Structure of the Barud Dome Complex, Eastern Desert, Egypt: Insights from Crustal Origins in the Northern Basement Terrains of the Arabian–Nubian Shield

Abstract

The Barud gneissic dome complex is situated along the ENE-trending dextral shear zone of the Qena–Safaga Line that serves as a significant tectonic boundary between the basement terrains of the Northern and Central Eastern Desert. These terrains exhibit distinct differences in crustal composition and deformation style. The Northern Eastern Desert and its extension into Sinai are predominantly composed of gneissic granites that are intruded by large batholiths of calc-alkaline and alkaline granites. Conversely, the Central and Southern Eastern Desert are commonly blanketed by a carapace of ophiolite-bearing volcano-sedimentary rocks of the Pan-African cover nappes. These northern terrains, just north of the Barud dome complex, the crust underwent significant NW–SE regional crustal extension across the Qena–Safaga Line, which sharply delineates the northern limit of the transpressional deformations linked to the Najd fault system in the Central and Southern Eastern Desert. Through comprehensive geological mapping and the integration of various geophysical, geochemical and geochronological data, this paper offers explanations for the contrasting geological features of the basement terrains on both sides of the Qena–Safaga Line and its analogous Fatira Shear Zone that plays a significant role in tectonic modeling of the Barud dome complex region. The Barud gneissic protolith experienced crustal shortening approximately 697 million years ago in the NW–SE direction, initiating dextral motion along the Fatira Shear Zone. Large batholiths of granodiorite/tonalite complex intruded the Barud gneissic dome protolith around 630 million years ago along the Qena–Safaga Line, at relatively shallow crustal depths, following the same orientation as the earlier shortening direction. Ongoing magmatic activity along the Qena–Safaga Line indicates intense magmatic underplating, resulting in significant intrusions of granodioritic melts into the early rifted crust of the Northern Eastern Desert and Sinai terrains. The crust of these northern terrains likely underwent isostatic compensation through uplifting and subsequent erosion. The disappearance of ophiolite-bearing belts and the presence of Paleo- to Mesoproterozoic continental-derived cobbles and ignimbrites in Sinai metasedimentary belts and Northern Eastern Desert molasse basins suggest that the northern terrains, located north of the Qena–Safaga Line, originated as a cohesive, thin continental crust that rifted off the eastern passive margin of the Sahara Metacraton during the early Neoproterozoic rifting of the Rodinia supercontinent.

Keywords

granite / shear zone / Qena–Safaga Line / Pan-African Orogeny

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2025 Geological Society of China