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Geologische Rundschau

, Volume 73, Issue 3, pp 1019–1036 | Cite as

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

  • Samir el-Gaby
  • Osman el-Nady
  • Ali Khudeir
Aufsätze

Abstract

The 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.

Keywords

Continental Margin Eastern Desert Gneiss Dome Rhyolite Composition Ophiolite Unit 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Zusammenfassung

Die Gesteine des ägyptischen Kristallins sind in drei Hauptgruppen unterteilt: Meatiq Group (älteste), Abu Ziran Group und Hammamat Group (jüngste); die letzten zwei Gruppen gehören dem Pan-Afrikanischen Zyklus an. Die Meatiq-Gruppe stellt einen alten Sokkel dar, der in Gneisdomen auftritt. Die Abu-Ziran-Gruppe umfaßt die Geosynklinal-Assoziation, die aus einer unteren ophiolitischen Einheit besteht, überlagert von Sedimenten, volkanoklastischen Sedimenten und lokalen intermediären Vulkaniten mit ausgeprägten Inselbogen-Eigenschaften. Die Hammamat-Gruppe besteht aus Molassetyp klastischen Sedimenten und zeitlich assoziierte Dokhan Volcanics andesitischer bis rhyolitischer Zusammensetzung. Die synbis spät-tektonische Kalkalkaligranite sind die plutonischen Aequivalente der Dokhan Volcanics.

Das untersuchte Gebiet liegt im Vorland-Falten- und Decken-Gürtel eines Kontinentalrand-Orogens. Ophiolite, insbesondere die Serpentinite, treten entlang dem Ausbiß der Überschiebungsfläche zwischen dem Meatiq-Sockelstockwerk und der Abu-Ziran-Decke auf.

Schwellen in Form zweier Geantiklinalen waren Zentren aktiver kalkalkaliner magmatischer Tätigkeit, begleitet zumindest von Goldvererzungen.

Résumé

Les roches du socle égyptien se répartissent en trois groupes majeurs: Meatiq Group (le plus ancien); Abu Ziran Group et Hammamat Group (le plus récent); les deux derniers groupes appartiennent au cycle orogénique Pan-Africain.

Le Meatiq Group est un socle cristallin ancien affleurant en dômes gneissiques. Le Abu Ziran Group comprend une association géosynclinale formée d'une unité ophiolitique inférieure suivie par des métasédiments, des volcanoclastites et localement par des roches volcaniques intermédiaires à caractere d'arc insulaire. Le Hammamat Group comprend des roches clastiques du type molassique, et des roches volcaniques pénécontemporaines de composition andésitique à rhyolitique (Dokhan Volcanics); des granites calco-alcalins syntectoniques à tardi-tectoniques sont les équivalents plutoniques des «Dokhan Volcanics».

Le terrain étudié se situe dans l'avant-pays plissé et charrié d'un orogène de marge continentale. Des ophiolites, particulièrement des serpentinites, affleurent le long de la surface de charriage entre le massif autochtone de Meatiq et la nappe complexe d'Abu Ziran.

Des dômes, développés le long de deux géanticlinaux, ont été les centres d'une forte activité magmatique calco-alcaline associée, au moins, à une minéralisation aurifère.

Краткое содержание

Породы египетского к ристаллина подразде ляют на три основные группы: „Meatiq Group“ (самая древняя), „Abu Ziran Group“ и „Hammamat Group“ (самая подзняя); последине две относя т к пан-африканскому ц иклу. Первая группа представляет собой древний цоколь, отмеч еииый в гнейсовых куп олах. Вторая группа охватывает в основном ассоциации, находящиеся в геосин клинали, составленные из офио литов, перекрытых осадочными породами, вулканокластически ми породами, а также породами вулканизма локально го значения, проявляю щегося периодически и облад ающими свойствами пород ост ровной дуги. Последня я, самая молодая группа соста влена кластическими седим ентами и ассоциирова на с вулканитами „Dokhan“ анде зитного до риолитового состава. Плутоническими экви валентами вулканитов „Dokhan“ являю тся синтектонические и п оздне-тектонические кальциево-щелочные г раниты.

Исследованная облас ть находится в предго рье складочного и покров иного пояса орогена материкового края. Оф иолиты и, в особенност и, серпентиниты встреч аются вдоль внедрения поверхнос ти надвига между цоко лем „Meatiq“ и покровом „Abu-Ziran“.

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Copyright information

© Ferdinand Enke Verlag Stuttgart 1984

Authors and Affiliations

  • Samir el-Gaby
    • 1
  • Osman el-Nady
    • 1
  • Ali Khudeir
    • 1
  1. 1.Department of GeologyAssuit UniversityAssuitEgypt

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