【作者】 吴元保； 郑永飞； 龚冰；

【Author】 WU Yuanbao ZHENG Yongfei GONG Bing CAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei,Anhui,230026

【机构】 中国科学院壳幔物质与环境重点实验室中国科学技术大学地球和空间科学学院；

【摘要】 大别-苏鲁造山带大理岩中榴辉岩包体的锆石有两种类型,为变质增生锆石和变质重结晶的残留碎屑锆石。变质增生锆石和完全变质重结晶锆石都具有较低的U、Th 含量和Th/U 比值,且给出两组变质年龄,分别为240.9±4.8～245.1±3.1 Ma 和223.7±4.2～226.0±3.9 Ma。年龄为240.9±4.8～245.1±3.1 Ma 的变质锆石的生长对应于板块俯冲过程中高压榴辉岩相变质作用期间的流体活动,而223.7±4.2～226.0±3.9 Ma 的变质锆石的生长可能对应了板块折返早期的流体活动。这些年龄同样可以很好地用来限定其寄主大理岩的变质演化历史。更多还原

【Abstract】 The fluid activity during subduction and exhumation,a very important problem with respect to timing and mechanism ofmetamorphic zircon growth,is elucidated in this paper by a combined study of zircon internal structure and U-Pb dating of UHP e-clogite boudins enclosed in marbles from the Dabie-Sulu orogenic belt in eastern Central China.CL imaging has identified two types ofzircon that are metamorphically new growth and recrystallized detrital grains,respectively.Both of them have low Th and U contentswith low Th/U ratios,yielding two groups of²⁰⁶pb/²³⁸U age at 243±2 Ma and 225±3 Ma,respectively.Therefore,the formationof the first episode of metamorphic zircons is correlated with fluid activity during the progressive high-pressure（HP）eclogite-faciesmetamorphism.The growth of the second episode of metamorphic zircons may correspond to fluid activity during the retrograde HP e-clogite-facies metamorphism.更多还原