EPMA and LA-ICP-MS Data of Clinopyroxene and Chromite from the Wadi Ghadir Ophiolites, Eastern Desert, Egypt

Abstract

New EPMA and LA-ICP-MS data of pyroxene and chromite are used to assess the so far published tectonic setting of Wadi Ghadir Ophiolite (WGO) in the Central Eastern Desert of Egypt. The low contents of TiO 2 (< 0.46 wt%) and high concentrations in the analyzed clinopyroxene suggest a depleted residual mantle source material. The trace element composition and REE patterns reflect transitional IAT-boninitic geochemical affinities in a suprasubduction zone setting. Chromite, on the other hand, shows high Cr#(Cr/(Cr+Al)) (0.83-0.88 mol) and relatively constant Mg#(Mg/(Mg+Fe +2 )) (0.66-0.70 mol), indicating a high degree of partial melting of the uPP.er mantle source. These features are typical for supra-subduction zone in a back-arc or inter-arc basin setting. The micro-analytical data of relict magmatic mineral phases in the WGO and other ophiolitic rocks in the Arabian-Nubian Shield can help in interpreting their precise tectonic setting as far as data of the immobile, incompatible elements are used.