U–Pb age dating and geochemical fingerprints of Cambrian granites in the North Moroccan Meseta. Implication for the continental rift opening in the Northwest Gondwana margin

Abstract

The Imouzzer Emsian conglomerate of the North Moroccan Meseta contains pebbles of granites. The granites are peraluminous and highly potassic, with a calc-alkaline trace element pattern (high lithophile element enrichment and Nb and Ta negative anomalies). They are dated to late Miaolingian (ca 500 Ma) by U–Pb zircon. The magmatic zircons have inherited cores of Ediacaran, Palaeoproterozoic, and Neoarchaean ages. Rb–Sr and Sm–Nd isotopic analyses display epsilon Nd values at 500 Ma ranging between −5.6 and −1.4. The TDM ages after DePaolo (1981) are calculated between 2701 and 1330 Ma. According to geochemical and isotopic data, the granitic magma may have originated from the melting of lower crustal Ediacaran to Palaeoproterozoic protoliths including Archaean remnants. This acidic magmatic occurrence is contemporaneous with neighbouring rhyolitic activities of bimodal volcanic complexes, which are related to the opening of the Cambrian intra-continental rift of Morocco.