Geochemical constraints on critical metals in the Jajarm bauxite deposit in Northeastern Iran

Two types of bauxite lenses and horizons are found in the Jajarm mining area: A-type and B-type. The B-type bauxite lenses and horizons occur as stratiform orebodies between the shallow-marine platform carbonate of the early-middle Triassic Elika Formation and the siliciclastic and molassic sedimentary rocks of the late Triassic Shahmirzad Formation from the Shemshak Group. Lithium concentrations in the ore samples vary significantly between profiles I and II, ranging from 7.9 to 3780 ppm (mean 593.6 ppm) in profile I and 94.8 to 723 ppm (mean 392.9 ppm) in profile II. Ore samples with moderate Al₂O₃ contents (30-40 wt%) and moderate Al₂O₃/SiO₂ ratios (< 2) show markedly higher Li and REE contents. This enrichment is likely due to the preferential uptake of REE and Li by clay minerals via isomorphic substitution and surface adsorption during kaolinization and early-stage lateritization. The Jajarm deposit is thus not only a major source of Al, but also holds significant potential as a strategic resource for critical metals, such as Li, TiO₂, Ga, Nb, Ta, V, and REE. This highlights its importance as a key exploration target for future mining endeavors focused on these essential elements.