Reaimantation regionale eocene, migration de fluides et mineralisations sur la bordure cevenole (France)

Abstract

Abstract Widespread remagnetization has been identified in fold belts and forelands inboard of mountain ranges and has usually been interpreted as resulting from fluid migration related to orogenesis in these mountain ranges. The geochemical properties of these fluids should be compatible with the formation or the transformation of ferrimagnetic minerals, thus allowing acquisition of remanent magnetization during fluid migration. Carbonate hosted lead-zinc (+ or -barite and fluorite) mineralization of the Mississippi Valley-type (MVT) are also generally considered to have formed during the migration of enormous volumes of fluids and are commonly located in foreland fold belts or their forelands. This suggests a similar origin for widespread carbonate remagnetization and MVT mineralization. The paleomagnetic dating of MVT deposits has been successfully applied in MVT districts, mainly of North America. Thus, it was used for the MVT deposits hosted by Mesozoic carbonate rocks of the Cevennes region of southern France. In view of the structurally complexity in the region, and because the results presented here are intended to provide an initial reference direction on which further results can be based, only sites belonging to the most stable parts of this border are considered here. Most samples were collected from three surface sites in the area of the Largentiee mine and from independently oriented cores of the two deep boreholes (Balazuc and Morte-Merie) from the Geologie Profonde de la France program. Several samples were also collected from three sites around the area of the Saint Felix-de-Pallieres mine. All these samples come from different stratigraphic levels: Carboniferous, Permian, Triassic, Liassic and Middle Jurassic.