The Krásná Hora, Milešov, and Příčovy Sb-Au ore deposits, Bohemian Massif: mineralogy, fluid inclusions, and stable isotope constraints on the deposit formation

• DOI: 10.1007/s00126-017-0734-8
• Publication Date: 2017-04-29T03:07:08Z
• Authors: Matěj Němec; Jiří Zachariáš
• Keywords: Stibnite; Massif; Arsenopyrite; Hypogene; Magmatic water; Ankerite

The Krasna Hora-Milesov and Přicovy districts (Czech Republic) are the unique examples of Sb-Au subtype orogenic gold deposits in the Bohemian Massif. They are represented by quartz-stibnite veins and massive stibnite lenses grading into low-grade, disseminated ores in altered host rocks. Gold postdates the stibnite and is often replaced by aurostibite. The ore zones are hosted by hydrothermally altered dikes of lamprophyres (Krasna Hora-Milesov) or are associated with local strike-slip faults (Přicovy). Formation of Sb-Au deposits probably occurred shortly after the main gold-bearing event (348–338 Ma; Au-only deposits) in the central part of the Bohemian Massif. Fluid inclusion analyses suggest that stibnite precipitated at ~250 to ~130 °C and gold at ~200 to ~130 °C from low-salinity aqueous fluids. The main quartz gangue hosting the ore precipitated from the same type of fluid at about 300 °C. Early quartz-arsenopyrite veins are not associated with the Sb-Au deposition and formed from low-salinity, aqueous-carbonic fluid at higher pressure and temperature (~250 MPa, ~400 °C). The estimated oxygen isotope composition of the ore-bearing fluid (4 ± 1‰ SMOW; based on post-ore calcite) suggests its metamorphic or mixed magmatic-metamorphic origin and excludes the involvement of meteoric water. Rapid cooling of warm hydrothermal fluids reacting with “cold” host rock was probably the most important factor in the formation of both stibnite and gold.