Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Mineralium Deposita [20 p.] Critical raw materials Volcanogenic sedimentary lithium deposits Dioctahedral smectite Lithium micas Macusanite PEROU MACUSANI VOLCAN 2026 fdi:010097369 ENG Mineralium Deposita 0026-4598 ISI:001775427400001 10.1007/s00126-026-01458-z https://www.documentation.ird.fr/hor/fdi:010097369 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2026-07/010097369.pdf [Early access] Horizon (IRD) 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. 064 UR234 Pérou