Deformational History of the Neoproterozoic Keraf Zone in NE Sudan, Revealed by Shuttle Imaging Radar

The location of the boundary between juvenile Neoproterozoic crust of the Arabian-Nubian Shield in the Red Sea Hills and older crust of the Nile craton to the west is defined by the Keraf zone in northern Sudan, but little is known about its deformation history. Shuttle Imaging Radar (SIR-A), Landsat Thematic Mapper (TM), and Large Format Camera (LFC) images, combined with ground investigation, were used to carry out the first detailed study of the Keraf zone. This N-trending zone is ~45 km wide and is defined by multiply deformed carbonate-rich turbidites and volcanogenic sediments. Six deformational phases (D1 to D6) were identified, associated with two tectonic events: (1) D1 and D2 are related to emplacement of SSE-verging ophiolitic nappes due to collision between the Haifa and Bayuda terranes along the ENE-trending Atmur suture at ~800-700 Ma. The Atmur suture marks the site of a former Neoproterozoic oceanic re-entrant that extended WSW from the Mozambique ocean into the interior of the Nile craton. D1 produced SSE-verging tight folds and thrusts, whereas D2 deformed the D1-structures into ENE-trending upright folds. (2) D3 to D6 reflect shortening across the Keraf zone. D3 produced N-trending, upright, isoclinal to open folds. D4 was superimposed on D3 as coaxial W-verging tight folds. D5 refolded older structures about steeply, east- to ENE-plunging fold axes. D6 manifests development of local NE-trending dextral and NW-trending sinistral shear zones. We suggest that this deformation reflects oblique collision between composite arc terranes of the Arabian-Nubian Shield and the Nile craton along the Keraf zone at ~750-650 Ma.

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