Anchimonomineralic fluorite vein mineralization was studied at six sites within the Proterozoic crystalline basement of the Brunovistulicum. The mineral composition is very simple, represented mainly by fluorite, locally accompanied by quartz and calcite. Fluid inclusion study shows that the parent fluids were low-saline (0–4.3 wt. % NaCl equiv.), low-temperature (homogenization temperatures 72–183 °C) aqueous solutions. The REE data indicate strong interaction of the fluids with host rocks. Stable isotope analyses reveal both variable oxygen isotope composition and an apparent admixture of the oxidized organic carbon in the parent fluids. The formation conditions can be easily compared with those characterizing the Neoidic (Tertiary-Quaternary) fluorite mineralization described from the North Bohemia region. The source of the fluid can be found in formation waters of the southeastern margin of the Bohemian Massif covered by the Carpathian Foredeep, Vienna Basin and Carpathian flysch nappes, which actually exhibit very similar geochemical signatures to the fluorite-precipitating fluids.