High-resolution sequence stratigraphic character and uranium ore formation in Hadatu area of Erlian Basin

Erlian Basin is a large Mesozoic-Cenozoic Uranium-producing basin in northern China. In recent years, exploration breakthroughs have been made in the exploration of sandstone Uranium deposits in the paleo-valley of the Erlian Basin, but high-resolution sequence stratigraphy has not been frequently used in exploration of northern sandstone-type uranium deposits. In this paper, a high-resolution sequence stratigraphy theory is applied, classifying and comparing the depositional cycles of the Saihan Formation section with ore-bearing structures by typical boreholes and sections, to identify and formulate a long-term cycle (LCS₁) and three medium-term cycles (MCS₁, MCS₂, MCS₃). Through the core geological record and combining with the characteristics of sandstone uranium mineralization in the paleo-valley of the Hadatu area, it is believed that the main output of the uranium ore area is the upswing of the MSC₂, in the Hadatu area which are controlled by the front line of the interlayer oxidation zone and hosted in the paleo-valley sandstone under low-accommodating space. The heterogeneity, better permeability, and reducing media such as enriched with pyrite of MCS₂ upper-middle-circle sand body are beneficial to the formation of interlayer oxidation zone and uranium mineralization. (authors)