Effect of salinity, pressure and temperature on the solubility of smithsonite (ZnCO3) and Zn complexation in crustal and upper mantle hydrothermal fluids

Modelling the reservoirs and fluxes of Zn in Earth's crust mantle requires data on solubility its mineral hosts ores coexisting fluids, as well complexation these fluids a function fluid composition, pressure, temperature. However, due to experimental challenges, availability such is limited pressures below 1 GPa, which are only representative upper conditions. Here, we report effects salinity (0–4.5 m total Cl), pressure (0.5–6 GPa) temperature (25–400 °C) smithsonite (ZnCO3) speciation aqueous fluids. Solubilities at mineral-fluid equilibria were determined situ high pressure-temperature (P-T) conditions by synchrotron X-ray fluorescence (XRF) absorption spectroscopy (XAS) using resistively heated diamond anvil cells (RH-DAC). The increases with salinity, In agreement previous studies, conducted lower (below GPa), observed gradual transition from octahedral hydrated [Zn(H2O)6]2+ tetrahedral chlorinated [Zn(H2O)4-nCln]2-n (n = 1–4) complexes increasing Our results suggest that remain stable under relevant cold slab dehydration. This change coordination further enhances Cl-rich provides likely mechanism for efficient uptake slab-derived