Zinc and cadmium isotope signatures: Insights into ore genesis and exploration strategies at the Xiaohongshilazi Pb-Zn-(Ag) deposit, Northeast China

• Zn-Cd isotopic signatures suggest the Xiaohongshilazi deposit is an MVT-like deposit. • Rayleigh fractionation is responsible for the Zn-Cd isotopic variation of sphalerite. • Further prospecting potential is indicated by Zn isotopic distillation model. • Zn-Cd isotopes are effective proxies for mineral exploration of Pb-Zn deposit. The Jizhong–Yanbian Cu-Mo-Au-Pb-Zn polymetallic metallogenic belt is a major nonferrous and precious metal resource base in Northeastern China. The genesis of ore deposits in this district has remained controversial. To constrain ore genetic models and provide information for exploration, we conducted precise Zn-Cd isotopic measurements on sphalerite and galena. The δ 66 Zn AA–ETH values of galena and sphalerite range from −0.07‰ to 0.03‰ and −0.68‰ to −0.12‰, respectively; and their δ 114/110 Cd NIST SRM 3108 values vary from −0.96‰ to 3.83‰ and −0.63‰ to 0.77‰, respectively. Our study suggests that the Xiaohongshilazi Pb-Zn-(Ag) deposit should be classified as a Mississippi Valley Type (MVT)-like deposit, because both its geological, sulfide trace elemental, and S-Pb-Fe-Zn-Cd isotopic characteristics are similar to those of the typical MVT deposit, except for the differences of the wall rocks. Rayleigh fractionation during sphalerite precipitation is identified as the primary mechanism for Zn-Cd isotopic variations, which is validated by the Zn-Cd fractionation models from 100 °C to 250 °C. Finally, we propose an ore prospecting model based on migration pathways of ore-forming fluid and the Zn isotopic fractionation model of sphalerite under 100 °C. This model indicates potential resources undiscovered at shallow/peripheral and deep zones of current mining level in both the Eastern and Western Ore Block, with parts of the potential resources having been corroborated by recent drilling. Despite the complexity of mineralization, processes, this study provides new insights into the application of Zn-Cd isotopes in understanding ore genesis and guiding mineral exploration in similar contexts.