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| 藏南冈底斯中段大竹卡桥南花岗闪长岩锆石U-Pb定年及地质意义 |
| 刘维亮,夏斌,张玉泉,钟云,刘鸿飞,蔡周荣,胡杨 |
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(1 中山大学海洋学院, 广东 广州 510275;
2 中国科学院广州地球化学研究所, 广东 广州 510640;
3 西藏自治区地质调查院, 西藏 拉萨 850000;
4 南华大学核资源与核燃料工程学院, 湖南 衡阳 421001) |
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| 摘要: |
| 冈底斯岩带中各岩体的准确定年对特提斯洋演化和青藏高原隆升研究有重要意义。日喀则大竹卡桥南花岗闪长岩体位于冈底斯岩带中段,前人曾开展过两次K-Ar法定年,但定年结果差距较大。本文利用LA-ICP-MS锆石U-Pb方法对该花岗闪长岩进行了定年。定年所选锆石发育有规律环带结构,Th/U比值为0.20~1.69,为岩浆锆石,获得80.3±3.6Ma(MSWD=3.2)的加权平均年龄,代表花岗闪长岩的结晶年龄。定年结果反映该岩体为新特提斯洋俯冲成因。岩体南侧紧邻雅鲁藏布江缝合带,其岩浆活动很可能是雅鲁藏布江新特提斯洋向北俯冲所引起的。这一岩体年龄数据的报道为深入探讨晚白垩世雅鲁藏布江洋是否存在平板俯冲提供了新的研究对象。 |
| 关键词: U-Pb年代学 新特提斯洋俯冲 花岗闪长岩 冈底斯岩带 西藏 大竹卡 |
| DOI： |
| 附件 |
| 投稿时间：2012-10-08修订日期：2013-05-20 |
| 基金项目:中国地质调查局“青藏高原重大关键地质问题研究”计划项目(1212011121259、1212011221105) |
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| Zircon U-Pb dating and geological implications for the granodiorites from the Dazhuka region in Xizang |
| LIU Wei-liang, XIA Bin, ZHANG Yu-quan, ZHONG Yun, LIU Hong-fei, CAI Zhou-rong, HU Yang |
(1. School of Marine Sciences, Sun Sat-sen University, Guangzhou 510275, Guangdong, China;
2. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China;
3. Xizang Institute of Geological Survey, Lhasa 850000, Xizang, China;
4. School of Nuclear Resources and Nuclear Fuel Engineering, University of South China, Hengyang 421001, Hunan, China) |
| Abstract: |
| The precise dating for the granodiorites from the Gangdise zone in Xizang is of great importance to the research of the Tethyan evolution and Qinghai-Xizang Plateau uplift. The granodiorite masses south of Dazhuka Bridge occur in the central part of the Gangdise zone in Xizang. There is the large discrepancy between the preexisting K-Ar age determinations given by the previous workers. The present paper deals with the zircon U-Pb re-dating of the granodiorite masses south of the Dazhuka Bridge with the aid of LA-ICP-MS method. The selected zircons for dating show regular oscillatory zonal structures. The Th/U ratios vary from 0.20 to 1.69. These characteristics suggest a magmatic origin of the zircons. The weighted average age of 80.3±6 Ma (MSWD=3.2) may represent the crystallization age of the granodiorites. Since the granodiorite masses are very close to the southern Yarlung Zangbo suture zone, the granodiorites may well be originated from the magmatism caused by the northward subduction of the Yarlung Zangbo Neo-Tethys oceanic plate. |
| Key words: U-Pb dating subduction of the Neo-Tethys oceanic plate granodiorite Gangdise zone Dazhuka Xizang |