Petrogenesis of carbonated meta-ultramafic lenses from the Neoproterozoic Heiani ophiolite, South Eastern Desert, Egypt: A natural analogue to CO2 sequestration

Abstract

Among a set of peculiar meta-ultramafics, carbonate-orthopyroxenites are observed for the first time in the Heiani ophiolite belt, South Eastern Desert, Egypt. They form massive lensoidal masses up to 50 m long and 20 m wide. The lenses show a marked structural concordance with their neighboring country rocks. The typical country rocks are represented by the following high-grade metamorphic rocks: kyanite–muscovite schists, amphibolites, kyanite-bearing biotite gneisses, migmatites, granite gneisses and mobilizates. The studied carbonate-orthopyroxenites consist mainly of metamorphic orthopyroxene + magnesite, among other metamorphic, relict primary and retrograde secondary minerals. According to primary chromian spinel (Cr#, 0.7–0.84) chemistry and morphology, absence of clinopyroxene and presence of primary mantle olivine (Fo89–91) as relicts in the metamorphic orthopyroxene, the Heiani carbonate-orthopyroxenites seem to have formed from a highly depleted mantle peridotite...