藏南然巴晚中新世矽卡岩型钨矿化特征及地质意义  

Characteristics and Geological Significance of Late Miocene Skarn-Type Tungsten Mineralization in Ramba,Southern Tibet

作　　者：任春萌 郑远川[1] 李鑫[1] 高雷 徐培言 吴昌炟 杨竹森[4] Ren Chunmeng;Zheng Yuanchuan;Li Xin;Gao Lei;Xu Peiyan;Wu Changda;Yang Zhusen(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Chengdu Center,China Geological Survey,Chengdu 610081,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质调查局成都地质调查中心,四川成都610081 [3]中国地质科学院地质研究所,北京100037 [4]中国地质科学院矿产资源研究所,北京100037

出　　处：《地球科学》2024年第10期3610-3628,共19页Earth Science

基　　金：优秀青年科学基金项目(No.4202290261);碰撞造山带典型地区岩石圈三维物质架构的示踪方法(No.2019YFA0708602)。

摘　　要：然巴岩体位于北喜马拉雅带东段,主要岩石类型为二云母花岗岩,与之接触的斜长角闪岩普遍发生矽卡岩化,并伴随有白钨矿化.为限定成岩成矿年龄和成矿流体性质,采用锆石U-Pb定年、云母Ar-Ar定年、矿物地球化学等分析方法开展研究.含钨石英脉中白云母Ar-Ar年龄(6.3 Ma)与二云母花岗岩锆石U-Pb年龄(7.3 Ma)相当,表明花岗岩的侵位及相关的钨成矿作用均发生于晚中新世,为迄今区域内已知最年轻的稀有金属成矿事件.矽卡岩内石榴子石与辉石矿物对的含铁率比值(3.12~3.74)与白钨矿极低的Mo含量(12.0×10^(-6)~56.8×10^(-6))显示成矿流体为还原性,与岩浆锆石氧逸度计结果(△FMQ=-5.78~-2.08)一致.白钨矿稀土元素特征明显继承自花岗岩,指示岩浆出溶的成矿流体与富钙围岩发生反应诱发了白钨矿的沉淀.研究揭示喜马拉雅淡色花岗岩与围岩的接触变质带为稀有金属有利的成矿部位,需给予更多关注.The Ramba leucogranite,located in the eastern part of the Northern Himalaya,is mainly composed of two-mica granite.The amphibolite in contact with it is commonly skarnized and accompanied by scheelite mineralization.To qualify the diagenetic and metallogenic ages and the ore-forming fluid characters,an integrated approach involving zircon U-Pb and mica Ar-Ar dating,and mineral geochemistry was carried out.The Ar-Ar age(6.3 Ma)of muscovite from the scheelite-bearing quartz vein yielded is comparable to the zircon U-Pb age(7.3 Ma)of two-mica granite,indicating that the granite emplacement and associated tungsten mineralization both occurred in the Late Miocene,which is the youngest known rare-metal mineralization event in the region.The iron ratios of garnet and pyroxene mineral pairs within the scheelite-bearing skarn(3.12 to 3.74),and the relatively low Mo content(12.0×10^(-6)-56.8×10^(-6))of scheelite,collectively indicate that the ore-forming fluid is reduced,which is consistent with the magmatic zircon oxygen fugacity calculated results(ΔFMQ=-5.78 to-2.08).The rare-earth element characteristics of scheelite are inherited from the leucogranite granite,further indicating that the W-rich ore-forming fluid was dissolved from the evolved granitic melt and subsequently reacted with the Ca-rich wall rocks to induce the precipitation of scheelite.This study reveals that the contact metamorphic zone between Himalayan leucogranite and surrounding wall rock is a favorable site for rare-metals,and deserves attention in future prospecting.

关 键 词：喜马拉雅淡色花岗岩 接触变质带 钨成矿作用 然巴 矿床学 

分 类 号：P618.67[天文地球—矿床学]