Petrographic and geochemical study of Jurassic-Cretaceous intrusive massifs (Gabbros-syenites) of the Eastern High Atlas, Morocco (Rich-Talsint axis)

Fieldwork, petrographic description and geochemistry are presented for the Upper Jurassic-Lower Cretaceous magmatic intrusions from the Mesozoic Eastern High Atlas in Morocco. The magmatic complexes are ellipsoid-shaped and a diapiric-dominated mechanism is suggested for the emplacement of the intrusions into Paleozoic faulted basement as well as in the overlying Triassic-Jurassic sedimentary rocks. The intrusions are massive and composed of mafic (olivine-, biotite-bearing gabbro, and ordinary gabbro), intermediate (diorite) and felsic (syenite) units. The major and trace element contents indicate transitional to alkaline affinities for the mafic and intermediate intrusions and alkaline for the felsic ones, evolved in an intracontinental setting. The data indicate a heterogeneous mantle source, likely metasomatized sub-continental lithosphere that had been enriched by plume-type melts. The Eastern High Atlas intrusives are part of a continuum of magmatic events that spanned from the Triassic Central Atlantic Magmatic Province to the late-Jurassic to early-Cretaceous magmatism of the High Atlas system.