The Constraints of the Depositional Environment of the Luohe Formation on Uranium Mineralization in the Zhenyuan Area of the Southwestern Ordos Basin

The sedimentary environment of uranium bearing rock series restricts the spatial distribution of uranium reservoirs and uranium mineralization, which is of great significance in the evaluation of uranium mineralization potential. There is controversy over the sedimentary environment of the Luohe Formation uranium bearing rock series in the southwestern edge of Ordos, and its relationship with uranium mineralization is unclear, which restricts the understanding of regional uranium mineralization laws. This article analyzes the sedimentary environment of the Upper Cretaceous Luohe Formation uranium bearing rock series in the southwestern edge of the Ordos Basin through methods such as debris composition analysis and particle size analysis. Research has found that the uranium bearing rock series in the Luohe Formation are mainly composed of red, gray, and grayish green fine coarse sandstone, with detrital components mainly composed of quartz, feldspar, and rock debris. The sandstone is mainly composed of rock debris quartz sandstone and feldspar quartz sandstone. The average particle size (Mz) of sandstone is 2.01. The average value of standard deviation (σ) is 0.49, indicating good sorting. The average skewness (Sk) value is 0.11, indicating that the sedimentation of the Luohe Formation is mainly composed of coarse material, with a tail of fine material remaining. The average kurtosis (Kg) is 1.05, and the change in kurtosis is not significant. The frequency curve shows good normal distribution characteristics, and the frequency histogram mostly shows a unimodal pattern. The probability value accumulation curve is a high slope one segment jump, one jump one suspension two segment, and one roll one jump one suspension three segment. Based on comprehensive analysis, it is believed that the sedimentary environment of the Upper Cretaceous Luohe Formation uranium bearing rock series in the study area is an aeolian sedimentary system, including aeolian sand dunes, inter hill sediments, channel sediments, and shallow lake sediments. The lithological combination and particle size characteristics of the genetic facies have their own characteristics. The river sediments and small lake sediments in the Upper Cretaceous Luohe Formation uranium bearing rock series in the research area constrain uranium mineralization, and the interaction between wind and water forms uranium reservoirs rich in organic matter with a relatively stable "mud sand mud" structure, which provides a prerequisite for large-scale uranium mineralization in the later stage. Therefore, the area of wind water interaction sedimentation at the edge of the basin is a favorable area for sandstone type uranium mineralization.