Dans le cadre du suivi environnemental de ses installations en conditions nominales d’exploitation ou en situation accidentelle, le CEA doit assurer la mise en place de méthodes et d’outils opérationnels permettant de mesurer, contrôler et prédire les rejets de ses installations dans l’atmosphère, les sols et les nappes. Cette thèse s’inscrit ainsi dans la mise en place d’un outil de transport réactif permettant de prédire la migration de radionucléides en concentration trace tels que 90Sr et 137Cs, les principaux radionucléides d’intérêt, dans les sols et les roches. L’objectif de cette thèse est d’évaluer l’applicabilité et le caractère prédictif d’un modèle couplé chimie-transport, dans le cas de la migration de Cs et Sr dans un sédiment naturel représentatif de la couche aquifère sous-jacente au site de Cadarache. Le modèle de rétention utilisé est basé sur la Théorie des Echangeurs d’Ions multi-sites (TEI), intégré dans PhreeqC couplé à HYDRUS 1D (HP1) ou dans Crunchflow.La caractérisation des propriétés physico-chimiques du sédiment étudié et l’identification des minéraux réactifs a permis dans un premier temps d’élaborer une base de données de rétention de Sr2+, Cs+ et Ca2+ (principal cation du milieu) sur les minéraux argileux majoritairement présents, illite et smectite. La construction de cette base de données s’est faite à partir d’une révision critique des données de la littérature, complétée par l’acquisition de données manquantes. A partir de cette base de données, et faisant l’hypothèse de l’additivité des propriétés de rétention des minéraux purs dans un matériau considéré comme un mélange de minéraux purs, il a été possible, dans un second temps, de vérifier l’applicabilité du modèle de rétention au cas de l’adsorption de Sr2+ et Cs+ sur le sédiment.Enfin, ce modèle de rétention a pu être couplé à un modèle de transport, et appliqué au cas de la migration de Sr et Cs dans des colonnes de sédiment. Ces expériences ont été réalisées sur deux types de colonne, à l’échelle centimétrique sur des colonnes standards et à l’échelle décimétrique sur un banc expérimental équipé d’un générateur X permettant de suivre en continu les paramètres physico-chimiques au sein de la colonne. Les simulations des expériences de transport réactif de Sr par le modèle d’échange d’ions multi-sites, couplé à l’équation d’advection-dispersion ont pu reproduire convenablement les courbes de percée de Sr sans aucun ajustement des paramètres. Les coefficients de dispersivité de chaque colonne ont été déterminés lors d’expériences de transport non réactif à l’aide de traceurs inertes (2H, Cl- et I-). Par ailleurs, les courbes de percée de Cs semblent plus difficiles à reproduire, ce qui serait imputable aux incertitudes existant encore sur les paramètres de rétention relatifs à cet élément ou un effet cinétique.La bonne concordance entre les résultats des expériences de transport réactif de Sr en colonne à deux échelles différentes et les simulations ont montré que le modèle de transport réactif mis en place permet de reproduire le comportement de Sr dans le sédiment de Cadarache étudié, sans ajustement de paramètres, en considérant la rétention chimique par un processus d’échange d’ions sur les minéraux argileux du système. Cette première étape indispensable à l’évaluation du modèle mis en place permet de confirmer le caractère prédictif de ce modèle, dans la mesure où les conditions physico-chimiques sont bien contraintes. / As part of the environmental monitoring of its installations under nominal operating conditions or in accident situation, CEA must ensure the implementation of operational methods and tools to measure, control and predict the discharge of its installations into the environment, atmosphere, soil and groundwater. This work is part of the implementation of a reactive transport tool, which allows predicting the migration of radionuclides in trace concentration such as 90Sr and 137Cs, the main radionuclides of interest, in soils and rocks. The aim of this thesis is to evaluate the applicability and predictive nature of a coupled chemistry-transport model in the case of migration of Cs and Sr in a natural sediment, representative of the aquifer underlying the nuclear site of Cadarache. The retention model used is based on the Multi-Site Ion Exchange Theory, integrated in PhreeqC coupled with HYDRUS 1D (HP1) or Crunchflow.The characterization of the physico-chemical properties of the sediment studied and the identification of the reactive minerals allow to develop a database of retention of Sr2+, Cs+ and Ca2+ (major cation of the medium) on the clay minerals mostly present, illite and smectite. The construction of this database was based on a critical review of the data in the literature, supplemented by the acquisition of missing data. From this database and assuming the additivity of the retention properties of pure minerals in a material considered as a mixture of pure minerals, it was possible to verify the applicability of the retention model in the case of the adsorption of Sr2+ and Cs+ on the sediment.Finally, this retention model could be coupled to a transport model and applied to the case of the migration of Sr and Cs in sediment columns. These experiments were carried out on two types of column, at the centimeter scale on standard columns and at a decimetric scale on an experimental device equipped with a X generator recording continuously the physicochemical parameters within the column. Simulations of the Sr reactive transport experiments by the multi-sites ion exchange model coupled with the advection-dispersion equation were able to adequately reproduce the Sr breakthrough curves without any parameter adjustments. The dispersivity coefficients of each column were determined in non-reactive transport experiments using inert tracers (2H, Cl- and I-). Moreover, the Cs breakthrough curves seem more difficult to reproduce, which could be due to the uncertainties still existing on the retention parameters related to this element or a kinetic effect.The good agreement between the results of the reactive Sr transport experiments in a column at two different scales and the simulations showed that the reactive transport model implemented allows reproducing the behavior of Sr in the Cadarache sediment without parameter adjustment by considering the chemical retention by an ion exchange process on the clay minerals of the system. This first step, essential to the evaluation of the model confirms the predictive nature of this model, insofar as physicochemical conditions are well constrained.

