Mixed primary mica - secondary ion-clay volcanogenic sedimentary lithium deposits in the Neogene Macusani Volcanic Field, Puno, Peru Segovia-More, M. Torró, L. Villanova-de-Benavent, C. Ramirez-Briones, J. /Baby, Patrice Ruiz, A. I. Cuevas, J. Vallance, J. Monnier, L. Laurent, O. Salvi, S. Proenza, J. A. Nieto, F. Critical raw materials Volcanogenic sedimentary lithium deposits Dioctahedral smectite Lithium micas Macusanite The Falchani Lithium Project, a volcanogenic sedimentary deposit in the Neogene Macusani Volcanic Field (Puno, Peru), hosts > 5.5 Mt Li2CO3 resources and represents a significant potential complementary source for South American lithium production, currently dominated by Andean salar deposits of the Lithium Triangle. The ore comprises volcanogenic tuff and breccia subdivided into the Lithium-rich Tuff and stratigraphically overlying and underlying Upper and Lower Breccia units, respectively. Primary minerals include quartz, feldspars, and trioctahedral Li-F micas (zinnwaldite and lepidolite). Secondary minerals define a vertical mineralogical zonation. The Lithium-rich Tuff is characterized by abundant kaolinite and the preservation of Li-F micas, whereas the Upper and Lower Breccia are dominated by dioctahedral smectites (beidellite-montmorillonite series) with scarce, corroded relict micas. Zeolites locally occur as the predominant secondary phase in brecciated Lithium-rich Tuff samples. Lithium contents peak in the Lithium-rich Tuff (3000-4200 ppm Li), with the bulk hosted by Li-F micas, and only 7% as exchangeable Li. Conversely, the Upper and Lower Breccia units contain < 3000 ppm Li predominantly in interlayer positions of smectites, yielding high exchangeable Li proportions (63-88%). This vertical variation reflects restricted fluid flow through the impermeable Lithium-rich Tuff versus pervasive alkaline hydrothermal fluid circulation through brecciated units. Falchani is unusual in having both magmatic and authigenic lithium-rich phases. These observations support a tentative classification of Falchani as a mixed primary mica-secondary ion-clay volcanogenic sedimentary lithium deposit, a mineralization type not previously documented. 2026 text https://www.documentation.ird.fr/hor/fdi:010097369 fdi:010097369 Segovia-More M., Torró L., Villanova-de-Benavent C., Ramirez-Briones J., Baby Patrice, Ruiz A. I., Cuevas J., Vallance J., Monnier L., Laurent O., Salvi S., Proenza J. A., Nieto F.. Mixed primary mica - secondary ion-clay volcanogenic sedimentary lithium deposits in the Neogene Macusani Volcanic Field, Puno, Peru. 2026, [Early access], [20 p.] EN PEROU MACUSANI VOLCAN