Isotopic Geochronological Evidence for the Caledonian Xiongdian Eclogite in the Northwestern Dabie Mountains,China

查看全文 作　　者：Jian PingYichang Institute of Geology and Mineral Resources. CAGS, Yichang City,Hubei Province 443003Yang Weiran China University of Geosciences, Wuhan, HubeiLi Zhichang Yichang Institute of Geology and Mineral Resources, CAGS, Yichang, HubeiZhou Huifang Tianjin Instutite of Geology and Mineral Resources, CAGS, Tianjin Zhu Xiling 出　　处：《Acta Geologica Sinica(English Edition)》索引1997年第71卷第4期,共11页 基　　金：This paper is a partial result of a major tundamental project (No. 8502206) of the Ministry of Geology and Mineral Resources and a project (No. 9514) of the Foundation for Development of Science and Technology in Geology, and financially supported by the 摘　　要：A typical HP/MT (high pressure/medium temperature) eclogite from Xiongdian, northwestern 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 crystallization age of 399.5±1.6 Ma. 40Ar-39Ar dating on amphibole gives a plateau age.of 399.2 ± 4 Ma, 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 ± 1.6 Ma, 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± 2 Ma, reflecting a later retrogression event. An age profile of post-eclogite metamorphism is documented, including amphibolite facies metamorphism at 399.2 Ma shortly after eclogitization and later retrogressive metamorphism at 301 Ma. Sm-Nd mineral isochron of garnet+omphacite 关 键 词：CALEDONIAN collision ECLOGITES geochronlogy NORTHWESTERN DABIE area Xiongdian Henan