摘要
定年和示踪一直是伟晶岩成岩成矿过程和稀有金属富集机制研究的关键问题。副矿物不仅是伟晶岩中稀有稀土元素的重要载体,还蕴含丰富的微量元素并常常具有较高的U-Th含量,是研究伟晶岩年代学、成岩成矿过程和物质源区的“理想探针”。伟晶岩中常用的适合于U-Pb同位素定年的副矿物有锆石、铌钽铁矿、独居石、锡石、榍石、褐帘石、磷钇矿和磷灰石等。由于封闭温度、矿物学特性和不同性质流体中元素行为的差异,伟晶岩中不同副矿物的U-Pb系统常表现出复杂的年龄谱系,可能记录了伟晶岩中潜在的后期地质过程,如:自交代、后期变质与流体改造等。因此,基于前期光学显微镜、扫描电镜、冷阴极发光、激光拉曼光谱分析等矿物微观结构研究,对不同期次或世代的副矿物进行原位微区U-Pb定年及主微量元素和同位素地球化学分析,对于全面认知多期地质事件和伟晶岩成岩成矿过程演化历史,进而更准确地构建其构造-岩浆-热液-成矿作用时空框架具有重要的科学意义。
Dating and tracing have been fundamental scientific issues in the study of pegmatite petrogenesis,mineralization processes,and rare metal enrichment mechanisms.Accessory minerals within pegmatites play a crucial role in this endeavor,serving not only as reservoirs for rare metals and rare earth elements but also as hosts for significant concentrations of trace elements like Th and U.This dual functionality positions them as an ideal probe for unravellingthe geochronology,petrogenesis,and mineralization processes of pegmatites,as well as tracing their magmatic sources.The accessory minerals,commonly applied for U-Pb dating in pegmatites,include zircon,columbite-groupminerals,monazite,cassiterite,titanite,allanite,xenotime,and apatite.However,the U-Pbisotope systems of these minerals can exhibit complex age spectra due to their diverse closure temperatures,mineralogical characteristics,and elemental behavior in fluids with varying compositions.These age spectra may reflect post-crystallization events in pegmatites,such as auto-metasomatism,late metamorphism,and fluid alteration.Therefore,prior to U-Pb dating,comprehensive microstructural investigations of accessory minerals from different pegmatite generations are essential.Employing techniquessuch as optical microscopy,scanning electron microscopy,cold cathodoluminescence,and laser Raman spectroscopyis crucial for deciphering the complex evolutionary history of pegmatites,encompassing multiple geological events,petrogenesis,and mineralization processes.Constructing an accurate spatiotemporal framework of tectonic-magmatic-hydrothermal mineralization events related to pegmatite formation is paramount for advancing our understanding of these complex geological systems.
作者
蒋少涌
张浩翔
刘思祺
李雯恬
尹燕梁
车玉滢
苏慧敏
JIANG Shaoyong;ZHANG Haoxiang;LIU Siqi;LI Wentian;YIN Yanliang;CHE Yuying;SU Huimin(State Key Laboratory of Geological Process and Mineral Resources,School of Earth Resources,Collaborative Innovation Center for Strategic Mineral Resources Exploration,China University of Geosciences,Wuhan,Hubei 430074,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2024年第5期1573-1599,共27页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号42030811)资助的成果。
作者简介
蒋少涌,男,1964年生。教授,矿床学和地球化学专业。E-mail:shyjiang@cug.edu.cn。
