Sutures and shear zones in the Arabian-Nubian Shield

Abstract

Deformational belts in the Arabian-Nubian Shield (ANS) are divided into: (1) those associated with sutures, both arc-arc and arc-continental; and (2) post-accretionary structures which include north trending shortening zones and northwest trending strike-slip faults. The arc-arc sutures manifest collision between arc terranes at -800-700 Ma. They are orientated east to northeast in the northern part of the ANS and north to north-northeast in the south. North or south verging ophiolitic nappes are associated with the east to northeast trending sutures. These nappes were steepened by upright folds associated with the final stages of collision between terranes. East or west verging ophiolitic nappes are associated with the north to north-northeast trending sutures. These were deformed by upright folds and strike-slip faults related to oblique collision between terranes and/or post-accretionary deformations. The arc-continental sutures define the eastern and western boundaries of the ANS and are marked by north trending deformational belts which accompanied collision of the ANS with east and west Gondwana at -750-650 Ma. The post-accretionary structures were developed between -650-550 Ma due to continued shortening of the ANS. This produced north trending shortening zones which offset the east to northeast trending sutures in the northern part of the ANS but were superimposed as co-axial deformation on the north to north-northeast trending sutures in the south. The shortening deformation culminated with the development of northwest trending strike-slip faults and shear zones.