Etude géochimique des granitoïdes du pluton d'Aouli, Haute Moulouya, Maroc

Abstract

A mapping and geochemical study of granitic rocks which are exposed in the Aouli Paleozoic window, Haute Moulouya area, Morocco, has revealed the presence of four distinct facies: (1) a granodiorite, which is the most mafic member of the complex; (2) a medium-grained grey granite; (3) a pinkish, medium-grained homogeneous granite; (4) a leucocratic muscovite granite. The four facies are calcalkaline to subalkaline in nature - none of them is truly alkaline as had been suggested previously. The available data show that the granodiorite and the muscovite granite are geochemically distinct. They also suggest that the pinkish facies evolved from the grey facies by fractional crystallization. The horizontal to subhorizontal spatial distribution of SiO₂ contours and observed field relationships both suggest that the grey phase is related to the pink phase by multiple injection supporting the hypothesis that the whole complex was emplaced into a pre-existing horizontal shear zone. A late-orogenic to post-orogenic tectonic environment of emplacement is suggested based on a number of discriminant diagrams.