Three-dimensional Geological Mineralization Analysis Of Sandstone-type Uranium Deposits In The Northeastern Margin Of The Ordos Basin Based On Borehole Big Data

The ordos basin is an important depositional basin of coal,uranium,oil and gas in China,has found multiple large-scale sandstone-type uranium deposits in its northeastern margin.With the in-depth exploration of basic geology and uranium deposits in the northeastern margin of the Ordos Basin from various fields by various departments,new prospecting ideas and metallogenic theories have been continuously proposed.During this period,a large amount of drilling data was accumulated,and new breakthroughs were achieved in the actual prospecting practice of the Ordos Basin.This article constitutes borehole big data based on thousands of boreholes data.Taking the northeastern margin of the Ordos Basin as the study area,the structure and depositional environment are analyzed.The method of constructing a three-dimensional geological model analyzes the uranium formation environment in the Daying area,which indicates the direction for further regional exploration.The main achievements are as follows:(1)By analyzing the sedimentary facies,the sedimentary environment and characteristics of the study area were studied.Braided river deposits dominated the early part of Zhiluo period and meandering river deposits dominated the middle and late part.The distribution map of sedimentary facies in lower subinterval of lower Zhiluo formation is drawn in detail to reveal the relationship between the source flow direction and the deposition environment.(2)From the paleogeomorphic recovery map of zhiluo formation in the northeast margin of the basin,it can be seen more intuitively.And The whole is a slope of northeast high and southwest low.There is a very obvious near east-west fault zone developed at the Hangjinqi-Bojianghaizi.A natural local physical barrier zone extending near east to west was formed here,which effectively restricted the migration of uranium from north to south.It concentrated the uranium mineralization in the Daying and Nalinggou areas on the north side of the fault zone.It is inferred that the fault may provide good conditions for the dissipation of ore forming fluids.(3)The three-dimensional geological model of the study area and series of cross-sectional studies have found that the distribution pattern of uranium mineralization in the Zhiluo Formation is inextricably linked to the planar heterogeneity of uranium reservoir sand bodies.Moreover,there are obvious physical differences between vertically stacked sand bodies,which have a limiting effect on the vertical migration of uranium sources.(4)Uranium mineralization is mainly developed where the wide and thick braided channel sand bodies diverge frequently from the narrow and thin sand bodies.The muddy barrier formed on the west side of Daying restricts the migration of oxygen-enriched uranium-containing fluids to the west,resulting in the formation of bow-shaped uranium deposits in the north-south direction in Daying.