新疆阿尔泰可可托海矿区伟晶岩成因与矿化潜力研究:来自石英SEM-CL和微量元素的指示  

A study of the genesis and mineralization potential of pegmatites in the Koktokayore district,Altay,Xinjiang:Indications from SEM-CL and trace elements in quartz

作　　者：曹冲[1,2] 申萍 冯浩轩[1,3] 罗耀清 楚翔凯 任文斌 CAO Chong;SHEN Ping;FENG HaoXuan;LUO YaoQing;CHU XiangKai;REN WenBin(Key Laboratory of Mineral Resources of Chinese Academy of Sciences,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Key Laboratory of Mining Development and Safety Technology of Hebei Province,North China University of Science and Technology,Tangshan 063210,China;University of Chinese Academy of Sciences,Beijing 100049,China;Xinjiang Rare Metals Co.,Ltd.,Fuyun 836300,China)

机构地区：[1]中国科学院地质与地球物理研究所,中国科学院矿产资源研究院重点实验室,北京100029 [2]华北理工大学,河北省矿业开发与安全技术重点实验室,唐山063210 [3]中国科学院大学,北京100049 [4]新疆稀有金属有限责任公司,富蕴836300

出　　处：《岩石学报》2024年第3期889-906,共18页Acta Petrologica Sinica

基　　金：新疆维吾尔自治区科技计划项目(2020E01043);河北省自然科学基金面上项目(D2023209016);国家自然科学基金项目(42002098、91962213);新疆维吾尔自治区人民政府国家305项目办公室、新疆维吾尔自治区“天池英才”引进计划联合资助.

摘　　要：新疆阿尔泰可可托海3号脉矿床是世界瞩目的伟晶岩型稀有金属Li-Be-Nb-Ta-Rb-Cs-Hf矿床。尽管前人对3号脉伟晶岩矿床已经进行了大量的研究工作,然而在伟晶岩稀有金属成矿潜力以及伟晶岩成因问题上仍存在一些争议。本文以发育在可可托海矿区不同规模的伟晶岩脉以及淡色花岗岩为研究对象,利用石英SEM-CL和原位微量元素技术手段,查明各伟晶岩脉和花岗岩的稀有金属禀赋差异及成因联系。研究结果表明,石英的Li和Al含量可以用来指示伟晶岩的矿化潜力。与1号和2号伟晶岩脉相比,3号伟晶岩脉具有更宽的分异范围,以石英中Ge/Ti变化于1.83×10^(-6)~159×10^(-6)范围为特征,更高的Li含量,其中外侧带平均Li含量为39×10^(-6),因而成矿潜力最大。此外,证实了白云母钠长花岗岩为矿化花岗岩,其微量元素组成和演化程度与3号脉伟晶岩外侧带相当,而白云母碱长花岗岩为贫矿花岗岩。更重要的是,本文利用各伟晶岩结构分带内的石英中Ge/Ti-Ge以及Ge/Ti-Al/Ti图解,确定了各伟晶岩脉具有相似的演化趋势,指示它们可能源于相同的花岗岩母岩。与世界上典型的RMG(花岗岩浆演化后残余熔浆结晶)和DPA(直接深部地壳熔融)成因的伟晶岩相比,可可托海矿区含矿伟晶岩和花岗岩中石英微量元素与RMG成因伟晶岩存在地球化学亲和性,这指示它们来源于花岗质岩浆的残留熔浆。The Koktokay No.3 pegmatitic deposit in Altay,Xinjiang,China is a world-famous rare metal Li-Be-Nb-Ta-Rb-Cs-Hf deposit.In the past,a lot of research work has been carried out on the No.3 pegmatitic deposit.However,there are still some arguments about the mineralization potential and genetic relationships of different pegmatites in the Koktokay field.In this paper,quartz SEM-CL and in-situ trace element analyses are conducted to provide important constraints on the above issues.The results show that the Li and Al contents of quartz can be used to evaluate the mineralization potential of the pegmatites.Compared with No.1 and No.2 pegmatites,quartz from No.3 pegmatite has a wider range of Ge/Ti ratios(1.83×10^(-6)~159×10^(-6)),as well as higher Li contents(averaged at 39×10^(-6))in the outer zone.Thus,No.3 pegmatite is considered to have higher mineralization potential.In addition,it is confirmed that the muscovite albite granite is mineralized granite with a trace element composition and degree of differentiation similar to that of the outer zone of the No.3 pegmatite,while the muscovite alkali granite is a barren granite.More importantly,the Ge/Ti vs.Ge and Ge/Ti vs.Al/Ti diagrams of quartz from each textural zonation within pegmatites show a similar evolutionary trend at Koktokay,indicating that they may originate from the same parent granite.Compared with the pegmatites of RMG(pegmatites derived from residual melts of granite magmatism)and DPA(pegmatites as direct products of anatexis)origins in the world,quartz trace elements of the rare metal-bearing pegmatites and granitic at Koktokay have geochemical affinities with the RMG-derived pegmatites,indicating that they are derived from residual melts of granite magmatism.

关 键 词：可可托海稀有金属伟晶岩型矿床 石英微量元素 成矿潜力 岩石成因 

分 类 号：P575.3[天文地球—矿物学] P588.121[天文地球—地质学]