Insights into the Heterogeneity of the Mercury Isotopic Fingerprint of the Idrija Mine (Slovenia)

To determine the range of the isotopic composition of mercury (Hg) from the Idrija mine, samples from the mine itself and from the Mercury Heritage Management Centre geological collection were analyzed. Samples from various geological periods, genesis types, ore types, formations, and excavation fields and levels were analyzed. Both Hg concentration and isotopic composition were measured. The δ202Hg ranged from −1.35‰ to 0.46‰, and the Δ199Hg ranged from −0.18‰ to 0.16‰. A relatively homogenous ore fingerprint was obtained from one of the excavation fields; otherwise, the isotopic fingerprint of the Idrija mine seems to be heterogenous. This study presents the first statistically robust constraints on the isotopic composition of Hg from the Idrija mine, which may help in further studies of the isotopic composition of similar ore bodies or the potential tracing of Hg from the mine to the environment in the vicinity or downstream of the mine.