Calc-alkaline Arc I-type Granitoid Associated with S-type Granite in the Pan-African Belt of Eastern Anti-Atlas (Saghro and Ougnat, South Morocco)

The Sidi Flah and Ougnat inliers are located in the eastern Anti-Atlas antiform between the Anti-Atlas Major Fault (AAMF) and South Atlas Fault (SAF). They consist of many granitoid intrusions emplaced into Neoproterozoic metasedimentary rocks and surmounted by upper Neoproterozoic A-type granites. The Sidi Flah (Saghro) and Ougnat granitoids are part of the Neoproterozoic magmatic activity related to northwards subduction of an oceanic plate beneath the Saghro continental margin. They are post-orogenic I- and S-type granitoids related to the ending of the compressional deformation in this Pan-African belt. A petrographic, geochemical and zircon typology study leads us to subdivide these rocks into three magmatic groups: (1) a medium- to high-K calc-alkaline group formed by quartz diorites and amphibole granodiorites is found in both Sidi Flah and Ougnat inliers; (2) a high-K calc-alkaline group is present in Sidi Flah. These two groups have a (deeper and) hybrid mantle-crust origin; (3) a peraluminous group in Ougnat is linked to the post-collisional setting and has a shallow crustal source. On a primitive mantle-normalized trace-element diagram, almost all of these rocks show a significant Nb depletion relative to K and La, which is typical of the calc-alkaline magmatism from the subduction-zone environment. Absence of structural marks of thrusting upon the West African craton (WAC) of this arc system and the ophiolitic suite in Bou-Azzer, and the presence of Imiter muscovite-bearing granite as part of Pan-African belt do not support the localization of northern limit of WAC at the level of SAF.