University of Khartoum

Nakasib Suture and Oko Shear Zone (Red Sea Hills, Sudan), Their Structural Settings and Tectonic Evolution.

Nakasib Suture and Oko Shear Zone (Red Sea Hills, Sudan), Their Structural Settings and Tectonic Evolution.

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Title: Nakasib Suture and Oko Shear Zone (Red Sea Hills, Sudan), Their Structural Settings and Tectonic Evolution.
Author: EL Tahir Bulo, Ahmed
Abstract: Nakasib Suture is a NE-trending ophiolite decorated belt separating the 750 Ma old Gebeit Terrains in the NW from the 850 Ma old Haya Terrains in the SE. The suture represents one of the late Proterozoic (Pan African) belts in NE Africa and W Arabia along which island arcs/back-arc basins were welded together. Nakasib Suture evolved through a three phase tectonic process. The first phase (pre 790 Ma ago) includes rifting of Haya Terrain) extrusion of Arbaat volcanic and the formation of a basin floored with oceanic crust (Nakasib ophiolites). During the second phase the clastic sediments of the Nakasib passive margin were deposited on the E. margin of the basin while a subduction zone was created on the W margin over which Gebeit arc volcanics were erupted (Shalhout group) 790-750 Ma ago. In the last phase the oceanic crust was consumed, forming the D I and D2 structures, and led the Gebeit Terrain to collide with Haya Terrain, forming the D3 structures. Nakasib Suture was formed due to that collision and the Nakasib ophiolites were thrusted from the decending oceanic slab as dismembered, imbricate slices which are now decorating the suture. This last phase ended about 740 Ma ago. These three phases were accompanied by the intrusion of syntectonic granitoids ranging in composition, - from gabbroic to granitic. Nakasib Suture is sinisterly offset by the post accretionary Oko shearing. Oko shearing resulted from the E- W oriented crustal shortening which has occurred in NE Africa and Arabia at about 700-560 Ma ago. That shortening produced the D4 structures and culminated in the formation of the NW to N-trending strike-slip D5 faults. Structures associated with D5 faults are recognized as flower - structure, tensional gashes and kink bands.
URI: http://khartoumspace.uofk.edu/handle/123456789/13910
Date: 2015-06-22


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