Rutile U-Pb age for the ultra-high pressure eclogite from the Dabie Mountains, central China: Evidence for rapid cooling  

作　　者：LI Qiuli LI Shuguang ZHOU Hongying LI Huimin HONG Ji’an WANG Qingchen H.J.Massonne 

机构地区：[1]Department of Earth and Space Science,University of Science and Technology of China,Hefei 230026,China [2]Tianjin Institute of Geology and Mineral Resources [3]Institule of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China [4]Institut fur Mineraloie&Kristallechemie,Universitat Stuttgart,Azenbergster.18,70174 Stuttgart,Germany

出　　处：《Chinese Science Bulletin》2002年第1期62-65,共4页

基　　金：This work was supportedby the State Key Basic Research Development Program (Grant No. G1999075503) ; the National Natural Science Foundation of China (Grant No. 49973020).

摘　　要：The U-Pb isotope compositions of rutile, om-phacite and garnet in the eclogite from the Jinheqiao area in the Southern Dabie ultrahigh-pressure metamorphic zonewere analyzed. The consistent high precision U-Pb age (218± 1.2) Ma of rutile in eclogite from the Dabie Mountains was obtained by two ways of isochron and common Pb correction based on the composition of omphacite. This proves that the omphacite in eclogite has a U/Pb ratio (μ = 2.8) low enough to be used for common Pb correction in the analyses of rutile. Under the rapid cooling condition (40℃/Ma) the closure temperature for U-Pb diffusion in rutile is about 470℃. Thus, this U-Pb age of rutile proves that 218 Ma should be the cooling age of eclogite at 470℃ instead of the peak meta-morphic age.The U-Pb isotope compositions of rutile, omphacite and garnet in the eclogite from the Jinheqiao area in the Southern Dabie ultrahigh-pressure metamorphic zone were analyzed. The consistent high precision U-Pb age (218 +/- 1.2) Ma of rutile in eclogite from the Dabie Mountains was obtained by two ways of isochron and common Pb correction based on the composition of omphacite. This proves that the omphacite in eclogite has a U/Pb ratio (mu = 2.8) low enough to be used for common Pb correction in the analyses of rutile. Under the rapid cooling condition (40degreesC/Ma) the closure temperature for U-Pb diffusion in rutile is about 470degreesC. Thus, this U-Pb age of rutile proves that 218 Ma should be the cooling age of eclogite at 470degreesC instead of the peak metamorpbic age.

关 键 词：U-PB DATING of RUTILE ECLOGITE DABIE Mountains. 

分 类 号：P578[天文地球—矿物学]