Tectonic evolution of the basement complex in the central eastern desert of Egypt

Abstract

With 2 figures ZusammenfassungDie Gesteine des /igyptischen Kristallins sind in drei Hauptgruppen unterteilt: Meatiq Group (/ilteste), Abu Ziran Group und Hammamat Group (jiingste); die letzten zwei Gruppen geh6ren dem Pan-Afrikanischen Zyklus an. Die Meatiq-Gruppe stellt einen alten Sokkel dar, der in Gneisdomen auftritt. Die Abu-Ziran-Gruppe umfaBt die Geosynklinal-Assoziation, die aus einer unteren ophiolitischen Einheit besteht, iiberlagert von Sedimenten, volkanoklastischen Sedimenten und lokalen intermedi/iren Vulkaniten mit ausgepr/igten Inselbogen-Eigenschaften. Die Hammamat-Gruppe besteht aus Molassetyp klastischen Sedimenten und zeitlich assoziierte Dokhan Volcanics andesitischer his rhyolitischer Zusammensetzung. Die syn-bis sp~it-tektonische Kalkalkaligranite sind die plutonischen Aequivalente der Dokhan Volcanics.Das untersuchte Gebiet liegt im Vorland-Falten-und Decken-Gtirtel eines Kontinentalrand-Orogens. Ophiolite, insbesondere die Serpentinite, treten entlang dem Ausbii3 der [)berschiebungsflfiche zwischen dem Meatiq-Sockelstockwerk und der Abu-Ziran-Decke auf.Schwellen in Form zweier Geantiklinalen waren Zentren aktiver kalkalkaliner magmatischer T/itigkeit, begleitet zumindest yon Goldvererzungen. AbstractThe Egyptian basement rocks are gathered into three major rock groups, viz. Meatiq Group (oldest), Abu Ziran Group and Hammamat Group (youngest); the last two groups belong to the Pan-African orogenic cycle. The Meatiq Group is an old crystalline basement cropping out in gneiss domes. The Abu Ziran Group comprises the geosynclinal association which is formed of a lower ophiolite unit overlain by metasediments, volcanoclastics and locally intermediate volcanics having clear island arc characters. The Hammamat Group comprises molasse-type clastics, and penecontemporaneous Dokhan Volcanics of andesite to rhyolite composition; syn to late-tectonic calc-alkaline granites are the plutonic equivalents of the Dokhan Volcanics.The studied area lies within the foreland fold and thrust belt of a continental margin orogen. Ophiolites, particularly serpentinites, crop out along the trace of the sole thrust between the Meatiq infrastructure and the imbricated Abu Ziran nappe. Swells, developed along two geanticlines, were centers of marked calc-alkaline magmatic activity associated, at least, with gold mineralization. R~sum~Les roches du socle ~gyptien se r~partissent en trois groupes majeurs: Meatiq Group (le plus ancien); Abu Ziran Group et Hammamat Group (le plus r6cent); les deux derniers groupes appartiennent au cycle orog6nique Pan-Africain.Le Meatiq Group est un socle cristallin ancien affleurant en d6mes gneissiques. Le Abu Ziran Group comprend une association g6osynclinale form6e d'une unit6 ophiolitique *) Authors' addresses: S. EL-GABY, O. EL-NADY and A. KHUDEIR, Department of Geology, Assuit University, Assuit, Egypt.Geologische Rundschau 73, 3, 1019-1036, Stuttgart 1984 1019 Des d6mes, d6velopp6s le long de deux g6anticlinaux, ont 6t6 les centres d'une forte activit6 magmatique calco-alcaline ...

Geomorphological hazard analysis along the Egyptian Red Sea coast between Safaga and Quseir

“…The Quaternary rocks are composed of wadi and terrace deposits consisting of detritus sand, pebbles, and rare boulders. The mountainous central zone consists of the basement rocks, intensively studied by many authors like Hume (1935), El-Ramly (1972), El Gaby et al (1984, El Shazly (1964), El Ramly (1960), andEl-Ramly et al (1970). They concluded that the mountainous areas are essentially composed of panAfrican assemblages comprising gneisses, migmatites, metasediments, ophiolitic melanges, metavolcanics, mafic intrusions, tonalite, granodiorite, younger volcanics, molasse sediments, post-tectonic granites, and trachyte plugs and sheets.…”

Age and tectonic setting of granitoid gneisses in the Eastern Desert of Egypt and south-west Sinai

“…These occur in antiformal, 'domal' positions, generally surrounded by lower grade supracrustal assemblages (see summary in Greiling et al, 1994). In the ED such rocks occur at Meatiq (Sturchio et al, 1983;E1-Gaby et al, 1984;Habib et al, 1985;Bennet and Mosley 1987), in three distinct domal structures at Hafafit (Greiling and ElRarely, 1990;Rashwan, 1991) and in the region along Wadis Bitan and Haimut (Geological Map 1:500 000, sheet NF 36 NE Bernice, Technische Fachhochschule Berlin 1987). In south-western Sinai similar rocks occur in the Wadi Feiran region (E1-Gaby and Ahmed, 1980;Shimron, 1980).…”

U–Pb ID-TIMS dating of igneous and metaigneous rocks from the El-Sibai area: time constraints on the tectonic evolution of the Central Eastern Desert, Egypt

“…The two first authors speculated that the granitoid gneisses were younger than the low-and medium-grade supracrustals surrounding the gneisses, whereas Sabet (1961) consider all the mafic rocks (both volcanics, metasediments and amphibolites) to be part of one supracrustal sequence. El-Gaby (1994) and El-Gaby et al (1984) advocated the idea that the gneisses in the Meatiq, Hafafit and El-Sibai domes were all pre-Neoproterozoic infrastructural rocks exposed in the hinge zone/core of one or more NW-trending antiform(s). The structural model proposed by El-Gaby et al (1984) may be correct, but the protolith age proposed for the gneisses finds little support in the emerging body of new isotope and geochronological data from CED (e.g.…”

“…El-Gaby (1994) and El-Gaby et al (1984) advocated the idea that the gneisses in the Meatiq, Hafafit and El-Sibai domes were all pre-Neoproterozoic infrastructural rocks exposed in the hinge zone/core of one or more NW-trending antiform(s). The structural model proposed by El-Gaby et al (1984) may be correct, but the protolith age proposed for the gneisses finds little support in the emerging body of new isotope and geochronological data from CED (e.g. Andresen et al 2009;Liégeois and Stern 2010).…”

“…Andresen et al 2009;Fowler and Osman 2008). The ElSibai gneiss complex has traditionally also been regarded as a gneiss dome (Abd Ell Wahed 2008;Bregar et al 2002;El-Gaby et al 1984). Fowler et al (2007), however, have recently challenged this view and argued that the infrastructural gneisses in the El-Sibai complex represent granitoids intruding the island arc affined allochthon synchronously with top-to-the-NW thrusting during nappe assembly.…”