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As Minas do Camaquã são compostas pelas Minas Uruguay e São Luiz, foram produtoras de Cu e localizam-se no extremo sul do Brasil (na região do Escudo Sul-rio-grandense) na chamada Bacia do Camaquã (Neoproterorozoico ao Paleozoico). A região das Minas do Camaquã é classicamente conhecida como “Janela Bom Jardim” e já foi objeto de diversos estudos porém ainda persistem dúvidas principalmente quanto a gênese do minério e a sua relação temporal. As mineralizações ocorrem alojadas em falhas e como disseminações nos arenitos e conglomerados do Alogrupo Santa Bárbara desta Bacia. Os sulfetos presentes incluem a paragênese composta por calcopirita, bornita, calcocita e pirita, aparecendo o Au e a Ag como principais subprodutos. Na Mina Uruguay destaca-se a presença de um conglomerado com seixos zonados de composição granítica decorrentes dos processos de alteração hidrotermal atuantes nessas rochas. Amostras desses seixos foram coletadas em testemunhos de sondagem e analisados por petrografia, por difratometria de raios X e por microscopia eletrônica de varredura mostrando a presença de alteração hidrotermal de composição ilítica principalmente na porção mais central dos seixos. Assim, em 4 amostras coletadas em diferentes profundidades nos testemunhos foram separadas diferentes frações granulométricas (<1; <0,2; <0,3; >0,1<0,4; <0,4 mμ). Estas frações, ricas em ilita foram datadas pelo método 40K-40Ar e obteve-se diferentes idades (507,41 ± 10.37; 486,74 ± 9,96; 466,23 ± 9,54; 465,92 ± 9,48; 396,84 ± 8,1 e 250,61 ± 5,38 Ma). São então reconhecidos três grupos de idades: - 507,41 ± 10.37 a 465,92 ± 9,48 (Cambro-Ordoviciano); - 396,84 ± 8,1 (Devoniano); - 250,61 ± 5,38 (Triássico). O primeiro grupo foi relacionado aos processos hidrotermais geradores do minério na região com idades coerentes com dados geocronológicos já existentes. O segundo e terceiro grupo foram interpretados como o registro de atividades tectônica marcadas pelos falhamentos presentes em toda região ou pela reativação desses falhamentos. Conclui-se então que a datação 40K-40Ar de ilitas hidrotermais resulta em dados significativos para a interpretação de regiões mineralizadas. / The Camaquã Mines (consisting of the Uruguay and São Luiz Mines) are former producers of Cu and are located on the southern edge of Brazil (in the Sul- Rio-Grandense Shield region) in the Camaquã Basin (Neoproterozoic to Early Paleozoic). The Camaquã Mines region is classically known as the “Bom Jardim Window” and has been the subject of many studies. However questions still remain regarding the genesis of the ore and its temporal relationships. Mineralization occurs in faults and as disseminations in the sandstones and conglomerates of the Santa Bárbara Allogroup of this Basin. The sulfides present include the paragenesis composed of chalcopyrite, bornite, chalcocite and pyrite, with Au and Ag appearing as the main byproducts. The presence of a conglomerate with zoned pebbles of granitic composition resulting from the hydrothermal alteration processes acting on these rocks is highlighted in the Uruguay Mine. Samples from these pebbles were collected from drill cores and analyzed by petrography, x-ray diffraction and scanning electron microscopy, showing hydrothermal alteration of illitic composition, mainly in the innermost portion of the pebbles. Thus, in 4 samples collected from different boring depths, different particle-size fractions were separated (<1, <0.2, <0.3, >0.1<0.4, <0.4 mμ). These fractions, which were rich in illite, were dated by the 40K- 40Ar method, and different ages were obtained (507.41 ± 10.37, 486.74 ± 9.96, 466.23 ± 9.54, 465.92 ± 9.48, 396.84 ± 8.1 and 250.61 ± 5.38 Ma), resulting in the recognition of the following three age groups: - 507.41 ± 10.37 to 465.92 ± 9.48 (Cambro-Ordovician), - 396.84 ± 8.1 (Devonian), - 250.61 ± 5.38 (Triassic). The first group was related to the hydrothermal processes generating the ore in the region, showing ages consistent with existing geochronological data. The second and third groups were interpreted as records of tectonic activity marked by the faulting existing in the entire region or the reactivation of these faults. These findings demonstrate that 40K-40Ar dating of hydrothermal illites results in data that are significant for the interpretation of mineralized regions.

