骑田岭花岗岩体的岩浆混合成因：寄主岩及其暗色闪长质微细粒包体的锆石U-Pb 年龄和Hf同位素证据
Magmatic mingling origin of adamellite: zircon U-Pb dating and Hf isotopes evidence of microgranular dioritic enclaves and host rocks from Yangtianhu adamellite of Qitianling, South China
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摘要: 提要：南岭骑田岭复式岩体仰天湖单元燕山期二长花岗岩中广泛分布有暗色闪长质微细粒包体， 这些包体主要呈被打散的片云状或次圆状，大小不等，颜色较寄主岩深，粒度较细。本文在锆石内部结构的CL图像特征研究基础上， 用LA-ICP-MS和MC-ICP-MS测定了锆石U-Pb年龄及Hf同位素组成，探讨了寄主二长花岗岩、闪长质微细粒包体的锆石U-Pb年代学及Hf同位素组成特征。获得寄主二长花岗岩、闪长质微细粒包体的结晶年龄为（166.0±2.0） Ma和（169.8±4.1） Ma，对应的εHf(t)值为-13.2~-1.9与-8.3~+6.7。研究表明，骑田岭复式岩体中的仰天湖岩体是以古老地壳物质熔融为主体的壳源岩浆与幔源岩浆高度混合的产物。Abstract: Abstract：A large number of directional microgranular dioritic enclaves occur in Yangtianhu adamellite of Qitianling composite body. Microgranular dioritic enclaves，which commonly show cloudleted and sub-rounded shapes, display igneous textures and are from meter to centimeter in size. These enclaves are darker in color and finer in granularity than their hosting adamellite. Based on an analysis of the inner structural CL images of zircons, this paper discusses U-Pb ages and Hf isotopes of zircons from the host adamellite and mafic microgranular enclaves by using in situ zircon analysis of LA-ICP-MS and MC-ICP-MS. The ages of （157.2±3.7）Ma from host adamellite and （168.6±3.5） Ma from enclaves were obtained, respectively. The Yangtianhu adamellite intrusion was formed by the mingling between the partial melting products from the crustal materials and the magma derived from the mantle.
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