The evolution of the Pan-African granitoid rocks: geochemical evidences from SW Sinai massif, Egypt

Abstract

Wadi Seih area is covered by “Old Granites”, porphyritic granites, mafic-ultramafic cumulates, rhyolite porphyries, Younger Granites and Post-Granite Dykes which represent ≥200 Ma of Pan African orogeny. G-I “Old Granites” are given mainly by tonalites, monzodiorites and qz-monzodiorites. They are derived from calc-alkaline metaluminous to peraluminous I-type magma and were emplaced under prevailing compressional regime which are associated with subduction and arc granitic rocks formation. Porphyritic granites are given by monzogranites and were emplaced due to compressional forces during the late orogenic stage. “Younger Granites” are distinguished into two types: G-II and G-III granites. They have distinct petrologic, chemical and tectonic setting differences which supporting two independent magma sources. G-II granites are given by monzogranites and syenogranites and were derived from magma rich in Ba and Sr and depleted in Nb, Ce, Zr, Y, Rb and alkalies and were intruded under compressional regime prevailing in the granitic arc environment, at late- to post-orogenic stage. Whereas G-III granites are given by syenogranites and were derived from maga rich in Nb, Ce, Zr, Y, Rb and alkalies and were intruded under extensional forces prevailing within the plate frame which correspond to anorogenic regime. Rhyolite porphyries are enriched in alkalies and are related to the porphyritic and G-II granites. They were extruded under an environment transitional between volcanic arc and within plate regime.