The Ring Structure Characteristics Of South Ordos Basin And Its Deep Control Factors

The Ordos basin rests upon the North China Block (NCB) and is one of the largest sedimentary basins in north China, with more than 15 km of Phanerozoic strata. The body, which is about 23X10V in size, lies under 10-20 m of Quaternary sediment, possess abundant oil, natural gas, coal and sandstone type of uranium resources. Recently, the study of the enrichment rules of oil, coal, natural gas and uranium has got a special point in the Ordos Basin. Vertically, coal distributes in Permo-Carboniferous and Jurassic; oil and uranium exists mainly in Jurassic while gas rests in Ordovician and Permian. Laterally, oil distributes in the center and southern parts of the basin, uranium deposits are located at the edges of the basin, natural gas and coal set in the whole basin. There are seven association and accumulation forms of different energy resources, namely gas in oil, gas in coal, gas enriched in the upper while oil enriched in the lower, uranium in oil, uranium in coal, oil in coal and independent accumulation separately.During the development of the basin, tectonic evolution, sedimentary environment and hot evolution together cause the association and accumulation of different energy resource in Ordos basin. The tectonic evolution framework controls the characteristics of the basin, the internal sequences of basin-fill and the distribution of coal, oil, gas and uranium. Depositional environment is the base of mineral accumulation, that is to say, minerals are differentiated because of sedimentary environment and sedimentary facies; the hot evolution of basin contributes to the formation, accumulation and disappearance of coal, oil, gas and uranium.The geology of Ordos is an important indicator of the geologic history of the entire North China Block. Based on the whole, dynamic and synthetical basin analytical methods, the structural characteristic of the South Ordos basin in the Late Mesozoic and the Cenozoic is researched with the data of seismic, geological and former achievements. In order to discuss deeply to the geodynamical background of Ordos basin and study the dominant factors controlling the sediment evolvement of the basin, we discusses the evolvement of basin from an even more extensive view.It is testified that the ring structure has close correlation with deep-seated structure and dominated by the factors in the deep of the earth through the comprehensive study of physical geography and natural earthquake. It is the result of the united effects of the orogenic activities during Mesozoic to Cenozoic period (Indo-China movement, Yanshan movement, Himalayan movement and the restraining bend in plate oblique collision).