| 北祁连缝合带油葫芦沟蛇绿岩中花岗斑岩锆石U Pb年龄及地质意义 |
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| 引用本文： | 李冰,胡道功,陈宣华,张耀玲,吴环环,王超群.北祁连缝合带油葫芦沟蛇绿岩中花岗斑岩锆石U Pb年龄及地质意义[J].现代地质,2017,31(6):1170. |
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| 作者姓名： | 李冰 胡道功 陈宣华 张耀玲 吴环环 王超群 |
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| 作者单位： | 1中国地质科学院 地球深部探测中心，北京 100037；2中国地质科学院 地质力学研究所，北京 100081 |
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| 基金项目： | 中国地质调查局项目“祁连-天山及周缘盆山结合带深部地质调查”(DD20160083)和“中国及邻区成矿构造背景编图研究”(DD20160344)。 |
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| 摘 要： | 蛇绿岩是保存在陆或弧上的大洋岩石圈残片，是洋中脊扩张或板块俯冲消减过程的产物。花岗质岩石可存在于蛇绿岩形成的不同阶段，是研究蛇绿岩形成演化和精确定年的重要岩石单元。油葫芦沟蛇绿岩是北祁连缝合带中具有代表性的蛇绿岩残片之一，对侵入到玄武岩中的花岗斑岩进行地球化学分析，结果表明花岗斑岩具有过铝和高钾特征，稀土和微量元素表现出明显的LREE富集，具有典型的仰冲型花岗岩特征。对花岗斑岩进行LA ICP MS锆石U Pb测年，20个测点数据的206Pb/238U加权平均年龄为(4975±15) Ma，该年龄代表了花岗斑岩的形成年龄及蛇绿岩仰冲就位的时代。结合北祁连蛇绿岩带的地质概况、年龄数据和地球化学特征，认为油葫芦沟蛇绿岩在晚寒武世仰冲就位，为北祁连洋向北俯冲提供了重要的时间约束。
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| 关 键 词： | 北祁连缝合带 油葫芦沟蛇绿岩 仰冲型花岗斑岩 锆石U Pb年龄 |
Zircon U-Pb Age of Granite Porphyry Within Youhulugou Ophiolite in the Suture Zone of North Qilian Mountains and Its Geological Implications |
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| LI Bing,HU Daogong,CHEN Xuanhua,ZHANG Yaoling,WU Huanhuan,WANG Chaoqun.Zircon U-Pb Age of Granite Porphyry Within Youhulugou Ophiolite in the Suture Zone of North Qilian Mountains and Its Geological Implications[J].Geoscience——Journal of Graduate School,China University of Geosciences,2017,31(6):1170. |
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| Authors: | LI Bing HU Daogong CHEN Xuanhua ZHANG Yaoling WU Huanhuan WANG Chaoqun |
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| Institution: | 1SinoProbe Centre, Chinese Academy of Geological Sciences，Beijing100037，China;
2Institute of Geomechanics, Chinese Academy of Geological Sciences，Beijing100081，China |
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| Abstract: | Ophiolites as on land or arc slices of oceanic lithosphere, are the production of the mid ocean ridge expansion or subduction of the plates. The granitoids can be formed during the formation of ophiolites and are important for studying origin of the ophiolites, especially dating the precise ages of the ophiolites formation and evolution. The Youhulugou ophiolite is one of the representative ophiolite fragments in the suture zone of the North Qilian Mountain. In this study, major and trace elements geochemical study indicates that the granite porphyry within Youhulugou ophiolite has high Al2O3 and K2O content characteristics. According to the moderate LREE enrichment patterns, the granite porphyry is similar to the obduction type granitoids rocks within ophiolites. LA ICP MS U Pb dating was carried out for zircons from isotropic granite porphyry within Youhulugou ophiolite. Twenty point analyses yield a relatively consistent and apparent 206Pb/238U weighted mean age of (4975±15) Ma, which is considered to be the forming age of the granite porphyry and the obduction age of the Youhulugou ophiolite onto the continental crust. Combined with regional geological characteristics, chronological and geochemical data，we concluded that the Youhulugou ophiolite obducted during the Late Cambrian era, and the acquisition of forming age and determination of tectonic setting for Youhulugou ophiolite provide significant constraints on the age of intra oceanic subduction system in the North Qilian Ocean. |
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| Keywords: | North Qilian suture zone Youhulugou ophiolite obduction type granite porphyry zircon U Pb age |
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