Permian Tectonic Evolution in the Middle Part of Central Asian Orogenic Belt: Evidence from Newly Identified Volcanic Rocks in the Bilutu Area, Inner Mongolia |
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作者姓名: | WANG Shijie LIU Yang DONG Xiaojie XU Zhongyuan WANG Wenlong LI Shichao SHI Qiang CUI Weilong |
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摘 要: | In this study, zircon U-Pb ages, geochemical and Lu-Hf isotopic data are presented for the newly identified volcanic rocks which were considered as Bainaimiao group in Bainaimiao Arc Belt(BAB), Inner Mongolia, which could provide important constraints on the evolution of the northern part of North China Block(NCB) and BAB. Basalt to basaltic andesite and andesite to dacite were collected from two sections, which showed eruption ages of 278.2±4.1 Ma and 258.3±3.0 Ma respectively. All samples are characterized by high abundances in Al_2O_3, LREEs, and LILEs, but depleted in HFSEs. Together with high Mg# ratios and low K/tholeiite to calc-alkaline series, these features indicated that basalt to andesite was likely derived from relatively low degree partial melting of the subduction-fluid related mantle in the spinel phase. And dacite was mainly from the partial melting of crust, then affected by mantle. All samples barely went through fractional crystallization process with the slight Eu anomaly. Compared with the contemporary basalt in NCB, rocks in BAB have a complex composition of zircon and a more positive ε_(Hf)(t) value(-6.6–6.4), indicating that they had different magma sources of rocks. Though with different basements, NCB and BAB have become an integrated whole before 278 Ma. Therefore, it could be concluded that NCB and BAB belonged to the active continental margin and the PAO had not closed yet until late Permian and then it disappeared gradually and the CAOB developed into a condition of syn-post collision.
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收稿时间: | 2019/5/15 0:00:00 |
修稿时间: | 2019/8/14 0:00:00 |
Permian Tectonic Evolution in the Middle Part of Central Asian Orogenic Belt: Evidence from Newly Identified Volcanic Rocks in the Bilutu Area,Inner Mongolia |
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Authors: | WANG Shijie LIU Yang DONG Xiaojie XU Zhongyuan WANG Wenlong LI Shichao SHI Qiang and CUI Weilong |
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Institution: | 1 College of Earth Science, Jilin University, Changchun 130061, China,2 Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China,1 College of Earth Science, Jilin University, Changchun 130061, China,1 College of Earth Science, Jilin University, Changchun 130061, China,2 Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China,1 College of Earth Science, Jilin University, Changchun 130061, China,1 College of Earth Science, Jilin University, Changchun 130061, China and 3 State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China |
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Abstract: | In this study, zircon U‐Pb ages, geochemical and Lu‐Hf isotopic data are presented for the newly identified volcanic rocks which were considered as Bainaimiao group in Bainaimiao Arc Belt (BAB), Inner Mongolia, which could provide important constraints on the evolution of the northern part of North China Block (NCB) and BAB. Basalt to basaltic andesite and andesite to dacite were collected from two sections, which showed eruption ages of 278.2±4.1 Ma and 258.3±3.0 Ma respectively. All samples are characterized by high abundances in Al2O3, LREEs, and LILEs, but depleted in HFSEs. Together with high Mg# ratios and low K/tholeiite to calc‐alkaline series, these features indicated that basalt to andesite was likely derived from relatively low degree partial melting of the subduction‐fluid related mantle in the spinel phase. And dacite was mainly from the partial melting of crust, then affected by mantle. All samples barely went through fractional crystallization process with the slight Eu anomaly. Compared with the contemporary basalt in NCB, rocks in BAB have a complex composition of zircon and a more positive εHf (t) value (–6.6–6.4), indicating that they had different magma sources of rocks. Though with different basements, NCB and BAB have become an integrated whole before 278 Ma. Therefore, it could be concluded that NCB and BAB belonged to the active continental margin and the PAO had not closed yet until late Permian and then it disappeared gradually and the CAOB developed into a condition of syn‐post collision. |
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Keywords: | Permian volcanic rocks Bilutu Bainaimiao Arc Belt North China Block Central Asian Orogenic Belt |
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