| 摘要: |
| 本文系统总结了沉积岩定年的意义和常用的定年手段，详细介绍了火山灰锆石U-Pb定年在沉积岩定年上的应用。从火山事件层的分布、火山灰夹层的识别、火山灰锆石的区分、应用实例等方面对前人的研究进行概述，旨在为科研工作者运用火山灰锆石U-Pb定年提供借鉴经验。与传统的成岩矿物K-Ar/Ar-Ar和Rb-Sr定年技术相比，火山灰锆石U-Pb定年在沉积岩定年上具有显著的优势。火山灰夹层具有广泛性和等时性，且锆石U-Pb同位素体系不容易受到扰动，因此火山灰锆石U-Pb定年是高精度沉积岩定年的首选方案。沉积岩定年涉及到野外观察、样品采集、室内岩相学观察及地质年代学分析和年龄解释等多个环节。在这些环节中，识别火山灰夹层是最关键的一点，也是一大难点。这需要明确火山灰夹层的岩石类型并了解火山事件沉积层的分布，在此基础上通过野外观察和室内研究进一步判别，这样可以更加准确地识别出火山灰夹层。此外，火山灰锆石定年需要区分火山灰锆石、碎屑锆石、继承/捕获锆石，可以通过矿物形态学和矿物化学特征来加以区分。 |
| 关键词: 火山灰 锆石 U-Pb年龄 沉积岩定年 |
| DOI：10.19826/j.cnki.1009-3850.2023.04001 |
| 相关附件： 20230129002-曹熔-附表.pdf |
| 投稿时间：2023-01-29修订日期：2023-03-29 |
| 基金项目:中国科学院地质与地球物理研究所岩石圈演化国家重点实验室开放课题（SKL-Z202001） |
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| Application of zircon U-Pb dating of volcanic ash to dating of sedimentary rock |
| Cao Rong, Zhang Shujing, Lan Zhongwu |
(1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;
2. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 101408, China;
3. Department of Geology, Trinity College, Dublin 999015, Ireland) |
| Abstract: |
| This paper has summarized the significance of dating of sedimentary rock, and introduced the application of volcanic ash zircon U-Pb dating method to dating of sedimentary rocks. Specifically, it has summarized previous studies on the distribution of volcanic event layers, identification of volcanic interlayers, differentiation of volcanic tuff zircons and application examples so as to provide experience for geoscientists in the application of volcanic zircon U-Pb dating. Compared to traditional K-Ar/Ar-Ar and Rb-Sr dating techniques for diagenetic minerals, volcanic ash zircon U-Pb dating has a significant advantage in dating of sedimentary rocks. Volcanic ash interlayer is widespread and isochronous, and zircon U-Pb isotopic system is robust and not easily disturbed. Therefore, volcanic ash zircon U-Pb dating is the first choice for high precision dating of sedimentary rocks. Dating of sedimentary rocks involves field observation, sample collection, indoor petrographic observation, geochronological analysis and age interpretation. Of these, identification of volcanic ash interlayer is the most important despite difficulty. It is necessary to clarify different types of volcanic interlayer and understand the distribution of sedimentary layers of volcanic events. Based on this, field observations and indoor study can be used to further distinguish volcanic interlayers and identify them accurately. In addition, dating of volcanic tuff zircons requires the distinction between volcanic ash zircons, detrital zircons, inherited zircons and xenocrystal zircons, which can be distinguished by mineral morphology and mineral chemistry. |
| Key words: volcanic tuff zircon U-Pb age dating of sedimentary rocks |
