Segovia-More M. auteur aut IRD Torró L. auteur aut IRD Villanova-de-Benavent C. auteur aut IRD Ramirez-Briones J. auteur aut IRD Baby Patrice auteur aut IRD Ruiz A. I. auteur aut IRD Cuevas J. auteur aut IRD Vallance J. auteur aut IRD Monnier L. auteur aut IRD Laurent O. auteur aut IRD Salvi S. auteur aut IRD Proenza J. A. auteur aut IRD Nieto F. auteur aut IRD text journalArticle eng text/pdf reformatted digital access 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. specialized Critical raw materials Volcanogenic sedimentary lithium deposits Dioctahedral smectite Lithium micas Macusanite PEROU MACUSANI VOLCAN 064 [Early access] [20 p.] 2026 0026-4598 https://www.documentation.ird.fr/hor/fdi:010097369 10.1007/s00126-026-01458-z 0026-4598 [F B010097369] https://www.documentation.ird.fr/hor/fdi:010097369 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2026-07/010097369.pdf IRD - Base Horizon / Pleins textes 2026-07-09 2026-07-09 fdi:010097369 fre