As Minas do Camaquã são compostas pelas Minas Uruguay e São Luiz, foram produtoras de Cu e localizam-se no extremo sul do Brasil (na região do Escudo Sul-rio-grandense) na chamada Bacia do Camaquã (Neoproterorozoico ao Paleozoico). A região das Minas do Camaquã é classicamente conhecida como “Janela Bom Jardim” e já foi objeto de diversos estudos porém ainda persistem dúvidas principalmente quanto a gênese do minério e a sua relação temporal. As mineralizações ocorrem alojadas em falhas e como disseminações nos arenitos e conglomerados do Alogrupo Santa Bárbara desta Bacia. Os sulfetos presentes incluem a paragênese composta por calcopirita, bornita, calcocita e pirita, aparecendo o Au e a Ag como principais subprodutos. Na Mina Uruguay destaca-se a presença de um conglomerado com seixos zonados de composição granítica decorrentes dos processos de alteração hidrotermal atuantes nessas rochas. Amostras desses seixos foram coletadas em testemunhos de sondagem e analisados por petrografia, por difratometria de raios X e por microscopia eletrônica de varredura mostrando a presença de alteração hidrotermal de composição ilítica principalmente na porção mais central dos seixos. Assim, em 4 amostras coletadas em diferentes profundidades nos testemunhos foram separadas diferentes frações granulométricas (<1; <0,2; <0,3; >0,1<0,4; <0,4 mμ). Estas frações, ricas em ilita foram datadas pelo método 40K-40Ar e obteve-se diferentes idades (507,41 ± 10.37; 486,74 ± 9,96; 466,23 ± 9,54; 465,92 ± 9,48; 396,84 ± 8,1 e 250,61 ± 5,38 Ma). São então reconhecidos três grupos de idades: - 507,41 ± 10.37 a 465,92 ± 9,48 (Cambro-Ordoviciano); - 396,84 ± 8,1 (Devoniano); - 250,61 ± 5,38 (Triássico). O primeiro grupo foi relacionado aos processos hidrotermais geradores do minério na região com idades coerentes com dados geocronológicos já existentes. O segundo e terceiro grupo foram interpretados como o registro de atividades tectônica marcadas pelos falhamentos presentes em toda região ou pela reativação desses falhamentos. Conclui-se então que a datação 40K-40Ar de ilitas hidrotermais resulta em dados significativos para a interpretação de regiões mineralizadas. / The Camaquã Mines (consisting of the Uruguay and São Luiz Mines) are former producers of Cu and are located on the southern edge of Brazil (in the Sul- Rio-Grandense Shield region) in the Camaquã Basin (Neoproterozoic to Early Paleozoic). The Camaquã Mines region is classically known as the “Bom Jardim Window” and has been the subject of many studies. However questions still remain regarding the genesis of the ore and its temporal relationships. Mineralization occurs in faults and as disseminations in the sandstones and conglomerates of the Santa Bárbara Allogroup of this Basin. The sulfides present include the paragenesis composed of chalcopyrite, bornite, chalcocite and pyrite, with Au and Ag appearing as the main byproducts. The presence of a conglomerate with zoned pebbles of granitic composition resulting from the hydrothermal alteration processes acting on these rocks is highlighted in the Uruguay Mine. Samples from these pebbles were collected from drill cores and analyzed by petrography, x-ray diffraction and scanning electron microscopy, showing hydrothermal alteration of illitic composition, mainly in the innermost portion of the pebbles. Thus, in 4 samples collected from different boring depths, different particle-size fractions were separated (<1, <0.2, <0.3, >0.1<0.4, <0.4 mμ). These fractions, which were rich in illite, were dated by the 40K- 40Ar method, and different ages were obtained (507.41 ± 10.37, 486.74 ± 9.96, 466.23 ± 9.54, 465.92 ± 9.48, 396.84 ± 8.1 and 250.61 ± 5.38 Ma), resulting in the recognition of the following three age groups: - 507.41 ± 10.37 to 465.92 ± 9.48 (Cambro-Ordovician), - 396.84 ± 8.1 (Devonian), - 250.61 ± 5.38 (Triassic). The first group was related to the hydrothermal processes generating the ore in the region, showing ages consistent with existing geochronological data. The second and third groups were interpreted as records of tectonic activity marked by the faulting existing in the entire region or the reactivation of these faults. These findings demonstrate that 40K-40Ar dating of hydrothermal illites results in data that are significant for the interpretation of mineralized regions.

