Geological characteristics, ore-forming fluids, and genetic models of uranium mineralization in superimposed basin and craton basin: a study on uranium-bearing basins in Xingmeng area, North China

The basins in Xingmeng area are superimposed and craton type. The basins host many large uranium deposits. Here, we studied the geological characteristics, uranium mineralization ages, and C-O-S isotopes in the basins. In addition, we discussed the uranium mineralization stages, uranium mineralization fluids, and established the regional mineralization models. In the basins, uranium mineralization occurs at specific periods during tectonic evolution. The uranium-rich basement strata and magmatic rocks created under a certain tectonic background are the sources of uranium for the large-scale uranium metallogenic belt. Uranium mineralization occurs through multiple stages and across a long duration. Uranium metallogenic ages progressively become newer from west to east. Analysis of the C-O-S isotopes revealed that the compositions of uranium ore-forming fluids in the craton basin are more complex. Specifically, we found that meteoric water, deep oil and gas, mantle fluids, dissolution of marine organic carbonates, reducing media in sand bodies, and conate water contribute to uranium mineralization. In superimposed basins, due to the development of crust-scale thrust and high heat flow, in addition to meteoric water, connate water, dissolution of carbonate in marine organic matter, and the reducing medium in host layers, the upper mantle fluid is very large scale participated in the mineralization, and the oil and gas did not obviously participate in the uranium mineralization. The host layers sand bodies of the uranium deposits provide storage space for uranium and a channel for migration of fluids. After deposition, the basins undergoes different degrees of structural inversion, forming different degrees of denudation windows, thereby providing a basis for the migration of meteoric water and deep reduce fluids. The denudation window promotes the migration and escape of ore-forming fluids into the basin. Under the redox action of uranium ore-forming fluids and reducing media, phreatic, phreatic-interlayer oxidation zone, and interlayer oxidation zone together with uranium ore bodies are formed. Based on the study of uranium metallogenic characteristics and ore-forming fluids, the hydrodynamic models and metallogenic models of the basins are established. Moreover, the geotectonic evolution and its dynamic models at different stages in this area are discussed.