High-resolution mineralogy of Lithium-rich Tuff from the Macusani Volcanic Field, Puno, Peru
Résumé
With Li contents ranging as high as ~2,000 to 4,000 ppm, the so-called Lithium-rich Tuff in the Macusani Volcanic Field hosts the main lithium resource in the recently discovered Falchani Project in southeastern Peru. These tuffs comprise quartz, plagioclase (albite), K-feldspar (sanidine), trioctahedral micas (zinnwaldite + lepidolite), kaolinite ± halloysite, and dioctahedral smectites, in addition to cristobalite and mordenite in a few samples. The highest Li contents (3,000-4,200 ppm Li) are found in the central portion of the Lithium-rich Tuff sequence, which is characterized by micas + kaolinite subgroup minerals ± mordenite. In the upper and lower domains of the tuff sequence, Li contents reach values of 2,000 ppm and the mineralogy is dominated by micas + dioctahedral smectite ± kaolinite ± halloysite. Lithium is contained mostly in zinnwaldite and lepidolite, and probably also adsorbed onto, or in interlayer positions in clay minerals