Ordos basin tectonic evolution and structural control of coal

Ordos basin, a huge intercontinental depression, influenced by Pacific and Tethys structural domains, was formed during Mesozoic Era. The present scope of the basin is the result of later recreation. The evolutionary processes of the depression can be divided into four epochs: Early Jurassic to the early period of Middle Jurassic, Middle Jurassic, Late Jurassic and Early Cretaceous, of which, Early Jurassic to the early period of Middle Jurassic is an important coal-accumulating period. Tectonics played a vital role in controlling the coal-accumulating period, coal-accumulating area, and the characteristics of the coal. The coal-accumulating period is controlled by the tectonic structure. The coal-accumulating area is distributed ring-shapely around the subsidence centre of the basin, and in which the number, thickness and change regularity of the seam may vary considerably in different positions of the basin. The period and area of tectonic turning are essential controlling factors for the forming of coal. The main tectonic units which are in favor of the coal forming in Ordos basin conclude the western fold thrust zone, Tianhuan depression, Yishan monocline, the Weibei fault uplift, and the Hedong fault-fold zone.