Geochronological evidence of Cambrian Series 2 calc-alkaline plutonism in the Paleozoic Western High Atlas (Moroccan Meseta)

Abstract

This study presents geochronological and geochemical data of intermediate-felsic plutonic rocks from the Paleozoic Western High Atlas (Moroccan Meseta). Samples were taken from Medinet diorite emplaced in Cambrian Taroudant Group volcanic and sedimentary rocks and Tiniskt microgranite intrusive in Ediacaran Ouarzazate Group volcano-sedimentary rocks and Tighardine granodiorite. Based on U–Pb analysis of zircon, two well-constrained ages of 514 ± 3 Ma and 521 ± 5 Ma (Cambrian Series 2), were determined for Medinet diorite and Tiniskt microgranite, respectively. It is suggested that both Cambrian Series 2 plutons may represent the deep-seated magma chambers of Terreneuvian-Cambrian Series 2 eruptions recognized in the Paleozoic Western High Atlas. These granitic and dioritic rocks are peraluminous and show compositional affinity with subalkaline calc-alkaline series comparable with the oldest Terreneuvian V2 volcanic rocks. These findings provide evidence of a protracted period of production of calc-alkaline granitic and dioritic magmas during the transition from an Ediacaran convergent setting to Cambrian intra-continental rifting in the northern Gondwana margin.