Fast exhumation rate during late orogenic extension: The new timing of the Pilat detachment fault (French Massif Central, Variscan belt)

A leucogranite sill in the footwall of extensional Pilat shear zone (PSZ) Eastern French Massif Central was emplaced and sheared a short time interval, between 301.8 ± 3.1 303.0 1.6 Ma (zircon U–Pb mica 40Ar/39Ar ages, respectively). Extension ended at 298.5 1.5 (40Ar/39Ar on mica) as shown by non deformed dike cross cutting zone. On hanging wall fault, opening St. Etienne Basin filled coarse clastic sedimentation confirms existence relief south PSZ. U-Pb dating lithic-rich ignimbrite bottom basin volcanic layer top delivered ages 310.5 3.4 299.3 1.3 Ma, respectively. Close from syn- to post-tectonic granites indicate very fast cooling (∼150 °C/Myr) exhumation rate (6 mm/yr) corresponding emplacement middle crust immediately followed their tectonic into upper crust. The development fault thermally softened is responsible for rapid Velay dome, Metamorphic Core Complex localized Here we propose that its due sub crustal lithospheric mantle dripping. These new data show there only one phase PSZ coeval with coal Basin. Finally, chronology obtained this study challenging previous suggesting 20 activity