Jurassic-to-present thermal history of the central High Atlas (Morocco) assessed by low-temperature thermochronology

Apatite fission track (AFT) and (U-Th)/He data from the High Atlas have been obtained for the first time to constrain the tectono-thermal evolution of the central part of the chain. Results from Palaeozoic basement massifs indicate long residence at low temperatures, consistently with their original location out of the deepest Mesozoic rift troughs and indicating minor exhumation. The best rocks for extracting the Alpine history of the Atlas Mountains are Jurassic intrusives, which yield AFT ages centred on c. 80 Ma; thermal models based on AFT data and constrained by (U-Th)/He suggest that these ages are included in a slow cooling trend from intrusion age to c. 50 Ma ago that we attribute to post-rift thermal relaxation. This is followed by a stability period of c. 30 Ma and then by a final exhumational cooling until present exposure. Eocene intrusives yield AFT ages similar to those of Rb-Sr and K-Ar suggesting rapid emplacement in the uppermost crust.