东天山镜儿泉花岗伟晶岩型锂铍矿中石榴子石的地球化学特征:岩浆过程和稀有金属矿化的指示  

Geochemical Characteristics of Garnet from Jing'erquan Granitic Pegmatite-type Lithium-beryllium Deposit in East Tianshan,China:Implications for Magmatic Processes and Rare-metal Mineralization

作　　者：依力扎提·居马洪 凤永刚 雷如雄[1] 吴昌志 唐国卿 JUMAHONG Yilizhati;FENG Yong-gang;LEI Ru-xiong;WU Chang-zhi;TANG Guo-qing(School of Earth Sciences and Resources,Chang'an University,Xi'an 710054,Shaanxi,China;Laboratory of Mineralization and Dynamics,Chang'an University,Xi'an 710054,Shaanxi,China;Xinjiang Natural Resources and Ecological Environment Research Center,Urumqi 832104,Xinjiang,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学成矿作用及其动力学实验室,陕西西安710054 [3]新疆自然资源与生态环境研究中心,新疆乌鲁木齐832104

出　　处：《地球科学与环境学报》2025年第1期16-33,共18页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(91962214);长安大学中央高校基本科研业务费专项资金项目(300102271302)。

摘　　要：石榴子石是花岗岩和花岗伟晶岩中的常见副矿物之一,能够保留岩浆演化和稀有金属矿化等重要信息。镜儿泉稀有金属矿床是东天山最为典型的花岗伟晶岩型锂铍矿床,其岩浆演化过程及Li-Be-Nb-Ta等稀有金属富集成矿动力学背景仍不清楚。对该矿床的白云母花岗岩和锂辉石伟晶岩中的石榴子石开展了电子探针(EPMA)及激光剥蚀电感耦合等离子质谱(LA-ICP-MS)仪原位微区主量、微量元素分析。结果表明:镜儿泉白云母花岗岩和锂辉石伟晶岩中的石榴子石主要以锰铝-铁铝榴石的固溶体形式产出,两端元组分总和超过95%,表现为富Mn、贫Ca的特征;白云母花岗岩中石榴子石富集重稀土元素(HREE)、亏损轻稀土元素(LREE)并具有Eu负异常,而锂辉石伟晶岩中石榴子石则以重稀土元素亏损和Eu负异常显著为特征,且Y、Sc、HREE含量在伟晶岩阶段有下降的趋势。综上所述,镜儿泉锂辉石伟晶岩中的石榴子石为典型的岩浆成因,石榴子石中Li、Na、Y、REE等元素具有耦合替代现象,随着岩浆分异程度增加,REE和Y含量呈递减趋势。此外,富锂伟晶岩中石榴子石具有较高的Nb、Ta含量,对伟晶岩铌钽矿化具有重要的指示意义。Garnet is one of common accessory minerals in granites and granitic pegmatites,and is capable of preserving crucial information regarding magma evolution and rare-metal mineralization.The Jing'erquan rare-metal deposit is the most representative granitic pegmatite-type lithium-berylium deposit in East Tianshan.The magmatic evolution processes and the metallogenic dynamic background for Li-Be-Nb-Ta enrichment are still unclear.EPMA and LA-ICP-MS in-situ microanalyses were conducted on garnets from the spoduemene-type pegmatite and its host muscovite granite from Jing'erquan rare-metal deposit.The results show that garnets in the muscovite granite and spoduemene-type pegmatite predominantly occur as spessartine-almandine solid solution,with the sum of the two endmember contents exceeding 95%,exhibiting Mn enrichment and Ca depletion;the garnet from the muscovite granite is enriched in HREE,depleted in LREE,and shows negative Eu anomaly,whereas the garnet from the spoduemene-type pegmatite is characterized by gradual depletion of HREE and significant negative Eu anomaly;the contents of Y,HREE,and Sc of the garnets exhibit a decreasing trend at the pegmatite stage.In general,the garnet in Jing'erquan spoduemene-type pegmatite is of typical magmatic origin.Trace elements including Li,Na,REE,and Y exhibit coupled substitution in the garnet,and the contents of REE and Y decrease with increasing magma differentiation.In addition,the garnets from the lithium pegmatite at Jing'erquan rare-metal deposit also show high Nb and Ta,which is capable of indicating Nb-Ta mineralization in granitic pegmatites.

关 键 词：稀有金属伟晶岩 花岗岩 石榴子石 微量元素 微区分析 岩浆演化 东天山 

分 类 号：P618.71[天文地球—矿床学]