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Marc Vinches – One of the best experts on this subject based on the ideXlab platform.

  • Tectonic and climate control on allochthonous Bauxite deposition. Example from the mid-Cretaceous Villeveyrac basin, southern France
    Sedimentary Geology, 2020
    Co-Authors: Emmanuelle Chanvry, Emilie Marchand, Michel Lopez, Michel Séranne, Gwenn Le Saout, Marc Vinches

    Abstract:

    Karst Bauxite deposits represent 11% of the global quantity of Bauxite (Bardossy and Aleva, 1990). Karst Bauxite is defined as Bauxite deposits overlying carbonate rocks above a more or less karstified surface. Allochtonous karst Bauxites result from two successive processes: (1) intense weathering and formation of a lateritic profile, involving the development of bauxitic and duricrust horizons; and (2) erosion of the lateritic profile and deposition above a carbonate unit located downstream. In the Villeveyrac basin (southern France), Lower to Mid-Albian allochtonous karstic Bauxites are deposited on a Jurassic karstified bedrock, and are overlain by a Late Albian marine siliciclastic cover. A drillcore, sampling the substratum, the Bauxites and their cover, is analyzed and offers the opportunity to investigate the depositional conditions and interactions of climate and tectonic during the mid- to late Cretaceous, through the analysis of mechanical and chemical weathering evidence. Sedimentological study allowed the definition of four Bauxite facies and three siliciclastic cover facies, overprinted by four different pedofacies. Mineralogical and geochemical analyses allowed the distinction of four mineralogical units controlled by climate-related weathering processes. The Bauxite deposits emplaced by mud-flow/debris-flow gravity currents are composed by boehmite-hematite and goethite. The top of the Bauxite presents a progressive upward decrease in Al2O3 and TiO2 associated with the occurrence of kaolinite. The base of the cover that overlies the Bauxite interval corresponds to a paralic environment, dominated by kaolinite, with a sub-ferricrete paleosol. The following paralic sequence presents a clay-rich suite dominated by smectite, associated with mica/illite and quartz, which suggests aridification of climate around the latest Albian. We interpret this sedimentary succession as the result of erosion of an autochthonous laterite cover, induced by major tectonic uplift in the upstream drainage area, which led to a significant increase in slope gradient, under a wet tropical climate. Mechanical erosion of autochthonous laterite Bauxite in the upstream drainage led to a reverse stacking of the reworked autochthonous lateritic profile in the depositional basin. A continuous transgressive trend was responsible for trapping of the allochtonous karst Bauxite. This was followed by stacking of siliciclastic paralic sequences, which record progressive erosion of the bedrock in the upstream drainage area, under dry tropical conditions. Our results thus suggest that dismantling of the autochthonous laterite cover was initiated by Albian uplift and this ended with a change towards drier and more seasonal climate at the Albian-Cenomanian transition.

  • LA‐ICP‐MS dating of detrital zircon grains from the Cretaceous allochthonous Bauxites of Languedoc (south of France): Provenance and geodynamic consequences
    Basin Research, 2020
    Co-Authors: Emilie Marchand, Michel Séranne, Olivier Bruguier, Marc Vinches

    Abstract:

    The Cretaceous of southern France is characterized by a long erosional hiatus, outlined with Bauxite deposits, which represent the only remaining sedimentary record of a key period for geodynamic reconstructions. Detrital zircons from allochthonous karst Bauxites of Languedoc (Southern France) have been dated using LA‐ICP‐MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry), in order to specify the age of deposition and to constrain the provenance of the weathered material. We analysed 671 single detrital zircons grains from 3 karst bauxitic basins, stretching from close to the Variscan Montagne Noire to the present‐day Mediterranean Sea. Analytical results provide Variscan (300‐350 Ma) and Late Proterozoic (550‐700 Ma) ages as primary groups. In addition, Middle‐, Late Proterozoic and Early Archean (oldest grain at 3.55 Ga) represent significant groups. Mid‐Cretaceous zircons (118‐113 Ma) provide a pooled age of 115.5 ± 3.8 Ma, which constitutes the maximum age for Bauxite deposition. Results also suggest a dual source for the Languedoc Bauxite: one generalized sedimentary source of regional extent and a localised source in the Variscan basement structural high, that has been progressively unroofed during Albian. Integration of these new findings with previously published thermochronological data support the presence of an Early Cretaceous marly cover on the Variscan basement, which has been weathered and then removed during the Albian. The Languedoc Bauxite provide a spatial and temporal link between the uplift of southern French Massif Central to the north, and the Pyrenean rift and its eastward extension to the south. These new results allow to constrain the timing and distribution of uplift/subsidence during the mid‐Cretaceous events in relation with the motion of the Iberian plate relative to Eurasia.

