Neoproterozoic tectonic evolution and exhumation history of transpressional shear zones in the East African orogen: implications from kinematic analysis of Meatiq area, Central Eastern Desert of Egypt

Abstract

The origin, structural history, and tectonic evolution of core complexes and associated shear zones in the East African orogen are fundamental issues in the recent geological studies. Meatiq dome is one of the best exposed complexes in the Arabian–Nubian shield. The dome is occupied by metamorphic rocks with amphibolite-facies grade, tectonites, and deformed granites which are structurally overlaid by low-grade metamorphosed ophiolitic and island-arc rock assemblage. This tectonic pile is intruded by several granite intrusions through their evolution history. Microstructural, strain, and vorticity data from deformed tectonites were used to investigate the kinematics of rock flow in the Meatiq and Atalla shear zones and to reconstruct their deformation and exhumation history. The strain and vorticity analyses of Atalla shear zone (ASZ) indicate that this zone experienced general shear transpression with a monoclinic symmetry. The mean vorticity number (Wm) estimated with the porphyroclast-based methods ranges from 0.65 to 0.72 which indicate a high pure shear contribution in the shear zone. The numerical estimates allow the kinematic modelling of ASZ which introduces valuable implication about the tectonic framework of the Central Eastern Desert during the collision of East and West Gondwana. The results of satellite image interpretation and structural analysis of Meatiq area reveal a poly-deformational structural history including five stages of deformation during the successive convergence and collision of East and West Gondwana continents at around 600 Ma. The first stage is represented by compressional structures and high-grade metamorphism in the amphibolite enclaves preserved in Um Baanib granite. The reconstructed structural history of the shear zones started with the second structural stage. It involves the initiation of Meatiq shear zone and associated ductile structures and fabrics. The third stage was related to the final oblique convergence and collision of East and West Gondwana and represented by the NW–SE thrust faults, NW–SE folds, and the initiation of Atalla shear zone. The fourth and fifth stages were evolved after the crustal thickening. They involve the initiation of the strike-slip faults and the NW–SE extensional structures. The tectonic and regional implications of the structural and kinematic analysis were discussed.