Geochemical Characteristics of the Syn-Tectonic Granitoids along Wadi El-Sheikh Area, South Sinai, Egypt.

Abstract

The Wadi El-Sheikh area is situated in south Sinai, and is distinguished by a high abundance of calc-alkaline and alkaline/peralkaline granitoid rocks, as well as related volcanics. These granitoid rocks are of particular geodynamic significance because they contribute to better understanding of how the continental crust of the Arabian Nubian Shield (ANS) formed. Thus, the present study introduces new comprehensive geological field studies, petrological data, and whole rock geochemical data of syn-tectonic granitoids along Wadi El-Sheikh. The composition of the syn-tectonic granitoids (SNG) ranges from quartz-diorite, tonalite, to granodiorite. Geochemically, these SNGs are mainly metaluminous, calc-alkaline, I-type, and correspond to syn-collision volcanic arc granitoids. The investigated syn-tectonic granitoids have high (Al 2 O 3 /TiO 2) ratios (17.85–80.70), rising toward the higher silica granitoid type (granodiorite), while they also show high (CaO/Na 2 O) ratios (0.33–1.44) representing a decrease from quartz-diorite to granodiorite. These characters indicate that the emplacements of SNG were greatly influenced by the magma mixing of mafic and felsic melts. The analyzed granitoids originated at temperatures ranging from 650°C to 700°C and water pressures ranging from 0.5 to 10 kbar. According to the depth of magma segregation, and they were produced at depths of more than 30 km of the lower crust. The considered SNG are commonly concerned with enrichment of LILE and LREE and depletion of HFSE in comparison to N-MORB values (negative Ta and Nb anomalies)