This paper is the result of mineral exploration engineering.
[Objective] The Qianjiadian uranium deposit is located in the southwestern songliao basin and the U -bearing rock series occur in the upper Cretaceous Yaojia Formation. There are a lot of clay minerals in the target strata, so it is very important to reveal the characteristics of clay minerals in sandstone of Yaojia Formation for uranium mineralization. [Methods] In this paper, method of microscopic identification, scanning electron microscopy and X-ray diffraction were used to systematically observe and study the microscopic characteristics, composition and content of clay minerals in the Yaojia Formation sandstones of the Qianjiadian area. Then, characteristics of the clay minerals were discussed in detail. [Results] The clay minerals are mainly kaolinites, followed by smectites, chlorites and illites. Clay minerals are important adsorbents for uranium enrichment in sedimentary rocks, and the adsorption capacity of different clay minerals to uranium is different. [Conclusions] The Yaojia ore-forming environment experienced the acidic environment in the early ore-forming stage and the weakly alkaline environment in the late ore-forming stage. And there are a series of mutual transformation relations between different clay minerals in this process. The change of clay mineral content not only affects the physical properties of uranium reservoir but also influences the enrichment of uranium. Under the action of clay mineral adsorption, a large amount of uranium was pre-enriched in the process of sandstone diagenesis of Yaojia formation, which laid a solid material foundation for the formation of extra-large uranium deposits in Qianjiadian area.
Highlights: The clay minerals are mainly kaolinites, followed by smectites, chlorites and illites of the Qianjiadian area. Under the joint action of different kinds of clay minerals, a large amount of uranium is preenriched in Yaojia Formation.