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Benoît QUESNEL

Nature and origin of mineralizing fluids in the hyperextensional systems: The case of cretaceous Mg metasomatism in the Pyrenees

Supervisors:
Marie-Christine Boiron and Michel Cathelineau – Université de Lorraine, CNRS, CREGU, GeoRessources
Laurent Truche – Université Grenoble Alpes, CNRS, ISTerre
Eric Gaucher – TOTAL, CSTJF, Pau

Major Results

Primary brines expelled from Triassic levels were probably at the origin of the Mg metasomatism documented in the Pyrenees during the Cretaceous hyper-extension of the continental crust.

Abstract

During the Albian, the hyper-extension of the Pyrenean passive margin led to a hyper-thinning of the continental crust and the subsequent sub-continental mantle exhumation. The giant Trimouns talc-chlorite deposit represents the most prominent occurrence of Albian metasomatism in the Pyrenees, with the occurrence of the largest talc deposit worldwide. Consequently, this deposit, which is located on a fault zone and a

lithological contact, represents one of the major drains at the scale of the Pyrenees and one of the best geological targets in order to determine the origin(s) of the fluid(s) that circulated during this period. Based on stable isotopes and halogen measurements of fluid inclusions and their host minerals we demonstrated that the mineralizing fluid was mainly primary brines expelled from the Triassic levels.

Scenarios of talc production by brines interaction with the basement considering
(1) an evolved brine of Triassic origin or
(2) a brine produced by serpentinization of mantle rocks

Nature and Origin of Mineralizing Fluids in Hyperextensional Systems: The Case of Cretaceous Mg Metasomatism in the Pyrenees

Quesnel, B., Boiron, M.-C., Cathelineau, M., Truche, L., Rigaudier, T., Bardoux, G., Agrinier, P., de Saint Blanquat, M., Masini, E., Gaucher, E. C. (2019) Nature and origin of mineralizing fluids in hyperextensional systems: The case of cretaceous Mg metasomatism in the Pyrenees. Geofluids.

keywords: Hydrothermal fluids, central Pyrenees, Talc, Dolomites, Mg-metasomatism

DOI: https://doi.org/10.1155/2019/7213050