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大别山西部熊店加里东期榴辉岩——同位素地质年代学的证据

ISOTOPIC GEOCHRONOLOGICAL EVIDENCE FOR THE CALEDONIAN XIONGDIAN ECLOGITE IN THE WESTERN DABIE MOUNTAINS,CHINA

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【作者】 简平杨巍然李志昌周慧芳

【Author】 Jian Ping(Yichang Instutute of Geology and Mineral Resources, CAGS, Hubei)Yang Weiran Li Zichang(China University of Geosciences, Wuhan, Hubei) (Yichang Insitute of Geology and Mineral Resources, CAGS, Hubei)and Zhou Huifang(Tianjin Institute of Geology and Mineral Resources, CAGS,Tianjing)

【机构】 地质矿产部宜昌地质矿产研究所中国地质大学地质矿产部天津地质矿产研究所 湖北武汉湖北

【摘要】 以UP-Pb单颗粒锆石同位素稀释法、角闪石40Ar—39Ar坪年龄和Sm-Nd全岩及矿物等时线相结合的研究方法,系统地研究了大别造山带西部熊店榴辉岩的峰变质年龄,可能的原岩年龄和退变质年龄,建立了这一榴辉岩的构造-变质时间序列,提出了大别地区存在加里东期榴辉岩的确凿证据。

【Abstract】 A typical HP/MT (high pressure/medium temperature) eclogite from Xiongdian, Western Dabie Mountains, has been geochronologically studied using the single zircon U-Pb,40Ar -39Ar and Sm-Nd methods. Prismatic zircons occurring as inclusions within garnets define a minimum crytallization age of 399. 5±1. 6Ma. 40Ar -39Ar dating on hornblende gives a plateau age of 399. 2±4Ma, which is interpreted as a retrogression age of amphibolite facies. This integrated study enables us to conclude that the age of high pressure metamorphism is older than 399. 5 ± 1. 6Ma , suggesting Caledonian collision between the North China and Yangtze plates. Round zircon within the aggregate of quartz and muscovite gives a concordant age of 301±2Ma, reflecting a later retrogression event. An age profile of post-eclogite metamorphism is documented, including amphibolite facies metamorphism at 399. 2Ma shortly after eclogitization, and later retrogressive metamorphism at 301Ma. Sm-Nd internal isochron of garnet+omphacite gives an unreasonalbe age of 544±23Ma, which is quite older than that of prismatic zircon and may be attributed to isotopic disturbance by retrogression.

【基金】 地质矿产部重大基础项目(编号8502206);地质行业基金(编号9514)的部分成果;国家计委30届国际地质大会项目(编号96-30-07)
  • 【文献出处】 地质学报 ,Acta Geologica Sinica , 编辑部邮箱 ,1997年02期
  • 【分类号】P597
  • 【被引频次】67
  • 【下载频次】207
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