Objective China, representing the world's largest consumer of lithium resources, suffers from a limited endowment of conventional lithium resources, rendering it inevitable for China to seek to develop and utilize abundant coal-hosted lithium resources. Through a comparative analysis of coal samples from the lithium-rich No. 8 and the ordinary No. 15 coal seams in the Taiyuan Formation, Yangquan mining area, Shanxi Province, this study explored the statistical relationships between the lithium and kaolinite contents and geophysical responses. Accordingly, the feasibility of the indirect detection of coal-hosted lithium resources using geophysical methods was assessed.

Methods First, by testing the lithium content and mineral components (e.g., kaolinite) of the coal samples, the fitted relationship between lithium and kaolinite contents was established. Subsequently, the geophysical parameters of the coal samples were systematically investigated, including density, as well as acoustic, electrical, and magnetic parameters. Using principal component analysis (PCA) and correlation analysis, the statistical relationships of the lithium and kaolinite contents with geophysical responses were explored thoroughly. Finally, the optimal sensitive parameters for distinguishing lithium-rich coals from ordinary ones were determined based on the comparison of the statistical parameters of various geophysical responses.

Results and Conclusions  The Nos. 8 and 15coal seams differ significantly in the distribution of test data. This occurs primarily due to their variations in mineral components, as well as their contents. For the No. 8 coal seam, there exists a strong linear positive correlation between the lithium and kaolinite contents, aligning with the existing understanding that kaolinites serve as the dominant carrier mineral of lithium resources in this coal seam. Results from histogram analysis, trend analysis, and PCA jointly reveal the presence of progressive relationships among the lithium content, kaolinite content, and geophysical responses in the No. 8 coal seam. Specifically, there are strong positive correlations between the lithium and kaolinite contents and between the kaolinite content and sensitive geophysical responses. Among the statistical parameters of geophysical responses, the range (Max-Min), the deviation between the local maximum and median (Max-Med), and the deviation between the median and local minimum (Med-Min) are identified as sensitive parameters, which allow lithium-rich coals to be effectively distinguished from ordinary coals. Overall, there exist progressive statistical relationships among the lithium content, kaolinite content, and geophysical responses of the No. 8 coal seam in the Yangquan mining area. This finding underscores the potential of geophysical methods for indirectly exploring lithium resources in the No. 8 coal seam.