From Pan-African transpression to Cadomian transtension at the West African margin: New U-Pb zircon ages from the Eastern Saghro inlier (Anti-Atlas, Morocco)

New U-Pb zircon ages from the Eastern Saghro massif in the Anti-Atlas of Morocco demonstrate a link between Pan-African transpressive collision at c. 600 Ma and transtension caused by the onset of Cadomian subduction and arc development from c. 570 Ma onwards. We present new U-Pb LA ICP-MS ages of detrital and magmatic zircon from the Saghro, M’Gouna, and Ouarzazate Groups. The siliciclastic deposits of the Saghro Group were deposited in a back-arc setting developed on stretched continental crust of the West African margin. Collision with the Atlas-Meseta domain led to the closure of the back-arc basin before 600 Ma. Time of exhumation and surface exposure of the newly formed Pan-African basement is bracketed to c. 30 Ma due to the maximum depositional age of 571  ± 4 Ma of the overlying M´Gouna Group. The U-Pb age of 567  ± 4 Ma for the lowermost ignimbrite of the Ouarzazate Group limits the time for the deposition of the M´Gouna Group to less than 4 Ma. The Pan-African orogeny was finished at c 600 Ma whereas the onset of transtension related to Cadomian back-arc formation was very much younger from c. 570 Ma onwards.