江南造山带中段仁里‒传梓源Li-Cs-Ta型伟晶岩中副矿物的稀土元素四分组效应  

The Lanthanide Tetrad Effect of Accessory Minerals in the Renli-Chuanziyuan Li-Cs-Ta Type Pegmatite,Central Jiangnan Orogen

作　　者：汪程 王岳军 邵拥军[3] 熊伊曲 张健 李昌元 陈泽毅 WANG Cheng;WANG Yuejun;SHAO Yongjun;XIONG Yiqu;ZHANG Jian;LI Changyuan;CHEN Zeyi(Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519082,Guangdong,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,Guangdong,China;School of Geosciences and Info-Physics,Central South University,Changsha 410083,Hunan,China;MOE Key Laboratory of Environment Change and Resources Use in Beibu Gulf,Nanning Normal University,Nanning 530001,Guangxi,China;Changsha Natural Resources Comprehensive Survey Center,China Geological Survey,Ningxiang 410600,Hunan,China;Geological Bureau of Hunan Province,Changsha 410014,Hunan,China)

机构地区：[1]中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,广东珠海519082 [2]南方海洋科学与工程广东省实验室(珠海),广东珠海519082 [3]中南大学地球科学与信息物理学院,湖南长沙410083 [4]南宁师范大学,北部湾环境演变与资源利用教育部重点实验室,广西南宁530001 [5]中国地质调查局长沙自然资源综合调查中心,湖南宁乡410600 [6]湖南省地质院,湖南长沙410014

出　　处：《大地构造与成矿学》2024年第3期478-492,共15页Geotectonica et Metallogenia

基　　金：国家自然科学青年基金项目(42302235);中山大学中央高校基本科研业务费专项资金(23ptpy143)联合资助。

摘　　要：Li-Cs-Ta(LCT)型伟晶岩是我国Li、Nb、Ta、Be等关键金属的重要资源类型,其副矿物的稀土元素四分组效应(TE1,3)是表征花岗伟晶质岩浆演化过程和稀有金属成矿效应的重要参数,但其形成机制还存在较大的争议。本文选择江南造山带中段仁里‒传梓源LCT型伟晶岩中的副矿物(独居石、磷灰石、石榴子石和铌钽铁矿)为研究对象,旨在揭示其稀土元素四分组效应的形成机制及其与花岗伟晶质岩浆演化过程的耦合关联。仁里‒传梓源四类LCT型伟晶岩带中副矿物均具有相似的“M”型稀土元素四分组效应,且表现出一致的Eu负异常,表明这些副矿物是从具有“M”型稀土元素四分组效应和强烈Eu亏损的岩浆中同时结晶的。随着微斜长石‒钠长石伟晶岩→钠长石伟晶岩→钠长石‒锂辉石伟晶岩的演化,副矿物的稀土元素含量逐渐降低,Y/Ho和TE1,3值升高,暗示矿物结晶分异与副矿物的稀土元素四分组效应存在一定的联系,但矿物的结晶分异可能并不是副矿物稀土元素四分组效应形成的直接原因。岩浆演化过程中矿物的结晶分异会使熔体富集挥发分,挥发分中的氯与稀土元素的络合作用可能是LCT型伟晶岩中副矿物产生稀土元素四分组效应的根本原因。LCT(Li-Cs-Ta)type pegmatite is an important resource type of Li,Be,Nb,Ta,and other rare metals in China.The lanthanide tetrad effect(TE1,3)in accessory minerals is an important parameter for characterizing the evolution of granitic pegmatitic magma and the metallogenic effects of rare metals,but its formation mechanism remains controversial.In this paper,accessory minerals(monazite,apatite,garnet and columbite-tantalite)from the Renli-Chuanziyuan LCT-type pegmatite zone in the central Jiangnan Orogen were analyzed,aiming to reveal the formation mechanism of the lanthanide tetrad effect and its coupling relationship with the evolution of granitic pegmatitic magma.These accessory minerals from the Renli-Chuanziyuan LCT-type pegmatite zone have similar“M”type rare-earth element tetrad effects and show consistent negative Eu anomalies,indicating that these accessory minerals crystallized simultaneously from a class of magmas with“M”type rare-earth element tetrad effects and strong Eu deficits.With the evolution of microcline-albite pegmatite→albite pegmatite→albite-spodumene pegmatite,the rare earth element contents of the accessory minerals gradually decrease,and the Y/Ho ratio and TE1,3 increase,suggesting that the mineral crystallization differentiation is related to the lanthanide tetrad effect of the accessory minerals.However,the crystal differentiation of minerals may not be the direct cause of the lanthanide tetrad effect.In the process of magmatic evolution,the crystallization and differentiation of minerals lead to the enrichment of volatile components in the melt.The complex interaction between chlorine and rare earth elements in the volatile components may be the root cause of the lanthanide tetrad effect in LCT pegmatite.

关 键 词：稀土元素四分组效应 LCT伟晶岩 仁里‒传梓源 江南造山带 

分 类 号：P612[天文地球—矿床学] P595[天文地球—地质学]