Meso-Archean to Mid-Paleozoic Granitoids in Oulad Dlim Massif (the Pericratonic Terrane of the Reguibat Shield, West African Craton, Morocco): Petrology, Geochemistry, Geochronology and Geological Implications

Abstract

The Oulad Dlim Massif, adjacent to the Reguibat Shield in South Morocco was considered up to now as part of the Variscan belt (Mauritanides) with a polyphase geologic history and a complex geodynamic evolution implicating oceans closures and accretion of exotic terranes (Avalonian and Meguman) during the Variscan - Alleghanian orogeny. The use of modern technology to characterize the petrology, the geochemistry and the geochronology of the lithological units forming this region, combined to field surveys has led to an updated geological architecture and different geological history. The Oulad Dlim Massif is mainly a deformed Archean terrane, as recorded by its eastern and western sectors, dominated in its central part by a bimodal felsic-mafic magmatism forming the Ediacaran sector. The study of these magmatic complexes supports strongly the intracontinental origin of this bimodal magmatism vs. the oceanic origin published before in literature. The exploration of this massif conducted also to the identification of a Silurian - Devonian sector in the western part. Therefore, up to date, different magmatic events lasting from the Meso-Archean to the Cretaceous are recorded in the Oulad Dlim Massif rocks, among them different generations of granitoids are reported. New data on granitoids from the Ediacaran sector are presented in this paper. This recent data demonstrates that Oulad Dlim Massif has been affected by the main Ediacaran—Cambrian extensional event widely documented in other structural domains of Morocco and other parts of North Gondwana. Additionally, the study of the Silurian—Devonian sector rocks highlighted the presence of a Caledonian tectonic event challenging the ideas about the paleogeography of this part of northwestern Africa and its geological evolution during the Paleozoic. However, despite the significant contribution of this extensive survey and the abundance of data on the Oulad Dlim Massif, more studies are required to reconstruct the puzzle at plate tectonic scale.

Keywords

Archean / Ediacaran bimodal magmatism / extension / intracontinental rifting / Caledonian tectonic event / petrology / geochemistry

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