ABSTRACT

Precambrian basement covers about 100,000 km2 in south Sinai and the Eastern Desert. Geological investigations, mostly concentrated on the central Eastern Desert, were conducted by a large number of workers. The basement of the Eastern Desert and Sinai constitutes part of the Arabian-Nubian shield that has been cratonized around the end of the Precambrian. A general consensus prevails among basement geologists as to the late Proterozoic volcano-sedimentary rock associations, regardless of whether they represent a eugeosynclinal association or an ophiolitic melange, as well as to the younger rocks. A suite of intrusive ultrabasic and basic rocks comprising spinel Iherzolite, clinopyroxenite, troctolite, olivine gabbro and meladiorite occurs as small, frequently layered intrusions and sills. In the Wadi Allaqi region, south Eastern Desert, orogenic stress obviously lasted longer so that ga-granodiorite and porphyritic monzogranite intrusions were partly deformed and locally mylonitized. The whole pile is intruded by a vast array of granite intrusions ranging in composition from quartz diorite to alkali-feldspar granite.