Published: Apr 2020
Pages: 85 - 112
Abstract: The Tatric Superunit of the Western Carpathians hosts many ore deposits and occurrences. Inspection of innumerable surface and underground outcrops, drill cores, and hand specimens in the past allowed to distinguish these mineralisation stages, ordered from the oldest to the youngest ones: molybdenite, scheelite, arsenopyrite–pyrite–gold, stibnite–sphalerite–Pb–Sb-sulfosalts, dolomite–baryte–tetrahedrite, siderite–ankerite, quartz–tourmaline, quartz– Cu-sulfide, galena–sphalerite, baryte, and hematite stages. This work gives a detailed account of the mineralogy, fluids, depth of formation, and stable isotope signatures of these stages, based on the extensive published and unpublished literature. The early molybdenite, scheelite, and arsenopyrite–pyrite–gold stages contain fluid inclusions with low-salinity (0–10 wt. % NaCl eq.), CO2-rich aqueous fluids. The homogenisation temperatures (TH) are 300–350 °C, in agreement with the results of arsenopyrite and chlorite geothermometry. Estimated formation depth is down to 12 km and stable isotopes (δ18O, δD) suggest a metamorphic source of the fluids and the genetic association with orogenic gold deposits. The voluminous stibnite–sphalerite–Pb–Sb-sulfosalts stage originated from aqueous fluids (with NaCl–KCl, below halite saturation), with traces or without CO2, and TH of 105–170 °C. This stage was concluded with precipitation of senarmontite, kermesite or other oxygen-bearing ores, suggesting increase of oxygen fugacity in the terminal phases of ore precipitation, and perhaps an influx of meteoric water. The rich assemblages of Sb minerals at the deposits in the Malé Karpaty Mts. allows to trace the evolution of the hydrothermal systems in the f O2–f S2–T space. The calculated δ18O fluid values for the siderite–ankerite stage may correspond to marine or formation waters influenced by the isotopic exchange with high-grade metamorphic rocks. The siderite–ankerite, galena–sphalerite and dolomite–baryte–tetrahedrite stages are related to NaCl–CaCl2 fluids, often supersatured with respect to halite at room temperature. Some fluid inclusions showed higher TH (230–290 °C), confirmed also by myrmekitic breakdown of meneghinite. Later fluids with TH of 120–170 °C were recorded at many localities of these stages.
Keywords: Mineralisation stages, sulfosalts, fluid inclusions, stable isotopesDownload PDF document