Mineralization of Shangong Gold Deposit in Henan Province —Constraints from carbon, hydrogen, and oxygen isotopes

The Shanggong Gold Deposit has proven gold resources exceeding 140 t, reaching a super-large scale. In recent years, deep validation boreholes have encountered polymetallic orebodies, which have raised new requirements for understanding its mineralization. Carbon, hydrogen, and oxygen isotope analyses were conducted on quartz and ankerite from different mineralization stages of the Shanggong Gold Deposit. The results show that the δ¹⁸ \rm O_\rmH_2\rmO values of quartz range from −2.5 ‰ to 1.6 ‰, with an average of −0.4 ‰; the δ \rm D_\rmH_2\rmO values range from −94.7 ‰ to −86.5 ‰, with an average of −90.6 ‰, which are close to magmatic water. The δ¹⁸ \rm O_\rmH_2\rmO−δ \rm D_\rmH_2\rmO diagram indicates a transitional trend from meteoric water to primary magmatic water for the ore-forming fluids of gold deposits in the region. The δ¹³ \mathrmC_\mathrmCO_2 values of quartz range from −11.9 ‰ to −5.3 ‰, with an average of −7.9 ‰, which are significantly higher than those of organic matter and freshwater CO₂ but lower than those of marine carbonates, and they are comparable to those of the crust, mantle, igneous rocks/magmatic systems, and atmospheric CO₂. The δ¹³C_V-PDB values of ankerite range from −2.0 ‰ to −1.2 ‰, with an average of −1.4 ‰, which are higher than the δ¹³C composition of other carbon reservoirs except marine carbonates. Mantle degassing and magmatic processes are the main sources of δ¹³C in the Shanggong Gold Deposit. However, there is an obvious gradual transition phenomenon among gold deposits in the region, which has been significantly influenced by low-temperature alteration and meteoric water. Differences in structural settings or magmatic activity backgrounds have led to variations in the δ¹³C sources of the gold deposits.