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| 台湾海峡西岸闽江口和九龙江口沉积物中碎屑锆石U-Pb定年及物源意义 |
| Provenance of sediments from the Minjiang and Jiulongjiang estuaries in western coast of the Taiwan strait: constraints from U-Pb ages of detrital zircons |
| 投稿时间：2010-01-13 修订日期：2010-04-14 |
| DOI： |
| 中文关键词: 台湾海峡 碎屑锆石 U-Pb年龄 物源 |
| 英文关键词:Taiwan Strait detrital zircons U-Pb age provenance |
| 基金项目:国家海洋局第三海洋研究所基本科研业务费专项资助项目(海三科2009014); 国家青年基金资助项目(40906047) |
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| 中文摘要: |
| 碎屑锆石能较好保存源区岩石组成的信息, 其U-Pb年龄是沉积物源区示踪有效的方法. 本文利用激光剥蚀等离子体质谱和多接收器等离子体质谱联机(LA-MC-ICPMS)技术, 对台湾海峡西部闽江口和九龙江口沉积物中的碎屑锆石进行原位U-Pb测年, 并同时获得锆石的微量元素. 研究表明大部分碎屑锆石的Th/U比值大于0.1, 稀土元素球粒陨石标准化配分曲线呈左倾型, 并具有明显的正Ce异常和负Eu异常, 结合CL图像表明这些锆石绝大部分为岩浆成因. 闽江口和九龙江口的碎屑锆石具有相同的印支期(峰值236 Ma)、燕山早期(峰值155 Ma)和燕山晚期(峰值110 Ma)等3个峰值, 这三期碎屑锆石占主要部分, 反映闽江口和九龙江口碎屑沉积物主要来自各流域上游印支期和中下游燕山期岩体. 而闽江口碎屑锆石具有明显的加里东期峰(峰值465 Ma)和较多前寒武纪(553～2765Ma)的碎屑锆石, 这些碎屑物质可能来自上游武夷山地区加里东期和前寒武基底的物质. 对比闽江口碎屑锆石U-Pb年龄与台湾岛西部海滨沙滩(苗栗－新竹、嘉义－台南)中的独居石年龄具有相似的谱峰特征, 表明台湾岛西部海滨沙滩碎屑物质可能有部分来自闽江. 闽江口碎屑物质明显区别于九龙江和浙江的瓯江, 这为判别台湾海峡沉积物的物质来源提供可靠的依据. |
| 英文摘要: |
| The source information of the sediments were preserved in detrital zircons, which can sufficiently interpret the provenance of the sediments. Detrital zircons from the Minjiang and Jiulongjiang estuaries were analyzed for U-Pb ages and trace elements by in situ laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Most zircons have Th/U ratios higher than 0.1 and show HREE-enriched feature with positive Ce anomaly and negative Eu anomaly in chondrite-normalized REE patterns, a feature of magmatic origin. The U-Pb ages of zircons from the Minjiang and Jiulongjiang estuaries can be divided into three groups: Indosinian (ca.236 Ma), Early Yanshanian (ca.155 Ma) and Late Yanshanian (ca.110 Ma). These age ranges are consistent with the ages of granitic rocks outcropped in the middle and lower reaches of the rivers. However, zircon U-Pb ages from the Minjiang estuary shows distinctly Caledonian (ca.465 Ma) and many Precambrian ages (553~2765Ma), which are possibly derived from the Caledonian and Precambrian rocks from upstream. In regard of similar age ranges of detrital zircons from Minjiang estuary and monazites from beach sands of the West Taiwan(Miaoli-Hsinchu, Chiayi-Tainan), the sediments of the West Taiwan are very likely derived from the Minjiang river. |
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