Geomechanism Model of the Central African Shear Zone and its Related Rift Basins

Abstract

Formation mechanism of the Central African Shear Zone (CASZ)and its related rift basins, such as the Muglad Basin, Salamat Basin, Doseo Basin, Doba Basin and Bongor basin, has not yet been perfectly defined. By analyzing the structure of the African plate basement, the structural events of the African plate and the peripheral plates during the Late Jurassic to the Early Cretaceous and contrasting to the formation mechanism of the transitional fault of the African Mid-Atlantic Ridge,this paper presents a new interpretation of the formation mechanism of the CASZ, which is that the formation mechanism is the same as the transition fault of mid-ocean ridge, and the formation time is from Late Jurassic to Early Cretaceous, and the tectonic position is the active belt between Sahara Craton and Congo Craton. The background of the formation is during Pan-African tectonic movement, the African Plate was composed of many stable craton nuclei and active belts, and the basement structure was heterogeneous. Since the Mesozoic, the disintegration of the western Gondwana Continent and the opening of the Atlantic Ocean from the south to the north had been undergoing. This difference in stress between the north and the south resulted in the rupture of the structural weak zone between the stable cratons and the strike-slip faulting, resulting in the formation of the CASZ between the Congo Craton and the Sahara Craton. When the shear zone extends in the north-east direction out of the Congo Craton, no longer subject to the con-straints of the Congo craton, the property of the basement changed again, which led to, at the end of the shear zone, the strike-slip stress field converting to stretch stress fields, forming the Muglad basin, the Bongor basin, and the Salamat, Doseo and Doba basins within the fault zone. This model of formation mechanism is very useful to explain the special formation time and position of the CASZ, and also provides evidence for the formation mechanism of the intracontinental rift basin, so it is of great significance.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018