Thermochronology of the Western Alps (Pelvoux Massif) Reveals the Longterm Multiphase Tectonic History of the European Paleomargin

Abstract The Variscan and Alpine long‐term thermal evolution of the European paleomargin in the external Western Alps is still unknown, although important for reconstructing the geodynamic evolution of this orogen. Here we combine zircon fission track and apatite fission track and U‐Pb double dating analyses of the Pelvoux massif in the Western Alps. Apatite U‐Pb ages of <310 Ma and >320 Ma define a bimodal age distribution that reflects differential cooling across the East Variscan Shear Zone. QTQt thermal history modeling reveals a two‐stage rifting evolution on the European paleomargin, initiated with the Alpine Tethys rifting episode during the Early Jurassic and reactivated during the Cretaceous Valais rifting event, leading to peak temperatures of ∼350°C at 90 Ma. The subsequent cooling records a pre‐Priabonian phase of exhumation between 80 and 50 Ma that is related to N‐S oriented Pyrenean shortening. It is followed by Alpine collision‐related burial of the Pelvoux massif from below the foreland basin and the Penninic Frontal Thrust at around 30–25 Ma.