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Research On Related Problems Of Basement Evolution And Sedimentary Cover In Ordos Basin

Posted on:2004-09-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:L J DiFull Text:PDF
GTID:1100360092498612Subject:Mineralogy, petrology, ore deposits
Abstract/Summary:PDF Full Text Request
It is directed by the 1atest theory of terrain stickin Plate Tectonic, and based o n petrographical series and stratum layers. From the aspects of Structural Analysis, Stratigraphy, Petrology, Sedimentology, Structure Geology, Remote sensing Geology, Geophysics as well as Tectonics, the author put the Ordos Basin into a bigger and deeper studying field while using the combination of sedimentation and Structure analyses, the data of outcrops around the basin and the deep drilling coring data in the middle of this basin, geochemistry analysis, seismic methods and non-seismic methods, etc. This paper discussed the relationship between the crystalline basement and the suprastructure in and surrounding the Ordos Basin, and also the influences of deep geology on the basin platform cover, and some new point of view and better understanding have been brought forward on the basement growth of Ordos Basin and it's platform cover.A large amount of data of the latest regional geoglogy and the latest correlation data of layers and rock formation have been quoted, and a description of distribution of crystalline basement, formation, evolution as well as the distribution characteristic of the fracture belt of Ordos Basin have been made in this paper, and the paper also pointed out that the g-layer which lies between the base of the basin and Tg reflector, is the extension of basinward of Guandaokou of Jixian system. The layer of Changcheng system and Jixian system, which had been divided before, can be correlated with the exposed Huangqikou Group and Wangquankou Group in Helan mountain, and divided into Qingbaikou system. So, the paper denied the viewpoint of the existence of aulacogen in Hutuo period and middle Proterozoic in this basin.Sedimentary and Structure analysis indicated that, in the combined area of three mountains (Qinling-Qilan-Helian) on the west and southwest margin of Ordos Basin, there were no geological condition for the formation of three-armed rift, so it is not likely to form Helan aulacogen, and it is certain that the rift shoulder can not be used to explain the reason for the forming of central paleo-uplift in this basin. Considering the sedimentation thickness, the formation of central paleo-uplift should be differential sedimentary structure caused by the thick layer carbonate deposition of Guandaokou group, Jixian system, which extended from the south-west margin to the inner part of the basin.The analysis of structural movement and expression shows that Qinqi tectonic active area is a volcano-sendimentary compressional depression formed by several times of compression movement from lower Proterozoic, and spreaded in the direction of north step by step till the forming of Xiangshan and Miboshan group in mid-later period ofOrdovician, bearing hardly with volcanical rock. The north border of the basement, extended from west to east along the north latitude 38 , this latitude structure zone is part of the zone in the middle of Ordos Basin along the north latitude 38 , this is caused by the rate of earth rotation, according with the condition of global harmonic function.The study on the structural feature opened out by the non-seismic (MT) profile of Xiaonangou in Qinglong mountain on the west edge of Ordos Basin and the seismic profile across Helan mountain shows that a series of thrust blocks-Qinglong-Luoshan -Nioushou-Helan mountain, were the thin-skin structure formed by the westward compression of Ordos Block and the dextral shear of Alashan Block.From the studying on the growing process of the basement and the spreading of the fracture belt, the research discovered that the distribution spreading expression of the oil-gas and the delta in Ordos Basin were strictly controlled by the basement fracture belt extended in the direction of north-east and east-west. And during each period of the process of the crystalline basement stick, the interface with relatively bad welding had coupled movement with the overlying layer. As a result, the overlying layer happen to be dip-slip drag...
Keywords/Search Tags:OrdosBasin, Crystallinebasement, Terrain-stick, aulacogen, thin-skinstructure, Qingbaikou system, Hutuo period, Guandaokouperiod, Compressional-depression, Enrichment zone of oil and gas
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