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

Hagag W., Hamimi Z., Abdelnasser A. A. A.

JOURNAL OF ASIAN EARTH SCIENCES, vol.224, 2022 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 224
  • Publication Date: 2022
  • Doi Number: 10.1016/j.jseaes.2021.105022
  • Journal Name: JOURNAL OF ASIAN EARTH SCIENCES
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Artic & Antarctic Regions, Geobase, INSPEC
  • Keywords: El Shalul Shear Zone, Post-collision extension, Central Eastern Desert, Najd Shear Deformation, Arabian-Nubian Shield, CENTRAL EASTERN DESERT, MAJOR-ELEMENT CHEMISTRY, A-TYPE GRANITES, U-PB, GEOCHEMICAL DISCRIMINATION, CRUSTAL EVOLUTION, ARABIAN SHIELD, CORE COMPLEX, GNEISS DOME, HISTORY
  • Istanbul Technical University Affiliated: No

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-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 Sinistral shearing (D-3a) and transpression (D-3b) along the NW-trending faults superseded the D-2 compression, while dextral shearing (D-3c) on the ENE-WSW and NE-SW faults overprinted the NW-SE penetrative structures and controlled the emplacement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.