Large iron isotope variation in the eastern Pacific mantle as a consequence of ancient low-degree melt metasomatism

doi:10.1016/j.gca.2020.07.029

CORC > 海洋研究所 > 中国科学院海洋研究所 > 海洋地质与环境重点实验室

	Large iron isotope variation in the eastern Pacific mantle as a consequence of ancient low-degree melt metasomatism
	Sun, Pu 1,2; Niu, Yaoling 1,3,4; Guo, Pengyuan 1,2; Duan, Meng 1,2; Chen, Shuo 1,2; Gong, Hongmei 1,2; Wang, Xiaohong 1,2; Xiao, Yuanyuan 1,2
刊名	GEOCHIMICA ET COSMOCHIMICA ACTA
	2020-10-01
卷号	286 页码:269-288
关键词	East Pacific Rise Mid-ocean ridge basalts Fe isotope Mantle heterogeneity Seamounts Mantle metasomatism
ISSN号	0016-7037
DOI	10.1016/j.gca.2020.07.029
英文摘要	Studies of mid-ocean ridge basalts (MORB) have revealed a heterogeneous asthenospheric mantle in chemical elements and radiogenic isotopes. Here we report that MORB mantle is also heterogeneous in Fe isotopes through studying the glass samples from seamounts flanking the northern East Pacific Rise between 5 degrees and 15 degrees N. These samples show large Fe isotope variation with delta Fe-56 values (+0.03 parts per thousand to +0.36 parts per thousand) exceeding the known range of MORB (+0.05 parts per thousand to +0.17 parts per thousand). Such highly varied delta Fe-56 values cannot be well explained by seafloor alteration, fractional crystallization or partial melting processes, but instead require a source mantle significantly heterogeneous in Fe isotope compositions. Importantly, the delta Fe-56 values of these basalts correlate significantly with major and trace elements and Sr-Nd-Pb-Hf radiogenic isotopes, reflecting melting-induced mixing of a two-component mantle with the enriched component having heavy Fe isotope compositions dispersed as physically distinct domains in the depleted mantle matrix. The major and trace element characteristics of the enriched mantle component, as inferred from these basalts, are consistent with a low-degree melting origin. Such low-degree melts with heavy Fe isotope compositions most likely formed at sites such as the lithosphere-asthenosphere boundary beneath ocean basins, which can metasomatize the overlying oceanic lithosphere by crystallizing dikes/veins of garnet pyroxenite lithologies. Recycling of these dikes/veins with isotopically heavier Fe can readily contribute to the Fe isotope heterogeneity in the MORB mantle. However, the extremely high primitive delta Fe-56 values of the two alkali basalts (up to 0.34 parts per thousand) require an enriched source component with unusually high delta Fe-56 values. We suggest that partial melts from the recycled dikes/veins of garnet pyroxenite lithologies can react with the ambient peridotitic mantle and generate a secondary garnet pyroxenite with heavier Fe isotope compositions than, but similar radiogenic isotope compositions as its precursor. Melting-induced mixing between these garnet pyroxenites (recycled and newly formed) and depleted mantle matrix can readily explain the compositional variations in elements, radiogenic isotopes and Fe isotopes observed in these seamount lavas. These new data and correlated variations offer a new dimension for understanding the origin of mantle chemical and isotopic heterogeneity in the context of chemical differentiation of the Earth. (C) 2020 Elsevier Ltd. All rights reserved.
资助项目	Qingdao National Laboratory for Marine Science and Technology[2015ASKJ03] ; NSFC-Shandong Joint Fund for Marine Science Research Centers[U1606401] ; Chinese Academy of Sciences[Y42217101L] ; National Natural Science Foundation of China (NSFC)[41776067] ; National Natural Science Foundation of China (NSFC)[41630968] ; 111 Project[B18048]
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	PERGAMON-ELSEVIER SCIENCE LTD
WOS记录号	WOS:000561935200015
内容类型	期刊论文
版本	出版稿
源URL	[http://ir.qdio.ac.cn/handle/337002/168336]
专题	海洋研究所_海洋地质与环境重点实验室
通讯作者	Sun, Pu; Niu, Yaoling
作者单位	1.Qingdao Natl Lab Marine Sci & Technol, Lab Marine Geol, Qingdao 266061, Peoples R China 2.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao 266071, Peoples R China 3.Univ Durham, Dept Earth Sci, Durham DH1 3LE, England 4.China Univ Geosci, Sch Earth Sci & Resources, Beijing 100083, Peoples R China
推荐引用方式 GB/T 7714	Sun, Pu,Niu, Yaoling,Guo, Pengyuan,et al. Large iron isotope variation in the eastern Pacific mantle as a consequence of ancient low-degree melt metasomatism[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2020,286:269-288.
APA	Sun, Pu.,Niu, Yaoling.,Guo, Pengyuan.,Duan, Meng.,Chen, Shuo.,...&Xiao, Yuanyuan.(2020).Large iron isotope variation in the eastern Pacific mantle as a consequence of ancient low-degree melt metasomatism.GEOCHIMICA ET COSMOCHIMICA ACTA,286,269-288.
MLA	Sun, Pu,et al."Large iron isotope variation in the eastern Pacific mantle as a consequence of ancient low-degree melt metasomatism".GEOCHIMICA ET COSMOCHIMICA ACTA 286(2020):269-288.