As Minas do Camaquã são compostas pelas Minas Uruguay e São Luiz, foram produtoras de Cu e localizam-se no extremo sul do Brasil (na região do Escudo Sul-rio-grandense) na chamada Bacia do Camaquã (Neoproterorozoico ao Paleozoico). A região das Minas do Camaquã é classicamente conhecida como “Janela Bom Jardim” e já foi objeto de diversos estudos porém ainda persistem dúvidas principalmente quanto a gênese do minério e a sua relação temporal. As mineralizações ocorrem alojadas em falhas e como disseminações nos arenitos e conglomerados do Alogrupo Santa Bárbara desta Bacia. Os sulfetos presentes incluem a paragênese composta por calcopirita, bornita, calcocita e pirita, aparecendo o Au e a Ag como principais subprodutos. Na Mina Uruguay destaca-se a presença de um conglomerado com seixos zonados de composição granítica decorrentes dos processos de alteração hidrotermal atuantes nessas rochas. Amostras desses seixos foram coletadas em testemunhos de sondagem e analisados por petrografia, por difratometria de raios X e por microscopia eletrônica de varredura mostrando a presença de alteração hidrotermal de composição ilítica principalmente na porção mais central dos seixos. Assim, em 4 amostras coletadas em diferentes profundidades nos testemunhos foram separadas diferentes frações granulométricas (<1; <0,2; <0,3; >0,1<0,4; <0,4 mμ). Estas frações, ricas em ilita foram datadas pelo método 40K-40Ar e obteve-se diferentes idades (507,41 ± 10.37; 486,74 ± 9,96; 466,23 ± 9,54; 465,92 ± 9,48; 396,84 ± 8,1 e 250,61 ± 5,38 Ma). São então reconhecidos três grupos de idades: - 507,41 ± 10.37 a 465,92 ± 9,48 (Cambro-Ordoviciano); - 396,84 ± 8,1 (Devoniano); - 250,61 ± 5,38 (Triássico). O primeiro grupo foi relacionado aos processos hidrotermais geradores do minério na região com idades coerentes com dados geocronológicos já existentes. O segundo e terceiro grupo foram interpretados como o registro de atividades tectônica marcadas pelos falhamentos presentes em toda região ou pela reativação desses falhamentos. Conclui-se então que a datação 40K-40Ar de ilitas hidrotermais resulta em dados significativos para a interpretação de regiões mineralizadas. / The Camaquã Mines (consisting of the Uruguay and São Luiz Mines) are former producers of Cu and are located on the southern edge of Brazil (in the Sul- Rio-Grandense Shield region) in the Camaquã Basin (Neoproterozoic to Early Paleozoic). The Camaquã Mines region is classically known as the “Bom Jardim Window” and has been the subject of many studies. However questions still remain regarding the genesis of the ore and its temporal relationships. Mineralization occurs in faults and as disseminations in the sandstones and conglomerates of the Santa Bárbara Allogroup of this Basin. The sulfides present include the paragenesis composed of chalcopyrite, bornite, chalcocite and pyrite, with Au and Ag appearing as the main byproducts. The presence of a conglomerate with zoned pebbles of granitic composition resulting from the hydrothermal alteration processes acting on these rocks is highlighted in the Uruguay Mine. Samples from these pebbles were collected from drill cores and analyzed by petrography, x-ray diffraction and scanning electron microscopy, showing hydrothermal alteration of illitic composition, mainly in the innermost portion of the pebbles. Thus, in 4 samples collected from different boring depths, different particle-size fractions were separated (<1, <0.2, <0.3, >0.1<0.4, <0.4 mμ). These fractions, which were rich in illite, were dated by the 40K- 40Ar method, and different ages were obtained (507.41 ± 10.37, 486.74 ± 9.96, 466.23 ± 9.54, 465.92 ± 9.48, 396.84 ± 8.1 and 250.61 ± 5.38 Ma), resulting in the recognition of the following three age groups: - 507.41 ± 10.37 to 465.92 ± 9.48 (Cambro-Ordovician), - 396.84 ± 8.1 (Devonian), - 250.61 ± 5.38 (Triassic). The first group was related to the hydrothermal processes generating the ore in the region, showing ages consistent with existing geochronological data. The second and third groups were interpreted as records of tectonic activity marked by the faulting existing in the entire region or the reactivation of these faults. These findings demonstrate that 40K-40Ar dating of hydrothermal illites results in data that are significant for the interpretation of mineralized regions.