Ductile shear zones in the northern Red Sea Hills, Sudan and their implication for crustal collision
✍ Scribed by David C. Almond; Farouk Ahmed
- Book ID
- 102845356
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- English
- Weight
- 732 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0072-1050
No coin nor oath required. For personal study only.
✦ Synopsis
In the northern Red Sea Hills. of Sudan, deformation is largely concentrated into a network of shear zones. Several of these zones strike north-south. hut the important Nakasih and Sol Hamid zones are northeast-trending, and there are also minor shear zones which strike east-west. We distinguish between massive shear zones, such as that of Nakasih. and more diffuse braided shear zones. typified by the Oko zonc. The massive type owes its character to an origin a s a reactivated oceanic suture. whereas the braided type was characterized by strikc-slip shearing from its inception. Most of thc shear zone rocks are mylonites formed under greenschkt facies conditions. but early shearing along the Oko zone took place at higher temperature and resulted in gneissose mylonites with amphiholitc facics mineralogy. The northeast-trending. Nakasib shearing appears to have preceded a phase of batholithic intrusion, whereas north-south shearing in the Oko and Abirkitib zones is younger than the batholithic intrusions and is i n turn post-dated by emplacement o f bimodal granite-gabbro complexes. Thcsc cvcnts cannot be dated precisely as yet, but took place between 95 Ma and 700 Ma. and probably towards the end of that interval. The pattern of shear and suturc zoncs in northeast Sudan suggests that the northeast-trending Hijaz and Asir arcs. recognized in Saudi Arabia. terminate to the west against a north-south suture which was later rejuvenated to form the Ahirkitib shear zone. West of this suturc was an immaturc volcanic arc which may have lain along the margin of the African continent. The rejuvenation which caused northeast and north-south strike-slip shear was probably a consequence o f soft collisions in East Arabia.