| Summary: | Selenium-rich Au⁻Ag mineralization has been discovered in the Kremnica ore district, central Slovakia. The mineralization is hosted by a single quartz⁻dolomite vein hosted by Neogene propyllitized andesites of the Kremnica stratovolcano. Ore mineralogy and crystal chemistry of individual ore minerals have been studied here. The early base-metal ore mineralization composed of pyrite, sphalerite, and chalcopyrite lacks selenium, whereas the superimposed Au⁻Ag paragenesis is Se-enriched. The Au⁻Ag alloys, uytenbogaardtite, minerals of the galena⁻clausthalite series, acanthite⁻naumannite series, diaphorite, miargyrite, pyrargyrite⁻proustite, polybasite group, minerals of the tetrahedrite group and andorite branch (andorite IV, andorite VI, Ag-excess fizélyite), freieslebenite, and rare Pb⁻Sb sulphosalts (scaiinite, robinsonite, plagionite) have been identified here. Besides selenides, the most Se-enriched phases are miargyrite, proustite⁻pyrargyrite, and polybasite⁻pearceite, whose Se contents are among the highest reported worldwide. In addition, one new phase has been found, corresponding to a Se-analogue of pearceite containing 2.08⁻3.54 <i>apfu</i> Se. The style of mineralization, paragenetic situation, and chemical trends observed in individual minerals are comparable to those of Au⁻Ag low-sulphidation epithermal Au⁻Ag mineralizations of the Kremnica and neighboring Štiavnica and Hodruša-Hámre ore districts. However, the pronounced enrichment in selenium is a specific feature of the studied vein only.
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