The effect of the Najd shear deformation on the Pan-African belt of the central Egyptian Nubian Shield: a synthesis for the post-collision tectonic events
Journal of Asian Earth Sciences • 2021
Publication Information
Authors
Wael Hagag; Zakaria Hamimi; Amr Abdelnasser
Keywords
El Shalul Shear Zone; Post-collision extension; Central Eastern Desert; Najd Shear Deformation; Arabian-Nubian Shield
Journal
Journal of Asian Earth Sciences
Publisher
Elsevier
Volume
224
Issue
Not Available
Pages
105022
publication.type
International
Paper Link
Open Link
Supplementary Materials
Not Available
Abstract
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-mélange, arc-related metavolcanics, metasediments, metagabbro-diorites and granitoids. The area experienced two stages of deformation, pre-Najd (∼850–630 Ma) and Najd-related (∼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. D1 is post-collision extensional event, depicting lateral spreading of tectonic terranes and NW-ejection of ophiolites. The emplacement of El Shalul granite (∼630 Ma) and deposition of molasse sediments in E-W and NW-SE extensional basins (Zeidun and Meesar) are D1- related. Following extension is a protracted phase of compression, shearing and transpression. It was commenced with NW-SE shortening (D2) and deformed the extensional basins by folding and thrusting with mild effect on the other basement units. Sinistral shearing (D3a) and transpression (D3b) along the NW-trending faults superseded the D2 compression, while dextral shearing (D3c) on the ENE-WSW and NE-SW faults overprinted the NW-SE penetrative structures and controlled the emplacement of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 ∼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.
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