Geochemical and Sr–Nd isotopic constraints on the petrogenesis of the Tiflet granitoids (Northwestern Moroccan Meseta): geological implications

Abstract

The Moroccan Variscan orogen contains numerous small felsic magmatic bodies from the Upper Neoproterozoic. The Tiflet granitoids (Northwestern Moroccan Meseta) consist of two lenticular bodies (Taicha and Sidi BouJemaa) with granodioritic composition and a zircon U–Pb age of 609 Ma, which outcrop in the BouRegreg corridor of the northern Moroccan Meseta. Both granitoids are magnesian with a calc-alkaline trend, mostly showing a peraluminous affinity but with a mineral association typical of I-type granitoids. Major element variations reflect a higher degree of evolution for Sidi BouJemaa than for the Taicha granitoid, but there is no clear evidence that they are related by fractionation processes. A predominantly metaigneous source in the lower crust or mixtures of continental crust and subcontinental lithosphere, presumably from the Paleoproterozoic basement, is possible for these granitoids judging from their low values of Al2O3/(FeO + MgO + TiO2) and (Na2O + K2O)/(FeO + MgO + TiO2), high (CaO/Na2O) values, in conjunction with relatively low initial 87Sr/86Sr ratios (0.7054–0.7108) and negative eNd(t) values (− 6.52 to − 8.45). REE patterns with elevated LREE/HREE fractionation, slight Eu anomalies and flat patterns from Er to Lu are typical of syn-collisional granitoids. In contrast, post-collisional HKCA granitoids are related to a transtensional tectonic regime, with low 87Sr/86Sr ratios and high 143Nd/142Nd values that indicate an important mantle contribution.