The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Trace element distribution and variations within inactive chimneys provide critical insights into submarine volcanic-hosted hydrothermal mineralization. To reveal the evolution of hydrothermal fluids during chimney growth, various pyrites in two zoned inactive chimney samples derived from basaltic-hosted Xunmei Hydrothermal field (26°S) on the Mid-Atlantic Ridge were analyzed by in-situ LA-ICP-MS. Morphologically different pyrite becomes more idiomorphic and denser with increasing temperature from the outer chimney wall to the intermediate zone, then to the inner zone, with late-stage pyrite filling interstice pores. The distribution of trace elements in pyrites across the chimney indicates a strong dependence on time, temperature, and associated sulfide minerals. Systematic variations in trace elements of different pyrites indicate that the hydrothermal system most likely evolved from low-temperature low-chloride liquid-dominated fluids (enriched in Zn, Cd, Tl, Ag, Pb, Mn, Mo, and V) to higher temperature, vapor-dominated fluids (Cu, Au, Te, and Bi), and then to high-temperature fluids (Co and Se). In the waning stage of the hydrothermal system, circulating hot fluids in auxiliary conduits were depleted in most trace elements. LA-ICP-MS time-depth reveals that Cu, Zn, Cd, Tl, Ag, Te, and Bi are associated with micro-/nano-inclusions, Co, Se, and Mo with lattice substitutions, and As, Pb, Au, and Sb with both occurrences. Adsorbed films on pyrites control the distribution of V and Mo. The incorporation of trace elements in pyrites evolves with fluid evolution, shifting from trapping micro-/nano-inclusions and surface adsorption, which are more frequent at lower temperatures, to lattice substitution, which occurs more often at higher temperatures.

pyrite, trace elements, LA-ICP-MS, hydrothermal fluid evolution, Xunmei hydrothermal field