Litho-Tectonic Evolution around Third Cataract, Sudan: An integrated Remote Sensing, Lithological, Structural and Geochemical Approaches

Abstract

Abstract This Study is focused on the geology of the area around the Third Cataract, Sudan. In terms of combined remote sensing, petrological, structural and geochemical criteria this article presents detailed lithological and tectonic evolution of this region. For preliminary visual interpretation of the different lithological units and structural elements a digital image processing has been applied using Landsat 8 OLI images that are verified by precise ground truthing. Petrography, geological and structural field relationships have led to preliminary classification of rock units into: Undifferentiated orthogneisses and migmatites; Low to medium-grade metavolcano-sediments; Syn-orogenic intrusions; Late to post-orogenic intrusions; Cretaceous sandstone formation; Cainozoic volcanics and Quaternary to Recent sediments. Geological map has been created at scale of 1:75,000. In this study, three deformation episodes are identified (D1, D2 and D3), where D1 is associated with the formation of tight to isoclinal recumbent fold (F1) with north-dipping fold plane and sub horizontal trending axes verging to the east. Deformation took place in green schist-facies rocks that is thought to be related to the arc-accretion event. D2 gave rise to open upright fold (F2) which folded the axial surfaces of (F1) with fold axes plunging gently to the NNW. NNW–SSE sinistral strike slip movement is a main characteristic of D3 deformation. The geochemical results show a clear calc-alkaline trend of the metavolcanics units that were derived from volcanic arc magmas. Whereas the granitic rocks classify as calc-alkaline metaluminous to slightly peraluminous, and is considered as I-type granites. Rb versus (Y+Nb) discrimination diagram indicates volcanic arc granites.