Highly Unradiogenic Pb Isotopes Revealed by Plagioclase-Hosted Melt Inclusions in E-MORB From the South China Sea

doi:10.1029/2022JB025348

IOCAS-IR > 海洋地质与环境重点实验室

	Highly Unradiogenic Pb Isotopes Revealed by Plagioclase-Hosted Melt Inclusions in E-MORB From the South China Sea
	Wu, Tao 1,2,3,4; Zhang, Wen 5; Wilde, Simon A.6; Lu, Jianggu 2; Zhang, Guoliang 7,8; Li, Chunfeng 1,3; Chen, Xuegang 1,3; Chen, Shuangshuang 9
	2023-04-01
发表期刊	JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
ISSN	2169-9313
卷号	128 期号:4 页码:15
通讯作者	Wu, Tao(taowu@zju.edu.cn) ; Zhang, Wen(tuyaken@hotmail.com)
摘要	Mid-ocean ridge basalts (MORBs) can record heterogeneity of the upper mantle. Early crystallized minerals and their melt inclusions commonly record greater isotopic variability than whole-rocks and are powerful tools to investigate the mantle source. In this study, we develop a new in situ Pb analytical protocol for Pb-poor materials (sub-ppm level) and apply it to the plagioclase-hosted melt-inclusions from IODP Expedition 349 Site U1433, South China Sea (SCS). Together with element mapping, in situ major and trace element analyzes and in situ Sr isotopes of plagioclase phenocrysts, we show that unlike the low and uniform whole-rock Sr-87/Sr-86 ratios, the plagioclase phenocrysts record extreme Sr isotopic heterogeneity. Strontium isotopic heterogeneity is observed between crystals even in a single thin section. Based on the high an contents of plagioclase phenocrysts and high Mg# values of their melt inclusions, we propose they crystallized early in the magma chamber and were most likely formed in different batches of mantle-derived melts. The plagioclase-hosted melt inclusions show highly variable Pb isotopes, exhibiting a typical linear variation in Pb-207/Pb-204 versus Pb-206/Pb-204. Such a mixing trend indicates an end-member with highly unradiogenic Pb isotopes. The LREE enrichment and negative correlations between La/Sm and Pb isotopes of the melt inclusions, indicate that ancient cratonic lower continent crustal materials, with low time-integrated U/Pb ratios, are likely present in the sub-ridge mantle of the southwest Sub-basin, SCS. Plain Language Summary The upper mantle of our Earth is highly heterogeneous. Early crystallized minerals and their melt inclusions are powerful tools to investigate the mantle source. In this study, we developed a new in situ Pb analytical protocol for Pb-poor materials (sub-ppm level) and apply it to the plagioclase-hosted melt-inclusions of E-MORBs from IODP Expedition 349 Site U1433, South China Sea (SCS). We also analyzed the major and trace elements and Sr isotopes of plagioclase phenocrysts, as well as undertaking element mapping. We found that unlike the low and uniform whole-rock Sr-87/Sr-86 ratios, the plagioclase phenocrysts record extreme Sr isotopic heterogeneity. Strontium isotopic heterogeneity is observed between crystals even in a single thin section. The plagioclase-hosted melt inclusions show highly variable Pb isotopic ratios, which exhibit a typical linear variation in Pb-207/Pb-204 versus Pb-206/Pb-204. Such a mixing trend indicates an end-member with highly unradiogenic Pb isotopes. The enrichment of LREE and negative correlations between La/Sm and Pb isotopes melt inclusions, suggest that ancient cratonic lower continent crustal materials are likely present in the sub-ridge mantle of the southwest Sub-basin, SCS, and that they are the highly unradiogenic component.
关键词	plagioclase phenocrysts melt inclusions in situ Sr-Pb isotopes MORB unradiogenic Pb isotopes South China Sea
DOI	10.1029/2022JB025348
收录类别	SCI
语种	英语
资助项目	National Natural Science Foundation of China[42072069] ; National Natural Science Foundation of China[41761134] ; Natural Science Foundation of Hainan Province[521QN274] ; Natural Science Foundation of Hainan Province[421CXTD441] ; Open Foundation of Key Laboratory of Submarine Geosciences, MNR[KLSG2101]
WOS研究方向	Geochemistry & Geophysics
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:001022783200030
出版者	AMER GEOPHYSICAL UNION
WOS关键词	MC-ICP-MS ; ULTRAPHYRIC BASALTS ; CONTINENTAL-CRUST ; SPREADING RIDGES ; MANTLE ; VARIABILITY ; SUBDUCTION ; ACCRETION ; EVOLUTION ; DYNAMICS
引用统计
文献类型	期刊论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/182647
专题	海洋地质与环境重点实验室
通讯作者	Wu, Tao; Zhang, Wen
作者单位	1.Zhejiang Univ, Ocean Coll, Zhoushan, Peoples R China 2.Minist Nat Resources, Inst Oceanog 2, Key Lab Submarine Geosci, Hangzhou, Peoples R China 3.Zhejiang Univ, Hainan Inst, Sanya, Peoples R China 4.Donghai Lab, Zhoushan, Peoples R China 5.China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Wuhan, Peoples R China 6.Curtin Univ, Inst Geosci Res, Sch Earth & Planetary Sci, Perth, WA, Australia 7.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao, Peoples R China 8.Chinese Acad Sci, Ctr Deep Sea Res, Qingdao, Peoples R China 9.Sun Yat Sen Univ, Sch Earth Sci & Engn, Guangzhou, Peoples R China
推荐引用方式 GB/T 7714	Wu, Tao,Zhang, Wen,Wilde, Simon A.,et al. Highly Unradiogenic Pb Isotopes Revealed by Plagioclase-Hosted Melt Inclusions in E-MORB From the South China Sea[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,2023,128(4):15.
APA	Wu, Tao.,Zhang, Wen.,Wilde, Simon A..,Lu, Jianggu.,Zhang, Guoliang.,...&Chen, Shuangshuang.(2023).Highly Unradiogenic Pb Isotopes Revealed by Plagioclase-Hosted Melt Inclusions in E-MORB From the South China Sea.JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,128(4),15.
MLA	Wu, Tao,et al."Highly Unradiogenic Pb Isotopes Revealed by Plagioclase-Hosted Melt Inclusions in E-MORB From the South China Sea".JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 128.4(2023):15.