Tectonic reworking in the Arabian-Nubian Shield: An analysis of the textural record of the exhumation of the Meatiq Gneiss dome (Egypt)

Abstract

[EN]Activity of late orogenic wrench tectonics, recognized in the Arabian Nubian Shield (ANS), dismembered and obscured the accretionary and collisional record. We have investigated the Meatiq Gneiss dome (MGD), in the Central Eastern Desert (CED, Egypt) where compressional, extensional and transcurrent structures converge. Three structural domains have been identified: Meatiq Dome (MDSZ), Murr (MSZ) and Atalla (ASZ) shear zones. We have conducted neutron diffraction quantitative texture analysis on mylonites, to investigate deformation conditions at different structural levels of the MGD and provide new evidence on its evolution and discuss regional implications for the CED. Results indicate that the MGD is an individual fault-related gneiss dome, bounded by a major extensional detachment with ~ NW-SE kinematics (MDSZ). Textural record documents tectonic denudation under deformation conditions from 750◦ to 350 ◦C, compatible with a fast isothermal exhumation from 620-580 Ma, as supported by existing age and metamorphic data. Field investigation suggest that the NW-SE elongated geometry of the dome is not related to the extensional activity, but with a coeval NESW shortening component. Large wrench shear zones (MSZ and ASZ) postdate this architecture and accommodate transpressional strain under low T conditions (<400 ◦C). Given that the activity of the MDSZ was contemporary with the main collisional phase of the formation of the Gondwana supercontinent in the Late Neoproterozoic, is postulated that the Meatiq Gneiss Dome exhumation was the result of a syn-collisional collapse, which was triggered by gravitational instabilities, and modulated by coeval contraction, without a genetic relation with late strike-slip tectonics (e.g., Najd fault system). MGD tectonothermal evolution indicates that the lithosphere of this EAO segment has followed a complex tectonic reworking where large-scale boundaries like the MDSZ and played a significant rheological role.