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The University of Texas at Dallas, Programs in Geosciences, Richardson, Tx 75083-0688, USA
The Oko Shear Zone is a late Precambrian, N- to NW-trending, post-accretionary deformational belt in the Red Sea Hills of the Sudan. It left-laterally offsets the c. 800750 Ma old, NE-trending Nakasib suture by about 10 km. The Shear Zone evolved through three phases of deformations: (1) an early E-W-directed flattening deformation which produced N-trending upright folds; followed by (2) major NW-trending, left-lateral and, minor NE-trending, right-lateral strike-slip faulting; and (3) late E- and W-verging thrusts and buckles associated with a flower structure.
The structural similarities between the Oko Shear Zone and other post-accretionary deformational belts in the Arabian-Nubian Shield suggest an evolutionary sequence for these belts: (1) suturing events were completed by c. 700 Ma ago 'and resulted in the formation of E- to NE-trending ophiolite-decorated sutures; (2) an E-W-directed flattening deformation was superimposed due to collision of the Arabian-Nubian Shield with the Nile craton in the west and the Ar Rayn micro-plate to the east at c. 670610 Ma ago; this produced discrete zones of N-trending upright folds; (3) the flattening deformation culminated in the initiation of major NW-trending, left-lateral, and minor NE-trending, right-lateral strike-slip faults as conjugate sets at c. 640560 Ma ago.
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