| 喜马拉雅东构造结地区雅鲁藏布江蛇绿岩地质年代学研究 |
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| 引用本文： | 耿全如,彭智敏,张璋.喜马拉雅东构造结地区雅鲁藏布江蛇绿岩地质年代学研究[J].地质学报,2011,85(7):1116-1127. |
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| 作者姓名： | 耿全如 彭智敏 张璋 |
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| 作者单位： | 1. 国土资源部成都地质矿产研究所,成都,610082
2. 国土资源部成都地质矿产研究所,成都,610082;中国地质大学(武汉)地球科学学院,武汉,430074 |
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| 基金项目： | 国家自然科学基金项目(40773001)资助 |
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| 摘 要： | 雅鲁藏布江结合带在东构造结地区形成弧形展布的蛇绿混杂带,此前对该带蛇绿岩的地球化学特征和成因已有研究,但年代学研究十分薄弱.本文报道对该带蛇绿岩的地质年代学研究成果.从变玄武岩和变辉长岩中分选出两类锆石.一类锆石为自形的柱状双锥,具有清晰的同心韵律环带,较高的Th/U比值(主要为0.63～2.79),SHRIMP Ⅱ测...
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| 关 键 词： | 喜马拉雅东构造结 雅鲁藏布江蛇绿岩 锆石U-Pb定年 新特提斯 构造演化 |
| 收稿时间： | 6/3/2010 12:00:00 AM |
| 修稿时间： | 2010/10/7 0:00:00 |
Geochronological study on ophiolite in the Yarlung Tsangpo grand bend in eastern Tibet |
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| Geng Quanru,Peng Zhimin and Zhang Zhang.Geochronological study on ophiolite in the Yarlung Tsangpo grand bend in eastern Tibet[J].Acta Geologica Sinica,2011,85(7):1116-1127. |
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| Authors: | Geng Quanru Peng Zhimin and Zhang Zhang |
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| Institution: | Chengdu institute of geology and mineral resources,Chengdu institute of geology and mineral resources,Chengdu institute of geology and mineral resources; China university of geosciences |
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| Abstract: | The Yarlung Tsangpo suture forms a bended ophiolitic mélange in the eastern syntaxis area. Its geochemistry and genesis has been studied previously, but the chronology study is very weak. This paper reports the results of geochronology study of the ophiolite. Two types of zircon were selected from metamorphosed basalt and gabbro. One type of zircon is cylindrical-shaped double cone, with clear rhythm concentric rings, that yields a weighted mean age at 185.8 ± 1.7 Ma (MSWD = 0.64, n=11) and high Th/U ratios (mainly 0.63-2.79) by SHRIMP II analyses. Another three such zircon grains give 207±29 Ma(MSWD=6.5) and 209 ±20Ma(MSWD=3.0) ages by SHRIMP II and LA-ICP-MS analyses respectively. Another type of zircon grains are semi-euhedral columns to short cylindrical double cones, with weak internal zoning and lower Th / U ratios (mainly 0.005-0.033) and yield a weighted mean age at 32.74 ± 0.65 Ma(MSWD = 0.92, n=11). There are also some metamorphosed zircon grains that give ages raging from 82.8 Ma to 70.8 Ma. Geochronological dating suggests that the ophiolite formed in early Jurassic and locally in late Triassic. We argue that the Neo-Tethys began northward subduction in the Early Jurassic to Late Triassic time and closed in the Late Cretaceous time and causing ophiolite tectonic emplacement. |
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| Keywords: | The eastern Himalayan syntaxis Yarlung Tsangpo ophiolite Zircon U/Pb dating Neo-Tethys Tectonic evolution |
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