Origin and geochemistry of Egyptian granitoid rocks in Nuweiba area, eastern Sinai

Geological, petrological and geochemical studies indicate two distinct types of granitoid rocks: an older quartz diorite to granodiorite assemblage and younger granitoids, the latter occurring in two phases. The older granitoids have a calc-alkaline character, with high MgO, (FeO)_t, TiO₂ and P₂O₅ and low SiO₂, K₂O and Rb. Their major and trace elements compositions, together with a low ⁸⁷Sr/⁸⁶Sr (0.7029 ± 0.0008) denote I-type affinites. The second and third phase granitoids range from calc-alkaline to alkaline respectively. The second phase granitoids have a peraluminous chemistry and high Sr, Ba, CaO, MgO, Al₂O₃ and Ti₂O, and low SiO₂, K₂O, Zr, Nb and Rb relative to the third phase granitoids. The corundum normative nature and field observations suggest that it was formed by partial melting of the lower crust (S-type). The third phase granitoids are characterized by high SiO₂, Rb, Y, Zr and low MgO, CaO, Sr and Ba values than younger granitoid phase II. They show A-type granitoids which are generated from below or within existing continental crust.