| 北祁连水洞峡蛇绿岩形成时代与构造环境 |
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| 引用本文： | 郭晶,李云帅,张建新,路增龙.北祁连水洞峡蛇绿岩形成时代与构造环境[J].地球科学,2021,46(5):1644-1656. |
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| 作者姓名： | 郭晶 李云帅 张建新 路增龙 |
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| 作者单位： | 山西大同大学建筑与测绘工程学院,山西大同 037001;天津大学地球系统科学学院,表层地球系统科学研究院,天津 300072;中国地质科学院地质研究所,北京 100037 |
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| 基金项目： | 中国地质调查局项目12120115027001 |
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| 摘 要： | 蛇绿岩的时空关系与构造归属是深入认识俯冲带演化和重建古板块构造格局的关键地质依据之一.水洞峡蛇绿岩作为北祁连南带蛇绿岩东段的重要组成部分，其形成时代和构造环境一直缺乏准确的限定.采用LA-ICP-MS对水洞峡蛇绿岩中的辉长岩进行了锆石U-Pb测年，所获得的206Pb/238U加权平均年龄为497.0±2.4 Ma（MSWD=0.84），该年龄代表了辉长岩的结晶年龄，表明水洞峡蛇绿岩的形成时代应该为晚寒武世，这与祁连南带蛇绿岩的形成时代基本一致.蛇纹岩的矿物化学特征以及镁铁质-超镁铁质岩的全岩地球化学研究结果表明，水洞峡蛇绿岩中的蛇纹岩、辉长岩和玄武岩均表现出明显的与俯冲带密切相关的地球化学特征.结合北祁连已有的研究资料，玉石沟-水洞峡蛇绿岩应该属于SSZ型，该蛇绿岩在弧-陆碰撞过程中向南仰冲到中祁连地块之上.
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| 关 键 词： | 锆石U-Pb定年 SSZ型 水洞峡蛇绿岩 北祁连 地球化学 |
| 收稿时间： | 2020-08-27 |
Age and Tectonic Affinity of Shuidongxia Ophiolite in North Qilian Orogen |
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| Guo Jing,Li Yunshuai,Zhang Jianxin,Lu Zenglong.Age and Tectonic Affinity of Shuidongxia Ophiolite in North Qilian Orogen[J].Earth Science-Journal of China University of Geosciences,2021,46(5):1644-1656. |
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| Authors: | Guo Jing Li Yunshuai Zhang Jianxin Lu Zenglong |
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| Abstract: | The spatial relationship and tectonic affinity of the ophiolite can provide key evidence for the evolution of the subduction zone and paleo-tectonic reconstruction. Ophiolite in Shuidongxia is an important part of the southern belt of the North Qilian orogen, however, the age and tectonic setting are poorly constrained. Zircon grains from the gabbro yield a weighted mean 206Pb/238U age 497.0±2.4 Ma (MSWD=0.84), indicating the Shuidongxia ophiolite formed in the Late Cambrian, which is consistent with the ages of ophiolites in the southern belt of the North Qilian orogen. The mineralogical characteristics as well as the whole-rock geochemistry of gabbro, serpentinite and basalt suggest that the Shuidongxia ophiolites are closely related to subduction zone. Combined with the regional geology of the North Qilian orogen, it is suggested that the Yushigou-Shuidongxia ophiolite belongs to SSZ-type and obducted southward onto the central Qilian block during the arc-continent collision. |
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