Pb-Zn-Ag vein mineralization of the central part of the Českomoravská vrchovina Upland (Czech Republic): S, C, and O stable isotope study


Authors: Malý K, Dolníček Z

Published in: Bulletin of Geosciences, volume 80, issue 4; pages: 307 - 319; Received 22 November 2004; Accepted in revised form 18 October 2005;

Keywords: polymetallic mineralization, stable isotopes, Českomoravská vrchovina Upland,

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The central part of the Českomoravská vrchovina Upland (Czech Republic) is characterized by the presence of base-metal vein mineralizations of various origins. Three groups of mineralizations were distinguished based on sulfur isotope analyses of sulfides and barite (329 analyses in total), and the carbon and oxygen isotope analyses of carbonates (124 analyses in total). 1) High-temperature mineralizations (ca 400-500 °C) show source sulfur values between +3 and +5‰CDT, and are derived from metamorphic or granitic rocks of the Moldanubicum. delta;18O values of carbonates are high; delta;13C values are low, indicating the involvement of originally organic carbon in the hydrothermal process. 2) Mesothermal mineralizations (ca 200-350 °C) show source sulfur values that are either markedly positive (up to +10‰CDT) or within the range of ca -3 to +3‰CDT. The delta;18 O values of water in the hydrothermal fluid were usually higher than 5‰SMOW, with water of low delta;18 O values being sometimes involved in the final stages of the mineralization processes (meteoric or marine waters). The values of delta;13C correspond to homogenized carbon of the Earth's crust, locally affected by carbon from marbles/limestones. 3) Low-temperature mineralization (< 130 °C) shows markedly negative sulfane fluid values, whereas the sulfate values range from +11 to +14‰CDT. In its delta;13C values, the carbon of the fluids corresponds to homogenized crustal values (with local influence of carbon from limestones and oxidized organic matter). The water of the hydrothermal fluid shows values around 0‰SMOW, thus indicating a prevalence of (i) marine water, (ii) meteoric water, or (iii) a mixture of waters of various origins in the hydrothermal system. The first and the third mineralization types can be considered as distinct genetic categories (minerogenetic type): high-temperature mineralizations are genetically associated with Variscan magmatic and metamorphic processes, while the low-temperature mineralizations are genetically associated with hypersaline brines of a still controversial but possibly marine origin. The mesothermal type most probably includes mineralizations genetically linked with a variety of geological processes.