ABSTRACT
Idria ore deposit is composed of epigenetic, hydrothermal, vein and disseminated mineralisation in the Upper Paleozoic and Lower Triassic sediments and syngenetic, sedimentary-exhalative Middle Triassic ore beds. It has almost monomineralic paragenesis, with the major mineral, cinnabar and rare pyrite, marcasite and metacinnabar. The fluid inclusion study revealed epithermal character of fluids (Th, 160-220°C), low to moderat salinity, between 2.1 and 5.8 wt % equ. NaCl, and CaCl2-NaCl-H2O composition, with narrow range of NaCl/CaCl2 ratios between 0.57 and 1.53. The fluids resemble, in their characteristics, to those within hydrothermal minerals in Triassic pillow lavas, formed by extrusion of basalts in the sea water.
