Petrogenesis of Neoproterozoic Ultramafic Rocks, Wadi Ibib–Wadi Shani, South Eastern Desert, Egypt: Constraints from Whole Rock and Mineral Chemistry

This contribution deals with new geology, petrography, and bulk-rock/mineral chemistry of the poorly studied ultramafics Wadi Ibib–Wadi Shani (WI–WS) district, South Eastern Desert, Egypt. These are dismembered ophiolitic rocks that can be subdivided into serpentinites serpentinized peridotites. Primary minerals such as olivine pyroxene absent in serpentinites, but relics them occur Pseudomorph after is indicated by common hourglass textures less mesh, whilst schistose bastites reflect a pseudomorph. Chromite Cr-spinel Al-spinel. ranges from chromite to magnesochromite composition, whereas Al-spinel belongs spinel field. includes YCr (Cr/(Cr+Al+Fe+3), YAl (Al/(Al+Cr+Fe+3), YFe+3 (Fe+3/(Fe+3+Al+Cr), similar forearc peridotite, more abyssal may formed during inanition subduction processes proto environments. The main secondary tremolite, talc, chlorite—which pycnochlorite diabantite—and their temperature 174 224 °C. examined had undergone high partial melting degrees (>25%), Cr# unaltered cores (Cr-spinel, >0.6), whole (Al2O3, SiO2, CaO, MgO), trace REEs, depleted Na2O, Al2O3, Cr2O3 clinopyroxene, forsterite content ((Fo = 100 Mg/Mg + Fe), av. 95.23 mol%), consistent settings.