LI Hua-ming¹, LI Ling^1*, PENG Yun-biao¹, WANG Gui¹,LUO Xiao-neng²,YI Chao²

(1. CNNC Geology Party No.208, Baotou 014010, China;
2. Beijing Research Institute of Uranium Geology, Beijing 100029, China)

Abstract: Systematic sampling and analysis of sandstones of the Middle Jurassic Zhiluo Formation in the uranium metallogenic belt of the northern Ordos Basin are carried out to explore the mineralogical characteristics of clay minerals in sandstones and their important significances. The relative contents and micro-morphologies of clay minerals were determined and observed by using X-ray powder diffraction and electron probe analysis. The results show that the clay minerals in sandstones in the study area are mainly montmorillonite, kaolinite, chlorite, and illite. With the exception of montmorillonite, Contents of other three kinds of clay minerals are the lowest ones for samples in the Nalinggou section of the central study area, the highest ones for samples in the Daying section of the western study area. The highest content of montmorillonite of samples is the sandstone in the Nalinggou section of the central area. The negative correlation between contents of montmorillonite and kaolinite indicate that the montmorillonite was mainly transformed from the kaolinite. The good negative correlation between contents of chlorite and montmorillonite for samples in the Daying section indicate that the chlorite was mainly transformed from montmorillonite. The alteration of clay minerals resulted in the local alkaline environment which is helpful for the uranium crystallization and precipitation.

Keywords: uranium deposits; the Ordos Basin; sandstone-type deposit; clay minerals

ACTA MINERALOGICA SINICA Vol. 40, No.5, 2020, page 539-548