Magmatic and hydrothermal evolution of the Weilasituo Sn polymetallic deposit recorded by the Li and O isotope compositions of zinnwaldite

Lithium and O isotopic compositions of zinnwaldite from magmatic (cassiterite), magmatic-hydrothermal transition (UST) and hydrothermal (tin‑tungsten, molybdenum and copper‑zinc) stages of the Weilasituo Sn polymetallic deposit and fluid inclusions in quartz are used to trace the magmatic-hydrothermal evolution. Fluid inclusion microthermometry and laser Raman analysis indicate that the H 2 O-NaCl-CO 2 -CH 4 fluids associated with the Weilasituo deposit have high to medium-high temperatures and moderate salinities . The δ 7 Li values of magmatic zinnwaldite decrease with magmatic differentiation , which cannot be explained by fractional crystallization alone and, therefore, reflect late-stage fluid exsolution . Lithium and O isotope fractionation during fluid evolution depends not only on the temperature, but also on fluid-rock reactions that affect the Li and O isotopic compositions of the fluids from the hydrothermal tin‑tungsten stage and liquid-vapor phase separations that decrease δ 7 Li and increase δ 18 O of the fluids from the copper‑zinc stage. • Zinnwaldite Li O isotope compositions are investigated at Weilasituo. • Fluid exsolution results in the decrease of δ 7 Li values in magmatic zinnwaldite. • Fluid-rock reactions and boiling affect the Li O isotopic compositions in fluids.