| 西藏普兰地区拉昂错蛇绿岩中辉绿岩的锆石SHRIMP U—Pb年龄及其地质意义 |
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| 引用本文： | 李建峰,;夏斌,;刘立文,;徐力峰,;何观生,;王洪,;张玉泉,;杨之青.西藏普兰地区拉昂错蛇绿岩中辉绿岩的锆石SHRIMP U—Pb年龄及其地质意义[J].中国区域地质,2008(10):1739-1743. |
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| 作者姓名： | 李建峰 ;夏斌 ;刘立文 ;徐力峰 ;何观生 ;王洪 ;张玉泉 ;杨之青 |
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| 作者单位： | [1]中国科学院广州地球化学研究所油气与资源研究中心,广东广州511640; [2]中国科学院研究生院,北京100039; [3]广东省地质勘查局七一九地质大队,广东肇庆526020; [4]江西核工业261地质大队,江西南昌330029; [5]北京离子探针中心,北京100037 |
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| 基金项目： | 国家自然科学基金重点项目（编号：40534019）资助. 致谢：在研究过程中北京离子探针中心刘敦一和王彦斌研究员提出许多宝贵意见.在成文过程中周国庆老师给予了指导.宋彪研究员审阅了初稿,在此一并表示真诚的感谢. |
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| 摘 要： | 蛇绿岩中的辉绿岩岩墙是洋脊扩张的产物．其形成年龄代表了扩张事件的时间，也代表了蛇绿岩的形成时代？对雅鲁藏布江缝合带西段拉昂错蛇绿岩中的辉绿岩岩墙进行锆石SHRIMPU—Pb定年，得出加权平均年龄为120．2Ma±2．3Ma，代表辉绿岩的结晶年龄。结合已有的关于雅鲁藏布江蛇绿岩的形成年龄（西段休古嘎布122．3Ma±2．4Ma，中段大竹卡126．0Ma±1．5Ma、吉定123．0Ma＋_1．8Ma，东段罗布莎162．9Ma±2．8Ma）的报道，表明拉昂错地区特提斯洋海底扩张的时代与体古嘎布地区一致．雅鲁藏布江西段与中段地区洋盆的形成时代一致，但晚于东段的发育时代。这意味着整个东提斯洋盆的发育时代存在东早西晚的特点。
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| 关 键 词： | 锆石SHRIMP U-Pb定年 蛇绿岩 辉绿岩 拉昂错 西藏 |
SHRIMP U-Pb zircon dating of diabase in the La＇nga Co ophiolite,Burang, Tibet,China, and its geological significance. |
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| Institution: | LI Jian-feng, XIA Bin, LIU Li-wen, XU Li-feng, HE Guan-sheng, WANG Hong, ZHANG Yu-quan, YANG Zhi-qing (1. Petroleum trod Resource Research Centre, Guangzhou Institute of Geochemistry, Chinese Academy of Scienees, Guangzhou 510640, Guangdong, China; 2. Graduate School, Chinese Academy of Scienees, Beijing 100039, China; 3. 719 Geological Party, Guangdong Bureau of Geology and Mineral Exploration and Developmen, Zhaoqing 526020, Guangdong, China; 4. Geological Party No. 261, Jiaugxi Nuclear Industry, Nanchang 330029, Jiangxi, China; 5. Beijing SHRIMP Centre, Beijing 100037, China ) |
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| Abstract: | Diabase dikes in ophiolites is the product of the middle ocean ridge spreading, and their age corresponds to the time of the spreading event and also represents the formation age of ophiolites. Zircon SHRIMP U-Pb dating of the diabase dikes in the La ＇nga ophiohte in the western segment of the Yarlung Zangbo suture zone yielded a ^206Pb/^238U weighted mean age of 120.2±2.3 Ma（2σ, MSWD=0.71 ）, which represents the crystallization age of the diabase. Based on the above, combined with the previous reports of the ophiolite ages in the Yarlung Zangbo suture zone （122.3±2.4 Ma for the Xiugugabu ophiolite in the western part, 126.0±1.5 Ma for the Dazhuka ophioilte and 123.0±1.8 Ma for the Jiding ophiolite in the central part and 162.9±2.8 Ma for the Luobusha ophiohte in the eastern part）, this age suggests that： the sea-floor spreading age of the Tethys ocean in the La＇nga area is consistent with that of the Xiugugabu oceanic basin in the western part; the oceanic basins in the western part and central part of the Yarlung Zangbo suture zone originated synchronously and later than that in the eastern part. From the geochronology data, the authors deduce that the eastern part of the Tethys ocean basin opened earlier than its western part. |
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| Keywords: | zircon SHRIMP U-Pb dating ophiolite diabase La＇nga Co Tibet |
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