Hydrothermal enrichment of lithium in intracaldera illite-bearing claystones.

Developing a sustainable supply chain for the global proliferation of lithium ion batteries in electric vehicles and grid storage necessitates the extraction of lithium resources that minimize local environmental impacts. Volcano sedimentary lithium resources have the potential to meet this requirement, as they tend to be shallow, high-tonnage deposits with low waste:ore strip ratios. Illite-bearing Miocene lacustrine sediments within the southern portion of McDermitt caldera (USA) at Thacker Pass contain extremely high lithium grades (up to ~1 weight % of Li), more than double the whole-rock concentration of lithium in smectite-rich claystones in the caldera and other known claystone lithium resources globally (<0.4 weight % of Li). Illite concentrations measured in situ range from ~1.3 to 2.4 weight % of Li within fluorine-rich illitic claystones. The unique lithium enrichment of illite at Thacker Pass resulted from secondary lithium- and fluorine-bearing hydrothermal alteration of primary neoformed smectite-bearing sediments, a phenomenon not previously identified.