Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)

Hydrothermal veins near Dukovany and their implication to subrecent seizmic activity evaluation

 

Přemysl Pořádek, Marek Slobodník

Geoscience Research Reports 50, 2017, pages 203–206

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Published online: 31 October 2017

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Abstract

Three samples of hydrothermal vein quartz were collected from sites near the Dukovany nuclear power plant; two samples are from amphibolite (boreholes), and one sample comes from granulite (outcrop). The objective of this study was to determine the P-T-X conditions of formation of quartz veins and to verify the evidence for subrecent seizmic events.
Both primary and secondary inclusions were observed in all three samples. Only primary inclusions were studied, while the secondary inclusions were not examined in detail due to their small size. Three types of primary (pseudo secondary) fluid inclusions were distinguished based on their phase compositions: (A) The first type is represented by monophase inclusions filled with liquid CO2 and traces of CH4. (B) The second and most common type of fluid inclusions contains two phases (aqueous solution and vapour; the vapour phase occupies about 10-20 vol. % exhibiting a chemistry of H2O-NaCl ± FeCl2 ± MgCl2 ± CaCl2, wide range of salinity from 1 to 18 wt. % NaCl equivalent, and Th = 140-260 °C (samples from amphibolite), Th = 300-400 °C (sample from granulite). (C) The third type of inclusions contains three phases - two immiscible liquids (aqueous solution and CO2 ± CH4 mixture), and vapour with salinity of 2.5-4 wt. % NaCl equivalent.
Quartz veins in amphibolite are likely to have been formed from heterogeneous hydrothermal fluids (aqueous solutions and a mixture of CO2-CH4). These fluids are thought to have been derived mostly from surrounding rocks during tectonometamorphic events. The formation of quartz veins in granulite is likely to have been associated with high temperature fluids that is indicated by high homogenization temperatures. Only a few secondary fluid inclusions or their trails were identified and these inclusions usually show similar microthermometric data as the primary inclusions what implies that only insignificant number of deformations and seizmic events occurred after the formation of quartz veins.