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LA‐ICP‐MS dating of detrital zircon grains from the Cretaceous allochthonous bauxites of Languedoc (south of France): Provenance and geodynamic consequences

Emilie Marchand 1 Michel Seranne 2 Olivier Bruguier 2 Marc Vinches 1
1 ERT - IMT Mines Alès - Eau, Ressources, Territoires
LGEI - Laboratoire de Génie de l'Environnement Industriel et des Risques Industriels et Naturels
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.
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https://hal.mines-ales.fr/hal-02625492
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Submitted on : Tuesday, May 26, 2020 - 2:43:01 PM
Last modification on : Monday, August 10, 2020 - 2:05:06 PM

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Emilie Marchand, Michel Seranne, Olivier Bruguier, Marc Vinches. LA‐ICP‐MS dating of detrital zircon grains from the Cretaceous allochthonous bauxites of Languedoc (south of France): Provenance and geodynamic consequences. Basin Research, Wiley, In press, ⟨10.1111/bre.12465⟩. ⟨hal-02625492⟩

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