Tellurium-rich mineralization in submarine magmatic–hydrothermal systems: Insights from the TA25 East vent field, Tonga arc

Copper-rich hydrothermal chimneys from the TA25 East vent field (TA25 EVF) in the Tonga Arc contain exceptionally high Te concentrations, reaching up to 1650 ppm in bulk samples. Here, we integrate mineralogical and geochemical data to constrain the occurrence and partitioning of Te and to clarify the processes responsible for its enrichment in an arc-related submarine hydrothermal system. Tellurium is hosted both as lattice-bound Te in sulfide minerals and as discrete polymetallic tellurides and native Te. Its distribution is governed by fluid evolution during chimney growth: under relatively reduced conditions, Te is preferentially incorporated into sulfide lattices, whereas fluid–seawater mixing decreases Te solubility and promotes the precipitation of tellurides and native Te, mainly through an increase in pH and, to a lesser extent, cooling. Sulfide recrystallization further redistributes Te and promotes its local reprecipitation as discrete Te-bearing phases along the grain boundaries of earlier sulfides. Mineralogical, geochemical, and sulfur isotope evidence collectively indicates a strong magmatic volatile contribution to hydrothermal mineralization at the TA25 EVF. Key evidence includes the occurrence of enargite–tennantite, specular hematite, and telluride–kaolinite clusters; enrichment in epithermal-suite elements (Au, Ag, As, Sb, Te, Bi, and Hg); elevated pyrite Te/As (up to 0.3) and Te/Sb (up to 6.58) ratios; sulfide δ 34 S values (+0.85 ‰ to + 5.12 ‰) that may record seawater modification of a magmatic volatile-derived sulfur contribution; and CO 2 -rich (600–2500 ppm) hydrothermal plumes. Strong whole-rock associations among Au, Bi, and Te, together with polymetallic telluride assemblages and locally melt-like textures, suggest that aqueous transport may not fully account for their enrichment and that Bi–(Te)-rich melts could have played an additional role in Au scavenging. Additionally, fluid-controlled decoupling of Au from Te and Bi indicates pronounced small-scale chemical heterogeneity in hydrothermal fluids within a single vent field (∼371 m), reflecting spatially variable mixing among magmatic volatiles, hydrothermal fluids, and seawater along caldera-controlled fluid pathways. Consequently, our results underscore the importance of coupled magmatic–hydrothermal processes in driving Te enrichment in arc-related seafloor hydrothermal systems.