| Dating of zircon from high-grade rocks： Which is the most reliable method？ |
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| 作者姓名： | Alfred Kroner ;Yusheng Wan ;Xiaoming Liu ;Dunyi Liu |
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| 作者单位： | [1]Beijing SHRIMP Centre, Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, 100037 Beijing, China; [2]State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China . |
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| 基金项目： | funded by the German Science Foundation（DFG）,grant KR590/94-1 to AK |
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| 摘 要： | Magmatic zircon in high-grade metamorphic rocks is often characterized by complex textures as revealed by cathodoluminenscence （CL） that result from multiple episodes of recrystallization, over- growth, Pb-loss and modifications through fluid-induced disturbances of the crystal structure and the original U-Th-Pb isotopic systematics. Many of these features can be recognized in 2-dimensional CL images, and isotopic analysis of such domains using a high resolution ion-microprobe with only shallow penetration of the zircon surface may be able to reconstruct much of the magmatic and complex post- magmatic history of such grains. In particular it is generally possible to find original magmatic domains yielding concordant ages. In contrast, destructive techniques such as LA-ICP-MS consume a large volume, leave a deep crater in the target grain, and often sample heterogeneous domains that are not visible and thus often yield discordant results which are difficult to interpret. We provide examples of complex magmatic zircon from a southern Indian granulite terrane where SHRIMP lI and LA-ICP-MS analyses are compared. The SHRIMP data are shown to be more precise and reliable, and we caution against the use of LA-ICP-MS in deciphering the chronology of complex zircons from high-grade terranes.
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| 关 键 词： | 变质岩 LA-ICP-MS 锆石 U-Pb同位素 离子探针 同位素分析 晶体结构 高分辨率 |
| 收稿时间： | 19 January 2014 |
http://www.sciencedirect.com/science/article/pii/S1674987114000577 |
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| Alfred Kroner,;Yusheng Wan,;Xiaoming Liu,;Dunyi Liu.http://www.sciencedirect.com/science/article/pii/S1674987114000577[J].Geoscience Frontiers,2014,5(4):515-523. |
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| Authors: | 《Geoscience Frontiers》 |
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| Institution: | 1. Beijing SHRIMP Centre, Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, 100037 Beijing, China;2. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an 710069, China |
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| Abstract: | Magmatic zircon in high-grade metamorphic rocks is often characterized by complex textures as revealed by cathodoluminenscence (CL) that result from multiple episodes of recrystallization, overgrowth, Pb-loss and modifications through fluid-induced disturbances of the crystal structure and the original U-Th-Pb isotopic systematics. Many of these features can be recognized in 2-dimensional CL images, and isotopic analysis of such domains using a high resolution ion-microprobe with only shallow penetration of the zircon surface may be able to reconstruct much of the magmatic and complex post-magmatic history of such grains. In particular it is generally possible to find original magmatic domains yielding concordant ages. In contrast, destructive techniques such as LA-ICP-MS consume a large volume, leave a deep crater in the target grain, and often sample heterogeneous domains that are not visible and thus often yield discordant results which are difficult to interpret. We provide examples of complex magmatic zircon from a southern Indian granulite terrane where SHRIMP II and LA-ICP-MS analyses are compared. The SHRIMP data are shown to be more precise and reliable, and we caution against the use of LA-ICP-MS in deciphering the chronology of complex zircons from high-grade terranes. |
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| Keywords: | Zircon datingHigh-grade rockSHRIMPLA-ICP-MS |
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