Origin of Neoproterozoic metamorphic suites along the Western Segment of Allaqi Shear Zone, Southern Egyptian Nubian Shi
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S. I. SCJGE-1 2019
Origin of Neoproterozoic metamorphic suites along the Western Segment of Allaqi Shear Zone, Southern Egyptian Nubian Shield Abdelhamid El Fakharani 1,2 & Abdelhady Radwan 1 & Mohammed Hassan Younis 1 & Ashraf Emam 1 & Sherif Fawzy 1 Received: 16 May 2020 / Accepted: 2 October 2020 # Saudi Society for Geosciences 2020
Abstract The Neoproterozoic basement complex of the western segment of the Allaqi Shear Zone (ASZ) in the extreme southern part of the Egyptian Nubian Shield comprises four main lithologic units: gneisses, amphibolites, island arc metasediments, and intrusives. In the present study, these units investigated at the outcrop scale, as well as petrographically and geochemically. Gneisses are subdivided into three types: hornblende, muscovite, and biotite gneisses. The hornblende and muscovite gneisses have para-gneissic origin, while the biotite gneiss has igneous protolith. Amphibolites have intermediate andesitic to basaltic andesite composition, with igneous origin, and were formed in island-arc environments. The metagabbros are subalkaline and have within-plate geochemical characteristics. The metasediments involve graphite-muscovite, albite, chlorite, biotite-muscovite, carbonate, and tremolite-actinolite schists, in addition to metagreywackes. The bulk chemistry of metasedimentary succession revealed their formation within active continental margin setting with pelitic to semi-pelitic and psammitic precursor. The previously mentioned lithologic units are poly deformed and intensively affected by shearing and thrusting. These structures strike in various direction: WNW-ESE, NNE-SSW, NW-SE, NW-SE, and E-W, which are consistent with the automatic and manual principal component analyses (PCA) lineament extraction. Keywords Allaqi Shear Zone . Egyptian Nubian Shield . Metamorphites . Lineament extraction
Introduction The East African Orogen (EAO) is a comprehensive orogenic belt evolved during the 900–550 Ma, affected the Arabian–Nubian Shield (ANS) and the Mozambique Belt (MB) in the south, with excess of 7000 km long (e.g., Stern 1994; Fritz et al. 2013). The ANS is made up commonly of juvenile low-grade metamorphic arc volcano-sedimentary rocks, whereas the MB is occupied primarily by high-grade gneisses of Archaean age (Stern 1994; Johnson 2003; Elisha et al. 2019). Stern (1994) suggested that the evolution of the EAO started with the fragmentation of Rodinia (950–850 Ma) and This article is part of the Topical Collection on Current Advances in Geological Research of Egypt * Mohammed Hassan Younis [email protected] 1
Geology Department, Faculty of Science, Aswan University, Aswan 81528, Egypt
2
Department of Structural Geology and Remote Sensing, Faculty of Earth Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
terminate with a continent–continent collision of the East and West Gondwanaland at 600 ± 50 Ma. The collision results in crustal thickening associated by metamorphism at granulite facies at deep levels as well as migmatization at higher levels and the em
