TECTONIC EVOLUTION OF THE NAKASIB SUTURE, RED-SEA HILLS, SUDAN - EVIDENCE FOR A LATE PRECAMBRIAN WILSON CYCLE

The Nakasib suture is a late Proterozoic (Pan-African) ophiolite-decorated structural belt in the central Red Sea Hills of the Sudan. It represents one of the sutures along which the island arc/back-arc terranes and continental microplates of the Arabian-Nubian Shield are welded together. The Nakasib suture separates the 900-850 Ma old Haya terrane in the south from the 830-720 Ma old Gebeit terrane to the north. Five thrust-bounded stratigraphical groups are identified across the suture. These are, from south to north, Arbaat volcanic group (c. 730 Ma rift-related volcanic rocks), Salatib group (early passive margin volcanic and sedimentary rocks), Meritri group (the lower part of which contains alluvial and submarine fans of an incipient ocean basin, while its upper part can be tentatively equated with a platform of clastic sedimentary and carbonate intercalations which mark the stage of mature ocean basin opening), Nakasib ophiolite, and Shalhout group (arc-related volcanic and sedimentary rocks). These are intruded by syn-tectonic and post-tectonic plutonic rocks. The tectonic setting of the above lithological groups suggests that the early stage of the Nakasib suture development was marked by rifting of older crust, probably the Haya terrane, which culminated in development of a passive margin on the south margin of an oceanic basin prior to collapse into an ophiolite-decorated suture. This indicates that the Nakasib suture evolved through a complete Wilson cycle orogeny from rifting, through passive margin formation, to closure of the basin and suturing.