Petrographic and geochemical characterization of cryogenian mafic dykes of the IguerdaTaïfast inlier (Central AntiAtlas, Morocco)

In the inlier of Iguerda-Taïfast (Anti-Atlas, Morocco) the Neoproterozoic basic rocks consist dominantly of dolérite dykes intruded the Palæoproterozoic basement and overlain by the late Neoproterozoic series. Major and immobile trace elements (HFS and REE elements) allow to identify two groups of mafic rocks: (i) the first is tholeiitic, (ii) the second shows a transitional affinity with chondrite normalized REE patterns more fractionated. Their geochemical signatures display similarities with those of intraplate series found in young continental rift structures (they are enriched in incompatible elements, excepted Y and Yb, relative to N-MORB, but they are depleted in Nb). This preorogenic magmatism can be related to begining of rifting in the northern border of the West-African craton, which allows the emplacement of bassins of Pan-African belt of Anti-Atlas. This rifting may be related to the opening of an oceanic domain in Siroua and Bou-Azzer areas.