Iron oxide copper-gold (IOCG) deposits form in spatial and genetic relation to hydrothermal iron oxide-alkali-calcic-hydrolytic alteration and thus show a mappable zonation of mineral assemblages toward the orebody. The mineral zonation of a breccia matrix-hosted orebody is efficiently mapped by regularly spaced samples analyzed by the scanning electron microscopy-integrated mineral analyzer technique. The method results in quantitative estimates of the mineralogy and allows the reliable recognition of characteristic alteration as well as mineralization-related mineral assemblages from detailed mineral maps. The Ernest Henry deposit is located in the Cloncurry district of Queensland and is one of Australia’s significant IOCG deposits. It is known for its association of K-feldspar altered clasts with iron oxides and chalcopyrite in the breccia matrix. Our mineral mapping approach shows that the hydrothermal alteration resulted in a characteristic zonation of minerals radiating outward from the pipe-shaped orebody. The mineral zonation is the result of a sequence of sodic alteration followed by potassic alteration, brecciation, and, finally, by hydrolytic (acid) alteration. The hydrolytic alteration primarily affected the breccia matrix and was related to economic mineralization. Alteration halos of individual minerals such as pyrite and apatite extend dozens to hundreds of meters beyond the limits of the orebody into the host rocks. Likewise, the Fe-Mg ratio in hydrothermal chlorites changes systematically with respect to their distance from the orebody. Geochemical data obtained from portable X-ray fluorescence (p-XRF) and petrophysical data acquired from a magnetic susceptibility meter and a gamma-ray spectrometer support the mineralogical data and help to accurately identify mineral halos in rocks surrounding the ore zone. Specifically, the combination of mineralogical data with multielement data such as P, Mn, As, P, and U obtained from p-XRF and positive U anomalies from radiometric measurements has potential to direct an exploration program toward higher Cu-Au grades.

中文翻译：

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绘制 ERNEST HENRY 氧化铁铜金矿床的矿物分带：使用模态矿物学引导铜金矿化

氧化铁铜-金 (IOCG) 矿床的形成与热液氧化铁-碱-钙-水解蚀变具有空间和成因关系，因此显示出朝向矿体的矿物组合的可绘制分带。通过扫描电子显微镜-集成矿物分析仪技术分析的规则间隔样品有效地绘制了角砾岩基质矿体的矿物分带。该方法可对矿物学进行定量估计，并允许从详细的矿物图中可靠地识别特征变化以及与矿化相关的矿物组合。Ernest Henry 矿床位于昆士兰的 Cloncurry 区，是澳大利亚重要的 IOCG 矿床之一。它以角砾岩基质中钾长石蚀变碎屑与氧化铁和黄铜矿的结合而闻名。我们的矿物测绘方法表明，热液蚀变导致矿物从管状矿体向外辐射的特征分带。矿物分带是一系列钠质蚀变、钾蚀变、角砾化，最后是水解（酸）蚀变的结果。水解蚀变主要影响角砾岩基质，并与经济矿化有关。黄铁矿和磷灰石等个别矿物的蚀变晕从矿体边界延伸数十至数百米，进入主岩。同样，热液绿泥石中的 Fe-Mg 比随着它们与矿体的距离而系统地变化。从便携式 X 射线荧光 (p-XRF) 获得的地球化学数据以及从磁化率计和伽马射线光谱仪获得的岩石物理数据支持矿物学数据，并有助于准确识别矿石带周围岩石中的矿物晕。具体而言，矿物学数据与多元素数据（如从 p-XRF 获得的 P、Mn、As、P 和 U）和辐射测量的正 U 异常数据相结合，有可能将勘探计划导向更高的 Cu-Au 品位。