percolé dans les aquifères carbonatés du Jurassique moyen et supérieur sont recherchées à l'aide des teneurs en éléments traces et de la composition isotopique (d18O, d13C, 87Sr/86Sr) des phases minérales authigènes, couplée aux mesures de chlorinité et des rapports D/H des eaux piégées en inclusions fluides. Dans les grès du Trias, les datations K-Ar de fractions granulométriques riches en illite documentent deux périodes de cristallisation à 179.4 ± 0.8 Ma et 149.4 ± 0.3 Ma, respectivement durant le Lias et à la période fini-Jurassique / début Crétacé / In the eastern Paris Basin, the succession of sedimentary rocks with variable hydro-thermo-mechanical properties leads to a compartmentalization of the system. Three aquifer units - the Middle and Upper Jurassic limestones and the Lower Triassic sandstones - are apart from each other by very low-permeable evaporites and clay-rich successions, among which the Callovian-Oxfordian claystones currently investigated by the French national radioactive waste management agency (Andra). This PhD thesis deals with the thermal history reconstruction and the fluid-rock interactions in the Mesozoic series through a multidisciplinary approach. In the first part of the manuscript, the P-T evolution of the Mesozoic series is documented based on thermal indicators (vitrinite reflectance, biomarker isomerization, fluid inclusions) and numerical modeling. In the second part, major and trace element concentrations (including REE) and isotopic compositions (d18O, d13C and 87Sr/86Sr) of authigenic minerals and fluid inclusions were used to estimate the origin of paleo-fluids and their evolution through water-rock interactions. In the Lower Triassic sandstones, K-Ar dating of authigenic illite documents two periods of crystallization at 179.4 ± 0.8 Ma and 149.4 ± 0.3 Ma

No description available.

Uma característica de destaque da Nhecolândia, uma sub-região do Pantanal Sul-Mato- Grossense, é a presença de lagoas doces (baías) e salgadas (salinas) com uma grande variabilidade química entre si. Apesar da presença de sal nas salinas ser historicamente atribuída a processos passados, estudos recentes sugerem que as águas salgadas estão sendo originadas atualmente devido à concentração por evaporação. O perfil químico das águas salinas estaria sendo originado principalmente pelo controle de elementos (Ca2+, Mg2+ e Si(OH)4) durante a concentração das águas, com o conseqüente envolvimento destes íons em dois processos: a formação de carbonatos e de silicatos magnesianos. Estudos preliminares em solos de salinas sugerem que a ocorrência de nódulos esbranquiçados e a presença de um horizonte enriquecido em argila podem evidenciar estes dois processos. Neste tipo de ambiente, carbonatos como calcita e dolomita são comumente neoformados, mas há divergências na literatura quanto ao mecanismo de origem autigênica dos silicatos magnesianos. Baseando-se no exposto acima, foram definidos os seguintes objetivos para a presente pesquisa: 1) ampliar o conhecimento sobre os solos associados às salinas através de uma caracterização baseada em dados de campo e laboratório dos solos presentes no entorno de uma lagoa salina representativa da Nhecolândia (lagoa do Meio); 2) identificar os processos envolvidos no controle do Ca2+, Mg2+ e Si(OH)4 nas águas salinas, através do estudo das relações entre as fases líquidas (águas superficiais e subsuperficiais) e sólidas (minerais) presentes nos solos do entorno da lagoa do Meio; e 3) identificar os mecanismos específicos de gênese dos minerais autigênicos possivelmente presentes nos solos do entorno da lagoa do Meio. As amostras de solo foram coletadas ao longo de uma topossequência nos arredores da lagoa do Meio e submetidas à análise granulométrica, análises químicas (ICP-MS, pH, CE, carbono total, carbonato de cálcio equivalente, bases trocáveis e testes de imersão em água, ácido e bases) e análises mineralógicas (DRX, MET-EDS). Amostras de água superficiais e subsuperficiais foram coletadas em um transecto que abarca a topossequência estudada e então encaminhadas às análises de pH, Eh, CE, temperatura, titulação com HCl, cromatografia de íons, EAA e ICP-MS. Os solos dos arredores da salina do Meio caracterizam-se pela textura areia a franco-arenosa, pela ausência de estrutura e, de maneira geral, por altos valores de pH, CE, CTC e saturação em Na+. O pH fortemente alcalino e o domínio de Na+ no complexo de troca desencadeiam a atuação do processo de solonização e dos seguintes processos específicos associados: migração de matéria orgânica perfil abaixo, precipitação de carbonatos (calcita, dolomita e nahcolita) em nódulos, solubilização/precipitação de sílica amorfa e formação autigênica de minerais de argila do grupo das esmectitas e micas. Diferentes esmectitas estão presentes ao longo da topossequência: a) na zona raramente atingida pelas variações sazonais do nível d\'água da salina, a esmectita é do tipo ferribeidelita, possui um grau de interestratificação com mica e vermiculita e apresenta teores de Fe3+ similares às micas identificadas no mesmo solo. Estas características sugerem que o mineral do tipo ferribeidelita é originado pela transformação de micas enriquecidas em Fe3+, sendo a vermiculita provavelmente uma fase intermediária nesta transformação; b) na zona de maior variação sazonal do nível d\'água da salina, as esmectitas são classificadas como do tipo saponita e estevensita. Os baixos teores de elementos terras-raras nas amostras enriquecidas nestes minerais, o controle do Mg2+ e do Si(OH)4 nas águas próximas à lagoa do Meio, a saturação das águas do entorno da lagoa em relação a saponita e estevensita e a presença destas esmectitas magnesianas nos locais onde são esperadas máximas taxas de evaporação, provam que estes minerais estão se originando por precipitação química diretamente da coluna d\'água da lagoa salina. Já as micas presentes nos solos estudados são do tipo ilita, glauconita e mica glauconítica, possuem interestratificação com camadas de esmectitas e parecem estar associadas a materiais amorfos. Experimentos de síntese disponíveis na literatura mostram que