安徽省岳西县碧溪岭片麻岩地球化学和锆石U-Pb年龄研究  

The geochemical characteristic and zircons U-Pb age of gneiss in Bixiling area,Anhui Province

作　　者：夏斌[1,2] 黄强太[2,3] 张玉泉[2] 崔莎莎 董冰华[2,3] 李贺[2,3] 张红[2,3] 

机构地区：[1]中山大学,广州510275 [2]中国科学院广州地球化学研究所,广州510640 [3]中国科学院研究生院,北京100049 [4]广东省有色金属地质局地质工程中心,广州510000

出　　处：《地质科学》2012年第2期376-386,共11页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家重点基础研究发展计划“973”项目(编号:2009CB219401);中国科学院地球化学研究所矿床地球化学国家重点实验室开放基金项目(编号:2009008)资助

摘　　要：本文通过对碧溪岭片麻岩综合研究表明,岩石化学成分高硅(SiO_2=73.18%～75.60%)、低铝(Al_2O_3=11.93%～12.79%)、富碱(Na_2O+K_2O=6.11%～7.23%)和高钠(Na_2O/K_2O=1.51～1.94);微量元素富集大离子亲石元素Rb、Ba、Th、U等和Pb,贫Nb、Ta、Zr、Hf、Ti等高场强元素;稀土元素含量范围变化较大(TREE=142.38～308.44×10^(-6)),富集轻稀土(LREE/HREE=5.93～6.01),和铕负异常明显(δEu=0.42～0.64)等。造岩矿物中斜长石聚片双晶常垂直晶体延长方向,以及继承锆石大部分是不同时代的岩浆碎屑锆石等,暗示其寄主岩是沉积岩;锆石LA-ICP-MS定年结果:1)获得超高压变质锆石U-Pb年龄为242 Ma;2)继承锆石U-Pb年龄,除了有比较多的属于元古代(768～639 Ma),还有大量的属于古生代(590～358 Ma)等,表明其寄主岩的时代不会早于古生代。According to the comprehensive research in this paper, the chemical composition of the gneiss in Bixiling represents high Si（SiO2 =73.18% -75.60% ）,low Al（ Al2O3 = 11.93% - 12.79% ） ,rich alkali （ Na2O ＋K/O = 6. 11% - 7.23% ） and high Na （ Na2O/K2O = 1.51 - 1.94）. And for the trace elements,large-ion lithophile elements such as Rb, Ba,Th, U and Pb are rich,while high field strength elements such as Nb,Ta, Zr, Hf and Ti are poor. For the rare earth elements （ TREE = 142.38 - 308.44 - 10-6 ）, the gneiss represents relatively rich LREE （LREE/HREE = 5.93 - 6.01 ） enrichments and obvious Eu （ δEu = 0.42 - 0.64 ） negative abnormality. The country rock of gneiss is sedimentary because of the polysynthetic twin of plagioclase grew along the vertical direction of crystal extension and most of inherited zircons were magmatic clastic zircons of different times. The date of zircon LA-ICP-MS U-Pb is 242 Ma which belongs to Indo-Chinese epoch and is equal to the Early Triassic. According to the ＂inheritance zircon＂ U-Pb different age （Proterozoic eon 768 - 639 Ma and Palaeozoic era 590 -358 Ma） ,the country rock of gneiss in Bixiling is felsic sedimentary rock which is rich in Na whose formation age is not earlier than Palaeozoic.

关 键 词：锆石U-PB年龄 地球化学 片麻岩 碧溪岭 岳西县 安徽省 

分 类 号：P588[天文地球—岩石学] P597[天文地球—地质学]