Mineralogy and Geochemistry of Late Carboniferous Coals From the Hedong Coalfield, Eastern Ordos Basin: With an Emphasis on the Li and <scp>REY</scp>

ABSTRACT The contradiction between the irreplaceability of critical metallic resources in economic development and national defence security, and their relatively small reserves and uneven distribution in nature, highlights the significance of exploring new types of mineral resources. The discovery of critical metals in coal has made it possible for coal to become an alternative source of these resources. This study provides geochemical and mineralogical data of the No. 13 coal in Xiegou Mine, Hedong Coalfield, North China, focusing on the occurrence and enrichment mechanisms of lithium (Li) and rare earth elements and yttrium (REY). The No. 13 coal is a high‐volatile bituminous coal with low ash yield and high total sulphur content. The kaolinite, pyrite and calcite are the main minerals, with a small amount of anatase, zircon, illite and REY‐bearing minerals. Compared to world hard coals, the studied coal samples have high Li and REY content; in addition to Li and REY, Ga and Zr (Hf) may also be of potential economic significance. Li occurs predominantly in kaolinite or Ti‐bearing kaolinite, and REY occurs dominantly in phosphate minerals (LREY is mainly related to goyazite). The geochemical parameters and mineral assemblages indicate that the Yinshan Oldland is the main sediment source of coal and host rocks. In addition, the geochemistry and mineralogy of the parting indicate that it is the product of alkaline felsic volcanic ash. The high content of Li and REY in the No. 13 coal is the result of alkaline volcanic ash input and the late modification of multi‐stage fluids.