Much controversy exists regarding the evolution and termination of accretionary orogens where typical continent-continent collision features are lacking. The Central Asian Orogenic Belt provides a key opportunity to explore the genetic relationships between the formation of high-Mg igneous associations and the evolution of accretionary orogens. In this study, two-stage Triassic magmatic events were identified in the southeastern segment of the Central Asian Orogenic Belt (including ca. 247 Ma andesites and ca. 222 Ma diorites), through precise secondary ion mass spectrometry (SIMS) and laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) zircon dating. The Olenekian andesites show typical sanukitoid affinities with high TiO2, MgO, Ni, and Cr contents, and enrichment in large ion lithophile elements (LILEs; K, Ba, and Sr). They yield depleted Hf isotopic compositions and high δ18O values, which along with Hf-O isotope modeling results indicate that they originated from the partial melting of mantle wedge peridotites with input of 20% terrigenous sediments. The Norian diorites have moderate SiO2, relatively high MgO, Cr, and Ni contents, Mg# values of 63−65, high Sr, low Y and Yb contents, relevant high La/Yb ratios, and negligible Eu anomalies, which makes them comparable to high-Mg andesites with adakitic affinity. Their depleted isotopic compositions are similar to coeval A-type granites that resulted from lithospheric delamination after the final collision. In addition, with high K2O/Na2O ratios and incompatible element ratios similar to those of the continental crust (e.g., Nb/U, Ce/Pb, and Nd/Sm), they conform to an origin in which partial melting of delaminated mafic lower crust subsequently interacted with mantle materials. These two-stage abnormal Triassic high-Mg rocks archive a hot slab window triggered by the break-off of the Paleo-Asian oceanic slab and lower crustal delamination related to collapse of the southeastern segment of the Central Asian Orogenic Belt. These findings provide beneficial information for the reconstruction of the East Asian blocks in Pangea.
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Research Article|
March 16, 2023
High-magnesium igneous associations record final-stage geodynamic process of the southeastern segment of the Central Asian Orogenic Belt
Yan Jing;
Yan Jing
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
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Wen-chun Ge;
Wen-chun Ge
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
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Hao Yang;
Hao Yang
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
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Yu Dong;
Yu Dong
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
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Zheng Ji;
Zheng Ji
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
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Jun-hui Bi;
Jun-hui Bi
3
Tianjin Center, China Geological Survey, Tianjin 300170, China
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Hong-ying Zhou;
Hong-ying Zhou
3
Tianjin Center, China Geological Survey, Tianjin 300170, China
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De-he Xing
De-he Xing
4
Shenyang Center, China Geological Survey, Shenyang 110034, China
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Yan Jing
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
Wen-chun Ge
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
Hao Yang
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
Yu Dong
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
Zheng Ji
1
College of Earth Sciences, Jilin University, Changchun 130061, China2
Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130026, China
Jun-hui Bi
3
Tianjin Center, China Geological Survey, Tianjin 300170, China
Hong-ying Zhou
3
Tianjin Center, China Geological Survey, Tianjin 300170, China
De-he Xing
4
Shenyang Center, China Geological Survey, Shenyang 110034, China
Publisher: Geological Society of America
Received:
29 Jan 2022
Revision Received:
22 Sep 2022
Accepted:
26 Oct 2022
First Online:
16 Mar 2023
Online ISSN: 1943-2674
Print ISSN: 0016-7606
© 2023 Geological Society of America
GSA Bulletin (2023)
Article history
Received:
29 Jan 2022
Revision Received:
22 Sep 2022
Accepted:
26 Oct 2022
First Online:
16 Mar 2023
Citation
Yan Jing, Wen-chun Ge, Hao Yang, Yu Dong, Zheng Ji, Jun-hui Bi, Hong-ying Zhou, De-he Xing; High-magnesium igneous associations record final-stage geodynamic process of the southeastern segment of the Central Asian Orogenic Belt. GSA Bulletin 2023; doi: https://doi.org/10.1130/B36472.1
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