JOURNAL OF ASIAN EARTH SCIENCES, vol.224, 2022 (SCI-Expanded)
This study concerns the structural setting of the central Egyptian-Nubian Shield (El Shalul area) utilizing field-structural, remote sensing, petrological and geochemical data. The exposed basement comprises ophiolitic-melange, arc-related metavolcanics, metasediments, metagabbro-diorites and granitoids. The area experienced two stages of deformation, pre-Najd (similar to 850-630 Ma) and Najd-related (similar to 630-580 Ma). The pre-Najd stage is represented by the assembly of arc-terranes and their N-ward extrusion while the Najd-related stage encompasses three deformation phases. D-1 is post-collision extensional event, depicting lateral spreading of tectonic terranes and NW-ejection of ophiolites. The emplacement of El Shalul granite (similar to 630 Ma) and deposition of molasse sediments in E-W and NW-SE extensional basins (Zeidun and Meesar) are D-1- related. Following extension is a protracted phase of compression, shearing and transpression. It was commenced with NW-SE shortening (D-2) and deformed the extensional basins by folding and thrusting with mild effect on the other basement units. Sinistral shearing (D-3a) and transpression (D-3b) along the NW-trending faults superseded the D-2 compression, while dextral shearing (D-3c) on the ENE-WSW and NE-SW faults overprinted the NW-SE penetrative structures and controlled the emplacement of post-granitic dykes. The significant conclusions of this study include (1) El Shalul granite complex is a large alkaline granitic sheet emplaced during a post-collision extensional regime and suffered the subsequent similar to 630-580 Ma top-to-NW sinistral shearing and SW-directed thrusting (not a gneissic core complex) and (2) The NW-SE and NE-SW structural trends are not conjugated.