The Ayawilca Zn-In-Ag-Sn-Cu project is located in the Central Andean polymetallic belt of Peru. It is a carbonate replacement deposit with strong similarities to porphyry-related epithermal polymetallic ("Cordilleran") deposits in the Central Andes. Forty-two ore samples were studied for petrographic and ore mineral chemistry determinations. Within an early low sulfidation stage, the most important economically and volumetrically, three generations of Fe-rich sphalerite were identified, the second being characterized by fine disseminations of chalcopyrite and the highest indium contents (up to 1.58 wt% In). Although In-bearing sphalerite is characterized by high iron contents (between ~ 9 and 32 mol. % FeS), atomic concentrations of In and Fe do not show any visible correlation. In contrast, In and Cu correlate at Cu/In = 1 (at. proportions), which is compatible with a solid solution bet...

The tin-rich polymetallic epithermal deposit of Poopó, of plausible Late Miocene age, is part of the Bolivian Tin Belt. As an epithermal low sulfidation mineralisation, it represents a typological end-member within the “family” of Bolivian tin deposits. The emplacement of the mineralisation was controlled by the regional fault zone that constitutes the geological border between the Bolivian Altiplano and the Eastern Andes Cordillera. In addition to Sn and Ag, its economic interest resides in its potential in critical elements as In, Ga and Ge. This paper provides the first systematic characterisation of the complex mineralogy and mineral chemistry of the Poopó deposit with the twofold aim of identifying the mineral carriers of critical elements and endeavouring to ascertain plausible metallogenic processes for the formation of this deposit, by means of a multi-methodological approa...

A volcanic dome complex of Miocene age hosts the In-bearing animas-Chocaya-Siete Suyos district in SW Bolivia. Ore mineralization occurs as banded and massive infillings in sub-vertical, NE-SW striking veins. In this article, a detailed petrographic study is combined with in situ mineral geochemistry determinations in ore from the Arturo, Chorro and Diez veins in the Siete Suyos mine, the animas, Burton, Colorada, and Rosario veins in the animas mine and the Nueva vein in the Chocaya mine. A three-stage paragenetic sequence is roughly determined for all of them, and includes (1) an early low-sulfidation stage that is dominated by cassiterite, pyrrhotite, arsenopyrite, and high-Fe sphalerite (FeS > 21 mol. %); (2) a second intermediate-sulfidation stage dominated by pyrite + marcasite +/- intermediate product, sphalerite (FeS < 21 mol. %), stannite, and local famatinite; and, (3) a late i...

The Huari Huari deposit, Potosí Department in SW Bolivia, hosts polymetallic stratiform and vein mineralization of Miocene age with significant concentrations of the critical metal indium (In). Vein mineralization records document early crystallization of quartz and cassiterite followed by prominent associations of sulfides and sulfosalts. The earliest sulfide was arsenopyrite, followed by pyrrhotite, and progressively giving way to pyrite as the main iron sulfide, whereas C-u-Ag-Pb sulfosalts constitute late hypogene associations. Sphalerite is the chief ore mineral, and its crystallization is extended during most of the mineralization lifespan as evidenced by its initial cocrystallization with pyrrhotine, then with pyrite, and finally with Ag-Pb sulfosalts. The composition of sphalerite varies from early to late generations with a continuous decrease in FeS that attests to a decrease ...