ABSTRACT
The Idrija mercury deposit, western Slovenia, is hosted within Carboniferous to Middle Triassic sedimentary rocks. Geochemical organic, inorganic, and isotopic (C, O, S) data help to constrain the ore fluid composition and pathway. The δ13C and δ18O variations of host and late void filling carbonates record hydrothermal alteration along fault zones and mineralized horizons. The cinnabar δ34S values range between −19.8 and +22.0‰ suggesting distinct sulfur sources (magmatic, seawater sulfate, sedimentary pyrite or organo-sulfur compounds). Idrija ore is stained by hydrothermal highly aromatic petroleum.
