CONICET | Buscador de Institutos y Recursos Humanos

The Nueva Esperanza and Restauradora are two of the twenty three veins described at Capillitas mine, an epithermal precious- and base-metal vein deposit of northern Argentina. Capillitas is genetically linked to the other mineralizations of the Farallón Negro Volcanic Complex which hosts several deposits, among them two world-class porphyry deposits: La Alumbrera and Agua Rica, some smaller as Bajo El Durazno and a few epithermal deposits: Farallón Negro, Alto de la Blenda, Cerro Atajo and Capillitas.The most abundant hypogenic minerals found at these two veins are: pyrite, sphalerite, galena, chalcopyrite, tennantite-(Zn) and tennantite-(Fe), with enargite, hübnerite, gold, stannite, stannoidite, mawsonite, silver, and indium- and tellurium-bearing minerals as accessory minerals, in a gangue mainly represented by quartz. Indium participates in the structure of sphalerite, tennantite-(Zn), ishiharaite and an indium-bearing mineral, still under study, being the former the most abundant and all belonging to the fourth stage of the mineralization. The chemical composition of sphalerite shows a wide range in indium content from less than the detection limit (0.03 wt.%) to values close to 22 wt.%, always this increment in indium is accompanied by a Cu increase with a ratio In:Cu that remains almost constant at 1:1 atoms per formula unit. Cd reaches values up to 0.68 wt.%, while Fe is almost absent from the structure of sphalerite and all the other sought elements (Ga, Ge, As, Se, Ag, Sn, Sb, Te, Au, Pb and Bi) are below their detection limits. The indium-bearing tennantite-(Zn) is scarcely restricted to the area where ishiharaite lies and has small amounts of indium (up to 0.24 wt.%), while ishiharaite and the indium-bearing mineral, though extremely scarce, carry up to 10 and 30 wt.% In, respectively.The zoning in sphalerite and the variable indium-content of the different bands could be ascribed to significant fluctuation in the composition of the fluids (possibly pulses) during the fourth stage of the mineralization, evidenced by the presence of a high f Te2 mineral like calaverite and a low f Te2 phase as silver in the same stage, with local periodic saturation on In and Cu that could also be associated with recurring reactivation of fractures.