Neoproterozoic serpentinites from the Bou Azzer ophiolite, Central Anti-Atlas (Morocco): geodynamic evolution and mantle processes beneath the West African Craton boundaries

Amina Wafik ¹, Roberto Visalli ², Rosalda Punturo ^2,3, Aida Maria Conte ³, Daniela Guglietta ³, Mohamed Ben Massoude ¹, Nouamane El Aouad ¹, Nazaire Nzaou Mabika ¹ & Rosolino Cirrincione ^2
1Semlalia Geosciences Lab- Geology Department, Faculty of Sciences Semlalia, Cadi Ayyad University, BP. 2390 Marrakech 40000 Morocco., ²Department of Biological, Geological and Environmental Sciences, University of Catania, 95129 Catania, Italy., ³Institute of Environmental Geology and Geoengineering, National Research Council of Italy (CNR IGAG), Research Area of Rome 1, 00010 Rome, Italy.

The complex evolutionary processes of Western Gondwana triggered significant chemical transformations within the West African Craton (WAC), including the melting and alteration of the upper peridotitic mantle. These alterations are well-documented in ultramafic rocks, providing evidence of these geological events. This study focuses on analyzing the petrographic and geochemical properties of serpentinites found within a Neoproterozoic ophiolitic complex. Specifically, it aims to combine insights from petrology, mineral chemistry, and geochemistry obtained from selected serpentinite formations, such as those in the Inguijem-Aït Ahmane massif within the Bou Azzer ophiolites located in the central Anti-Atlas region of Southern Morocco. These serpentinites originated from residual mantle harzburgites that underwent varying degrees of partial melting. Analysis of chromite chemistry suggests that the mantle protolith of these peridotites experienced partial melting > 25%. The data indicate that forearc peridotites predominate, while some samples exhibit characteristics of abyssal peridotites, potentially reflecting the evolution of the WAC during extensional events associated with continental breakup in the early Neoproterozoic, as well as island arc accretion during convergence in the mid-Neoproterozoic period.