Majzlan J., Berkh K., Koděra P., Števko M., Bakos F. & Milovský R., 2016: A mineralogical, fluid inclusion, and isotopic study of selected epithermal Ag-Au occurrences in the Banská Štiavnica–Hodruša-Hámre ore district, Western Carpathians. Acta Geologica Slovaca, 8, 2, 133–147.

A mineralogical, fluid inclusion, and isotopic study of selected epithermal Ag-Au occurrences in the Banská Štiavnica–Hodruša-Hámre ore district, Western Carpathians

Juraj Majzlan¹, Khulan Berkh¹, Peter Koděra², Martin Števko³, František Bakos⁴ & Rastislav Milovský⁵

¹Institute of Geosciences, Friedrich-Schiller University, Carl-Zeiss Promenade 10, D-07745 Jena, Germany; Juraj.Majzlan@uni-jena.de
²Department of Geology of Mineral Deposits, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 842 15 Bratislava, Slovakia
³Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, 842 15 Bratislava, Slovakia
⁴Green View, Nevädzová 5, 821 01 Bratislava, Slovakia
⁵Earth Science Institute, Slovak Academy of Sciences, Ďumbierska 1, 974 01 Banská Bystrica, Slovakia

Abstract

Here we present new data for samples from Treiboltz, Rabenstein, Bursa, Trojkráľová, and Schöpfer, all occurrences of epithermal ores in the Banská Štiavnica-Hodruša-Hámre ore district. The ores at Treiboltz and Rabenstein are simple hydrothermal breccias or silicified zones. The breccias contain strongly altered lithoclasts, the ore-bearing quartz, and latest drusy quartz. Fluid inclusions were found only in the late quartz, with salinities of 1.5-5.5 wt.% NaCl eq. and homogenization temperatures between 200-300 ºC. The drillhole samples from Bursa contain only weak base-metal mineralization (pyrite, galena, sphalerite, chalcopyrite). Fluid inclusions were measured in quartz that is likely associated with sulfide precipitation and late calcite that fills cavities in the ores. All these inclusions have similar salinity and homogenization temperature ranges as those reported for Treiboltz and Rabenstein. Rich ore samples from the Schöpfer vein, one of the largest ore veins in Hodruša-Hámre, revealed astonishing complexity at microscale. They show growth of minerals into open space in a dynamic environment, with frequent changes between precipitation of quartz and carbonate (mostly Mn-calcite) and pseudomorphs of quartz after bladed calcite. Adularia is also common in some zones. The ores comprise base-metal minerals and abundant polybasite-pearceite and electrum. Unusual chemical variability of carbonates associated with the ores could be a sign of sudden fluid change prior to ore precipitation. Fluid inclusions measured in different types of quartz and calcite gave salinities of 1.0-5.5 wt.% NaCl eq. and homogenization temperatures mostly between 200-300 ºC. Calculated isotopic composition of the fluids suggest large proportion of meteoric waters in these fluids.

Key words: epithermal veins, Banská Štiavnica-Hodruša, mineralogy, fluid inclusions, stable isotopes

Manuscript received: 2016-08-30

Revised version accepted: 2016-12-05