ABSTRACT
The Zabargad Island is a unique paradigm for in situ uplifted upper mantle lherzolite fragments in the Red Sea. The Southern Peridotite Mass (SPM) is the biggest and best-exposed mantle section in Zabargad Island. It is characterized by abundant plagioclase and up to 10 vol.% mafic Al-Di pyroxenite layers, and Cr-Di pyroxenite dykes. Field relationships indicate that the crystallization of the Al-Di pyroxenite predated the Cr-Di pyroxenite. Thermo-barometric calculations show that the SPM plots along the continental geotherm at the highest P-T conditions and then departs adiabatically to final equilibration at ~3.8 kbar. The rapid upwelling of the lithospheric mantle resulted in the formation of subsolidus plagioclase at the expense of Cr-spinel. During uplift, the lherzolite-Al-Di pyroxenite association was subjected to deformation, resulting in extensive foliation in the SPM. The crystallization of minor amphibole in the granoblastic domains in the highly deformed samples reinforces the invasion of H2O-bearing fluids. During deformation, the SPM has been variably impregnated with silicate melt crystallizing calcic plagioclase (An76.7–An92.4) and unexsolved pyroxenes (Mg# 0.88–0.91). Eventually, the mantle section and crustal rocks were emplaced on the seafloor and intruded by MORB-type basaltic dikes generally parallel to the axial trough of the Red Sea.
