| 北阿尔金南华纪双峰式火山岩的发现及构造意义 |
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| 引用本文： | 刘函,王国灿,曹树钊,罗彦军,高睿,黄文星.北阿尔金南华纪双峰式火山岩的发现及构造意义[J].地球科学,2012,37(5):917-928. |
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| 作者姓名： | 刘函 王国灿 曹树钊 罗彦军 高睿 黄文星 |
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| 作者单位： | 1.中国地质大学地球科学学院, 湖北武汉 430074 |
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| 基金项目： | 中国地质调查局项目1212011121261中国地质调查局项目1212010610103 |
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| 摘 要： | 北阿尔金恰什坎萨伊沟南口火山岩显双峰式特征, 由变玄武岩和变流纹岩组成.地球化学分析表明变玄武岩源自富集地幔, 上侵过程中遭受地壳混染, 形成于大陆裂谷环境; 而变流纹岩与铝质A型花岗岩特征类似, 为幔源岩浆底侵下地壳部分熔融成因.变流纹岩锆石LA-ICP-MS U-Pb年龄为749.8±4.6 Ma, 代表火山岩的喷发年龄, 为北阿尔金洋的初始裂解事件提供了时代证据; 与北祁连洋初始裂解时代相近, 从洋盆的初始裂解时间证明北阿尔金与北祁连同为一个带."西域板块"新元古代中期岩浆活动与Rodinia超大陆裂解事件密切相关, 与扬子板块周缘岩浆活动有相似性, 可划分为裂解初期与峰期两个阶段.所发现北阿尔金南华纪双峰式火山岩正是Rodinia超大陆裂解峰期岩浆活动的产物.
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| 关 键 词： | 双峰式火山岩 大陆裂解 地球化学 地质年代学 北阿尔金 |
| 收稿时间： | 2011-10-12 |
Discovery of Nanhuaian Bimodal Volcanics in Northern Altyn Tagh and Its Tectonic Significance |
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| Abstract: | The early Paleozoic ophiolite section of Qiashikansayi hollow is located at the segment of Hongliuguo-Lapeiquan ophiolite belt in the North Altyn Tagh Mountains, striking from south to north. The volcanics from the south entrance of the hollow consist of meta-basalts and meta-rhyolites, with typical "double peaks". The geochemistry data show that meta-basalts derived from enriched mantle have suffered from contamination of crust, and were formed in a continental rift setting; Meta- rhyolites are similar to the A-type granite in the composition, resulted from the partial melt of lower crust due to the underplating of mantle-derived magma. Zircon LA-ICP-MS dating of rhyolite yields a U-Pb age of 749.8±4.6 Ma, representing the time of crystallization of the bimodal volcanics, and providing time evidence for the initial breakup of North Altyn Ocean together with the published regional geological reports. There are similar time of initial breakup between North Altyn Ocean and North Qilian Ocean. We suggest that this volcanic action is closely related with the breakup of Rodinia supercontinent. |
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