In situ monazite isotopes reveal mantle fluids for giant Jiaodong gold mineralization

The giant Jiaodong gold province features gold mineralization ~ 1.9 Ga younger than its Precambrian host rocks, with the origin of its ore-forming fluids long debated. Here, we use in situ U–Pb geochronology and Sm–Nd isotope compositions of hydrothermal monazite to constrain fluid sources across ten representative gold deposits at Jiaodong. Monazite U–Pb ages define a synchronous regional metallogenic event at 120 ± 5 Ma. Hydrothermal monazite yields εNd(t) values of − 22.36 to − 10.96, and numerical mixing models show these large variations are best explained by variable degrees of fluid–rock interaction between enriched lithospheric mantle-derived fluids and different host rocks. Our results confirm mantle-derived fluids as the source of Jiaodong’s giant gold mineralization and demonstrate significant fluid–rock interaction during ore formation. Our study further shows that linking in situ U‑Pb dating and Sm‑Nd isotope analyses provide an efficient approach for resolving the genesis of hydrothermal gold deposits. Mantle-derived fluids from an enriched lithospheric mantle likely contributed to Jiaodong’s large gold deposits, with notable fluid–rock interaction during formation, according to geochemical analysis of hydrothermal monazite and numerical mixing models of Jiaodong gold deposits.