Very high geothermal gradient during mantle exhumation recorded in mylonitic marbles and carbonate breccias from a Mesozoic Pyrenean palaeomargin (Lherz area, North Pyrenean Zone, France)

摘要: Although they are famous among Earth scientists, the Lherz peridotites exposed within geological formations of North Pyrenean Zone (NPZ) still lacking detailed investigations. Our study focuses on metasediments Aulus basin hosting peridotite body and associated ultramafic fragments smaller size. The new data set comprises structural analysis mapping massive Mesozoic marbles that form prerift sequence typical NPZ ultramafic-rich clastic breccia surrounding bodies. display an evolution from hot ductile to cold brittle deformation, indicative exhumation process ending with sedimentary reworking both deformed exhumed rocks. Crystal Preferred Orientations (CPO) measured in support a deformation mechanism by dislocation creep calcite, which is dominant between 400 8C 600 8C; these temperatures range determined earlier Clerc et al. (2015), using RSCM (Raman Spectroscopy Carbonaceous Material) geothermometry. As consequence, we better describe transition clarify origin syn-rift breccias. Due continuous along detachments' faults, brecciated metamorphic carbonates cover were passively uplifted towards shallower levels progressively unroofed, while transported back footwall. These results consistent recent interpretations as remnants subcontinental mantle rocks pre-Pyrenean rift system. We emphasize importance tectonic decoupling Palaeozoic basement, leads juxtaposition metamorphosed Please cite this article press as: Lagabrielle Y, Very high geothermal gradient during recorded mylonitic carbonate breccias palaeomargin (Lherz area, Zone, France). C. R. Geoscience (2016), http://dx.