najih, amine chouaib doukkali university - sciences faculty - department of geology, El Jadida, Morocco , fekkak, abdelilah chouaib doukkali university - sciences faculty - department of geology, El Jadida, Morocco , ezzouhairi, hassan chouaib doukkali university - sciences faculty - department of geology, El Jadida, Morocco , baidder, lahssen hassan ii university - faculty of sciences ain chock, Casablanca, Morocco , berrada, ilyass chouaib doukkali university - sciences faculty - department of geology, El Jadida, Morocco , karaoui, brahim moulay ismaïl university - faculty of sciences and technics, Errachidia, Morocco , mahmoudi, abdelkader moulay ismaïl university - faculty of sciences, Meknes, Morocco

The Tafilalt magmatic complex (Eastern Anti Atlas, Morocco): New insights into petrology and geochemistry; and preliminary interpretation

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In the eastern Moroccan Anti-Atlas, the Tafilalt Province exposes folded Cambrian-Visean series intruded by a number of dykes, sills and laccoliths. These intrusions constitute the Tafilalt Magmatic Complex, TMC. New field, petrographic and geochemical data from the TMC provide an opportunity to decipher the nature of their sources and approach their geotectonic significance. Three petrographic facies have been recognized, i.e., olivine dolerites in some of the sills, kaersutite-bearing lamprophyres occurring in dykes and sills, and eventually gabbro-syenites in the laccoliths. The olivine dolerites are composed of olivine, pyroxene, plagioclase and kaersutite. Geochemically, they show high values of MgO, Mg#, Cr and Ni indicating a genesis with a minor fractionation in olivine and clinopyroxene. Geochemical data of these rocks include high LREE with (La/Yb)Pm ≈2.44 with no Eu anomalies and a discrete negative Ti anomaly. The kaersutite lamprophyres (dykes and sills) and the gabbro-syenites (laccoliths) contain low percentages in olivine and pyroxene, but display abundant kaersutite and high Fe/Mg content. The analyzes show more or less similar values in MgO, Mg#, Cr, Ni and high LREE values with (La/Yb)Pm≈6.86. They share geochemical characteristics in Sr and Ti anomalies indicating a fractionation of plagioclase and ferrotitanium oxides. All the TMC rocks display a high-Ti OIB alkaline character and show ratios (Gd/Yb)C 2 and Ti/Y ≥ 500 which attest for a genesis from mantle plume. The TMC rocks cannot be ascribed to any Devonian-Carboniferous magmatism for structural reasons. They differ geochemically from the tholeiitic intrusions of the Central Atlantic Magmatic Province. They have to be ascribed to a post-Visean and pre-Triassic magmatic event.

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Anti , Atlas , Tafilalt , Magmatism , Plume , High , Ti , Late Paleozoic

bulletin de l’institut scientifique, section sciences de la terre

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