Origin and geochemistry of Pan-African granitoid rocks in the Gabal Um Shomer area, Southwestern Sinai, Egypt

Abstract

Geological, petrological and geochemical studies indicated that there are two distinct types of granitoid rocks: older quartz diorites to granodiorite assemblage and younger granitoids, the latter occurring in two phases. The older granitoids have a meta-aluminous chemistry and a calc-alkaline character, with high MgO, Fe 2 O 3 , TiO 2 , CaO, P 2 O 5 , Sr and low SiO 2 , K 2 O, and Rb. Their major and trace elements data, together with low 87 Sr/ 86 Sr ratios (0.7029±0.0008) are indicative of I-type affinities. The second-and third-phase granitoids range from calc-alkaline to alkaline, respectively. The second-phase granitoids have a peraluminous chemistry and high relative to the third-phase granitoids. The corundum normative nature and field observations suggested that it was formed by partial melting of the lower crust. The third-phase granitoids are alkaline in nature and characterized by higher SiO 2 , Rb, Y, Nb and lower MgO, Sr and Ba values than the younger granitoids (phase II). They are A-type granitoids which were generated from below or within the existing continental crust.

Constraints of Mantle and Crustal Sources Interaction during Orogenesis of Pre‐ and Post‐collision Granitoids from the Northern Arabian‐Nubian Shield: A Case Study from Wadi El‐Akhder Granitoids, Southern Sinai, Egypt

“…Table 6). These characteristics are conformable with those of regional post-collisional YG in the ANS (Abdel-Rahman and Martin, 1987;Abdalla, 2006;Abdel-Rahman, 2006;Farahat et al, 2007;Katzir et al, 2007;Mohamed and El-Sayed, 2008;El-Bialy and Streck, 2009;El-Tokhi et al, 2009;Sherif et al, 2013; (Brown et al, 1984). Gahlan et al, 2018;Khalil et al, 2018).…”

“…1.23). The high Sr/Rb ratio in the AOG indicates that magma formation started at intermediary or even greater depths ( El-Tokhi et al, 2009).…”

“…The Precambrian rocks at the southern part of the Sinai Peninsula can be divided into metamorphic complexes (old continental gneissose metasediments), intermediate to acidic subduction-related volcanics and metasediments (island arcs and greenstone belt), subduction-related granites (older granites), post-orogenic granites (younger granites), rift-related volcanics and finally alkaline anorogenic granites (El-Tokhi et al, 2009).…”

Geochemistry and Petrogenesis of the Calc-Alkaline Granitoids From the Northern Arabian–nubian Shield. A Case Study From Wadi El-Akhder Granitoids, Southern Sinai, Egypt

“…The studied AGR have high Sr/Rb ratio (av. 8.76) indicating that magma formation started at intermediary or even greater depths (>40 km; El-Tokhi et al 2009). Furthermore, the multi-element spider plots could be used as an effective indicator for the discriminating the tectonic setting of the Egyptian granitoids rocks, especially the calc-alkaline (I-type) ones (Moghazi 2002).…”

“…The Precambrian rocks occuring at the southern part of the Sinai Peninsula can be divided into metamorphic complexes (old continental gneisses), intermediate to acidic subduction-related volcanics and metasediments (island arcs), subduction-related granites (older granites), post-orogenic granites (younger granites), rift-related volcanics and finally alkaline anorogenic granites (El-Tokhi et al 2009).…”