Mesozoic tectonic events in the southern European basement revealed by thermochronology - insight for margin paleogeography (Pelvoux and Maures-Tanneron massif)

It is now well established that the tectonic structure and thermal properties inherited from the orogens and rifting play an important role in the subsequent collision. This study focuses on the thermal inheritance of crystalline massifs from the SW Alps (Pelvoux and Maures-Tanneron) and their geodynamical implications during the Mesozoic continental rifting. Thermochronometers, including U-Pb/Apatite, Zircon fission tracks (ZFT) and Apatites fission tracks (AFT), (U-Th)/He on zircon and apatite (Zhe, AHe), their QTQt modelling and Rb/Sr dating on phengite in one shear zone, show successive tectonic events. The ZFT in the Pelvoux indicates a complex thermal history with central ages ranging from 158 to 45 Ma, thereby revealing significant resetting and cooling in the Jurassic and Eocene periods. The thermal modelling of a separate block of the massif highlights a thermal history emphasized by three distinct periods of: (1) Jurassic-lower Cretaceous heating associated with the Alpine Tethys and Valaisan opening, (2) pre-Alpine upper Cretaceous to Priabonian cooling linked to tectonic inversion of the European margin, which agrees with onset of Pyreneo-Provençal phase of shortening during the upper Cretaceous as revealed by a Rb/Sr age of 79.7 ± 3.7 Ma in an E-W (top-to-the-South) shear zone, (3) Miocene Alpine cooling/exhumation event. In contrast, in the Maures-Tanneron Massif multiple thermal events are highlighted by thermochronology, including (1) a cooling phase at approximately 200 Ma associated with CAMP volcanism preserved in the Tanneron massif, which is followed by (2) a Mesozoic (120 Ma) cooling event, after which the massif remained close to the surface until a final Eocene cooling phase. These results provide insights on how the architecture of rifted domains of the European margin in the wide plate boundary between Adria, Iberia and Europe controlled exhumation between the Alps and the Pyrenees-Provence orogenic systems.