Hydrothermal mineralization at Domašov nad Bystřicí in the Nízký Jeseník Uplands

 

Authors: Zimák J, Novotný P, Dobeš P

Published in: Bulletin of Geosciences, volume 80, issue 3; pages: 213 - 221; Received 2 December 2002; Accepted in revised form 24 March 2005;

Keywords: Moravian-Silesian Culm, hydrothermal veins, sulphides, chlorite compositional geothermometry, fluid inclusions,

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Abstract

Hydrothermal veins of the Alpine type, some of which contain sulphides of Cu, Pb, and Zn, cross-cut the Variscan flysch sequences (composed of sandstones, conglomerates, shales, and siltstones) in the Nízký Jeseník Uplands (in the NE part of the Bohemian Massif). Apart from numerous ore occurrences without economic significance, this mineralization also generated several ore deposits that were formerly worked mainly for silver and lead. Hydrothermal veins of differing type, composition, and age are abundant in the quarry at Domašov nad Bystřicí (north of a historical ore district in the Bystřice valley). The oldest of them are syntectonic veins (sometimes coarse-fibrous) composed mainly of quartz, calcite, and chlorite of the clinochlore-chamosite solid solution series; albite is sporadically present in the gangue. These veins do not contain sulphides aside from occasional pyrite. The study of primary fluid inclusions indicates solution concentrations of 15 to 23 wt.% NaCl equiv. At the studied locality, sulphides (pyrite, chalcopyrite, galena, sphalerite) occur in younger veins and veinlets composed mainly of quartz and carbonates (calcite, and minor carbonate of the dolomite-ankerite series). Three groups of fluid inclusions are distinguished based on the salinity of solutions trapped in the calcite and quartz (in wt.% NaCl equiv.) in the ranges of 17-22, 8-11, and 0.4-4.3. Homogenization temperatures of the fluid inclusions in calcite and quartz from both vein types range from 65-90 °C indicate relatively low precipitation temperatures. Thermometric data obtained by fluid inclusion techniques are not in agreement with the temperatures estimated from the chlorite compositional geothermometers that give temperatures corresponding to mesothermal conditions.