冀北赤城榴辉岩的时间序列:来自锆石SHRIMP U-Pb年龄的证据  

TIME SEQUENCE OF EVOLUTION FOR THE RRETROGRADED ECLOGITE FROM CHICHENG,NORTHERN HEBEI PROVINCE:EVIDENCE FROM ZIRCON SHRIMP U-Pb DATING

作　　者：孔旭[1] 倪志耀[1] 翟明国[2] 石玉若[3] 严刚[1] 张静[1] 

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]中国科学院地质与地球物理研究所,北京100029 [3]中国地质科学院北京离子探针中心,北京100037

出　　处：《矿物岩石》2011年第2期15-22,共8页Mineralogy and Petrology

基　　金：国家自然科学基金项目(41072050;41030316;40472041)

摘　　要：冀北赤城退变榴辉岩的原岩为兼具洋中脊和岛弧地球化学属性的拉斑玄武岩类,其变质演化经历了早期的榴辉岩相进变质,以及后期的麻粒岩相和角闪岩相退变质等阶段。锆石SHRIMP U-Pb年代学研究表明,退变榴辉岩的原岩形成于438 Ma±,峰值榴辉岩相变质发生在355 Ma±,后期麻粒岩相和角闪岩相退变质年龄则分别为341 Ma±和322 Ma^326 Ma。冀北赤城退变榴辉岩演化时间序列的确定,对探讨华北克拉通北缘中段的大地构造演化具有十分重要的意义。The protolith of retrograded eclogite samples occurred in Chicheng,northern Hebei Province is of tholeiitic oceanic crust with geochemical characteristics of mid-ocean ridge（MORB） or island arc（IAT） environment.Three main metamorphic evolutional stages are recognized and characterized by the early peak eclogite facies stage,the later granulite facies retrogressive metamorphism stage and amphibolite facies retrogressive metamorphism stage.Zircon SHRIMP isotopic dating of two different textural varieties of retrograded eclogite samples show four different ages.The 206Pb/238U age of ~438 Ma from an inherited magmatic zircon core in sample L3 implies that it may be the age of the igneous precursor.The age of ~355 Ma from a metamorphic zircon in sample L1 may be interpreted as the peak metamorphic age of the eclogites.A weighted mean age of ~341 Ma and 322 Ma^326 Ma may represent the later granulite facies and amphibolite facies metamorphic ages respectively.The confirmation of time sequence for the retrograded eclogite is important for the understanding of tectonic evolution in the central part of the northern margin of North China Craton（NCC）.

关 键 词：锆石SHRIMPU-PB年龄 时间序列 退变榴辉岩 赤城 冀北 

分 类 号：P597.3[天文地球—地球化学]