Analysis On Ore-forming Conditions Of Sandstone-type Uranium Deposits In The Northwestern Margin Of Ordos Basin,Inner Mongolia

The northern Ordos Basin is the largest uranium resource base in China.In recent years,several superlarge,superlarge and large sandstone uranium deposits have successively discovered.A series of major breakthroughs have made in the exploration of sandstone-type uranium deposits in China.Through comprehensive research,a complete set of sandstone-type uranium mineralization theory has formed.The northwestern margin of Ordos Basin,as the western extension part of Dongsheng uranium resource base,has similar uranium mineralization geological conditions and has great potential of uranium resources.Based on the comprehensive study of the geological conditions of uranium mineralization in the northwestern margin of Ordos Basin,this paper summarizes the rules of uranium mineralization,delineates the target area of uranium mineralization,and predicts the potential of uranium resources,providing a basis for the next stage of uranium exploration.The Ordos Basin is located in the west of the north China platform,which has the characteristics of craton basin.In the north of the basin,the igeng uplift and yishan slope form a wide,gentle and stable slope belt,which creates extremely favorable structural conditions for the stable and continuous distribution of the middle Jurassic zhiluo formation sedimentary facies.The basement fault of the basin mainly developed in the peripheral zone of the basin.The fault activities in the northern part of the basin have long-term and multi-period characteristics,which control the distribution of lithology-lithofacies of zhiluo formation.The structure leads through the coal-bearing rock system of Yan'an Formation in the lower part,and the CBM overflows along the fault,which enhances the regenerating capacity of Zhiluo Formation,and plays an important role in controlling the spatial distribution of interlayer oxidation zone.We summarize the stratigraphic characteristics of the basin.The basin consists of crystalline basement,stable platform sedimentary cover and active basin sedimentary cover.The first two forms the "double" basement of the basin and provide abundant material source and uranium source for the basin cover deposition.Mesozoic sedimentary cover of the basin developed relatively well.The fluvial-deltaic sand bodies in the lower part of the middle Jurassic dong-luo formation are developed,and there is a "mud-sand-mud" stratigraphic structure.There is a reducing medium in the grey sand body,which is the main prospecting target in the area.We studied the spatial distribution of sand body in ore-prospecting area.The sedimentary system of the lower Cretaceous Huachi-Huanhe formations in the basin-prague area in the eastern part of the study area identified as mainly alluvial fan sedimentary system,which is not used as ore prospecting target.The lower member of the middle Jurassic Zuluo Formation is distributed stably in the basin-prague area.Analyze and study the collected borehole and construction borehole.The vertical lower section of the area can be divided into upper and lower subsections,and the rock dip Angle is small.The sand bodies of the lower member of the middle Jurassic zhiluo formation in the western orendohi region are more stable.The sand body is generally connected,the boundary of upper and lower subsections is not clear,and the rock strata have large dip Angle.The geochemical characteristics of rocks of Zhiluo Formation,the main ore-prospecting target in the study area,were analyzed.The geochemical zoning of rocks was established.It is found that the interlayer oxidation is more developed in the lower sand body of the middle Jurassic zhiluo formation in the east and west of the study area.It is speculated that the oxidation zone grows to 10 km.The yellow interlayer oxidation zone was developed in the western urenduxi area,and the oxidation zone was initially controlled to grow up to 15 km.In the Yihewusu-yastu area,the lower cretaceous huachi-huanhe formation developed the diving oxidation,which spread out in a plane.The characteristics of uranium mineralization at the surface and depth of the study area are summarized.The cause of uranium mineralization is analyzed and studied.Compare the genetic types of uranium deposits found in the vicinity of the study area and the origin of uranium deposits.The uranium mineralization in the study area was reasonably classified.The uranium mineralization in the basin-prague area in the eastern part of the study area was converted into interlayer oxidation zone sandstone type.The type of uranium ore prospecting in the western Wurenduxi area is the yellow interlayer oxidation zone sandstone-type controlled by the folding fault zone.In the middle of the study area,the type of uranium ore prospecting in the Yihew usu-yastu area is the subsea oxidation zone sandstone type.Through the study area geological data collation and research.Preliminary delineation of uranium ore prospecting target area 2: bainimag and asto;Two prospects for uranium mineralization: Wurenduxi and Yihewusu.It is believed that the sandstone-type uranium mineralization conditions are good in the paleostratigraphic oxidation zone in the Bayinbulage area in the eastern part of the study area,and the uranium resource has great potential,which is the main prospecting type.The uranium mineralization potential is relatively small in the asto area,which is controlled by diving oxidation.In the western part of the study area,the sand bodies of the lower member of the middle Jurassic zhiluo formation in the ore-prospecting area of Wurenduxi and Yihewusu are developed,and the yellow interlayer oxidation zone is developed in the pleistocene zone,and the uranium mineralization potential is good.