Hypogene sulfide precipitation during phyllic alteration: insights from copper isotopic evolution of the Dexing porphyry Cu–Mo–Au deposit, South China

IF 4.4 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Jia-Feng He, Guo-Guang Wang, Matthew J. Brzozowski, Pei Ni, Xiang-Long Luo, Jun Mu, Weiqiang Li
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Abstract

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 (δ65Cucpy 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 δ65Cucpy 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 δ65Cucpy 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 δ65Cucpy values in hypogene zones may be used to delineate the boundary of high-grade ore zones.

Abstract Image

植蚀作用过程中的下生硫化物沉淀:从华南德兴斑岩铜-钼-金矿床铜同位素演化中获得的启示
利用三个矿脉阶段下伏黄铜矿铜同位素组成的变化,确定了华南德兴斑岩铜-钼-金系统早期钾盐化阶段和后期植物化阶段对铜赋存的贡献。黄铜矿的δ65Cu值(δ65Cucpy值)从钾蚀变阶段(第1阶段:-0.05‰至0.21‰)到植物蚀变阶段(第2阶段:-0.03‰至0.24‰)相对不变,但丙基蚀变阶段(第3阶段)的黄铜矿的同位素值明显较低(-0.35‰至0.02‰)。最新矿脉阶段的 δ65Cucpy 值急剧下降,很可能是在植蚀作用环境中大量同位素重的黄铜矿沉淀的结果。利用瑞利分馏模型可以模拟出整体的同位素演变过程,即大部分铜是在植蚀作用阶段沉淀的。通过将我们的数据与其他斑岩矿床已公布的铜同位素结果进行比较,我们证明不同热液蚀变阶段的 δ65Cucpy 值的系统性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。德兴铜同位素空间分布图表明,下伏带δ65Cucpy值的急剧下降可用于划分高品位矿带的边界。
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来源期刊
Mineralium Deposita
Mineralium Deposita 地学-地球化学与地球物理
CiteScore
11.00
自引率
6.20%
发文量
61
审稿时长
6 months
期刊介绍: The journal Mineralium Deposita introduces new observations, principles, and interpretations from the field of economic geology, including nonmetallic mineral deposits, experimental and applied geochemistry, with emphasis on mineral deposits. It offers short and comprehensive articles, review papers, brief original papers, scientific discussions and news, as well as reports on meetings of importance to mineral research. The emphasis is on high-quality content and form for all articles and on international coverage of subject matter.
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