Thrusting and multiple folding in the Neoproterozoic Pan-African basement of Wadi Hodein area, south Eastern Desert, Egypt

Abstract

Detailed field mapping and structural studies of the area around the mouth of Wadi Hodein, some 20 km west of Shalatein at the Red Sea coast in the south Eastern Desert of Egypt, revealed four phases of structural deformation (D1–D4) affecting the Neoproterozoic Pan-African basement rocks. D1 is related to arc–arc collision and is represented by ENE–WSW oriented megascopic upright open folds associated with low angle thrusts and mesoscopic tight, overturned and recumbent F1 folds. Kinematic indicators indicate thrusting towards the SSE. D2 is represented by NNW–SSE oriented megascopic and mesoscopic folds, which are tight, verge towards the WSW and display a left-stepping en echelon pattern. D3 includes major NNW–SSE trending sinistral shear zones that show subordinate reverse fault components and dip steeply towards the ENE. These sinistral shear zones are comparable with the Najd Fault System, as they display a similar sense of movement and relationships to earlier structures. Therefore, they are interpreted to be the continuation of the Najd Shear System in southern Egypt. D2 and D3 are related to accretion of east and west Gondwana. D4 is represented by E–W oriented dextral faults with left-stepping segments. The first three deformation events are in agreement with the general evolutionary model for the East African Orogen in the Arabian–Nubian Shield that begins with NNW–SSE shortening, followed by ENE–WSW compression and subsequent deformation by the NNW–SSE striking Najd Fault System. The E–W dextral faults may be the conjugate shear fractures to the D3 NNW–SSE oriented sinistral wrench faults or are related to a subsequent event, D4. NW–SE oriented gold-bearing quartz veins originated during D1 and were subsequently deformed by D2–D4 events.