摘要
辽宁赛马岩体是我国典型的产铀碱性杂岩体,但其稀土矿化机制尚不明确.通过光学显微镜、扫描电镜和电子探针分析,得知该岩体从霞石正长岩经霓霞正长伟晶岩至晚期异霞正长岩,代表性稀土矿物层硅铈钛矿[Na2Ca4REETi(Si2O7)2OF3]不断富集,Nb、Zr和REE(特别是HREE)等高场强元素含量不断升高,部分颗粒具Zr、REE等元素成分环带,以上成分变化与稀土等不相容元素性质、碱性岩浆成分和岩浆结晶分异过程密切相关.此外,层硅铈钛矿经历了一系列的热液蚀变,蚀变部分Ti、Ca、Sr、Na含量增加而Zr、REE含量降低,最终形成由残余层硅铈钛矿+方解石+萤石+铈硅磷灰石组成的假晶,可能与富碱质、F和CO2的自交代流体作用有关.该研究揭示了碱性岩浆演化过程中,层硅铈钛矿成分变化及热液蚀变组合对指示岩浆结晶分异程度、探究稀土元素分馏及其热液活动性的具有重要意义.
The Saima complex is a typical alkaline complex with uranium mineralization in Liaoning Province,China.In order to explore its REE mineralization mechanism,the optical microscope,SEM and EPMA were used to study the rare earth minerals in the Saima complex.From nepheline syenite through aegirine-bearing nepheline syenite pegmatite to late lujavrite,the REE mineralization is characterized by the enrichment of the representative rare earth mineral,rinkite(Na2Ca4REETi(Si2O7)2OF3),the increases in Nb,Zr,REE(especially for HREE)and other high field strength elements of it,and the compositional zonation caused by compositional variations of Zr,REE and other elements in some rinkite grains.The above proportional and compositional variations of rinkite are closely related to the behavior of incompatible elements,the nature and fractional crystallization process of alkaline magma.In addition,the later series of hydrothermal alteration in the rinkite is represented by the initial enrichment in Ti,Ca,Sr,and Na but depletion in Zr and REE contents in altered parts of crystal,and ultimate pseudomorph after rinkite,which is comprised of residual rinkite+calcite+fluorite+britholite-(Ce).It is likely that an alkali,F and CO2-rich hydrothermal fluid is involved in the rinkite alteration.Our study suggests that rinkite is an ideal mineral in the aspects of deciphering the fractional crystallization of alkaline magma,fractionation behavior and hydrothermal mobilization of rare earth elements by its compositional variations and secondary alteration mineral assemblage.
作者
邬斌
王汝成
郭国林
李成祥
宋振涛
Wu Bin;Wang Rucheng;Guo Guolin;Li Chengxiang;Song Zhentao(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;State Key Laboratory for Mineral Deposits Research,Nanjing University,Nanjing 210023,China;Airborne Survey and Remote Sensing Center of Nuclear Industry,Shijiazhuang 050002,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2020年第2期467-478,共12页
Earth Science
基金
国家自然科学基金青年科学基金项目(No.41702033)
南京大学内生金属矿床成矿机制研究国家重点实验室开放研究基金(No.2017-LAMD-K07)
东华理工大学博士启动基金(No.DHBK2016124)
核资源与环境国家重点实验室自主基金(No.Z1907).
关键词
赛马碱性岩体
稀土矿化
层硅铈钛矿
岩浆-热液演化
矿物学
the Saima alkaline complex
REE mineralization
rinkite
magmatic-hydrothermal evolution
mineralogy
