Variscan structural evolution and metallogenic implications at the paleozoic maider basin, eastern anti-atlas, Morocco

Abstract

In the Moroccan eastern Anti-Atlas, the Paleozoic Maider basin, hosts a range of economic mineral deposits, including Cu, Pb, Fe, and barite forming an important mineralized vein system. In this study, detailed mapping of fractures and veins, structural analysis, and measurements have been integrated to understand the structural control, the tectonic evolution, and fault kinematic history in the Paleozoic outcrops of the Southern margin of the Maider basin. The structural analysis shows two folding phases: (i) a first phase, which generates WNW-ESE-trending folds, in response to an NNE-SSW compression, likely, of Late Westphalian age. And (ii) a second phase which develops N–S metric folds, under a NE-SW to E-W compression, compatible with the Late Variscan shortening, known in the East Anti-Atlas and the Ougarta belt during the Stephano-Autunian period. Moreover, three main fault systems were distinguished: WNW-ESE to E-W, NE-SW and scarcely N–S. These fault systems record evidence of a previous extensional tectonic event that probably corresponds to the Devonian extensional event. During the late Variscan shortening, these faults were reactivated into a left-lateral strike-slip movement with a small reverse component for the WNW-ESE to E-W faults, and right lateral strike-slip motion for NE-SW ones. The mineralization primarily takes place within a vein-type system, which is predominantly found in a network of faults oriented between N30 and N60. These ore bodies present frequently lenticular and banded geometries, and do not show any evidence of deformation, suggesting probably a post Variscan emplacement age. Thus, we could link the mineralization emplacement to the Triasic Central Atlantic rifting.