The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited

The Neoproterozoic Bou Azzer ophiolite in the Moroccan Anti-Atlas Panafrican belt hosts numerous chromitite orebodies within peridotite section of oceanic mantle. chromitites are strongly affected by serpentinization and metamorphism, although they still preserve igneous relicts amenable for petrogenetic interpretation. major, minor trace element composition unaltered chromite cores reveal two compositional groups: intermediate-Cr (Cr# = 0.60 – 0.74) high-Cr 0.79 0.84) estimates parental melt compositions suggest crystallization from pulses fore-arc basalts (FAB) boninitic melts, respectively, that infiltrated supra-subduction zone (SSZ) A platinum group elements (PGE) mineralization dominated Ir-Ru-Os is recognized chromitites, which has its mineralogical expression abundant inclusions Os-Ir alloys coexisting magmatic laurite (RuS2) their products metamorphic alteration. Unusual mineral phases chromite, not previously reported this ophiolite, include super-reduced and/or nominally ultra-high pressure minerals moissanite (SiC), native Cu silicates (oriented clinopyroxene lamellae), but “exotic” zircon diaspore have also been identified. We interpret lamellae a origin, whereas originated during processes linked to late circulation low-silica fluids related rodingitization. Zircon grains, on other hand, with apatite serpentine inclusions, could either formed after interaction mantle-derived melts or represent subducted detrital sediments later incorporated into chromitites. offer comparison Precambrian ophiolitic worldwide, rather scarce geological record. studied very similar Arabian-Nubian shield, orogeny. Thus, we conclude subduction-initiation geodynamic setting two-stages evolution, formation FAB-derived early stage boninite-derived stage.