ON THE GEOCHEMISTRY OF AMPHIBOLITE ENCLAVES IN THE PAN-AFRICAN GNEISSES OF WADI FEIRAN, SW SINAI, EGYPT, AND THEIR RELATION TO ARC MAGMATISM

Abstract

Geochemistry of amphibolite enclaves from the Pan-African Wadi Feiran area, SW Sinai, is presented with the aim to assess the petrogenetic characteristics of their protliths. These enclaves are concordantly enclosed in biotite, hornblende and quartzofeldspathic gneisses and schists, that overlie partially migmatized granitic gneisses. They occur as variably sized, massive to highly foliated and often strongly stretched, lenses and boudins. The studied enclaves are of magmatic origin with precursors ranging from calc-alkaline andesites to tholeiitic basalts. Rare enclaves of high-Mg appinitic monzogabbro and monzodiorite are recorded in the biotite gneisses, indicating a primary magma that was generated along a subduction zone. The geochemical characters of the studied enclaves indicate that during the Pan-African, the Wadi Feiran area constituted a back-arc continental lithosphere environment that witnessed plumesubduction interaction.