Millimeter-scale mineral-Li mapping and mineralization mechanism analysis of clay-type lithium deposits using hyperspectral core imaging

With the rapid growth of the green energy industry, lithium resources are becoming increasingly important. Bauxite-associated clay-type lithium deposits represent a newly identified type of sedimentary lithium deposits that occur extensively in the Central Yunnan region. However, the key lithium-bearing minerals and their enrichment mechanisms in these deposits are still being researched. Imaging hyperspectral technology provides high spatial and spectral datasets and is widely used for drill core analysis. However, there are relatively few studies on quantitative analysis using hyperspectral images of drill cores. When the Transformer-multilayer perceptron−based lithium content inversion model was constructed and applied to the hyperspectral data of drill cores from Xiaoshiqiao area, the results demonstrated extremely high accuracy, with R2 values of ∼0.9 in the training set, test set, and validation set. The inversion models for clay minerals, including montmorillonite, illite, kaolinite, and chlorite, also achieve high accuracy. The spatial distribution of montmorillonite strongly correlates with that of lithium, suggesting that montmorillonite is the primary lithium-bearing mineral. Based on the results and paleogeographic analysis, the sedimentary process can be classified into four stages for the transition from a lacustrine basin to a lacustrine swamp marked by exceptionally enriched lithium-bearing layers. The millimeter-scale spatial distribution of lithium and clay minerals derived from imaging hyperspectral technology reveals a cyclic pattern of lithium enrichment, where lithium-rich (montmorillonite) and lithium-poor (illite and kaolinite) zones alternate within the enriched lithium-bearing formation. It is obvious that lithium enrichment is primarily driven by the strong adsorption capacity of montmorillonite and the high concentration of lithium ions in the lake basin. The detailed investigation into lithium enrichment mechanisms in this study offers valuable insights for exploring large-scale lithium deposits in the Central Yunnan Basin.