Emilie Marchand – One of the best experts on this subject based on the ideXlab platform.

  • Tectonic and climate control on allochthonous Bauxite deposition. Example from the mid-Cretaceous Villeveyrac basin, southern France
    Sedimentary Geology, 2020
    Co-Authors: Emmanuelle Chanvry, Emilie Marchand, Michel Lopez, Michel Séranne, Gwenn Le Saout, Marc Vinches

    Abstract:

    Karst Bauxite deposits represent 11% of the global quantity of Bauxite (Bardossy and Aleva, 1990). Karst Bauxite is defined as Bauxite deposits overlying carbonate rocks above a more or less karstified surface. Allochtonous karst Bauxites result from two successive processes: (1) intense weathering and formation of a lateritic profile, involving the development of bauxitic and duricrust horizons; and (2) erosion of the lateritic profile and deposition above a carbonate unit located downstream. In the Villeveyrac basin (southern France), Lower to Mid-Albian allochtonous karstic Bauxites are deposited on a Jurassic karstified bedrock, and are overlain by a Late Albian marine siliciclastic cover. A drillcore, sampling the substratum, the Bauxites and their cover, is analyzed and offers the opportunity to investigate the depositional conditions and interactions of climate and tectonic during the mid- to late Cretaceous, through the analysis of mechanical and chemical weathering evidence. Sedimentological study allowed the definition of four Bauxite facies and three siliciclastic cover facies, overprinted by four different pedofacies. Mineralogical and geochemical analyses allowed the distinction of four mineralogical units controlled by climate-related weathering processes. The Bauxite deposits emplaced by mud-flow/debris-flow gravity currents are composed by boehmite-hematite and goethite. The top of the Bauxite presents a progressive upward decrease in Al2O3 and TiO2 associated with the occurrence of kaolinite. The base of the cover that overlies the Bauxite interval corresponds to a paralic environment, dominated by kaolinite, with a sub-ferricrete paleosol. The following paralic sequence presents a clay-rich suite dominated by smectite, associated with mica/illite and quartz, which suggests aridification of climate around the latest Albian. We interpret this sedimentary succession as the result of erosion of an autochthonous laterite cover, induced by major tectonic uplift in the upstream drainage area, which led to a significant increase in slope gradient, under a wet tropical climate. Mechanical erosion of autochthonous laterite Bauxite in the upstream drainage led to a reverse stacking of the reworked autochthonous lateritic profile in the depositional basin. A continuous transgressive trend was responsible for trapping of the allochtonous karst Bauxite. This was followed by stacking of siliciclastic paralic sequences, which record progressive erosion of the bedrock in the upstream drainage area, under dry tropical conditions. Our results thus suggest that dismantling of the autochthonous laterite cover was initiated by Albian uplift and this ended with a change towards drier and more seasonal climate at the Albian-Cenomanian transition.

  • LA‐ICP‐MS dating of detrital zircon grains from the Cretaceous allochthonous Bauxites of Languedoc (south of France): Provenance and geodynamic consequences
    Basin Research, 2020
    Co-Authors: Emilie Marchand, Michel Séranne, Olivier Bruguier, Marc Vinches

    Abstract:

    The Cretaceous of southern France is characterized by a long erosional hiatus, outlined with Bauxite deposits, which represent the only remaining sedimentary record of a key period for geodynamic reconstructions. Detrital zircons from allochthonous karst Bauxites of Languedoc (Southern France) have been dated using LA‐ICP‐MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry), in order to specify the age of deposition and to constrain the provenance of the weathered material. We analysed 671 single detrital zircons grains from 3 karst bauxitic basins, stretching from close to the Variscan Montagne Noire to the present‐day Mediterranean Sea. Analytical results provide Variscan (300‐350 Ma) and Late Proterozoic (550‐700 Ma) ages as primary groups. In addition, Middle‐, Late Proterozoic and Early Archean (oldest grain at 3.55 Ga) represent significant groups. Mid‐Cretaceous zircons (118‐113 Ma) provide a pooled age of 115.5 ± 3.8 Ma, which constitutes the maximum age for Bauxite deposition. Results also suggest a dual source for the Languedoc Bauxite: one generalized sedimentary source of regional extent and a localised source in the Variscan basement structural high, that has been progressively unroofed during Albian. Integration of these new findings with previously published thermochronological data support the presence of an Early Cretaceous marly cover on the Variscan basement, which has been weathered and then removed during the Albian. The Languedoc Bauxite provide a spatial and temporal link between the uplift of southern French Massif Central to the north, and the Pyrenean rift and its eastward extension to the south. These new results allow to constrain the timing and distribution of uplift/subsidence during the mid‐Cretaceous events in relation with the motion of the Iberian plate relative to Eurasia.

