Indium distribution in sphalerites from Pitkäranta mining district (South Karelia, Russia)
Ivashchenko V. I.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2021. V. 150. N 3. P. 50-67
The high-precision analytical study of sphalerites from Pitkäranta ore deposits used microprobe and La-ICP-MS analyses. Average concentrations of minor (Fe, Cu, Mn, Cd) and trace elements (In, Сo, Ni, Ga, Ge, As, Ag, Sn, Sb, Te, Au, Tl, Pb, Bi) in sphalerite were calculated from 169 analyses. It is shown that most of analyzed elements are present in sphalerite as isomorphic components. The average content of In in sphalerite is 1927 ppm, and its maximum content is 1.5 wt %. The In-enriched sphalerite displays medium concentrations of Fe (3–6 wt % Fe), low Mn contents (300–400 ppm), but high Co ones (0.1–0.2 wt %). Parameters of the “indium window”, favorable for penetration of the maximum entering of indium into the sphalerite crystalline lattice, according to the scheme Cu+ + In3+ ↔ 2Zn2+, correspond to 0.6–1.2% Cd. The highest contents of In in sphalerite are characteristic for chalcopyrite-free ore-bearing mineral associations. However, for the properly indium mineral – roquesite, the sphalerite-chalcopyrite association is typical. Sphalerite in this association is distinguished by low content of In (260–657 ppm). Ratio of In contents in sphalerite and chalcopyrite (InZn/InCu) in roquesite-bearing associations varies from 2 to 4, while in roquesite-free assemblages it is much higher (from 10 to 215). In distribution in studed sphalerite, having also an elevated contents of Cd, Ag and Au, indicate that roquesite-free propylitized skarns with Sn–Zn–Fe mineralization in sites with relatively abrupt (40°–50°) dipping of the Salmi rapakivi massif roof, and without Li–F granites, are most perspective for indium and those other metals (Kitelä deposit, Kuolismajoki and Hopunlampi ore occurrences).
Keywords: sphalerite, indium, roquesite, skarns, granite rapakivi, Pitkäranta Mining District