Petrology and geochemistry of the Neoproterozoic Siroua granitoids (central Anti-Atlas, Morocco): evolution from subduction related to within-plate magmatism

International audienceThe Siroua massif includes many plutons of Neoproterozoic age. The mineralogical and geochemical character of the plutons allows us to describe an evolution of the magmatism, in space and time, from a subduction-related type in the northern part, to a within-plate subalkaline type in the southern part. The first magmatic activity coeval with the closing of the Khzama oceanic basin in the north is little evolved and of oceanic type (dominantly gabbros and basalts). It is followed by a low potassic calc-alkaline magmatism (gabbro-diorites, tonalites and trondhjemites of Nebdas pluton) and by a voluminous highly potassic calcalkaline magmatism (Askaoun and Ifouachguel plutons) that marks the collisional period. The end of crustal uplift and the beginning of the extension is marked in the south by a sub-alkaline magmatism corresponding to the Ida ou Illoun, Imdghar and Affela N'ouassif granites. Magmatic activity, in the Siroua massif, is marked at the end of the Neoproterozoic (PIII) by a continental tholeiite with an alkaline affinity, which occurs as dykes crosscutting the Neoproterozoic granites, and later by dominantly alkaline granites