Abstract

The Nakasib suture is a prominent structural belt in the central Red Sea Hills, Sudan. It is one of the ophiolite-decorated sutures along which the late Proterozoic (Pan-African) island arc/back arc terranes and continental micro-plates of the Arabian–Nubian Shield were welded together. It juxtaposes the 900–800 Ma Haya terrane in the south with the 830–700 Ma Gebeit terrane to the north. New structural data from the Nakasib suture show that the suture had evolved through three phases of deformation which gave rise to a fold and thrust belt. During the early two phases of deformation, SE-verging tight folds and thrusts were developed. The third phase of deformation refolded the earlier structures into NE-trending, upright, and horizontal antiforms and synforms and culminated in the development of NW-verging thrusts. The structural data are used, together with previous stratigraphic and geochemical data, to suggest a tectonic model for the evolution of the Nakasib suture. The suture followed a Wilson Cycle. This started with rifting of the Haya terrane, extrusion of rift volcanics and deposition of passive margin sediments, and development of a NW-dipping subduction zone over which the arc volcanics of the Gebeit terrane erupted. The closing of the oceanic basin gave rise to the Nakasib suture with the present structural configuration.

The structural styles of other sutures of the Arabian-Nubian Shield are examined in light of structural data from the Nakasib suture. These sutures show a common feature of steepening of the early subhorizontal ophiolite-obduction structures during a late event of upright folding which may be related to collision between terranes.

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