气候变化领域集成服务门户(CCPortal): Syn-Exhumation Magmatism in an Active Continental Margin above a Continental Subduction zone: Evidence from Late Triassic Mafic Igneous Rocks in the Southeastern North China Block

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DOI	10.1130/B35656.1
	Syn-Exhumation Magmatism in an Active Continental Margin above a Continental Subduction zone: Evidence from Late Triassic Mafic Igneous Rocks in the Southeastern North China Block
	Fang W.; Dai L.-Q.; Zheng Y.-F.; Zhao Z.-F.; Chen Q.; Zhou Y.
发表日期	2021
ISSN	167606
起始页码	1267
结束页码	1282
卷号	133
英文摘要	Syn-subduction arc magmatism is absent above continental subduction zones, providing important constraints on the nature of petrogenetic processes during continental collision. Nevertheless, we have identified syn-exhumation mafic igneous rocks in an active continental margin above a continental subduction zone, where the South China Block (SCB) was deeply subducted beneath the North China Block (NCB) for collisional orogeny in the Triassic. These mafic igneous rocks occur in the southeastern margin of the NCB, showing consistent Late Triassic zircon U-Pb ages of ca. 219–218 Ma, coeval with exhumation of the deeply subducted continental crust. These rocks are categorized into two series of sub-alkaline and alkaline, all exhibiting arc-like trace element distribution patterns, highly enriched radiogenic Sr-NdHf and high zircon O isotope compositions. In particular, they exhibit two-stage wholerock Nd and Hf model ages and zircon Hf model ages of Paleoproterozoic, which are comparable to those of ultrahigh-pressure metamorphic rocks with the SCB affinity in the Dabie-Sulu orogenic belt. Such geochemical features indicate that these mafic igneous rocks were derived from partial melting of ultramafic metasomatites generated by reaction of felsic melts from the subducted SCB with the mantle wedge peridotite beneath the NCB. The geochemical differences in element and isotope compositions between the two series igneous rocks can be mainly ascribed to different proportions of the crustal component in the metasomatites, which is verified by quantitative modellings of the geochemical transfer in the continental subduction zone. The systematic variations in some geochemical variables such as Fe/Mn, Zn/Fe, and Nb/ Ta ratios indicate pyroxenite-rich and hornblendite-rich lithologies, respectively, for the sub-alkaline and alkaline series igneous rocks. With the tectonic extension for exhumation of the deeply subducted continental crust in the Late Triassic, the fertile and enriched metasomatites in the mantle wedge underwent partial melting for the syn-exhumation mafic magmatism in the southeastern NCB. Therefore, the mafic igneous rocks in the active continental margin not only record the crust-mantle interaction in the continental subduction zone, but also witness the generation of syn-exhumation magmatism in the late stage of continental collision. © 2020 Geological Society of America
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184685
作者单位	Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China; Center of Excellence for Comparative Planetology, Chinese Academy of Sciences (CAS), Hefei, 230026, China
推荐引用方式 GB/T 7714	Fang W.,Dai L.-Q.,Zheng Y.-F.,et al. Syn-Exhumation Magmatism in an Active Continental Margin above a Continental Subduction zone: Evidence from Late Triassic Mafic Igneous Rocks in the Southeastern North China Block[J],2021,133.
APA	Fang W.,Dai L.-Q.,Zheng Y.-F.,Zhao Z.-F.,Chen Q.,&Zhou Y..(2021).Syn-Exhumation Magmatism in an Active Continental Margin above a Continental Subduction zone: Evidence from Late Triassic Mafic Igneous Rocks in the Southeastern North China Block.Bulletin of the Geological Society of America,133.
MLA	Fang W.,et al."Syn-Exhumation Magmatism in an Active Continental Margin above a Continental Subduction zone: Evidence from Late Triassic Mafic Igneous Rocks in the Southeastern North China Block".Bulletin of the Geological Society of America 133(2021).