| 大别-苏鲁造山带大理岩中榴辉岩包体的锆石U-Pb年龄及其地质意义 |
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| 引用本文：吴元保,郑永飞,龚冰.2005.大别-苏鲁造山带大理岩中榴辉岩包体的锆石U-Pb年龄及其地质意义[J].地球学报,26(z1):118-120. |
| DOI：10.3975/cagsb.2005.s1.39 |
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| 基金项目:本文为国家自然科学基金项目（编号：40334036）资助成果。 |
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| 中文摘要: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±4.8~25.1±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。 |
| 中文关键词:大理岩 流体活动 U-Pb年龄 板块俯冲 板块折返 |
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| Zircon U-Pb Dating of Marble-associated Eclogite in the Dabie-Sulu Orogenic Belt and Its Geological Implications |
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| Abstract:The fluid activity during subduction and exhumation, a very important problem with respect to timing and mechanism of metamorphic zircon growth, is elucidated in this paper by a combined study of zircon internal structure and U-Pb dating of UHP eclogite boudins enclosed in marbles from the Dabie-Sulu orogenic belt in eastern Central China. CL imaging has identified two types of zircon that are metamorphically new growth and recrystallized detrital grains, respectively. Both of them have low Th and U contents with low Th/U ratios, yielding two groups of 206Pb/238U age at 243±2 Ma and 225±3 Ma, respectively. Therefore, the formation of the first episode of metamorphic zircons is correlated with fluid activity during the progressive high-pressure (HP）ectogite-facies metamorphism. The growth of the second episode of metamorphic zircons may correspond to fluid activity during the retrograde HP eclogite-facies metamorphism. |
| keywords:marble fluid activity U-Pb age plate subduction plate exhumation |
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