The mechanisms that concentrated metals in the world’s single largest nickel–copper–platinum-group element (Ni–Cu–PGE) sulfide deposit, the Jinchuan deposit in northwestern China, remain enigmatic. Nickel and Cu isotopes are novel isotopic systems that may fill this knowledge gap as they are major constituents of sulfide melt, the main carrier of economically important metals. Sulfide ores in the Jinchuan deposit are characterized by systematically high δ60/58Ni and δ65Cu values, which are positively correlated (r2 = 0.84), and show well-defined correlations with PGEs, S, Ni, and Cu contents, and Ni/Pd, Cu/Pd, and Pd/Ir ratios. The isotopic signatures can be best explained by the early segregation of sulfide melt at depth prior to ascent of the parental magmas, storing isotopically light Ni and Cu in deep magma chambers. Subsequent sulfide melt segregation and fractionation in shallow portions of the magmatic conduit generated the currently explored sulfide ores, with heavy and positively correlated Ni–Cu isotopic signatures. Therefore, hidden deep orebodies are promising targets for further exploration beneath the Jinchuan deposit.

The Tuwu–Yandong belt contains five porphyry Cu deposits (Fuxing, Yandong, Tuwu, Linglong, and Chihu), constituting the largest Cu metallogenic belt in Northwest China. However, the metallogenic framework for porphyry Cu deposits in the belt remains controversial. Rhenium-osmium dating of molybdenite from the Tuwu, Linglong, and Chihu deposits and comparisons with previous geochronological data of five deposits suggest that two episodes (335–330 Ma and 323–315 Ma) of porphyry Cu–Mo mineralization occurred in the Tuwu–Yandong belt, and the metals were mainly sourced from the mantle. Moreover, combined with the geodynamic framework of this belt, the compressional environment may be more favorable for porphyry Cu mineralization, and further exploration into the Early Carboniferous porphyry Cu deposits in this belt is expected.