矿床地质2024，Vol.43Issue(3)：503-526,24.DOI:10.16111/j.0258-7106.2024.03.003
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
Geochemical characteristics of biotite from composite pluton and its implications for diagenesis and mineralization in Hongniu-Hongshan copper deposit,northwestern Yunnan
摘要
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 mon-zonitic 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 obvi-ously different.In the deep part,granite porphyry with weak chalcopyrite and molybdenite mineralization is ex-posed,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 Abla-tion 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 con-ditions of the granite porphyry-quartz monzonitic porphyry composite pluton in this area and the restrictive fac-tors 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 fu-gacity 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.TheⅣ(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 val-ues of hydrothermal fluid coexisting with quartz monzonite porphyry are 0.96～1.17.It shows that the two litholo-gies 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 halo-gen content may be the main reason for the difference in ore-bearing between quartz monzonite porphyry and granite porphyry.关键词
黑云母/元素地球化学/结晶温度/成岩成矿作用/红牛-红山铜矿/西南三江Key words
biotite/element geochemistry/crystallization temperature/petrogenesis and mineralization/Hongniu-hongniu copper deposit/southwestern Sanjiang分类
天文与地球科学引用本文复制引用
周杰虎,陆波德,刘雪,刘学龙,周云满,赵成峰,陶兴雄,魏志毅,李守奎,曹振梁,李方兰..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,2024,43(3):503-526,24.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 （编号:KKF0202121292）
