Volume 93, Issue 5 pp. 1281-1299
Original Article
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Permian Tectonic Evolution in the Middle Part of Central Asian Orogenic Belt: Evidence from Newly Identified Volcanic Rocks in the Bilutu Area, Inner Mongolia

Shijie WANG

Shijie WANG

College of Earth Science, Jilin University, Changchun, 130061 China

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Yang LIU

Yang LIU

Tianjin Center of Geological Survey, China Geological Survey, Tianjin, 300170 China

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Xiaojie DONG

Corresponding Author

Xiaojie DONG

College of Earth Science, Jilin University, Changchun, 130061 China

Corresponding author. E-mail: [email protected]Search for more papers by this author
Zhongyuan XU

Zhongyuan XU

College of Earth Science, Jilin University, Changchun, 130061 China

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Wenlong WANG

Wenlong WANG

Tianjin Center of Geological Survey, China Geological Survey, Tianjin, 300170 China

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Shichao LI

Shichao LI

College of Earth Science, Jilin University, Changchun, 130061 China

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Qiang SHI

Qiang SHI

College of Earth Science, Jilin University, Changchun, 130061 China

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Weilong CUI

Weilong CUI

State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029 China

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First published: 03 October 2019
Citations: 5

About the first author:

WANG Shijie, male; born in 1993 in Heilongjiang, doctor; mainly engaged in tectonic geology, in Jilin University. E-mail: [email protected]

About the corresponding author:

DONG Xiaojie, male, born in 1984 in Hebei, lecturer; mainly engaged in tectonic geology and Precambrian geology, in Jilin University. E-mail: [email protected]

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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