Abstract:

Based on Cu isotope compositions of loess from Xifeng loess section, Gansu Province, average value of δ⁶⁵ Cu in crust is determined. According to distribution of Cu isotope in various sources, types of ore deposit as well as copper-bearing minerals, authors suggest the composition Cu isotope be used to trace ore-forming temperature, fluid exsolution, mineralization process and deep mineralization. Values of  δ⁶⁵ Cu in low-temperature deposits vary more largely than those in high-temperature deposits. Cu isotopes fractionated during the fluid exsolution and the light Cu isotope is preferentially enriched in the early exsoluted fluid while heavy Cu isotope enriched in later exsoluted fluid. In a metallogenic province, different deposits with the same genesis have the similar composition of Cu isotope, which can be used to distinguish whether they are product of a same mineralization event. When ore-forming materials including Cu leached from the region, the heavy Cu isotopes are preferentially leached than the light Cu isotope. In addition, in an oreforming system, light Cu isotope enrichment of leaching cap may reflect strong leaching occurred, and then indicates the Cu mineralized enrichment zone occur in deep.

Key words: Xifeng loess, Cu isotopes, temperature of metallogenesis, fluid exsolution, source variations