Revised stratigraphic framework for the lower Anti-Atlas Supergroup based on U–Pb geochronology of magmatic and detrital zircons (Zenaga and Bou Azzer-El Graara inliers, Anti-Atlas Belt, Morocco)

Abstract

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Geochemistry and Geochronology of the Neoproterozoic Backarc Basin Khzama Ophiolite (Anti-Atlas Mountains, Morocco): Tectonomagmatic Implications

“…759 Ma obtained by [12]; for the Northern Ait Ahmane ophiolites of Bou Azzer and have the same age as our Khzama plagiogranite dated at 777 ± 4.7 Ma (777 ± 5 Ma). These ophiolites postdate the 885-883 Ma Iguerda-Taïfast Large Igneous Province that are hypothesized to mark the onset of the rifting on the northern edge of the West African craton and the disassembly of Rodinia [24,116,117]. Similar-aged LIPs also occur on other cratons such as the Tarim Terrane (North China) and the Congo Craton (Central Africa); these might reflect rifting during the late stage in the assembly of the Rodinia supercontinent ( [24]; and references therein).…”

“…These ophiolites postdate the 885-883 Ma Iguerda-Taïfast Large Igneous Province that are hypothesized to mark the onset of the rifting on the northern edge of the West African craton and the disassembly of Rodinia [24,116,117]. Similar-aged LIPs also occur on other cratons such as the Tarim Terrane (North China) and the Congo Craton (Central Africa); these might reflect rifting during the late stage in the assembly of the Rodinia supercontinent ( [24]; and references therein). The age of the Anti-Atlas ophiolites should also predate the oldest magmatic flare-up at 760-730 Ma in the development of the Anti-Atlas Belt oceanic arc complexes [28].…”

“…In the West African Craton (WAC) the Late Neoproterozoic marks the onset of a period of rifting leading to opening of an ocean basin on its northern edge. This rifting has been associated with the extension leading to the break-up of the supercontinent Rodinia [23,24,117]. In the Bou-Azzer (Ait Ahmane) and Siroua (Khzama) inliers, relic of the oceanic crust then formed (Bou-Azzer Group) is found as highly sheared allochthonous ophiolite complexes ( [12], and references therein), yet crustal (mafic meta-cumulates, meta-basaltic sheeted dikes, and, to a smaller extent, pillow lavas) and mantle rocks (serpentinized peridotites with chromite pods) are recognizable [13][14][15].…”

“…762 Ma plagiogranite of [22], suggesting a long-lived supra-subduction zone for the Neoproterozoic Khzama ophiolite. [23], modified by [24]. (C) Simplified geological map of the central part of Khzama inlier showing the main lithotectonic units (modified after [25]).…”

“…Note that the northern boundary of the WAC is the Anti-Atlas Major Faults or the South Atlas Fault [26]. Morocco showing the studied area in the Siroua inlier [23], modified by [24]. (C) Simplified geological map of the central part of Khzama inlier showing the main lithotectonic units (modified after [25]).…”