Gneiss-cored interference dome associated with two phases of late Pan-African thrusting in the Central Eastern Desert, Egypt

Structural analysis of the Wadi Um Had area in the Central Eastern Desert (CED) of Egypt reveals the presence of another NW-trending elliptical gneissic and migmatitic domal structure west of Gabal Meatiq, outlined by a thick schistose and mylonitized carapace. The sheared carapace formed during a NW/NNW-ward thrusting event which emplaced thrust slices of ophiolitic mélange, Dokhan Volcanics and Hammamat Group sediments over the higher grade gneisses. The gneisses are subdivided by retrograde shear zones of this event. The sheared carapace is interpreted as the roof thrust of an imbricate stacked antiformal duplex. A second thrusting and folding event associated with NE-SW shortening deformed the earlier structures producing the dome and re-thrusting low-grade units against it as SW- and NE-dipping thrusts. The features of this gneiss dome are inconsistent with it being a metamorphic core complex. Caution must be exercised in the recognition of transcurrent shears in the Eastern Desert since folded low-angle thrust-related mylonite zones may be steepened by folding, producing steep shear zones with low-pitching slip lineations. Extension, bi-directional thrusting and Najd faulting in the CED may be explained in an escape tectonic deformation regime involving extrusion of material away from the pivotal collision zone in the Mozambique belt, to the south.