Geochronological data on the Rabat–Tiflet granitoids: Their bearing on the tectonics of the Moroccan Variscides

The northern border of the Variscan Moroccan Meseta is characterized by the presence of Cambrian rocks affected by pre-Variscan deformation (the Sehoul block) thrust to the south onto Ordovician, Silurian and Devonian sediments and volcanics of the Bou Regreg corridor. A correct appraisal of the significance of this tectonic contact in the framework of the Variscan orogen needs new data on the age, geochemical features and field relationships of granitoids cropping out in the Sehoul block (Rabat granitoids) and the Bou Regreg corridor (Tiflet granitoids). Accordingly, we provide here with new geochemical data and accurate U–Pb geochronology of these granitoids, which lead us to conclude that: (i) the Rabat granitoids are Late Devonian in age (367 Ma); (ii) the Tiflet granitoids are Late Proterozoic in age (605–609 Ma) and display Andean-arc features, thus being genetically linked to the Cadomian/Pan-African subduction and forming part of the Variscan basement during the Palaeozoic; (iii) the previously accepted 430 Ma Rb–Sr age, common for the Rabat and Tiflet granitoids, which would imply a trivial Carboniferous displacement of the Sehoul thrust, must be rejected; and (iv) the Sehoul thrust might be a major Variscan boundary, perhaps hiding the Rheic Ocean suture.