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Open AccessFeature PaperArticle

Indium Mineralization in the Volcanic Dome-Hosted Ánimas–Chocaya–Siete Suyos Polymetallic Deposit, Potosí, Bolivia

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Geological Engineering Program, Faculty of Sciences and Engineering, Pontifical Catholic University of Peru (PUCP), Av. Universitaria 180, San Miguel, Lima 15088, Peru
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Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), C/Martí i Franquès s/n, 08028 Barcelona, Spain
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Instituto de Geología, Universidad Nacional Autónoma de México. Ciudad Universitaria, Coyoacán, CDMX 04510, Mexico
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Departament de Mineralogia, Museu de Ciències Naturals de Barcelona, 08003 Barcelona, Spain
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Department of Earth Sciences, University of Geneva, Rue des Maraîchers 13, 1205 Geneva, Switzerland
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Facultad de Ciencias Geológicas, Universidad Mayor San Andrés, Av. Villazón N° 1995, Plaza del Bicentenario–Zona Central, La Paz 2314, Bolivia
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Departament d’Enginyeria Minera, Industrial i TIC, Universitat Politècnica de Catalunya, Av. de les Bases de Manresa 61-73, Manresa, 08242 Barcelona, Spain
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Colegio de Geólogos de Bolivia, Edificio Señor de la Exaltación Nro. 4683, Av. Hernando Siles entre calles 1 y 2, Zona de Obrajes, Casilla 8941, La Paz, Bolivia
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Author to whom correspondence should be addressed.
Current address: Eloro Resources Ltd. Av. La Floresta 497, Of. 101, San Borja, Lima 15037, Perú.
Minerals 2019, 9(10), 604; https://doi.org/10.3390/min9100604
Received: 31 August 2019 / Revised: 21 September 2019 / Accepted: 29 September 2019 / Published: 1 October 2019
(This article belongs to the Special Issue Mineral Deposits of Critical Elements)
A volcanic dome complex of Miocene age hosts the In-bearing Ánimas–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 Ánimas, Burton, Colorada, and Rosario veins in the Ánimas 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 intermediate-sulfidation stage dominated by galena and Ag-Pb-Sn sulfosalts. Electron-probe microanalyses reveal high indium enrichment in stage-2 sphalerite (up to 9.66 wt.% In) and stannite (up to 4.11 wt.% In), and a moderate enrichment in rare wurtzite (up to 1.61 wt.% In), stage-1 sphalerite (0.35 wt.% In), cassiterite (up to 0.25 wt.% In2O3), and ramdohrite (up to 0.24 wt.% In). Therefore, the main indium mineralization in the district can be associated to the second, intermediate-sulfidation stage, chiefly in those veins in which sphalerite and stannite are more abundant. Atomic concentrations of In and Cu in sphalerite yield a positive correlation at Cu/In = 1 that agrees with a (Cu+ + In3+) ↔ 2Zn2+ coupled substitution. The availability of Cu in the mineralizing fluids during the crystallization of sphalerite is, in consequence, essential for the incorporation of indium in its crystal lattice and would control the distribution of indium enrichment at different scales. The highest concentrations of indium in sphalerite, which is found in the Diez vein in the Siete Suyos mine, occur in crustiform bands of sphalerite with local “chalcopyrite disease” texture, which has not been observed in the other studied veins. In stannite, the atomic concentrations of In are negatively correlated with those of Cu and Sn at Cu + In = 2 and Sn + In = 1. Thus, atomic proportions and correlations suggest the contextualization of the main indium mineralization in the sphalerite–stannite–roquesite pseudoternary system. View Full-Text
Keywords: critical metals; high-tech metals; indium; sphalerite; Bolivian-type deposits critical metals; high-tech metals; indium; sphalerite; Bolivian-type deposits
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Torró, L.; Cazorla, M.; Melgarejo, J.C.; Camprubí, A.; Tarrés, M.; Gemmrich, L.; Campeny, M.; Artiaga, D.; Torres, B.; Martínez, Á.; Mollinedo, D.; Alfonso, P.; Arce-Burgoa, O.R. Indium Mineralization in the Volcanic Dome-Hosted Ánimas–Chocaya–Siete Suyos Polymetallic Deposit, Potosí, Bolivia. Minerals 2019, 9, 604.

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