Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Types of organicfluids of the Praque synform of the Barrandian mobilized during Variscan tectogenesis
Abstract
Syntectonic variscan veins occur throughout whole stratigraphic units of the Prague synform and Palaeozoic of the Barrandian. They differ from other (younger) vein generations in its characteristic structural positions and types of the parent fluids. Presence of organic components in fluid inclusions and within a vein mineral assemblage is much characteristic. Calcite and quartz are the principal hydrothermal phases of the veins which are somewhere completed by solid organic matter. Fluid inclusions of the minerals have been investigated by microthermometry, Raman spectrometry and fluorescence technique. Determination of organic matter was completed by gas chromatography (GS-MS). Two major fluid systems containing organic compounds are trapped in fluid inclusions: 1. liquid hydrocarbons ± aqueous solution, 2. aqueous solution ± CH4. Liquid hydrocarbons have a variable composition - from heavy black oil to volatile oil. Solid bitumens in vein cavities are interpreted as residual hydrocarbons. Aqueous solutions within studied fluid systems have generally lower salinities (2.6-7.2 mass% NaCl eq). Occurrence and distribution of organic compounds well reflect stratigraphic position and related temperature of origin – they were derived just from the surrounding host-rocks under particular burial/metamorphic conditions.
