Chalcopyrite from the Cu–PGE sulfide deposits in the Eastern Gabbro, Coldwell Complex, Canada, exhibit a > 2‰ variation in δ65Cu. In the Marathon deposit, the δ65Cu of chalcopyrite increases from the lower Footwall Zone (− 1.49 to − 0.75‰), to the Main Zone (− 1.04 to 0.08‰), to the upper W Horizon (− 0.35 to 1.07‰). In the northern deposits, chalcopyrite at Four Dams and Sally have δ65Cu that range from − 0.08 to 0.47‰ and − 0.59 to − 0.05‰, respectively. Notably, samples from the Marathon deposit with lower chalcopyrite δ65Cu values tend to have higher S/Se and Cu/Pd ratios. Integrated geological and geochemical evidence suggests that secondary hydrothermal alteration and redox processes are unlikely to have been the primary causes of the observed Cu isotope variation. Numerical modeling of δ65Cu–Cu/Pd–S/Se of mineralization in the Eastern Gabbro illustrates three key aspects of Cu isotope behavior in magmatic Ni–Cu–PGE systems. First, R factors less than ~ 10,000 can exhibit significant control on the δ65Cu of sulfides. Second, sulfide liquid–silicate melt fractionation factors for Cu (Δ65Cusul–sil) greater than − 0.5‰ are applicable to Ni–Cu–PGE systems. Third, sulfide segregation exhibits no measurable control on the δ65Cu of sulfides at degrees of fractionation typical of Ni–Cu–PGE systems (< 0.3%). In the Marathon deposit, the range of δ65Cu–S/Se–Cu/Pd is attributed to the addition of Archean sedimentary Cu to a pool of sulfide liquid located at depth, followed by progressive dilution of the contaminated δ65Cu–S/Se signature and decrease in Cu/Pd ratio by influxes of uncontaminated pulses of magma (i.e., increasing R factor), some of which had Cu isotope compositions heavier than the mantle. Variably contaminated and enriched, with respect to Pd, sulfides from this pool were entrained by magma pulses and emplaced to form the Marathon deposit. This contribution demonstrates that Cu isotopes can fractionate at high temperatures and, when combined with other geochemical proxies, can be valuable in characterizing magmatic–post-magmatic processes in Ni–Cu–PGE sulfide deposits and for identifying PGE-rich sulfide deposits.

中文翻译：

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加拿大 Coldwell Complex 东部辉长岩管道型 Cu-PGE 矿化的 Cu 同位素系统学

来自加拿大 Coldwell Complex 东部辉长岩中 Cu-PGE 硫化物矿床的黄铜矿的 δ65Cu 变化大于 2‰。在 Marathon 矿床中，黄铜矿的 δ65Cu 从下盘带（- 1.49 到 - 0.75‰），到主带（- 1.04 到 0.08‰），到上 W 层（- 0.35 到 1.07‰）增加。在北部矿床中，四坝和 Sally 的黄铜矿的 δ65Cu 分别为 - 0.08 至 0.47‰ 和 - 0.59 至 - 0.05‰。值得注意的是，来自 Marathon 矿床的黄铜矿 δ65Cu 值较低的样品往往具有较高的 S/Se 和 Cu/Pd 比率。综合地质和地球化学证据表明，二次热液蚀变和氧化还原过程不太可能是观察到的 Cu 同位素变化的主要原因。东部辉长岩矿化的 δ65Cu-Cu/Pd-S/Se 数值模拟说明了岩浆 Ni-Cu-PGE 系统中 Cu 同位素行为的三个关键方面。首先，小于 ~ 10,000 的 R 因子可以显着控制硫化物的 δ65Cu。其次，大于 − 0.5‰ 的 Cu (Δ65Cusul-sil) 硫化物液态硅酸盐熔体分馏因子适用于 Ni-Cu-PGE 系统。第三，在 Ni-Cu-PGE 系统的典型分馏度（< 0.3%）下，硫化物偏析对硫化物的 δ65Cu 没有可测量的控制。在 Marathon 矿床中，δ65Cu-S/Se-Cu/Pd 的范围归因于太古宙沉积铜添加到位于深处的硫化物液体池中，随后被污染的 δ65Cu-S/Se 特征逐渐稀释和由于未受污染的岩浆脉冲的流入，Cu/Pd 比率降低（即，增加 R 因子），其中一些具有比地幔重的铜同位素组成。就 Pd 而言，该池中的硫化物受到不同程度的污染和富集，被岩浆脉冲夹带并形成 Marathon 矿床。这一贡献表明，Cu 同位素可以在高温下分馏，并且当与其他地球化学指标结合时，在表征 Ni-Cu-PGE 硫化物矿床中的岩浆-后岩浆过程和识别富含 PGE 的硫化物矿床方面具有重要价值。