Elsevier

Precambrian Research

Volume 27, Issues 1–3, January 1985, Pages 277-300
Precambrian Research

Ophiolites and the evolution of tectonic boundaries in the late proterozoic Arabian—Nubian shield of northeast Africa and Arabia

https://doi.org/10.1016/0301-9268(85)90016-6Get rights and content

Abstract

The Arabian—Nubian shield is currently regarded as one of the best examples to demonstrate that processes of lateral crustal growth and modern-type obduction—accretion tectonics have operated since at least late Precambrian times.

In Arabia a number of Pan-African volcano-sedimentary/plutonic belts have been identified that display internal evolutionary patterns suggesting a development from primitive intraoceanic arcs some 900–950 Ma ago to mature, andesite-dominated arcs some 640 Ma ago through processes of ocean-crust obduction, arc collision and magmatic crustal thickening. Several ophiolite-decorated sutures are preserved, but many early tectonic boundaries were obliterated during later overthrusting, faulting and shield-wide granitoid plutonism towards the end of Pan-African evolution and stabilization in the earliest Palaeozoic.

In southeastern Egypt and in the Red Sea Hills of the Sudan early Pan-African clastic sediments suggest that a passive continental margin was probably separated from several evolving arcs to the east by marginal seas. These arc segments were later thrust over each other, from east to west, during widespread and considerable horizontal shortening and gave rise to spectacular nappe structures and extensive ophiolite mélanges.

The apparent lack of well-defined accretionary thrust stacks, high-pressure metamorphic assemblages and widespread ophiolitic mélanges in Arabia indicates that accretion either did not occur along margins with deep ocean trenches but involved buoyant crust, or extensive overthrusting took place through which the forearc segments were overridden and are now concealed. This, together with the recognition of distinct tectonic belts and isolated fragments of possible ancient continental crust and oceanic plateaus, supports the contention that Arabia may represent a collage of previously independent exotic terranes that accreted by oblique convergence and strike-slip translation during shield evolution.

It is suggested that the Arabian shield contains remnants of microcontinents with pre-Pan African (i.e., > 1000 Ma) crustal history and, perhaps, oceanic plateaus and that its evolution bears similarities with aspects of terrane accretion in the North American Cordillera and in the present western Pacific. The evolution in Egypt and in the Sudan, however, seems characterized by the transformation of a passive continental margin into a tectonically active belt along which ophiolites and arc volcanics were thrust over each other at approximately the same time when the exotic terranes and arcs of Arabia accreted farther east. Final stabilization of the shield occurred when the evolving Arabian plate “docked” with Nubia after marginal basin closure and cessation of arc magmatism some 600–640 Ma ago.

References (73)

  • R.J. Stern

    Petrogenesis and tectonic setting of Late Precambrian ensimatic volcanic rocks, central eastern desert of Egypt

    Precambrian Res.

    (1981)
  • J.R. Vail

    Pan-African crustal accretion in north-east Africa

    J. Afr. Earth Sci.

    (1983)
  • A.A.M. Ahmed

    General outline of the geology and mineral occurrences of the Red Sea Hills

    Geol. Min. Res. Dept. Sudan, Bull. 30

    (1979)
  • T. Alabaster et al.

    The volcanic stratigraphy and petrogenesis of the Oman ophiolite complex

    Contrib. Mineral. Petrol.

    (1982)
  • A.M. Al-Shanti et al.

    The Upper Proterozoic ophiolite mélange zones of the easternmost Arabian shield

    J. Geol. Soc. London

    (1983)
  • A.M. Al-Shanti et al.

    Mafic—ultramafic complexes of the Arabian shield and their mineral occurrences

  • E.Z. Basta et al.

    Proterozoic ophiolitic mélange and associated rocks of Gebel Ghadir area, Eastern Desert, Egypt

  • Z. Ben-Avraham et al.

    Early evolution of the Bering Sea by collision of oceanic rises and North Pacific subduction zones

    Geol. Soc. Am. Bull., Part 1

    (1981)
  • Z. Ben-Avraham et al.

    Continental accretion and orogeny: from oceanic plateau to allochthonous terranes

    Science

    (1981)
  • J.Y. Calvez et al.

    Geologic evolution of western, central and eastern parts of the northern Precambrian shield, Kingdom of Saudi Arabia

    BRGM Open-File Report 03-17

    (1983)
  • S. Claesson et al.

    Samarium—neodymium data on two Late Proterozoic ophiolites of Saudi Arabia and implications for crustal and mantle evolution

    Contrib. Mineral. Petrol.

    (1984)
  • P. Coney et al.

    Cordilleran suspect terranes

    Nature

    (1981)
  • J. Delfour

    Geologic, tectonic and metallogenetic evolution of the northern part of the Precambrian Arabian shield (Kingdom of Saudi Arabia)

    B.R.G.M., sér. 2 sec.

    (1981)
  • J.F. Dewey et al.

    Growth and differentiation of the continental crust

    Philos. Trans. R. Soc. London, Ser. A

    (1981)
  • W.R. Dickinson

    Plate tectonic evolution of north Pacific rim

    J. Phys. Earth

    (1978)
  • R.M.A. El Bayoumi

    Ophiolites and associated rocks of Wadi Ghadir, east of Gebel Zabara, Eastern Desert, Egypt

  • R.M. El Bayoumi et al.

    Ophiolite mélange complex of Wadi Mubarak area, Eastern Desert, Egypt

  • M.F. El Ramly et al.

    On the tectonic evolution of the Wadi Hafafit area and environs

    Fac. Earth Sci., Univ. Jeddah, Bull. 6

    (1984)
  • J.C.B. Embleton et al.

    A new approach to the stratigraphy and tectonic evolution of the Red Sea Hills, Sudan

    Fac. Earth Sci., Univ. Jeddah, Bull. 6

    (1984)
  • A.E.J. Engel et al.

    Late Precambrian evolution of Afro—Arabian crust from ocean arc to craton

    Geol. Soc. Am. Bull., Part 1

    (1980)
  • R.J. Fleck et al.

    Rubidium—strontium geochronology and plate tectonic evolution of the southern part of the Arabian shield

    U.S. Geol. Surv., Prof. Pap. 1131

    (1980)
  • M.S. Garson et al.

    Precambrian—Lower Paleozoic plate tectonics and metallogenesis in the Red Sea Region

    Geol. Assoc. Can., Spec. Pap.

    (1976)
  • M.E. Gettings

    The isostatic gravity anomaly field of southwestern Saudi Arabia and its interpretation

    USGS Open File Report

    (1984)
  • W.R. Greenwood et al.

    Late Proterozoic cratonization in southwestern Saudi Arabia

    Philos. Trans. R. Soc London, Ser. A

    (1976)
  • W.R. Greenwood et al.

    Late Proterozoic island-arc complexes and tectonic belts in the southern part of the Arabian shield, Kingdom of Saudi Arabia

    USGS Open File Report 02-8

    (1982)
  • Cited by (0)

    View full text