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变质岩中锆石U—Pb计时问题评述——兼论大别造山带锆石定年
引用本文:陈道公,李彬贤,等.变质岩中锆石U—Pb计时问题评述——兼论大别造山带锆石定年[J].岩石学报,2001,17(1):129-138.
作者姓名:陈道公  李彬贤
作者单位:中国科学技术大学地球和空间科学系,
基金项目:本文为国家重点基础研究发展规划项目(编号499075503)和国家自然科学基金(编号49973019 和49794042)资助项目.
摘    要:锆石是U-Pb计时的首选对象,对于地质历史复杂的变质岩地区,如大别碰撞造山带的年代学研究,具有不可替代的重要性。变质岩中锆石经历了Pb的扩散丢失作用;晶格损伤导致的蜕晶化作用;增生-混合作用和重结晶作用。这些过程对锆石计时的准确性和有效性带来不同程度的影响。为了使测定的年龄有确定的地质意义,在进行锆石U-Pb定年前,必需对锆石进行成因矿物学和矿物内部结构研究,特别是阴极荧光和背散射电子成像研究,通过内部结构特征确定锆石成因过程。在化学U-Pb法定年时注意普通铅校正和^204Pb测定值对年龄的影响,尽量选择单一成因锆石。特别强调在大别造山带年代学中引入锆石微区离子探针定年技术。

关 键 词:锆石计时  岩浆锆石  变质锆石  蜕晶化作用  增生-混合作用  铀-铅计时  变质岩  大别造山带
修稿时间:2000年11月10

An evaluation of zircon U-Pb dating for metamorphic rocks and comments on zircon ages of Dabie orogen.
CHEN DaoGong,LI BinXian,XIA QunKe,WU YuanBao and CHENG Hao.An evaluation of zircon U-Pb dating for metamorphic rocks and comments on zircon ages of Dabie orogen.[J].Acta Petrologica Sinica,2001,17(1):129-138.
Authors:CHEN DaoGong  LI BinXian  XIA QunKe  WU YuanBao and CHENG Hao
Institution:CHEN DaoGong,LI BinXian,XIA QunKe,WU YuanBao and CHENG Hao. Department of Earth and Space Sciences,University of Science and Technology of Chin,Hefei,China
Abstract:Zircon is the most widely used mineral for U Pb age determinations, and shows particular importance to a complicated geological history of a metamorphic terrain, like Dabie Shan collision orogen. Zircon from metamorphic rocks may suffer from Pb diffusion loss, metamictization caused by lattice radiation damage, overgrowth mixing and recrystallization. All of these processes would affect the accuracy and validity of zircon ages to some extent. In order to get geological meaningful ages, one must pay particular attention to mineral genesis and texture of zircons, and decide firmly zircon genetic process through internal structure observation, especially CL and BSE image before zircon U Pb dating. The selection of reasonable common Pb correction, reasonable measured 204 Pb value and simple genetic zircon is preferred for TIMS dating. Here, we emphasize the advantage of SIMS dating technology in Dabie orogen research.
Keywords:Zircon dating  Magmatic zircon and metamorphic zircon  Metamictization  Overgrowth-mixing  Recrystallization  Dabieshan geochronology
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