The contributions of early potassic and later phyllic alteration stages to Cu endowment of the giant Dexing porphyry Cu–Mo–Au system in South China are determined using changes in the Cu isotope composition of hypogene chalcopyrite from three vein stages. The δ⁶⁵Cu values of chalcopyrite (δ⁶⁵Cu_cpy values) from the potassic (stage 1: -0.05‰ to 0.21‰) to the phyllic alteration stages (stage 2: -0.03‰ to 0.24‰) are relatively invariable, but chalcopyrite in the propylitic alteration stage (stage 3) has notably lower isotopic values (-0.35‰ to 0.02‰). The sharp decrease in δ⁶⁵Cu_cpy values in the latest vein stage is likely a result of precipitation of significant amounts of isotopically heavy chalcopyrite in the phyllic alteration environment. The overall isotopic evolution can be simulated, using a Rayleigh fractionation model, with the majority of Cu having precipitated during the phyllic alteration stage. By comparing our data with published Cu isotope results from other porphyry deposits, we demonstrate that the systematics of δ⁶⁵Cu_cpy values during different hydrothermal alteration stages could convincingly trace the relative timing and mechanism(s) of Cu precipitation in porphyry Cu systems. Spatial mapping of Cu isotopes at Dexing suggest that sharp decreases of δ⁶⁵Cu_cpy values in hypogene zones may be used to delineate the boundary of high-grade ore zones.

利用三个矿脉阶段次生辉石的铜同位素组成的变化，确定了华南地区巨型德兴斑岩Cu-Mo-Au系统早期和叶状蚀变阶段对Cu禀赋的贡献。从钾质（阶段 1：-0.05‰ 至 0.21‰）到叶状蚀变阶段（阶段 2：-0.03‰ 至 0.24‰）的黄铜矿的⁶⁵Cu 值（δ⁶⁵Cu_cpy 值）相对不变，但丙酸盐蚀变阶段（阶段 3）中的黄铜矿具有明显较低的同位素值（-0.35‰ 至 0.02‰）。δ在最新的矿脉阶段，δ⁶⁵Cu_cpy 值的急剧下降可能是由于在叶状蚀变环境中沉淀了大量同位素重黄铜矿的结果。可以使用 Rayleigh 分馏模型模拟整体同位素演变，其中大部分 Cu 在叶状改变阶段沉淀。通过将我们的数据与其他斑岩矿床已发表的铜同位素结果进行比较，我们证明了在不同热液蚀变阶段δ⁶⁵Cu_cpy 值的系统学可以令人信服地追踪斑岩铜系统中铜沉淀的相对时间和机制。Dexing 铜同位素的空间映射表明，在次生区中急剧下降^{δ 65}Cu_cpy 值可用于划定高品位矿带的边界。