Research Progress on Copper Isotope in High-temperature Magmatic System and Its Implications for Magmatic Sulfide Deposits

Copper isotope exhibits significant variations during high-temperature geological processes such as mantle partial melting, magmatic differentiation, and mantle metasomatism. Notably, a ～4‰ variation in Cu isotope has been observed in magmatic Ni-Cu sulfide systems, challenging the conventional understanding that fractionation of metal stable isotopes is predominantly controlled by temperature. Beyond the Sudbury deposit, which formed via meteoritic impact, Ni-Cu deposits in intraplate and orogenic settings show a wide range of Cu isotope variations, highlighting their potential for studying complex magmatic and metallogenic processes. Current insights include: ① Cu isotope in mantle is highly heterogeneous. Mid-ocean ridge basalts and komatiites better represent the Cu isotopic composition of the mantle source. ② The coupled behavior of Cu concentrations and isotopes, as well as the fractionation coefficients between sulfides and silicates, are crucial for understanding Cu isotopic changes during magma formation and evolution. ③ Research on Cu isotope fractionation during metamorphic dehydration in subduction zones remains limited, resulting in significant uncertainty in using Cu isotope to trace Cu migration paths. Since most Cu is retained in the subducting slab, Cu isotopic deviations from mantle values in subduction-related rocks may be coincidental. ④ Cu isotope variations in Ni-Cu deposits are controlled by multiple geological processes and fractionation mechanisms, including: heterogeneity in mantle Cu isotope, crustal contamination, sulfide segregation and differentiation, and redox state changes in the magmatic system. The crucial role of Cu isotopes in revealing the processes of diagenesis and mineralization is increasingly prominent. In the future, efforts should be intensified to explore the synergistic effects of Cu isotopes with other isotope systems (such as Fe, Zn, Ni, etc.), combining experiments and simulations to refine the mineralization models of magmatic Cu-Ni sulfide deposits. This has significant implications for gaining a deeper understanding of crust-mantle material cycling and its resource effects.