Multi-isotopic system geochronology of low temperature eclogite from Huangzhen,Southern Dabie Terrain  

作　　者：CHEN Daogong1, E. Deloule2, CHENG Hao1, XIA Qunke1 & WU Yuanbao1 1. School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China 2. CRPG-CNRS Nancy, 54501, France 

出　　处：《Science China Earth Sciences》2004年第10期931-942,共12页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.40273028 and 40033010);the State Key Basic Research Project(Grant No.G1999075503).

摘　　要：Zircon U-Pb thermal ionization mass-spectrometer (TIMS) and secondary ion mass-spectrometer (SIMS) dating, mica and amphibole 40Ar-39Ar dating and mineral Sm-Nd isotopic compositions of Huangzhen low temperature eclogite and country granitic gneiss are carried out. The zircon U-Pb weighted average SIMS age is (231.6?9.7) Ma for one eclogite. The mica 40Ar-39Ar isochron age is (232.6?2.1) Ma and the lowest plateau age is (221.7?2.4) Ma from same sample. U-Pb TIMS concordant ages from other eclogite zircons are from (221.3?1.4) Ma to (222.5?2.3) Ma. U-Pb SIMS low intercept age from country granitic gneiss is (221?35) Ma. The retrograde amphibole 40Ar-39Ar isochron age is (205.9?1.0) Ma. Except for mica, which may contain excess 40Ar, all the ages represent peak and retrograde metamorphism of low temperature eclogites. It is indicated that the Huangzhen low temperature eclogites differ from Xiongdian low temperature eclogites of north of the Northern Dabie Terrain in metamorphic ages. Huangzhen low temperature eclogites share one coherent HP-UHP terrain with high temperature eclogites from Southern Dabie Terrain and they may have differences in subduction depth and cooling rates during exhumation.Zircon U-Pb thermal ionization mass-spectrometer (TIMS) and secondary ion mass-spectrometer (SIMS) dating, mica and amphibole 40Ar-39Ar dating and mineral Sm-Nd isotopic compositions of Huangzhen low temperature eclogite and country granitic gneiss are carried out. The zircon U-Pb weighted average SIMS age is (231.6±9.7) Ma for one eclogite. The mica Ar-39Ar isochron age is (232.6±2.1) Ma and the lowest plateau age is (221.7±2.4) 40 Ma from same sample. U-Pb TIMS concordant ages from other eclogite zircons are from (221.3 ±1.4) Ma to (222.5±2.3) Ma. U-Pb SIMS low intercept age from country granitic gneiss is (221 ±35) Ma. The retrograde amphibole Ar-39Ar isochron age is (205.9±1.0) Ma. Except for mica, 40 which may contain excess Ar, all the ages represent peak and retrograde metamorphism of low 40 temperature eclogites. It is indicated that the Huangzhen low temperature eclogites differ from Xiongdian low temperature eclogites of north of the Northern Dabie Terrain in metamorphic ages. Huangzhen low temperature eclogites share one coherent HP-UHP terrain with high temperature eclogites from Southern Dabie Terrain and they may have differences in subduction depth and cooling rates during exhumation.

关 键 词：low temperature eclogite  multi-isotopic dating  HP-UHP metamorphism  Dabieshan. 

分 类 号：P533[天文地球—古生物学与地层学]