Enrichment of lithium in bauxite deposits of Benxi Formation in Shenmu-Mizhi area, Ordos Basin

Key words: 
• Ordos Basin /
• Bauxite deposits /
• Lithium /
• Occurrence state /
• Enrichment mechanism

Abstract: Objective: Lithium constitutes a critical strategic and new energy metal within China. The Ordos Basin features a widespread distribution of bauxite deposits. Recent years have seen a major breakthrough in bauxite gas exploration within the Ordos Basin's Longdong area. The exploration has uncovered a considerable volume of lithium resources associated with the bauxite deposits. Considering the occurrence and enrichment patterns of Li in bauxite deposits, this not only holds significant academic value for studying paleoclimate and paleoenvironment but also offers robust support for the exploration and development of Li resources. Methods: Focusing on the aluminum-bearing rock series of the Benxi Formation in the central and eastern Ordos Basin, this study builds upon classical understandings and recent research advancements to investigate the fundamental characteristics, modes of occurrence, and enrichment patterns of Li, employing core observation, drilling data, and geochemical testing. Results: The findings reveal that Li distribution within the bauxite deposits is notably uneven, with a substantial range of variation. Generally, Li exhibits higher concentrations in the middle and upper segments of the bauxite deposits. Within the lithological sequence, Li predominantly concentrates in bauxite clay rock and clay bauxite rock, while it is comparatively scarce in bauxite iron ore. Initially, a positive correlation exists between Li and Al2O3, SiO2, as well as the Al2O3/SiO2 ratio, which subsequently transitions to a negative correlation. Conclusion: The paleoclimate's hot, humid, and rainy conditions, alongside alkaline environment, facilitate clay mineral formation and enhance the isomorphic substitution of Li+ with Al3+ and Mg2+. As desilication and aluminum enrichment intensify, Li content in bauxite rock sharply decreases, attributed to the insufficient presence of clay minerals.