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藏西北多龙矿集区拿若斑岩铜(金)矿床磷灰石矿物学特征及地质意义

Mineralogical characteristics and geological significance of apatite in the Naruoporphyry Cu(Au)deposit in Duolong ore district,northwestern Xizang(Tibet)
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摘要 拿若矿床目前是藏西北改则县多龙矿集区第三大斑岩型铜(金)矿床,前人开展了系统的成岩成矿年代学、成矿地质背景等研究,但空间蚀变分带和岩浆演化过程等方面研究较为薄弱。笔者等以拿若矿床磷灰石作为研究对象,在大量钻孔科研编录的基础上,开展了磷灰石矿物学和矿物化学研究,探讨拿若矿床磷灰石矿物彩色阴极发光特征与蚀变分带的耦合关系,揭示含矿岩浆演化期次及氧化还原状态。磷灰石彩色阴极发光特征显示,拿若矿床磷灰石彩色阴极发光(CL)特征主要表现为黄褐色、绿色—亮黄色和灰黑色,分别对应未蚀变、钾化蚀变和绢英岩化蚀变环境,磷灰石彩色CL特征与其所处蚀变环境的关系验证了笔者等重新厘定的拿若矿床斑岩系统“双钾化带”空间蚀变分带结构。磷灰石电子探针(EPMA)主量元素测试结果显示,磷灰石的CaO=53.5%~56.5%,P_(2)O_(5)=39.5%~42%,F=1.26%~3.24%,Cl=0.01%~1.99%,SO_(3)=0~1.28%,由此计算的X_(F)=0.68~1.76,XCl=0.001~0.58,X_(OH)=0.21~1.05。不同类型、阶段的磷灰石挥发分(F、Cl、OH)、SO_(3)等成分含量变化趋势反映了拿若矿床岩浆—热液演化过程发生了气体饱和→流体出溶→金属沉淀的过程,并揭示了成矿岩浆高氧逸度的性质。此外,环带状岩浆磷灰石反映了隐爆角砾岩系统发育了三期次岩浆作用,并指示了第I、III期岩浆活动具有更高氧逸度特征,与成矿关系更加密切。因此,笔者等认为在多期次岩浆热液叠加型斑岩铜矿床中,磷灰石在辅助厘定蚀变类型和反演岩浆—热液演化过程中具有重要的价值。 The Naruo Cu(Au)deposit is currently the third biggest in the Duolong ore concentrated area in northwestern Xizang(Tibet).The study on chronology of petrogenesis an mineralization,metallogenic geological background,and so on,have been conducted comprehensively,but research on spatial alteration zoning and magmatic development process is quite limited.The apatite of the Naruo deposit serve as the study subject in this work.The study of apatite mineralogy and major elements geochemistry is carried out on the basis of a large number of drilling scientific research catalogs,and the colorful cathodoluminescence features of the apatite in the Naruo deposit are described.The coupling connection with alteration zone indicates the development stage of ore-bearing magma as well as the redox state change rule.The apatite in the Naruo deposit is mostly yellow—brown,green—bright yellow,and gray-black,correlating to unmodified magma,potassic alteration,and sericitization alteration,respectively.Those relationship validated the spatial alteration zoning structure of the“double potassic zone”of the Naruo deposit porphyry system,which was redefined in this work.The main element test results of apatite via EPMA show that CaO=53.5%~56.5%,P_(2)O_(5)=39.5%~42%,F=1.26%~3.24%,Cl=0.01%~1.99%,SO_(3)=0~1.28%,and the calculated X_(F)=0.68~1.76,XCl=0.001~0.58,X_(OH)=0.21~1.05.The change trend of elements such as volatile components(F,Cl,OH)and SO_(3) of apatite in different types and stages reflects the process of gas saturation fluid exsolution metal precipitation in the magmatic hydrothermal evolution of the Naruo deposit,and reveals the nature of high oxygen fugacity of the ore-forming magma.In addition,the zonal magmatic apatite reflects that the cryptoexplosive breccia system has developed three stages of magmatism,and indicates that the I and III stages of magmatism are characterized by high oxygen fugacity,which are more closely related to mineralization.This paper therefore holds that the multiphase magmatic hydrothermal alteration superimposed porphyry copper deposits can also benefit greatly from apatite inversion of the magmatic hydrothermal evolution process and auxiliary determination of alteration zoning in addition to the concealed porphyry copper deposits in the till covered area.
作者 李发桥 唐菊兴 宋扬 林军 林彬 杨欢欢 唐攀 郑明 郭朵朵 LI Faqiao;TANG Juxing;SONG Yang;LIN Jun;LIN Bin;YANG Huanhuan;TANG Pan;ZHENG Ming;GUO Duoduo(MNR Key Laboratory of Metallogeny and Mineral Resource Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing,100037;Tibet Jinlong Mining Co.,Ltd,Ali,Xizang(Tibet),859299;Southwest University of Science and Technology,Mianyang,Sichuan,621010;Resources Exploration Laboratory,China University of Geosciences,Beijing,100083;Tibet University,Lhasa,850000)
出处 《地质论评》 CAS CSCD 北大核心 2024年第3期885-906,共22页 Geological Review
基金 国家重点研发计划项目(编号:2022YFC2905001) 中国地质科学院基本科研业务费项目(编号:JKYZD202316、JKYQN202331) 地质调查局项目(编号:DD20230054、DD20230358、DD20230286)的成果。
关键词 矿物学 矿物化学 磷灰石 斑岩型矿床 拿若 西藏 mineralogy mineral chemistry apatite porphyry deposit Naruo deposit Duolong ore concentrated area Xizang(Tibet)
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