The younger granites and ring complexes of the Southeastern Desert of Egypt and their relation to mineralization

Abstract

More than 70 small younger granite masses and 10 ring complexes are exposed in the Southeastern Desert of Egypt (about 80,000 km²). The granites comprise three main varieties: the Sn mineralized; stanniferous and Sn barren granites. the Sn mineralized granites are usually smaller in size; circular to elliptical in outline and contain higher concentrations of Sn, Nb, Be, Mo, Bi, Y, Cu and Pb and are usually subjected to greisenizaiotn and albitizationn processes which changed their original texture and composition with the development of lode and disseminated cassiterite and beryl mineralization. The stanniferous granties may contain only few accesories of cassiterite. the sn-barren granites are usually larger in size and show hghier Zr values. The granties are calcalkaline, highly aluminous, enriched F with Na_aO > K₂O and low CaO and MgO. The ring complexes comprise alkaline rocks mostly of Cretaceous age (although some complexes are older) and range in composition from ultramafic to acidic and from undersaturated to quartz bearing. Disseminated U, Th, Pb, W, ?Nb, Y, Be and Mo are recorded in some ring complexes.