The Thickness Of The Original Formation Of The Early Cretaceous Of The Ordos Basin And Post-transformation Of Mineral Mineralization (tibet)

Ordos Basin is regarded as one of the most important Mesozoic and Cenozoic petroliferous basin congruence on the Paleozoic Craton in North China Block with the carbonate platform in the Lower Palaeozoic, the transitional deposits of marine and nonmarine intercalated with coal seams in the Upper Palaeozoic and the Inland Sag River-Lake System in Mesozoic, which produces multitude energy resource and mineral product that has been developed since Middle-Late Triassic to Early Cretaceous period. Base on field investigation, analyzing the data of well logging, the author studied the sedimental pattern of Early Cretaceous in Ordos Basin and calculated the denudation thickness caused by the tectonic movement, also the author tried to make available accounts to generalize the effect for petroleum, natural gas, coal and uranium, the mineral product as a result of the tectonic movement.Denudation generally exists in multistage sedimentary basin, especially the denudation of the infilling sequence caused by the tectonic movement in the main reversal stage of the original basin, thus it intensively influents the formation migration accumulation of oil and gas in sedimentary basin, and presents an entirely new appearance of the existing sedimentary basin, meanwhile this restricts the further study of basin tectonic evolutionary history, fill history, sedimentary evolutionary history, heat history as well as the pool-forming history of oil and gas. So the conformity and recovery of the amount of strata denudation are very important tasks in the study of sedimentary basin. At present, many methods have been employed in the research of the strata denudation in sedimentary basin, including geologic method, geochemistry method and physical geography method, and so on. The present paper estimates the denudation since Early Cretaceous based on the change tendency of the acoustic transit time in the normal compacted mudstone belt, and also the paper estimates the thickness of strata denudation in Early Cretaceous in terms of the stratum correlation, and more to recover the sedimentary construction in the basin of Early Cretaceous stage.On the base of the relic isopachous map, denudation isopachous map,thickness recovery map, the present paper completely studies the sedimentary scope and the distribution of the deposits of the basin in Early Cretaceous. The paper also points out that the gradually increasing deposits of Lower Cretaceous in Early Cretaceous was the main stage for the formation of current basin, with the east sedimentary borderline locating around the banks of Yellow River in west of Leuliang Mountains, whereas the western part of the basin gradually transiting into Liupan mountain. Estimating that the denudation thickness in the east part of basin is more intensive than that in the west part of basin by means of acoustic transit time, wells correlation, etc.For the tectonic evolutionary history, especially the background of denudation dynamics in the tectonic evolutionary stages since Mesozoic, three large scale tectonic movements have had happened since Mesozoic: Indo-china movement, Yanshan movement and Himalayan movement. Especially Yanshan movement curtain Ⅱ and Ⅲ, and Himalayan movement affected the tectonicevolution in the basin. Furthermore these two movements controlled holistic tectonic sedimentary pattern of the basin. These have illustrated the control role of the underriding of pacific-oceanic plate and the uplifting of Himalayan fold belt for the Ordos Basin.Finally, the present paper analyzes the change of formation pressure caused by burden-reducing of rock based on the denudation and explains the effects on the pool-forming of multitude energy resource mineral products like petroleunu natural gas, coal, uranium and so on. Denudation produces many fractures to release pressure, the slight crevices force the oil and gas to pool forming or dissipation; or force the coal bed to uplift to be an open air coalfield (like Shenfu Coalfield) or suffering from auto ignition. Process of migration of oil and gas produces reductive gas, like H2S, ect, then the chemical action of the gases propels the concentration of uranium.