  • Rôle des interactions tectonique-sédimentation sur l’évolution et la variabilité spatiale d’un gisement de Bauxite karstique : exemple au bassin de Villeveyrac (Sud de la France)
    , 2019
    Co-Authors: Emilie Marchand

    Abstract:

    Cette thèse propose d’identifier les rôles de la tectonique et de la sédimentation responsables des variabilités spatiales d’un gisement de Bauxite karstique et particulièrement dans le bassin de Villeveyrac (SE de la France). Pendant le Crétacé « moyen », le sud de la France a connu des évènements géologiques conduisant à la formation et l’accumulation de Bauxite. Les Bauxites reposent en discordance sur un substratum Jurassique carbonaté, karstifié et déformé ; cela implique une évolution polyphasée de l’événement bauxitique: 1-latérisation et bauxitisation in-situ de roches alumino-siliceuses et 2-démantèlement et piégeage des Bauxites dans des karsts situés en aval.Les études sédimentologiques associées à des analyses minéralogiques et géochimiques sur deux forages carottés, à travers le remplissage bauxitique et sa couverture, mettent en évidence des sources latéritiques diverses et de degrés d’altération différents. Les profils latéritiques ont été érodés, transportés et piégés dans les cavités karstiques, suivant une séquence inverse d’un profil d’altération, confirmant l’allochtonie des dépôts. Le matériel est issu de coulées boueuses périodiques et rapides, sous climat latérisant. La couverture sédimentaire Crétacé supérieur correspond à des séries détritiques marneuses déposées en domaine paralique. Les assemblages argileux montrent une diminution de la kaolinite au profit de la formation de smectite et la préservation du détritisme au sommet de la couverture, suggèrent des conditions hydrolysantes moins intenses et un climat plus aride.L’analyse structurale du substratum Jurassique du bassin de Villeveyrac permet d’établir une chronologie des déformations enregistrées et d’identifier un régime extensif NE-SW responsable de la structuration en blocs de failles NW-SE en Languedoc, conduisant à l’érosion et la karstification du substratum Mésozoïque. Un réseau de joints N060/N150, présent dans le Jurassique, a été utilisé comme vecteur principal de karstification conduisant à une topographie de lapiaz métrique. Les failles normales NW-SE ont provoqué des zones d’effondrement dans le bassin, augmentant l’espace disponible pendant le dépôt des Bauxites. La compression Pyrénéenne, ultérieure, a conduit au plissement synclinal et a entraîné la formation de fractures dans le gisement, dont certaines directions (N060) ont été utilisées comme drains principaux à un fluide mobilisateur en fer.L’analyse géostatistique des puissances minéralisées dans l’ensemble du bassin, identifie 3 phénomènes structurant les dépôts bauxitiques : 1- la surface karstifiée (paléolapiaz de ± 4 m de profondeur, identifiée sur le terrain), 2- des dolines d’effondrement (± 300 m de diamètre) et 3- l’activité des failles NW-SE (espacées de ±1300 m associées aux plus fortes puissances minéralisées). L’analyse géostatistique des teneurs moyennes (SiO2, Al2O3, TiO2, Fe2O3) montre que les variables ont un comportement fortement aléatoire, excepté dans la direction N060, parallèle à l’axe du pli Pyrénéen tardif. Ces résultats suggèrent que les fractures liées au plissement et affectant le gisement, sont associées à une déferrification le long de ces fractures, concentrant les autres oxydes dans cette direction.Enfin, la datation U-Pb des zircons détritiques extraits des Bauxites dans trois gisements du Languedoc, permet de dater les dépôts de l’Albien inférieur à moyen. Le traçage des sources latéritiques indique : 1- une source issue de l’altération du socle Hercynien de la Montagne Noire, dont l’influence diminue vers l’est et 2- une source d’origine sédimentaire, généralisée à l’ensemble du bassin du Sud-Est.La caractérisation des phénomènes structuraux et sédimentaires contrôlant l’épisode bauxitique en Languedoc, constitue un apport significatif à la géodynamique régionale du Crétacé « moyen », mais aussi à la compréhension du gisement de Bauxite de Villeveyrac, en proposant un guide fiable pour son exploitation durable.

Michel Séranne – One of the best experts on this subject based on the ideXlab platform.

