Serpentinites and associated chromitites of the Neoproterozoic Bou Azzer ophiolite (Central Anti-Atlas, Morocco) provide key constraints on mantle depletion, melt–rock interaction, and the tectono-metamorphic evolution of a supra-subduction zone (SSZ) system. This study integrates field observations, petrography, Raman spectroscopy, and whole-rock/mineral chemistry to decipher the history of this highly dismembered ultramafic suite. The mantle sequence is dominated by antigorite-bearing serpentinites derived primarily from refractory harzburgitic and dunitic protoliths. Whole-rock geochemistry and highly depleted chromite compositions (Cr# = 0.50–0.68; Mg# = 0.43–0.77; TiO₂ ≤ 0.18 wt.%) demonstrate that these peridotites represent refractory residues formed after high degrees of partial melting (~15–25%). The data delineate a clear evolutionary trend from abyssal to fore-arc and back-arc environments, where infiltrating boninitic melts drove localized podiform chromitite formation through intense melt–rock interaction. Crucially, thermodynamic and mineral–chemical constraints challenge previous models of simple greenschist-facies obduction. Equilibration temperatures exceeding 600 °C and chromite stability within the lower amphibolite to near-granulite facies indicate that the oceanic lithosphere underwent deep subduction prior to its exhumation. This high-temperature, high-pressure metamorphism was followed by multistage retrogressive serpentinization and intense CO₂-rich metasomatism (talc-magnesite alteration) during Pan-African transpressional tectonics. Ultimately, the Bou Azzer ophiolite represents a mature SSZ mantle wedge, recording a complete geodynamic cycle from deep subduction-zone metamorphism to final tectonic emplacement along the northern margin of the West African Craton.

The Bou Azzer inlier of the Central Anti-Atlas (Morocco) exposes a relic of a Neopro-terozoic ophiolitic complex, in which serpentinites constitute a volumetrically im-portant constituent of the mantle sequence. These serpentinites form WNW-ESE-trending discontinuous bands and lenses that are emplaced as steeply dip-ping sheets along major thrust faults. Field mapping, drill-core observations, petrog-raphy, SEM, XRD, and geochemical analyses collectively suggest corroboration that complete serpentinization has erased primary olivine and pyroxene, save relic bastite textures and chromian spinel cores that carry crucial information on the mantle source. The serpentinites exhibit textures ranging from well-preserved mesh and bas-tite pseudomorphic textures to strongly foliated and talc-carbonate–altered ones, par-ticularly along shear zones, indicating multistage serpentinization under evolving de-formation conditions. Mineral assemblages are dominated by antigorite ± chrysotile ± lizardite, with secondary magnetite, talc, and carbonates formed during late-stage fluid–rock interaction. Bulk-rock major and trace element geochemistry is typical of depleted mantle, with low Al₂O₃, CaO, and TiO₂, high Mg# (0.81–0.85), and elevated Cr and Ni compared to primitive mantle, consistent with a harzburgitic mantle residuum produced by high degrees of partial melting. Petrographical and geochemical analyses collectively suggest that the Bou Azzer serpentinites are essentially derived from harzburgitic and dunitic, and minor wehrlites and lherzolite protoliths. These features highlight significant mantle heterogeneity beneath Bou Azzer, shaped by variable de-grees of melt extraction and subsequent metasomatism. Chromite chemistry (Cr# = 0.50–0.67, Mg# = 0.43–0.77, TiO₂ ≤ 0.18 wt.%) and Cr–Al–Fe³⁺ compositional plots indi-cate a supra-subduction zone (SSZ) tectonic setting. All of these results together rein-force the interpretation of the Bou Azzer serpentinites as isolated remnants of a Pan-African SSZ-type mantle wedge that was hydrated, carbonated, and deformed during obduction and later transpression at the West African Craton margin.