Geology, geochemistry, and source characteristics of Neoproterozoic arc-related clastic metasediments, Central Eastern D
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ARABGU2016
Geology, geochemistry, and source characteristics of Neoproterozoic arc-related clastic metasediments, Central Eastern Desert, Egypt Gaafar El Bahariya 1 Received: 23 January 2017 / Accepted: 7 February 2018 # Saudi Society for Geosciences 2018
Abstract The present work concerns two occurrences of Neoproterozoic volcaniclastic metasediments in the Central Eastern Desert (CED) of Egypt namely Alam occurrence and Atalla occurrence. They are mainly composed of bedded successions of feldspathic and feldspathic-lithic metagreywackes, arkosic metagreywackes, metasiltstones, and subordinate metaconglomerates. The rocks have been subjected mainly to various ductile deformational events (D1 and D2) due to NE–SW compression and later deformation (D3). The D1 deformation is synchronous with greenschist facies metamorphism (M1). The Alam metagreywackes show oceanic arc tectonic setting. The greywackes have clasts of quartz, feldspar, and metamorphic amphibole after pyroxene and show variable abundances of Cr, Ni, and V. Their provenance components are mainly of evolved felsic and mafic (bimodal) island arcs. The rocks are suggested to be deposited in a localized Bintra-arc basin.^ The metagreywackes of Atalla show tectonic setting affinity similar to continental sland arc or active continental margin. Their geochemical characteristics reflect the presence of felsic rocks as the main sources, together with minor inputs of intermediate rocks and reworked mineral grains of quartz and feldspar. They are deposited in a localized Bretro-arc basins^ of an active continental margin. The whole sequences of both Atalla and Alam sediments have been subjected to deformation and contemporaneous regional metamorphism during arc-arc or arccontinent collision. Newproterozoic clastic metasedimentary rocks in the CED appear to have been deposited in arc-related basins, including interarc or back-arc basins, intra-arc basins, and retro-arc basin of active continental margin. Keywords Neoproterozoic . Volcaniclastic . Metasediments . Egypt . Intra-arc basins . Arc-related basins
Introduction The composition and geochemical characters of clastic sedimentary rocks are primarily controlled by the source rocks and by the tectonic setting of the sedimentary basins (e.g., Bhatia 1983; Bhatia and Crook 1986; Roser and Korsch 1986, 1988; Yan et al. 2007; Kutterolf et al. 2008; Manville et al. 2009). Therefore, it is commonly found that for each tectonic setting there is a specific geochemical signature as a consequence of source rocks as well. Sedimentary rocks provided constraints on the composition and evolution of the continental crust through time (e.g., Condie 1993). The
This article is part of the Topical Collection on Current Advances in Geology of North Africa * Gaafar El Bahariya [email protected] 1
Tanta University, Tanta, Egypt
volcaniclastic sediments formed from volcanic activity or after reworking of volcaniclastic detritus on the lower slopes of the source volcanoes (Fisher 1984). They occur in various arc-related basins
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