| 新疆东天山卡拉塔格二叠纪火山岩成因及构造意义 |
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| 引用本文： | 张雪,翁凯,赵晓健,杜守礼,尚颖.新疆东天山卡拉塔格二叠纪火山岩成因及构造意义[J].吉林大学学报(地球科学版),2021,51(4):1119-1138. |
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| 作者姓名： | 张雪 翁凯 赵晓健 杜守礼 尚颖 |
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| 作者单位： | 1. 长安大学地球科学与资源学院, 西安 710054;2. 自然资源部岩浆作用成矿与找矿重点实验室/中国地质调查局西安地质调查中心, 西安 710054;3. 中国石油长庆油田分公司勘探开发研究院, 西安 710018;4. 中国地质科学院国家地质实验测试中心, 北京 100037 |
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| 基金项目： | 中央高校基本科研业务费资助项目（300102270110）；陕西省自然科学基金项目（2021JQ-329，2020JQ-440）；国家自然科学基金项目（41602236） |
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| 摘 要： | 新疆东天山中北部的卡拉塔格地区广泛出露一套二叠纪陆相火山熔岩，本次对其采集的玄武岩和英安岩进行岩相学、锆石U-Pb定年、Lu-Hf同位素和岩石地球化学分析。年代学研究获得2个英安岩样品LA-ICP-MS锆石U-Pb加权平均年龄为（267.5±1.5）Ma和（296.7±1.7）Ma，代表了英安岩的结晶年龄为早二叠世。岩石地球化学数据显示：玄武岩为碱性系列，具有高Al2O3质量分数和Na2O/K2O值，低TFeO、Cr质量分数和Mg#值的特征；微量元素Yb标准化的Ta、La和Nb值指示该区玄武质岩浆起源于富集型地幔；低La/Ba值，（Th/Nb）N>1，Nb/La<1，表明岩浆在上升过程中受到了地壳岩石圈物质的混染；样品w（Zr）>100×10-6，Zr/Y>5，显示大陆板内玄武岩特征。英安岩为钙碱性系列，富硅铝，Rb、Ba、Th、U、Zr等元素质量分数较高，Ti、Nb、Ta、Sr、P等元素质量分数较低，明显不同于玄武岩元素分布特征，却与地壳元素分布相似；εHf（t） 值（5.4~14.7）为正，表明英安岩源区为新生地壳；w（Rb）-w（Y+Nb）构造环境判别图解表明其形成于大陆伸展环境。结合前人的研究成果，认为卡拉塔格早二叠世火山岩形成于板内伸展环境，为天山石炭纪—二叠纪大火成岩省裂谷火山作用的组成部分，限定了该区古亚洲洋闭合于早二叠世之前。
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| 关 键 词： | 东天山 二叠纪 火山岩 锆石U-Pb测年 地球化学 岩石成因 |
| 收稿时间： | 2020-06-01 |
Permian Volcanic Rocks in Kalatage Area,Eastern Tianshan,Xinjiang:Petrogenesis and Tectonic Implications |
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| Zhang Xue,Weng Kai,Zhao Xiaojian,Du Shouli,Shang Ying.Permian Volcanic Rocks in Kalatage Area,Eastern Tianshan,Xinjiang:Petrogenesis and Tectonic Implications[J].Journal of Jilin Unviersity:Earth Science Edition,2021,51(4):1119-1138. |
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| Authors: | Zhang Xue Weng Kai Zhao Xiaojian Du Shouli Shang Ying |
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| Institution: | 1. School of Earth Science and Resources, Chang'an University, Xi'an 710054, China;2. Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MNR/Xi'an Center of Geological Survey, China Geological Survey, Xi'an 710054, China;3. Research Institute of Exploration and Development, Changqing Oilfield Company, PetroChina, Xi'an 710018, China;4. National Research Center for Geoanalysis, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The Kalatage area is located in the north central part of the Eastern Tianshan, where the Permian continental volcanic rocks are widely distributed. Their petrography, geochemistry, zircon U-Pb geochronology,and Lu-Hf isotope analysis for basalt and dacite are presented in this paper. The LA-ICP-MS zircon U-Pb dating of (267.5±1.5) Ma and (296.7±1.7) Ma from two dacite samples represents the crystallization age of dacite in the Early Permian. The geochemical data show that the basalt is of alkaline series with high Al2O3,Na2O/K2O, low TFeO, Mg#, and Cr. The Ta, La, and Nb contents standardized by Yb indicate its basaltic magmatic origin from the enriched mantle source. The low La/Ba, (Th/Nb)N>1 and Nb/La<1 suggest that the magma was mixed with lithospheric material during its ascent. The samples have w(Zr)>100×10-6 and Zr/Y>5, indicating the characteristics of continental intraplate basalt. The dacite is of calc-alkaline type with enrichment of silicon and aluminum, high contents of Rb, Ba, Th, U, Zr, etc, and low content of Ti, Nb, Ta, Sr, P, etc. These features are obviously different from those of the basalt but similar to the crust. The dacite has positive εHf(t) value (5.4-14.7), indicating that the source region is the new crust. The w(Y+Nb)-w(Rb) discrimination diagrams of tectonic setting show that the dacite was formed in the continental extensional setting. Combined with the previous research results, we believe that the Kalatage Early Permian volcanic rocks formed in the continental extensional setting, and they are part of the Carboniferous-Permian rift-related volcanism in Tianshan, which restricted the closure of Paleo-Asian Ocean in this area before the Early Permian. |
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| Keywords: | Eastern Tianshan Permian volcanic rocks zircon U-Pb dating geochemistry petrogenesis |
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