águas semelhantes às associadas à lagoa do Meio são ideais para a cristalização de micas a partir da precipitação inicial de hidróxidos amorfos. Desta forma, as evidências obtidas sugerem que estas micas são neoformadas a partir da precipitação inicial de amorfos e posterior cristalização. Os resultados obtidos certamente ampliaram o conhecimento sobre os solos presentes no entorno de lagoas salinas, uma vez os estudos disponíveis na literatura são baseados quase que exclusivamente em dados de campo. Mostrou-se que o controle do Ca2+ das águas mais salinas está sendo realizado pela formação de calcita e dolomita em nódulos, enquanto o controle do Mg2+ e do Si(OH)4 está ocorrendo pela formação de esmectitas magnesianas do tipo saponita e estevensita. Estes processos são provavelmente os responsáveis pela alta variabilidade entre as águas doces das baías/vazantes e as salgadas das salinas/arredores, conforme hipótese lançada em literatura. Assim, o presente trabalho fornece fortes evidências de que a presença de sal nas águas das lagoas salinas da Nhecolândia é atual ou, ao menos, tem contribuição de processos atuais. Por fim, mostrou-se ser possível a formação conjunta de ilita, glauconita e mica glauconítica e de esmectitas do tipo saponita e estevensita pelo mecanismo de precipitação diretamente das águas ou soluções em ambientes sujeitos a concentração evaporativa. / A distinctive feature of Nhecolândia, a sub-region of the Pantanal wetland, is the presence in close proximity of freshwater and saline lakes with a huge chemical variability. The salt has been generally attributed to Pleistocene processes, but recent studies have suggested that saline waters arise from present-day concentration of freshwater by evaporation. The chemical profile of saline waters would be originated by chemical control of Ca2+, Mg2+, and Si(OH)4 as the water becomes more saline. Two processes would be responsible for this control: formation of carbonates and formation of Mg-silicates. The presence of whitish nodules and clayey horizons in soils associated to the saline lakes would be evidences of these processes. In saline-alkaline environments, carbonates such as calcite and dolomite are commonly formed by chemical precipitation, but the mechanisms responsible for Mgsilicates genesis are still under debate. The objectives of this research are: a) increasing the general knowledge about soils associated to Pantanal saline lakes through a detailed characterization of the soils located around a representative saline lake of Nhecolândia (\"Salina do Meio\"); b) identifying the processes involved in Ca2+, Mg2+ and Si(OH)4 control from saline waters, through the study of relationships between waters and minerals present in the soils around \"Salina do Meio\"; c) identifying the specific mechanisms of authigenic genesis of the minerals possibly found around \"Salina do Meio\". Soils were sampling along a toposequence and submitted to physical (particle-size), chemical (ICP-MS, pH, EC, total carbon, inorganic carbonate, exchangeable bases, and soaking in H2O, HCl 1N, and NaOH 4M), and mineralogical analyses (XRD and TEM-EDS). Water was collected along a transect involving the lake and submitted to pH, Eh, EC, temperature, titration with HCl, ion chromatography, and ICP-MS analyses. The studied soils are sandy, structureless, and present, in general, high values of pH, CE, CEC, and Na+ saturation. Prevailing of Na+ in the waters and exchangeable sites and dominance of extremely high pH strongly suggest the general action of solonization in these soils and its influence on the following processes: organic matter translocation toward deeper horizons, precipitation of carbonates (calcite, dolomite, and nahcolite) in nodules, precipitation of amorphous silica, and authigenic formation of smectites and micas. Different authigenic smectites occur along the toposequence: a) in the zone hardly reached by the lake level variation, the smectite is classified as ferribeidellite-type, present an interstratification with mica and vermiculite, and has similar amounts of Fe3+ than the Fe-mica present in the soils. These characteristics suggest that this ferribeidellite-type mineral originates from transformation of Fe-mica and that vermiculite may be an intermediate phase in this transformation; b) in the zone of seasonal lake level variation, the smectites are classified as saponite- and stevensite-type minerals. Low REE amounts in the samples enriched in saponite and stevensite, geochemical control of Mg2+ and Si(OH)4, saturation with respect to Mg smectite in the more saline waters, and presence of Mg-smectite where the maximum of evaporation is expected, prove that saponite- and stevensite-like minerals originate by chemical precipitation from the water column of the saline lake. The micas present in the studied soils are classified as illite-, glauconite- and glauconitic mica-type minerals. They present 20% or less smectite layers and seem to be associated to amorphous materials. Synthesis of micas available in the literature shows that water conditions similar to the study area allow for dioctahedral mica crystallization from initial precipitation of amorphous hydroxides. Therefore, it suggests that micas of study area are neoformed. The results of this dissertation contributed to a better understanding about the soils associated to Nhecolândia saline lakes, since most of the published researches are based on field data. The control of Ca2+ from more saline waters occurs by formation of calcite and dolomite in nodules, while the control of Mg2+ and Si(OH)4 occur by formation of Mg-smectites classified as saponite- and stevensite-type. These processes are probably responsible for the chemical variability between freshwater and saline lakes, as supposed in a previous research. Therefore, the present work gives strong evidences about the current origin of Nhecolândia salt water. Also, it showed the possibility of genesis of illite, glauconita, glauconitic mica, saponite, and stevensite minerals through direct precipitation of waters or soil solutions under concentration by evaporation.