Lithium enrichment during clay mineral transformation in Carboniferous bauxite deposits in central Guizhou, SW Yangtze Block, China

• Lithium occurs in clay minerals, including illite, kaolinite and cookeite. • Paleoenvironment controls the transformation of clay minerals. • Lithium enrichment occurs via entry into octahedral sites and interlayers during clay mineral reorganization. Lithium-rich claystones found in the Carboniferous bauxite of the southwestern Yangtze Block represent a significant type of lithium resource. However, the origin of these claystones and the mechanisms underlying lithium enrichment remain poorly understood. This study investigates Li-rich claystone samples from three locations in central Guizhou using petrography, X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Tescan Integrated Mineral Analyzer (TIMA), and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to elucidate the occurrence and enrichment mechanisms of lithium. Mineralogical and geochemical analyses indicate that lithium is primarily hosted in clay minerals, with cookeite (average 5175 ppm), kaolinite (up to 10703 ppm), and illite (average 1810 ppm) serving as the key carriers. Accessory minerals (e.g., diaspore, pyrite) contain negligible amounts of lithium (<25 ppm). Lithium enrichment occurs through multi-stage dissolution–recrystallization during diagenesis. Paleoenvironmental factors influence the distribution of lithium: terrestrial environments preserve detrital kaolinite with the lowest lithium concentration; transitional zones feature cookeite-dominated assemblages with peak enrichment; and marine settings host illite-rich facies with moderate lithium concentrations. Lithium incorporation occurs via entry into octahedral sites and interlayers during clay mineral reorganization, with terrigenous Li-rich muscovite identified as a critical precursor. Environmental evolution and fluid-mediated clay transformations control lithium enrichment, reflecting the four-stage genesis of lithium-rich claystone. These findings provide valuable insights for targeting exploration of this promising lithium resource.