投稿时间：2023-06-13
修订日期：2024-01-24
网络发布日期：2024-06-26
中文摘要:滇西北红牛-红山斑岩-矽卡岩型大型铜矿床位于格咱铜多金属矿集区中部，其成矿作用与晚白垩世花岗质岩浆活动存在密切联系，矿区内发育燕山晚期花岗斑岩-石英二长斑岩复式岩体，矿体主要产于斑岩体以及与斑岩有关的矽卡岩中。铜钼矿化在空间上的分布具有明显的差异性，深部揭露的花岗斑岩发育弱黄铜矿化、辉钼矿化，而石英二长斑岩中发育较强的铜钼矿化，局部出现全岩矿化的特点，总体表现出浅部、接触带矿化程度高，向深部逐渐降低的趋势，导致这种差异的原因尚未明确。在详细的岩相学观察基础上，文章对复式岩体中的黑云母开展了EMPA及LA-ICP-MS原位微区分析，旨在查明矿区花岗斑岩-石英二长斑岩复式岩体形成时的物理化学条件以及导致二者含矿差异性的制约因素。结果表明，2种类型黑云母具有低Al，高Mg、Ti的特征，均属于镁质黑云母；黑云母成分显示红牛-红山燕山晚期复式岩体为具壳幔混源特征的I型花岗岩，属于高温、浅成-超浅成相、高氧逸度岩体。花岗斑岩结晶温度为737~751℃，压力为46~72 MPa，对应深度1.74~2.73 km，平均为2.17 km；石英二长斑岩结晶温度为722~754℃，压力为37~58 MPa，对应深度1.42~2.20 km，平均为1.91 km，氧逸度略高于花岗斑岩。花岗斑岩中黑云母的Ⅳ(F)值为0.91~1.06，Ⅳ(Cl)值为-4.67~-4.48，石英二长斑岩中黑云母Ⅳ(F)值为0.56~0.77，Ⅳ(Cl)值为-5.16~-4.81，与花岗斑岩共存的热液流体log(fH2O/fHF)fluid值为1.31~1.47，与石英二长斑岩共存的热液流体log(fH2O/fHF)fluid值为0.96~1.17，表明该复式岩体2种岩性均显示高F、Cl特征，石英二长斑岩流体中更富含HCl和HF。这些特征表明红牛-红山燕山晚期复式岩体具有同时发生Cu、Mo矿化的潜力，并且Cu、Mo元素更趋向于在石英二长斑岩中富集。较高的氧逸度和卤素含量可能是导致石英二长斑岩和花岗斑岩含矿差异性的主要原因。
Abstract:The Hongniu-Hongshan porphyry-skarn large-scale copper deposit in northwestern Yunnan is located in the central part of the Gezan copper polymetallic ore concentration area. The mineralization of this deposit is closely related to the Late Cretaceous granitic magmatic activity, and the Late Yanshanian granite porphyry-quartz monzonitic porphyry composite pluton is developed in the area. The ore bodies are mainly disseminated and veinlet in the porphyry and porphyry-related skarn. The spatial distribution of copper-molybdenum mineralization is obviously different. In the deep part, granite porphyry with weak chalcopyrite and molybdenite mineralization is exposed, while strong copper-molybdenum mineralization is developed in the shallow quartz monzonite porphyry. The characteristics of whole rock mineralization are generally characterized by high degree of mineralization in the shallow and contact zone, and gradually decreasing to the deep. The reasons for this difference are not yet clear. On the basis of detailed petrographic observation, Electron Microprobe Analysis (EMPA) and Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS) techniques were used to investigate the major and minor element compositions of biotite in the composite rock mass, so as to identify the physicochemical conditions of the granite porphyry-quartz monzonitic porphyry composite pluton in this area and the restrictive factors leading to the difference of ore-bearing between the two rocks. The results show that the two types of biotite have the characteristics of low Al, high Mg and Ti, and both belong to magnesian biotite. The biotite composition shows that the Hongniu-Hongshan Late Yanshanian composite rock mass is an I-type granite with crust-mantle mixed source characteristics, which belongs to high temperature, shallow-ultrashallow phase and high oxygen fugacity rock mass. The crystallization temperature of granite porphyry is 737~751℃, the pressure is 46~72 MPa, corresponding to the depth of 1.74~2.73 km, with an average of 2.17 km. The crystallization temperature of quartz monzonite porphyry is 722~754℃, the pressure is 37~58 MPa, and corresponding to the depth of 1.42~2.20 km, with an average of 1.91 km, the oxygen fugacity is slightly higher than that of granite porphyry. The Ⅳ(F) values of biotite in granite porphyry are 0.91~1.06, and the Ⅳ(Cl) values are -4.67~-4.48. The Ⅳ(F) values of biotite in quartz monzonite porphyry are 0.56~0.77, and the Ⅳ(Cl) values are -5.16~-4.81. The log(fH2O/fHF) fluid values of hydrothermal fluid coexisting with granite porphyry are 1.31~1.47, and the log(fH2O/fHF) fluid values of hydrothermal fluid coexisting with quartz monzonite porphyry are 0.96~1.17. It shows that the two lithologies of the complex rock mass show high fluorine and chlorine characteristics, and the fluid of quartz monzonite porphyry is more rich in HCl and HF. These characteristics indicate that the Hongniu-Hongshan Late Yanshanian composite pluton has the potential for simultaneous copper and molybdenum mineralization. Moreover, copper and molybdenum elements tend to be enriched in quartz monzonite porphyry. Higher oxygen fugacity and halogen content may be the main reason for the difference in ore-bearing between quartz monzonite porphyry and granite porphyry.
keywords:biotite element geochemistry crystallization temperature petrogenesis and mineralization Hongniu-hongniu copper deposit southwestern Sanjiang
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基金项目:本文得到云南黄金集团校企合作项目（编号：KKF0202121292）、国家自然科学基金项目（编号：42362010）、云南省高层次科技人才及创新团队选拔专项（编号：202305AT350004-4）和云南省三江成矿系统与评价顶尖团队培育项目（编号：202305AS350015）联合资助
引用文本：
周杰虎,刘学龙,周云满,赵成峰,陶兴雄,魏志毅,李守奎,曹振梁,李方兰,陆波德,刘雪.2024.滇西北红牛-红山铜矿床复式岩体黑云母特征及成岩成矿指示意义[J].矿床地质,43(3):503~526ZHOU JieHu,LIU XueLong,ZHOU YunMan,ZHAO ChengFeng,TAO XingXiong,WEI ZhiYi,LI ShouKui,CAO ZhenLiang,LI FangLan,LU BoDe,and LIU Xue.2024.Geochemical characteristics of biotite from composite pluton and its implications for diagenesis and mineralization in Hongniu-Hongshan copper deposit, northwestern Yunnan[J].Mineral Deposits43(3):503~526
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