Structural and Tectonic Framework of Neoproterozoic Basement of Egypt: From Gneiss Domes to Transpression Belts

Abstract

The Neoproterozoic tectonic evolution of the Egyptian Eastern Desert (EED) basement is documented, principally through its history of structural events, and to a lesser degree, important magmatic and sedimentation events. The essential facts, range of opinions and outstanding problems associated with the key structural-tectonic events are presented. Following the introduction (Sect. 3.1), the regional context of the EED in the Arabian-Nubian Shield and East African Orogen is discussed in Sect. 3.2, including introduction to the popular tripartite division of the EED into the Northern, Central and Southern Eastern Deserts (NED, CED and SED, respectively). Major tectonic events are dealt with from oldest to youngest, so that the following sections, begin with Sect. 3.3: the evidence for the latest Mesoproterozoic rifting of Rodinia in the Sinai, and features of the oldest gneissic complexes (Feiran-Solaf and Sa’al complexes); followed by Sect. 3.4: aspects of the intra-oceanic subduction stage and consequent arc-arc and arc-continent collisions, and suturing of terranes (e.g. the Allaqi–Heiani–Onib–Sol Hamed suture), and with reference to earlier models based on proposed subduction zones within the CED; then Sect. 3.5: the orogenic extension stage, including appraisal of the evidence and scale of extension, its possible tectonic origins (rifting, tectonic escape and extrusion, orogenic collapse, mantle delamination, etc.), and its role in the exhumation of distinctive gneissic dome structure, best represented by the Meatiq complex; and finally, Sect. 3.6: post-extension compressional events, primarily as recorded in the deformation of the extension-stage Hammamat molasse basins, and divided into substages of NW-SE compression, NE-SW compression (both of which are marked by thrusting and folding), regional transpression (including strike-slip zones and flower structures), and high-strain N-S shortening zones represented by the Hamisana Zone and the Oko Shear Zone. The chapter concludes with a short list of comments highlighting key problems and opportunities, with recommendations for future work.