Structural interpretation of the Wadi Hafafit culmination: A Pan-African gneissic dome in the central Eastern Desert, Egypt

Abstract

The emplacement and exhumation of gneissic domes of continental lithospheric fragments within the Pan-African oceanic crust in the Arabian-Nubian shield have been subjects of debate in the recent literature. The Wadi Hafafit culmination is one of the largest metamorphic dome complexes, not only in the Eastern Desert, but also in the Arabian-Nubian shield. The culmination forms a northwest-trending folded belt including five individual gneissic domes that show complex interference fold patterns, bounded by northwest-to west-northwest-trending marginal shear zones (the Nugrus and Hafafit shear zones), which belong to the late Proterozoic Najd fault system in the Eastern Desert of Egypt. The Hafafit metamorphic dome forms a positive flower structure that is characterized by a vertical stretch in the central part with subvertical foliation at the individual dome peripheries, subhorizontal flattening in the roof, and near simple shear at the complex margins defined by the Nugrus and Hafafit shear zones. This study presents arguments concerning the folding pattern and exhumation of the culmination and its relation to sinistral, transpressional kinematics along the branches of the Najd fault system. The folded axial surfaces of the gneissic domes are interpreted in terms of interference of two fold generations: (1) an early fold generation that developed east-northeasttrending axial surfaces, which may have formed during late Pan-African northwestward nappe stacking, and (2) a late fold generation that developed north-south-trending fold axes that deformed the axial surfaces of the first fold generation, and probably associated with sinistral shearing on the Nugrus and Hafafit shear zones. The fold interference patterns associated with exhumation of the Hafafit gneissic domes are consistent with published geochronological data and the tectonic evolution of the Arabian-Nubian shield.

Neoproterozoic Tectonic Events of Egypt

“…Although recent studies have dealt in considerable detail with the gneissic domes of the CED; their origin remains controversial. Intrinsically, four scenarios are posited; (i) orogen parallel crustal extension (Wallbrecher et al, 1993;Fritz et al, 1996Fritz et al, , 2002Loizenbauer et al, 2001;Abdel Wahed, 2008;Makroum, 2017), (ii) development of fault-bend fold (Greiling et al, 1988) antiformal stacks, (iii) development within regional domal structures (Ibrahim and Cosgrove, 2001) followed by extension parallel to their fold axes (Fowler et al, 2007), (iii) emplacement within a core of a sheath fold origin and (iv) emplacement due to overlap of regional sheath folds (Fowler and El Kalioubi, 2002). The model of orogen parallel crustal extension is widely accepted where extension within NW-trending zones bounded by sinistral strike-slip shears of the Najd Fault System was accompanied by NE-SW striking normal faults that created intramontane molasse basins (Wallbrecher et al, 1993;Fritz et al, 1996Fritz et al, , 2002Neumayr et al, 1998;Fritz and Messner, 1999;Loizenbauer et al, 2001;Bregar et al, 2002;Abd El-Wahed, 2007Makroum, 2017).…”

“…Many workers have regarded the Nugrus shear zone as a NW-striking sinistral strike-slip shear zone related to the Najd Fault System (e.g. Fritz et al, 1996;Unzog and Kurz, 2000;Shalaby et al, 2005;Abd El-Wahed et al, 2016;Makroum, 2017). Fowler and Osman (2009) argued instead that the Nugrus shear zone was a strike-slip shear zone, as the NW-trending, along strike, schistose shear foliations ceased at the intersection of Wadi Sha'it with Wadi Nugrus, which is supported by the absence of field evidence for the extension of the Nugrus shear zone structure nortwestwards as a strike-slip shear zone into the central Eastern Desert (Fig.…”

“…CTB, Congo-Tanzania Cratons. El-Naby et al, 2008;Andresen et al, 2009Andresen et al, , 2010Lundmark et al, 2012;Ali et al, 2012;Hamdy et al, 2017;Makroum, 2017;Hamimi and Abd El-Wahed, 2020;El-Bialy, 2020;El Kalioubi et al, 2020).…”

“…Kamal El Din et al, 1992). Oblique convergence transpression, whether dextral or sinistral, is a proposed mechanism adopted by many authors (Fritz et al, 1996;Loizenbauer et al, 2001;Makroum, 2001;Bregar et al, 2002;Shalaby et al, 2005;Abd El-Wahed, 2008, 2010Shalaby, 2010;Kamh, 2010, 2013;Zoheir and Lehmann, 2011;Zoheir and Weihed, 2014;Abd El-Wahed et al, 2016Abd El-Wahed and Thabet, 2017;Makroum, 2017;Hamdy et al, 2017;Stern, 2017;Zoheir et al, 2019;Hamimi et al, 2019;Abd El Monsef, 2020;Abd El-Wahed and Hamimi, 2021a and b;Abd El-Wahed et al, 2021) to explain and imply the deformation styles in the Eastern Desert.…”

Intrusion‐related Gold Deposits in Egypt

“…The Najd Fault System (NFS) is a complex set of leftlateral strike-slip faults and ductile shear zones that strike NW-SE across the Precambrian of Arabia and Egypt. This system is also known in Egypt as the Wadi Hodein-Wadi Kharit shear system (Greiling et al, 1994;Stern, 1994) and Hamrawin (Duwi) shear zone (Makroum, 2017).…”