辽宁赛马碱性岩体异性石化学成分特征及其蚀变组合对碱性岩浆-热液演化的指示意义  

Chemical composition and alteration assemblages of eudialyte in the Saima alkaline complex,Liaoning Province,and its implication for alkaline magmatic-hydrothermal evolution

作　　者：邬斌 王汝成[2] 刘晓东[1,3] 郭国林 宋振涛[4] WU Bin;WANG RuCheng;LIU XiaoDong;GUO GuoLin;SONG ZhenTao(State Key Laboratory Breeding Base 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;Jiujiang University, Jiujiang 332005, China;Airborne Survey and Remote Sensing Center of Nuclear Industry, Shijiazhuang 050002, China)

机构地区：[1]东华理工大学省部共建核资源与环境国家重点实验室培育基地,南昌330013 [2]南京大学内生金属矿床成矿机制研究国家重点实验室,南京210023 [3]九江学院,九江332005 [4]核工业航测遥感中心,石家庄050002

出　　处：《岩石学报》2018年第6期1741-1757,共17页Acta Petrologica Sinica

基　　金：国家自然科学青年基金项目(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(2017-LAMDK07);东华理工大学博士启动基金(DHBK2016124)联合资助

摘　　要：辽宁赛马碱性岩体早年因产铀矿而闻名,该岩体主要由响岩、霞石正长岩和异霞正长岩组成,其中铀、锆和稀土等元素矿化主要集中于异霞正长岩岩浆阶段。异性石是异霞正长岩中特征的锆-稀土矿物,主要分为两期,晚期异性石表现出更加富集Nb、REE等高场强元素的特点。早期异性石经历了一系列的热液蚀变,根据蚀变强弱程度,蚀变矿物组合可分为:(1)异性石+钠锆石+霓石±钠沸石;(2)异性石+钠锆石+锆石+钠沸石±霓石;(3)异性石假晶,假晶主要由残余异性石+钠锆石+锆石+钠沸石+霓石+钾长石+铈硅磷灰石组成。相比于岩浆锆石,蚀变组合中次生锆石具有富Ca、Al、Fe的特点,与异性石本身化学成分和流体性质密切相关。通过对异性石及其蚀变组合的精细矿物学研究,我们得知假晶的形成可能是异性石"溶解-再沉淀"的结果,致使假晶形成的流体至少包括:(1)占主导的富Na(±K)、Al、F的自交代流体;(2)少量晚期富Ca流体。假晶中次生锆石和铈硅磷灰石的结晶说明了Zr和REE等高场强元素的热液活动性,自交代碱性流体和富Ca流体在此过程中起到"搬运"和"提纯"的作用,这对认识碱性岩稀有、稀土成矿机制具有重要的指示意义。The Saima alkaline complex of Liaoning Province is famous for its uranium deposit in early years. This complex is mainly comprised of phonolite, nepheline syenite, and lujavrite with strong mineralization of uranium （U）,zirconium （Zr） and rare earth elements （REEs）. As the characteristic Zr and REEs-bearing mineral in the lujavrite, eudialyte can be divided to two generations with the enrichment of Nb, REEs and other HFSEs in the late stage. Early eudialyte grains have undergone varying degrees of hydrothermal alteration. Overall, the areas of weak, medium, and strong alterations are characterized by the following associations：（1） eudialyte＋secondary catapleiite＋aegirine±natrolite; （2） eudialyte＋secondary catapleiite＋zircon＋natrolite±catapleiite; （3） pseudomorph after eudialyte which consists of residual eudialyte＋secondary catapleiite＋zircon＋natrolite＋aegirine＋K-feldspar＋britholite-（Ce）. The secondary zircon grains in the alteration associations are rich in Ca, Al, and Fe when compared with magmatic zircon, which is close related to eudialyte composition and fluid nature. The careful observation of eudialyte and its alteration products reveals that the pseudomorph results from the dissolution-reprecipitation process of primary eudialyte grain. This process has involved at least two episodes of fluid activity：（1） the dominant phase, auto-metasomatic Na （±K）, Al, F-rich fluids; （2） and the secondary phase, Ca-rich fluids. The presence of secondary zircon and britholite-（Ce） in the pseudomorph suggests the hydrothermal remobilization of Zr and REE, the transportation and refinement effects of auto-metasomatic Na（±K）, Al, F-rich fluids and Ca-rich fluids, respectively. The study of chemical composition and alteration assemblages of the eudialyte in the Saima alkaline complex provides a chance to explore the mineralization mechanism of rare metal and rare earth elements in the alkaline rock.

关 键 词：赛马碱性岩体 岩浆-热液体系 异性石 高场强元素 热液活动性 

分 类 号：P575.1[天文地球—矿物学] P588.15[天文地球—地质学]