NEOPROTEROZOIC TECTONO-METAMORPHIC EVOLUTION OF HAFAFIT DOME "A" AND THE ABUTTING SHAIT OPHIOLITIC MÉLANGE DOMAIN AT GABEL MUDARGAG AREA, CENTRAL EASTERN DESERT, EGYPT

Abstract

The Mudargag area, 740 km 2 builds up two Neoproterozoic tectono-stratigraphic units separated by a NW trending subhorizontal thrust plane along which deformed rocks from both units are confined. The lower infrastructural unit is represented by the northern dome "A" of Wadi Hafafit culmination which forms a macroscopic ovalshaped asymmetrical antifromal domal structure with a fold axis extends over 10 km in a NW-SE direction. It is differentiated into four structural subunits composed of interlayered sequences, mainly of para-granite gneisses, psammitic gneisses and paraamphibolites with medium to high-grade metamorphic facies. Granite gneisses and psammitic gneisses dominate the lower and the upper subunits, respectively, paraamphibolites dominate the second subunit, whereas the third subunit has subequal proportions of psammitic gneisses and amphibolites. The upper suprastructural unit is represented by Shait ophiolitic mélange domain (SOMD), which comprises deformed normally faulted thin-skinned napped sequence of low-grade metamorphosed volcanosedimentary island-arc type assemblages incorporating dismembered ophiolite and partially carbonated serpentinite fragments. Petrographic examinations carried out on both dome "A" and SOMD show distinct evidences of polyphase deformation (D1-D3) in addition to tow metamorphic events (M1-M2). Field data revealed that the exhumation of the Hafafit culmination domes to which the present dome "A" is considered and the large-scale crustal extension of SOMD run within a left-lateral dominated transpressional wrenching of Najd Shear System.