Neoproterozoic granitoids from Khzama, central Anti-Atlas, Morocco: evolution markers from arc magmatism to alkaline magmatism

Petrological study and zircon typology provide important information that is related to the classification and genesis of Neoproterozoic granitoids in the Khzama area (northeast Siroua). The Pan-African granitoids show a transition from island-arc magmatism to alkaline magmatism. A space and time zonation of magmatism from the north to the south is evident. Early Pan-African granitoids were generated from various magma sources through different petrogenetic mechanisms. The first association corresponds to the low-K calc-alkaline plutons of Ait Nebdas, the second one corresponds to high-K calc-alkaline post-collisional granites (Tamassirte-Tiferatine and Ifouachguel). Finally, shoshonitic magmatism Orhiri) ends the magmatic evolution of the region. Thus, the late Pan-African granitic plutonism began with calc-alkaline associations and ended with K-alkaline magmatism in a transtensional setting, heralding the onset of the Moroccan Palaeozoic cycle. ((C)) 2002 Elsevier Science Limited. All rights reserved.