Abstract
Arc magmas are enriched in sulfur relative to mid-ocean ridge basalts, commonly attributed to slab-derived sulfur inputs during subduction. However, the contribution of slab fluids remains debated because sulfur concentrations in sub-arc fluids have not been directly measured. Here we quantify sulfur in slab-derived fluids preserved as multiphase fluid inclusions composed of H2O, calcite, and chalcopyrite in omphacite from ultrahigh-pressure eclogites in the Sumdo orogenic belt. Three-dimensional Raman spectroscopy reveals high sulfur concentrations averaging ~6 wt.%. Mass-balance calculations indicate that such fluids can efficiently enrich the mantle wedge and supply up to ~70% of the sulfur emitted by arc volcanism. We further suggest that chalcopyrite formed through post-entrapment reduction of oxidized sulfur species by host omphacite, followed by precipitation with co-entrapped copper and iron. Our findings identify sub-arc depths as a critical window for slab sulfur release and provide key constraints on deep sulfur cycling and copper mobilization in arc systems.
Data availability
All data supporting the findings of this study are available in the Supplementary materials and in a public repository (Figshare) at https://figshare.com/s/56febb3cbcea3e8f0e45.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (grant 42230304 to Y.X., grant 42302050 to D.-B.T. and grant 42302053 to Y.-B.L.), the National Key Research and Development Program of China (2023YFF0807103 to H.-Y.L.), and the Taishan Scholar Program of Shandong (tsqn202507278 to H.-Y.L.). We thank Dr. Wancai Li, Tingting Xiao, and Rui Shi for assistance with the EPMA analyses.
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Y.X., D.-B.T. conceived and designed the study. Y.-Y.W., H.-H.G. collected the samples. D.-B.T., H.-Y.L., D.-S.J., and X.-G.L. performed the geochemical analyses. Z.-L.G. conducted the thermodynamic modeling. D.-B.T. wrote the initial draft of the manuscript. Y.X., Y.-B.L., Carlos J. Garrido, and Timothy Kusky contributed to manuscript revision. Funding was acquired by Y.X., D.-B.T., Y.-B. L., and H.-Y. L. All authors discussed the results and contributed to the final manuscript.
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Tan, DB., Xiao, Y., Li, Y. et al. Sulfur-enriched sub-arc fluids drive deep sulfur cycling in subduction zones. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71439-3
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DOI: https://doi.org/10.1038/s41467-026-71439-3
