Epithermal metal deposits along convergent plate margins are of large economic value, however, the origin of the typical metal spectrum (Au, Ag, Sb, As, Hg) in these deposits remains debated. Here, we study the Hg isotope geochemistry of the vein-style Erdaokan Ag-Pb-Zn deposit of epithermal type in the eastern part of the Central Asian Orogenic Belt in NE China, to provide direct constraints on its metal source. Bulk ore samples and early-stage hydrothermal minerals (magnetite, pyrite, and quartz) show negative 8202Hg (-1.52 to -0.18%) and positive A199Hg (-0.03 to 0.17%) values similar to those of previously reported epithermal Au deposits in NE China, and also of marine systems in general. However, latestage calcite shows weak negative to positive 8202Hg (-0.61 to 0.90%) and significant negative A199Hg (-0.18 to -0.02%), similar to the Late Paleozoic sandstone country rocks (8202Hg, -1.09 to 0.76%; A199Hg, -0.09 to 0.04%). Hydrothermally altered gabbro and diorite show large variations in 8202Hg (-1.83 to 0.50%) and A199Hg (-0.14 to 0.15%) which overlap with those of the ore and country rocks, indicating a mixed source. The A199Hg signature in the bulk ore and early-stage hydrothermal minerals likely derives from dehydration of the subducted oceanic slab, whereas Hg in late-stage calcite is likely derived from the sedimentary country rocks. Hydrothermal deposits in different tectonic settings have distinct A199Hg signals, and our study suggests that Hg isotopes are a robust tool to distinguish metal sources of hydrothermal ore deposits. (c) 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 

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