中祁连湟源群中片麻岩的岩石学成因及构造意义  

Petrogenesis and Tectonic Implications of Gneisses from the Huangyuan Group,Middle Qilian

作　　者：张江苏[1,2] 吕志成[3] 刘明强[4] 刘铮[5] ZHANG Jiang-su;LU Zhi-cheng;LIU Ming-qiang;LIU Zheng(College of Earth Sciences1 , Chengdu University of Technology, Chengdu 610059, P. R. China;Third Geology and Mineral Resources Exploration Academy of Gansu Province2 , Lanzhou 730050, P. R. China;The Development of Chinese Geological Survey Research Center3 , Beijing 100037 , P. R. China;Geological Survey of Gansu Province4 , Lanzhou 730050 ,P. R. China;School of Earth Sciences5 , Lanzhou University, Lanzhou 730000, P. R. China)

机构地区：[1]成都理工大学地球科学学院,成都610059 [2]甘肃省地矿局第三地质矿产勘查院,兰州730050 [3]中国地质调查局发展研究中心,北京100037 [4]甘肃省地质调查院,兰州730050 [5]兰州大学地质科学与矿产资源学院,兰州730000

出　　处：《科学技术与工程》2016年第30期181-186,共6页Science Technology and Engineering

基　　金：中国地质调查局地质调查专项(1212010510407)资助

摘　　要：湟源群中的刘家台组为一套以长英质片麻岩为主,夹黑云变粒岩的低角闪岩相的中-深变质岩系。长英质片麻岩的原岩为酸性侵入岩体,其具有低CaO(1.80~1.85 wt%)、高SiO_2(68.78~71.58 wt%)和碱含量(Na_2O+K_2O=7.6~7.7 wt%)。样品相对富集轻稀土,亏损Nb、Ta、Ti等高场强元素,富集Ba、Sr等大离子亲石元素,并且具有明显的Eu负异常(δEu=0.23~0.38)。它们最主要的特征是具有较高含量的高场强元素,使得Zr+Nb+Ce+Y=(402~420)×10^(-6)(ppm)[>350×10^(-6)(ppm)],而10 000Ga/Al=3.2~3.3(>2.6)。这些岩石地球化学特征表明这套片麻岩的原岩为A型花岗岩。单颗粒锆石U-Pb同位素测年获得的不一致曲线的上交点年龄1 124±29 Ma,属中元古代,比前人认为的湟源群形成时代古元古代要年轻。The Liujiatai Formation in the Huangyuan Group is a middle-high grade metamorphic series of low amphibolites facies mainly composed of felsic gneiss with biotite granulite.The protolith of the felsic gneiss is acid intrusion.They have low CaO(1.80~1.85wt%),but high Si02(68.78~71.58wt%)and alkali contents(Na20+K20=(7.6~7.7wt%).These samples are relatively enriched in LREE and LILE(e.g.Ba and Sr),but depleted in HFSE(e.g.Nb,Ta and Ti),with the presence of notably negative Eu anomalies.They are mainly characterized by high HFSE abundances,with Zr+Nb+Ce+Y=(402~420)X10^6(ppm)[>350X10^6(ppm)]and10000Ga/Al=3.2~3.3(>2.6).All the geochemical data indicated that these gneisses show A-type affinities.LA-ICP-MS zircon U-Pb dating give a upper intercept age of1124±29Ma,implying that the Huangyuan Group was formed in the Mesoproterozoic.The new age data is evidently younger than previously thought.

关 键 词：中祁连 湟源群 中元古代 片麻岩 A型花岗岩 

分 类 号：P583[天文地球—岩石学] P584[天文地球—地质学]