Modélisation magnétique de la suture ophiolitique de Bou Azzer–El Graara (Anti-Atlas central, Maroc). Implications sur la reconstitution géodynamique panafricaine

Abstract

Les roches ophiolitiques de l'Anti-Atlas central sont responsables d'une importante anomalie magnétique qui longe « l'Accident majeur de l'Anti-Atlas ». La modélisation magnétique de l'ophiolite de Bou Azzer-El Graara montre son enracinement au sein de la partie supérieure de la croûte continentale et son pendage orienté vers le nord. Ces résultats corroborent les modèles géodynamiques en faveur d'une subduction vers le nord de la croûte océanique néoprotérozoïque précédant la collision panafricaine. La polarité de la subduction panafricaine dans l'Anti-Atlas est ainsi conforme avec celles des autres domaines orogéniques panafricains, où les plans de subduction contournent et pendent de façon divergente par rapport au craton Ouest-Africain lors de l'assemblage du Gondwana occidental au Néoprotérozoïque.

The Anti-Atlas Pan-African Belt (Morocco): Overview and pending questions

“…This consensus is summarized as follows, mostly after Blein et al (2014a), Hefferan et al (2014) and Triantafyllou et al (2016Triantafyllou et al ( , 2018: the oceanic domain includes ophiolitic sequences and oceanic arc units, partly dismembered along the polyphased, and eventually sinistral AAMF; the ophiolitic sequences formed during the Cryogenian, with dates spanning between 760-660 Ma (Table 1, Supplementary Materials); their geochemical signature points to an emplacement in a supra-subduction zone setting; the rocks typical of intra-oceanic arc setting consist of (i) low-grade metamorphic rocks such as greywackes, basalts, andesites, rhyolites and tuffites in the Tichibanine arc domain, north of the Bou Azzer inlier; (ii) highgrade orthogneiss, intrusive metagabbro, and crosscutting leucogneiss in the Bougmane (aka Bougmmane) arc complex, south of the main ophiolitic axis of the Bou Azzer inlier (Blein et al, 2014b;Triantafyllou et al, 2018), and (iii) a single, Iriri-Tachakoucht-Tourtit complex arc composed of schists, gneiss, and intrusive leucogneiss and hornblendites in the Siroua inlier (Triantafyllou et al, 2016); according to most authors, the subduction of the oceanic crust was outboard with respect to the WAC (i.e. northdipping in present coordinates), at least up to 640-630 Ma (Soulaimani et al, 2006).…”

Post‐Variscan exhumation of the Central Anti‐Atlas (Morocco) constrained by zircon and apatite fission‐track thermochronology

“…The large, WNW‐ESE trending Bou Azzer‐El Graara inlier straddles the outcropping Pan‐African suture zone, which again crops out west ward south of the Siroua Massif (Fig. C; Leblanc, ; Saquaque et al ., ; Soulaimani et al ., ; Admou and Soulaimani, ; Ouanaimi and Soulaimani, ; with ref. therein).…”

The Bou Azzer Co–Ni–Fe–As(±Au ± Ag) District of Central Anti-Atlas (Morocco): A Long-Lived Late Hercynian to Triassic Magmatic-Hydrothermal to Low-Sulphidation Epithermal System

“…The district has been extensively studied over the last few decades resulting in the release of a wealth of geological, mineralogical, and geochemical data, in hundreds of research papers, theses, geological maps at different scales, and unpublished mining company reports. The regional and local geological descriptions presented here draw extensively from the pioneering work of Leblanc (1975Leblanc ( , 1986 together with recent studies of Hefferan et al (2000), Thomas et al (2002Thomas et al ( , 2004, Walsh et al (2002), Inglis et al (2004Inglis et al ( , 2005, Gasquet et al (2005), Soulaimani et al (2006), El Hadi et al (2010), and Blein et al (2014). Accordingly, only a summary of major conclusions relevant to the present synthesis is given below.…”