  • Tectonic and climate control on allochthonous Bauxite deposition. Example from the mid-Cretaceous Villeveyrac basin, southern France
    Sedimentary Geology, 2020
    Co-Authors: Emmanuelle Chanvry, Emilie Marchand, Michel Lopez, Michel Séranne, Gwenn Le Saout, Marc Vinches

    Abstract:

    Karst Bauxite deposits represent 11% of the global quantity of Bauxite (Bardossy and Aleva, 1990). Karst Bauxite is defined as Bauxite deposits overlying carbonate rocks above a more or less karstified surface. Allochtonous karst Bauxites result from two successive processes: (1) intense weathering and formation of a lateritic profile, involving the development of bauxitic and duricrust horizons; and (2) erosion of the lateritic profile and deposition above a carbonate unit located downstream. In the Villeveyrac basin (southern France), Lower to Mid-Albian allochtonous karstic Bauxites are deposited on a Jurassic karstified bedrock, and are overlain by a Late Albian marine siliciclastic cover. A drillcore, sampling the substratum, the Bauxites and their cover, is analyzed and offers the opportunity to investigate the depositional conditions and interactions of climate and tectonic during the mid- to late Cretaceous, through the analysis of mechanical and chemical weathering evidence. Sedimentological study allowed the definition of four Bauxite facies and three siliciclastic cover facies, overprinted by four different pedofacies. Mineralogical and geochemical analyses allowed the distinction of four mineralogical units controlled by climate-related weathering processes. The Bauxite deposits emplaced by mud-flow/debris-flow gravity currents are composed by boehmite-hematite and goethite. The top of the Bauxite presents a progressive upward decrease in Al2O3 and TiO2 associated with the occurrence of kaolinite. The base of the cover that overlies the Bauxite interval corresponds to a paralic environment, dominated by kaolinite, with a sub-ferricrete paleosol. The following paralic sequence presents a clay-rich suite dominated by smectite, associated with mica/illite and quartz, which suggests aridification of climate around the latest Albian. We interpret this sedimentary succession as the result of erosion of an autochthonous laterite cover, induced by major tectonic uplift in the upstream drainage area, which led to a significant increase in slope gradient, under a wet tropical climate. Mechanical erosion of autochthonous laterite Bauxite in the upstream drainage led to a reverse stacking of the reworked autochthonous lateritic profile in the depositional basin. A continuous transgressive trend was responsible for trapping of the allochtonous karst Bauxite. This was followed by stacking of siliciclastic paralic sequences, which record progressive erosion of the bedrock in the upstream drainage area, under dry tropical conditions. Our results thus suggest that dismantling of the autochthonous laterite cover was initiated by Albian uplift and this ended with a change towards drier and more seasonal climate at the Albian-Cenomanian transition.

  • LA‐ICP‐MS dating of detrital zircon grains from the Cretaceous allochthonous Bauxites of Languedoc (south of France): Provenance and geodynamic consequences
    Basin Research, 2020
    Co-Authors: Emilie Marchand, Michel Séranne, Olivier Bruguier, Marc Vinches

    Abstract:

    The Cretaceous of southern France is characterized by a long erosional hiatus, outlined with Bauxite deposits, which represent the only remaining sedimentary record of a key period for geodynamic reconstructions. Detrital zircons from allochthonous karst Bauxites of Languedoc (Southern France) have been dated using LA‐ICP‐MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry), in order to specify the age of deposition and to constrain the provenance of the weathered material. We analysed 671 single detrital zircons grains from 3 karst bauxitic basins, stretching from close to the Variscan Montagne Noire to the present‐day Mediterranean Sea. Analytical results provide Variscan (300‐350 Ma) and Late Proterozoic (550‐700 Ma) ages as primary groups. In addition, Middle‐, Late Proterozoic and Early Archean (oldest grain at 3.55 Ga) represent significant groups. Mid‐Cretaceous zircons (118‐113 Ma) provide a pooled age of 115.5 ± 3.8 Ma, which constitutes the maximum age for Bauxite deposition. Results also suggest a dual source for the Languedoc Bauxite: one generalized sedimentary source of regional extent and a localised source in the Variscan basement structural high, that has been progressively unroofed during Albian. Integration of these new findings with previously published thermochronological data support the presence of an Early Cretaceous marly cover on the Variscan basement, which has been weathered and then removed during the Albian. The Languedoc Bauxite provide a spatial and temporal link between the uplift of southern French Massif Central to the north, and the Pyrenean rift and its eastward extension to the south. These new results allow to constrain the timing and distribution of uplift/subsidence during the mid‐Cretaceous events in relation with the motion of the Iberian plate relative to Eurasia.