湘东北涧溪冲变质火山岩的Sm-Nd同位素年龄及其成因  

Sm-Nd DATING AND GENESIS OF THE JIANXICHONG GROUP METAMORPHIC VOLCANIC ROCKS IN NORTHEAST HUNAN

作　　者：伍光英[1] 李金冬[1] 车勤建[1] 肖庆辉[1] 唐晓珊[2] 彭和求[2] 

机构地区：[1]中国地质大学地球科学与资源学院 [2]湖南省地质矿产勘查开发局,湖南长沙410011

出　　处：《现代地质》2004年第3期339-345,共7页Geoscience

基　　金：中国地质调查局基础地质计划项目(1212010310206);中国地质调查局区域地质调查工作项目(200013000107)。

摘　　要：最近的区域地质调查研究发现,湘东北地区原中元古代冷家溪群实际上应划分为4部分,它们均形成于不同的时代和不同的构造环境,将其中分离出的最老的基本无序的变质沉积—火山岩系建立为"涧溪冲岩群"。根据其岩石学、岩石地球化学及同位素年代学等方面的研究认为:"涧溪冲岩群"是变质火山岩夹变质粘土质沉积岩经构造叠置起来的变质岩系,属绿片岩相—高绿片岩相。变质火山岩的Sm Nd全岩等时线年龄为(2594±48)Ma,其形成的地质时代可能是新太古代。变质火山岩的原岩为在大洋拉张环境下形成的以拉斑玄武岩为主、钙碱性玄武岩次之的火山—次火山岩系,其物源为亏损地幔。Recent regional geologic investigations show that the original 'Mesoproterozoic Lengjiaxi Group' in northeast Hunan should be divided into four parts, they were formed at different ages and in different tectonic settings. 'Jianxichong Group' is the oldest one among them. They belong to metamorphic volcanic-sedimentary series. According to the study of petrology, geochemistry and isotopic geochronology, we conclude that the volcanic rocks series mainly belong to tholeiites basalt and a little belong to calc-alkaline series. The whole rock Sm-Nd age of the mafic-ultramafic volcanic rocks is(2,594±48) Ma, it belongs to Neoarchean. The metamorphic facies of those rocks belong to blue schist facies.The source of the mafic-ultramafic volcanic rocks is depleted mantle. And their tectonic settings are the ocean or ocean island .

关 键 词：SM-ND年龄 构造环境 新太古代 “涧溪冲岩群” 湘东北 

分 类 号：P58[天文地球—岩石学]