The Nugrus-Hafafit and El Shalul areas are regarded as key regions for many enigmatic problems and debatable issues concerning the tectonic setting of the Najd-related shear zones in the Eastern Desert of Egypt. The Neoproterozoic basement succession in the studied areas is well-developed and represented by four rock groups arranged from older to younger as infrastructure unite (amphibolites, migmatized hornblende-biotite gneiss, psammitic gneiss and chlorite-biotite schist), suprastructure units including ophiolitic mélange (metaultramafics and related derivatives) and island arc assemblages
(metagabbros and metavolcanic-metasedimentary association), syn-tectonic granitoids (gneissic to undeformed granodioritetonalite), late-tectonic to post-tectonic/post-collision granites (mylonitized muscovite granite, biotite granite and perthitic alkali granite), and post-granitic dykes (pegmatites and quartz veins). The tectonic structures in the studied regions indicate at least three successive phases of deformation (D1, D2, and D3). D1 represents NE-SW (to ENE-WSW) shortening associated with major thrusting of the supracrustal rocks over the infracrustal rocks in Nugrus-Hafafit area and NW-SE shortening accompanied the
orogen-parallel extension/extrusion in El Shalul area. D2 is characterized by NW-SE (to NNW-SSE) transpression along the Najd-related shear zones. During D3, the NW-SE (to NNW-SSE) shortening produced dextral shearing along the NE-SW Mubarak-Barramiya Shear Belt (MBSB). Field relations and observations indicate that the NW Najd-related Nugrus and El Shalul shear zones and the NE-oriented shears are not a conjugate pairs. Furthermore, the tectonic-magmatic-metamorphic evolution of the Pan-African belt in the Eastern Desert of Egypt has been progressively changed and/or developed from south
to north, in terms of tectonic transportation/thrust direction and deformational style. |
