Les granitoïdes hercyniens post-collisionnels affleurent dans la partie orientale de la chaîne hercynienne du Maroc. L'étude pétrographique et géochimique comparée permet de rendre compte d'une ressemblance de composition entre les différentes intrusions. Ces granitoïdes appartiennent à des associations magmatiques peralumineuses à cafémiques, évoluant suivant des lignées similaires à celles des associations calco-alcalines fortement potassiques à shoshonitiques.

The late Neoproterozoïc Toubkal inlier (Ancient Massif of the High-Atlas, Morocco) contains two igneous basaltic series (Tircht and Sidi Chamharouch). Investigated rocks display characteristics of within-plate continental tholeiitic and are similar to rocks originated in orogenic contexts. The geochemical results allow the assumption that subduction active processes are indirectly responsible for the genesis of theses rocks. The orogenic signature is linked probably to a Pan-African magmatic source previously metasomatized in the northern margin of the West African Craton.

The geochemical composition of fifteen fresh Triassic sandstone samples from two localities (Oukaimeden and Ourika Valley, Morocco) was carried out, in order to assess their provenance, weathering and tectonic setting. These sandstones are classified as litharenites and wackestones. The CIA (Chemical Index of Alteration; mean value GK= 57.6 and GI = 71.77) values and Al 2 O 3 -CaO +Na 2 O-K 2 O suggest that the source materials for these sandstones must have been subjected to low and moderate degree of weathering and reworking. Sandstones from studied areas had a high SiO2content in the range of 62-82% due to their mineralogical maturation. However, the negative correlation between SiO2content and the other major elements proposes another contribution of silica. AIT KEJOU sandstones show the presence of a small amount of clay minerals than IGHERMANE sandstones. The Upper Continental Crust (UCC) and North American Shales (NASC) normalization showed depletion in light rare earth elements (LREE) and enrichment in HREE. The negative europium (Eu/Eu*) anomaly support a felsic rocks provenance of the studied sandstones. The cerium (Ce/Ce*) anomaly indicated an oxidizing depositional environment. The depletion in LREE in relation to the HREE and low La/Lu ratio values suggest that the sandstones are as a result of fluvial/river channel system with a slight sea contribution. According to the provenance discrimination diagram, the sandstones were derived from the adjacent Cambrian basement units of Tifnout granitic massif, associated andesites and the granodiorites of the Precambrian basement units of Central High Atlas, located to the south of the studied areas. Discrimination diagrams suggested a passive margin tectonic setting for AIT KEJOU sandstones and an active continental margin tectonic setting for the IGHERMANE sandstones.Copy Right, IJAR, 2016,. All rights reserved.

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Cette note présente la première étude pétrographique et géochimique détaillée réalisée sur les granitoïdes hercyniens des massifs de Zekkara, Tarilest et Béni-Snassen. Ceux-ci correspondent à des magmas métalumineux ou hyperalumineux, mis en place de manière étagée dans le temps et à différents niveaux de la croûte continentale. Les compositions des éléments majeurs et traces, montrent une évolution typique des suites calco-alcalines potassiques post-collision-nelles. Les trois intrusions dérivent d'un magma crustal de nature ignée dont l'évolution est contrôlée par la cristallisation fractionnée. Aucun argument ne permettant d'évoquer des témoins d'une croûte océanique ancienne ce magmatisme serait à rattacher à une tectonique tangentielle tardi-hercynienne et un modèle d'amincissement crustal et de remontée du manteau est privilégié.