What question did this study set out to answer?

To investigate the Hg isotopes of mafic dikes and delineate their role in the genesis of gold deposits in the Jiaodong gold province.

April 10, 2026

Hg isotope compositions of syn-gold mafic dikes confirm an anomalous metasomatized mantle lithosphere source for the giant Jiaodong orogenic gold province, China

Puntos clave

To investigate the Hg isotopes of mafic dikes and delineate their role in the genesis of gold deposits in the Jiaodong gold province.
Analyzed Hg isotopes in 101 mafic dike samples from the Jiaodong gold province.
Determined mass-independent fractionation of Hg isotopes, measuring Δ199Hg values.
Compared δ202Hg values against previous studies of auriferous materials.
Obtained Δ199Hg values ranging from −0.16‰ to 0.12‰ indicative of varying Hg contributions.
Found δ202Hg values of mafic dikes at −1.99‰, lower than auriferous pyrites and native gold grains.
Results suggest that metasomatized mantle significantly contributes to the gold deposit formation.

Resumen

The Jiaodong gold province in eastern China hosts large gold resources of ∼5700 tons Au within a relatively small area of 10,000 km2. This exceptional gold endowment is still confusing. Isochronous mafic dikes derived from the lithospheric mantle are widespread in the Jiaodong gold province and may contain key information on the genesis of the Jiaodong orogenic gold deposits. Mercury (Hg) is an important associate metal in gold deposits, and photoreactions produce mass-independent fractionation of Hg isotopes (Δ199Hg ≠ 0) in land-ocean systems. We analyzed Hg isotopes of 101 mafic dike samples from the Jiaodong gold province, which yielded an astonishingly variable spectrum of mass-independent fractionation with Δ199Hg of −0.16‰ to 0.12‰. The pronounced negative and positive Δ199Hg values suggest that the lithospheric mantle beneath the Jiaodong gold province was fertilized by both continental subduction of the Yangtze block and oceanic subduction of the paleo-Pacific plate. The contribution of Hg from subducted terrestrial and oceanic sediments yields varying Δ199Hg values in the lithospheric mantle (−0.16‰ to 0.12‰; −0.03‰ ± 0.12‰, 2SD), which aligns well with previous results for auriferous sulfides (−0.19‰ to 0.16‰; 0.01‰ ± 0.16‰, 2SD) and native gold grains (−0.08‰ to 0.02‰; −0.05‰ ± 0.07‰, 2SD), suggesting that the metasomatized lithospheric mantle is the dominant source of metals. The δ202Hg values of mafic dikes (−1.99‰ ± 0.90‰, 2SD) are much lower than previous results for auriferous pyrites (−0.27‰ ± 0.64‰, 2SD) and native gold grains (0.27‰ ± 0.87‰, 2SD) in the Jiaodong orogenic gold deposits. This is most likely caused by the exsolution of auriferous fluids from the metasomatized mantle and the subsequent depressurization boiling and immiscibility of these fluids in the crust. Our study highlights the potential critical role of dual-stage metasomatism of mantle lithosphere in creating the exceptional gold endowment of the Jiaodong gold province, during which an increased variety and volume of volatiles efficiently facilitate gold migration and deposition.

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