Photochemical processes generate mass-independent fractionation (MIF) of mercury (Hg) isotopes in the atmosphere-ocean system, and the subduction of marine sediments or hydrated oceanic crust may recycle the resultant Hg isotope signature into the volcanic-arc environment. This environment typically hosts epithermal gold deposits, which are characterized by a specific Hg-Sb-As metal association. We investigated the Hg isotopic composition of seven volcanic-arc-related epithermal gold deposits in northeast China and revisited the isotopic composition of Hg in hydrothermal ore deposits in circum-Pacific and Mediterranean volcanic arcs. The gold ore samples in northeast China mostly display positive Delta Hg-199 values (0.11 parts per thousand +/- 0.07 parts per thousand, 1 sigma, n = 48) similar to those observed in the Pacific Rim (0.07 parts per thousand +/- 0.09 parts per thousand, 1 sigma, n = 182) and the Mediterranean Cenozoic volcanic belt (0.09 parts per thousand +/- 0.08 parts per thousand, 1 sigma, n = 9). Because Hg in marine sediments and seawater has positive Delta Hg-199, we infer that Hg-bearing epithermal deposits in active continental margin settings receive most Hg from recycled seawater in marine sediments, through the release of Hg by dehydration from the subducting oceanic slab. However, negative to near-zero Delta Hg-199 values were observed in Hg-bearing deposits in the South China craton (-0.09 parts per thousand +/- 0.05 parts per thousand, 1 sigma, n = 105) and in the intraplate magmatic-hydrothermal Almaden Hg deposit in Spain (-0.02 parts per thousand +/- 0.06 parts per thousand, 1 sigma, n = 26), which are considered to relate to basement and mantle sources, respectively. Hg isotopes have the potential to trace lithospheric Hg cycling. 

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