Variscan fluids of the Barrandian Lower Paleozoic: case study from the Žák's quarry at Velká Chuchle

Hydrothermal veins in the Paleozoic of the Barrrandian testify for fluid migration during diagenesis and/or epigenesis. A more detailed mineralogical and geochemical research of these veins has started since the end of the 20th century. The subject of a research included in this thesis is determination of conditions of formation of syntectonic calcite and quartz-calcite veins in the lokality called Žák's quarry in Velká Chuchle. This thesis is based on field determination of succession of hydrothermal veins and laboratory study of fluid inclusions in minerals as a basic tool for determination of temperatures during formation of veins. In total, there were distinguished four types/generations of calcite and quartz-calcite veins in Žák's quarry (from oldest to youngest): 1) veins of ,,beef calcite", 2) veins with flat crystals of smoky quartz located in joints perpendicular to bedding, 3) shear veins with calcite located in the big fold, 4) a big calcite vein with tectonic striae spatially bound to significant local fault. Veins have thickness aproximatelly from 1 mm to about 15 cm. By the way, veins of ,,beef calcite" are characteristic by orientation of prolonged grains of calcite in the direction orthogonal towards to the plane of vein. The microscopic study of fluid inclusions revealed presence of..