Persistent Amazonian and West African detrital zircon signature in the northern Mauritanide Belt

Abstract

We provide new detrital zircon U/Pb geochronological data from nine samples of Neoproterozoic–Cambrian metasedimentary rocks of the northern Mauritanide Belt, aiming at constraining depositional ages and provenance in the paleotectonic context of the Rodinia to Gondwana supercontinent transition. The youngest detrital zircon populations indicate the following maximum depositional ages: c. 900 Ma (early Tonian) for the Atilis Quartzite Formation, c. 660 Ma (Cryogenian) for the gneissic Hajar Dekhen-Kleouat Unit, c. 580 Ma (middle Ediacaran) for the Atomai Formation, and c. 540 Ma (late Ediacaran–early Cambrian) for the Sainte Barbe Formation and the ophiolite-like Agoualilet Unit. Two types of zircon age distributions were identified, reflecting the most reliable original sources. Type I age spectra include c. 2.8 Ga, 2.1 Ga and 0.6 Ga age populations, which are interpreted to derive from West African Craton sources (Leonian/Liberian, Eburnean, Pan-African orogenies). Type I signature is found in the Atomai and Sainte Barbe formations and the Agoualilet Unit. Type II age spectra include, besides the type I populations, c. 1.8, 1.5, 1.2 and 1.0 Ga age populations, which are thought to derive from sources in the Amazonian Craton (Central Amazonian, Trans-Amazonian, Rio Negro-Juruena, RondonianSan Ignacio, Sunsas-Grenvillian ´ and Brasiliano orogenies). Type II signature is found in the Atilis Quartzite and Atomai formations, Hajar Dekhen-Kleouat Unit, and the Cambrian Nouatil Group (intra-WAC Taoudeni Basin). The changes in the detrital zircon record through the studied Neoproterozoic–Cambrian successions resulted from shifts in drainage systems and alternating sediment supply from both the West African and the Amazonian cratons along most of the Neoproterozoic period. Finally, we interpret that the subsequent opening of a shortlived oceanic realm (the Clymene Ocean) during the latest Ediacaran between the West African and the Amazonian cratons interrupted the direct sediment supply from the Amazonian Craton.