Abstract: The Nalinggou uranium deposit is located in the northeastern Ordos Basin and the U-bearing rock series occur in the
Middle Jurassic Zhiluo Formation. 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 Zhiluo Formation sandstones of the Nalinggou area. Then, characteristics of the clay minerals were discussed in detail and
compared preliminariy with those of the adjacent Yili and Erlian basins. Results show that the clay minerals are mainly smectites,
followed by kaolinites, chlorites and illites. There is a mutual transformation between smectites and kaolinites, while some chlorites
are transformed from smectites and kaolinites. In contrast, smectites did not spontaneously transform to illites during the diagenesis.
The total amount of clay minerals in sandstones is relatively high. Compared with those in the Yili Basin, the sandstones in the study
area are rich in smectites, with less content of kaolinites, and have a strong adsorption capacity caused by clay minerals. During the
diagenesis, the adsorption of clay minerals led to a large amount of pre-enrichment of uranium, which is an important prerequisite for
the formation of many uranium deposits and even super-large uranium deposits in the northeastern Ordos Basin.

Key words: Nalinggou area, clay minerals, Zhiluo Formation, sandstone-type uranium deposit, Ordos Basin