Studied locality is situated in western part of the Silesian Unit of the Outer Western Carpathians. In an abandoned monchiquite quarry at Žilina village near Nový Jičín NW–SE -trending calcite veinlet containing ferrierite-Mg has been found. Ferrierite-Mg forms colorless to red aggregates of acicular crystals about 400 μm in size. Fluid inclusions hosted by younger vein calcite showed low both homogenization temperatures (90–130 °C) and salinities (0.5–2.6 wt. % NaCl eq.). These data are consistent with vein formation during the later stage of postmagmatic hydrothermal alteration. The hydrothermal solutions represented mixed heated seawater and diagenetic water pointing to an open-system hydrothermal circulation during this stage.Studied locality is situated in western part of the Silesian Unit of the Outer Western Carpathians. In an abandoned monchiquite quarry at Žilina village near Nový Jičín NW–SE -trending calcite veinlet containing ferrierite-Mg has been found. Ferrierite-Mg forms colorless to red aggregates of acicular crystals about 400 μm in size. Fluid inclusions hosted by younger vein calcite showed low both homogenization temperatures (90–130 °C) and salinities (0.5–2.6 wt. % NaCl eq.). These data are consistent with vein formation during the later stage of postmagmatic hydrothermal alteration. The hydrothermal solutions represented mixed heated seawater and diagenetic water pointing to an open-system hydrothermal circulation during this stage
