Space-Time Coordinate of the Evolution and Reformation and Mineralization Response in Ordos Basin

Ordos basin has developed during middle—late Triassic and early Cretaceous and has been reformed since late Cretaceous. It mainly possesses the characters of intra-craton and is a residual basin with multi-stage and different reformation. Ordos basin also belongs to multi-superimposed basin which overlapped on the early and late Paleozoic basins. Therefore, Multi-energy mineral deposits are abundant and petroleum, coal and uranium are beared in the same basin. According to the the main geological structure features and geological events in ordos baisn and peripheral areas, together with the comprehensional research of the fission track ages in various district of the basin, the paper concludes that there exists four evident stages of structural fluctuation at least during basin development and also four stages of evolution and sedimentation in the basin. middle—late Triassic and early—middle Jurassic Fuxian and Yan'an stage is the two most prosperous stages during which the lake is broad and basin deposits extensively with an area over two times of that of present, the main oil and coal bearing strata develop. The two stages are divided by the regional early Jurassic uplift fluctuation, which causes interruption in deposition and development of the roughness of relief on the upper part of the Yanchang formation by reason of forceful and uneven cutting erosion. The uplift fluctuation is weak and the depositional interruption and erosion continuous time is short at the evening of Yan'an stage. Then basin subsides and enters the third evolution stage of middle Jurassic Zhiluo—Anding stage in which sedimentary range is still broad and the lake area is minish in the basin. There happens strongly structural movement and developed the thrust-nappe belt in western margin of the basin in late Jurassic during which the different depth of conglomerate deposit in the foredeep part in the east side of the western margin, erosion reform occurs in the middle and east of the basin. The structural movement causes the form of structure framework of regional east uplift and west subside in the west area of Yellow river. Broad sediments unconformablely overlap on the west margin thrust belt and sideral uplift of the basin north and south at the early Cretaceous stage. Ordos basin uplifts wholly to disappear and enters the late reformation period. In the first three stages, the depocenters lie near or to the east of Yan'an city, while deposit center in the west of the basin near provenance. The two centers differs in space in different stage. Until early Cretacious, the location of sedimentary depocenters and accumulation center is nearly same which is on the middle-south part of the west of the basin. There happen six major geological events in Ordos basin in late reformation period since late Cretaceous. (1) The main part of the basin uplifts continuously, episodically and differently, which causes the strong and uneven erosion, for example, the max erosion depth in Mesozoic can be two thousand meters near Yellow river on the east. (2) This uplift forms two or three stages of regional erosion-planation surfaces with ages of E 3-1__2,E_3 and N2_1. (3) The side of Ordos block subsides and the peripheral faulted basins form successively to deposit with heavy depth. (4) The regional east uplift and west subside movement continuing two bill years has been reversed which means the east subsides to widely deposit red clay and Liupianhshan, western margin of Ordos block and west part of basin uplift successively. The reverse event embodies the important influence of the regional structural movement of the west of China. (5) Aeolian red clay and loess begin to sediment broadly in 8Ma BPand 2.5Ma BP, respectively. Also the red mud semi-plateau, loess plateau and loess plateau surface develop successively. (6) Drainage system of Yellow river grows and fluid outside to erode the side rock. According to the above major geological events and the evolution of dynamics environment, five evolution stages is divided since late Cretaceous in Ordos basin which are late Cretaceous to Paleocene, Eocene to Oligocene, early—middle Miocene, late Miocene to Pliocene and Quaternary. The happening of these geological events and structural fluctuation are closely related with the compound, superimpose, change with time and strong-weak of major structural movement of peripheral structural domain especially that of the east and west of China. These activity and reformation change the Mesozoic prototype basin topography greatly.The main times and stages of the occurrence and formation and reset of miltiple energy resources have evident recall and decoupling relations with those of the Mesozoic and Cenozoic evolution and reformation in Ordos basin. The whole different uplift and regional erosion in and after the late of basin evolution own the important influence to the formation and distribution of the milti-mineral deposits and the coaction among them in Ordos basin.