【摘要】 松潘-甘孜造山带广泛分布伟晶岩型稀有金属矿床，是我国重要的稀有金属成矿带。厘清该区伟晶岩的岩浆-热液演化过程及其对稀有金属成矿的控制，对于区域勘查与找矿具有重要意义。本文以川西可尔因地区业隆沟伟晶岩型锂多金属矿床为例，基于详细的野外调查与显微观察，系统研究了含矿与不含矿伟晶岩中白云母及铌铁族矿物的显微结构与微区成分，并与可尔因二云母花岗岩中的白云母进行综合对比，旨在揭示伟晶岩与花岗岩的成因关系及Li-Be-Nb-Ta成矿机制。电子探针与LA-ICP-MS分析结果显示，从可尔因二云母花岗岩、业隆沟不含矿伟晶岩到含矿伟晶岩，白云母中Fe、Ti含量及K/Rb、Nb/Ta比值逐渐下降，而Al含量逐渐升高，反映演化程度增加；CGM1表现为结构和化学成分均一，而CGM2则发育环带与交代溶蚀结构，有时呈增生边生长于CGM1边缘。白云母与CGM的结构与成分表明，研究区伟晶岩演化经历了岩浆阶段与岩浆-热液过渡阶段两个主要阶段。在岩浆阶段（微斜长石-钠长石伟晶岩至钠长石-锂辉石伟晶岩），分离结晶促使Nb、Ta、Cs、Rb、Be、B、P等元素持续富集，而锂辉石的结晶导致体系Li含量逐渐降低，同时形成结构与成分均一、Ta含量较低的CGM1。在岩浆-热液过渡阶段（钠长石-锂辉石伟晶岩至糖粒状钠长石集合体），流体出溶过程使白云母中的Li、Cs、Rb、Nb、Ta等元素含量明显下降，同时出现环带白云母及发育环带与交代溶蚀结构的CGM2。环带白云母低Ta、Nb含量与CGM2高Ta、Nb含量对应，表明晚期富挥发分流体通过对早期矿物及围岩的交代，实现了Nb和Ta元素的小规模再富集。可尔因二云母花岗岩和业隆沟伟晶岩中白云母均具有极高Li含量。从微斜长石-钠长石伟晶岩到钠长石-锂辉石伟晶岩，白云母K/Rb和Nb/Ta变化幅度较小，显示成矿初始熔体极富Li，且后续演化程度有限。成分及显微结果表明，铌钽铁矿经历两阶段成矿：岩浆阶段形成结构与成分均一、较低的CGM1(Nb成矿)；岩浆-热液过渡阶段形成T和Mn~#较高的CGM2(Ta成矿)。此外，野外与显微观察发现，伟晶岩中普遍发育钠长石化，可作为业隆沟Nb-Ta成矿伟晶岩的重要识别标志。更多还原

【Abstract】 The Songpan-Ganze orogenic belt hosts widespread pegmatite-type rare metal deposits and represents an important raremetal metallogenic province in China.Clarifying the magmatic-hydrothermal evolution of pegmatites in this region and their control on rare-metal mineralization is of great significance for regional mineral exploration and prospecting.Taking the Yelonggou pegmatite-type Li-polymetallic deposit in the Ke’eryin area of western Sichuan as an example,this study systematically investigates the micro structures and microchemical compositions of muscovite and columbite-group minerals(CGM) in both mineralized and non-mineralized pegmatites,based on detailed field surveys and microscopic observations.Comparisons with muscovite from the Ke’eryin two-mica granite were also conducted,aiming to elucidate the genetic relationship between pegmatites and granites and the Li-Be-Nb-Ta mineralization mechanism during magmatic-hydrothermal evolution.EPMA and LA-ICP-MS results show that from Ke’eryin two-mica granite through non-mineralized to mineralized Yelonggou pegmatites,the Fe and Ti contents,as well as K/Rb and Nb/Ta ratios in muscovite,decrease progressively,while Al content increases,indicating increasing degrees of evolution.CGM1 exhibits homogeneous structure and chemical composition,whereas CGM2 develops zonation and replacement-dissolution features,sometimes growing as overgrowths on CGM1 rims.The structures and compositions of muscovite and CGM indicate that pegmatite evolution in the study area experienced two main stages:a magmatic stage and a magmatic-hydrothermal transitional stage.During the magmatic stage(from microcline-albite pegmatite to albite-spodumene pegmatite),fractional crystallization promoted continuous enrichment of Nb,Ta,Cs,Rb,Be,B and P.In contrast,continuous crystallization of spodumene gradually reduced the Li content in the system and led to the formation of homogeneous CGM1 with low Ta content During the magmatic-hydrothermal transitional stage(from albite-spodumene pegmatite to saccharoidal albite aggregates),fluid exsolution caused significant decreases of Li,Cs,Rb,Nb and Ta in muscovite,and the development of zoned muscovite and CGM2 with both zoned and replacement-dissolution structures.The low Ta and Nb in the rims of zoned muscovite correspond to the high Ta and Nb in CGM2,indicating that late-stage volatile-rich fluids induced localized reenrichment of Nb and Ta via replacement of early-formed minerals and host rocks.Muscovite in both Ke’eryin biotite monzogranite and Yelonggou pegmatites contains extremely high Li.From microcline-albite pegmatite to albite-spodumene pegmatite,the K/Rb and Nb/Ta ratios in muscovite vary little,suggesting that the initial mineralizing melt was extremely Li-rich and underwent limited subsequent evolution.Compositional and microscopic observations indicate that Columbite-group minerals underwent two stages of mineralization:the magmatic stage produced homogeneous,low-Ta CGM1(Nb mineralization),while the magmatic-hydrothermal transitional stage formed CGM2 with higher Ta~# and Mn~#(Ta mineralization).Moreover,field and microscopic observations reveal widespread albitization in pegmatites,which can serve as an important indicator for identifying Nb-Ta mineralized pegmatites in the Yelonggou area.更多还原