Indium-bearing paragenesis from the Nueva Esperanza and Restauradora veins, Capillitas mine, Argentina

[摘要] The Nueva Esperanza and Restauradora are two of the twenty-three veins described at Capillitas mine, an epithermalprecious- and base-metal vein deposit located in northern Argentina. Capillitas is genetically linked to other mineralizations of the Farallón Negro Volcanic Complex, which hosts several deposits. These include two world-class (LaAlumbrera and Agua Rica) and some smaller (e.g., Bajo El Durazno) porphyry deposits, and a few epithermal deposits(Farallón Negro, Alto de la Blenda, Cerro Atajo and Capillitas). The main hypogene minerals found at these two veins include pyrite, sphalerite, galena, chalcopyrite, tennantite-(Zn) and tennantite-(Fe). Accessory minerals comprisehübnerite, gold, silver, stannite, stannoidite and mawsonite, and also diverse indium- and tellurium-bearing minerals.Quartz is the main gangue mineral.Indium participates in the structure of sphalerite, tennantite-(Zn), ishiharaite and an indium-bearing mineral, still understudy, the former being the most abundant of these phases. The chemical composition of sphalerite shows very lowconcentrations of Fe and a wide range in indium contents from below the detection limit (0.03 wt. %) to values close to22 wt. %. Atomic proportions of In and Cu correlate positively at a ratio In : Cu = 1 : 1 atoms per formula unit. Cadmiumreaches up to 0.68 wt. %. Other analyzed elements (Ge, As, Se, Ag, Sn, Te, Au, Pb and Bi) are systematically belowtheir respective detection limits. Indium-bearing tennantite-(Zn) (up to 0.24 wt. % In) is rare and restricted to the areawhere ishiharaite appears. Ishiharaite and the unclassified indium-bearing mineral are extremely scarce and host up to10 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). They are evidenced by the presence of a high f Te2 mineral, likecalaverite, and a low f Te2 phase, such as silver, within the same stage, with local periodic increments on In and Cu thatcould also be associated with recurring reactivation of fractures.

[学科分类] 自动化工程

[关键词] Indium-bearing minerals;ishiharaite;sphalerite;epithermal;Farallón Negro Volcanic Complex;Argentina