Calcium isotopic fractionation during plate subduction: Constraints from back-arc basin basalts

doi:10.1016/j.gca.2019.12.004

	Calcium isotopic fractionation during plate subduction: Constraints from back-arc basin basalts
	Zhu, Hongli 1,2,3; Du, Long 4; Li, Xin5 ; Zhang, Zhaofeng 5; Sun, Weidong1,2,3,6
	2020-02-01
发表期刊	GEOCHIMICA ET COSMOCHIMICA ACTA
ISSN	0016-7037
卷号	270 页码:379-393
通讯作者	Zhang, Zhaofeng(zfzhang@gig.ac.cn) ; Sun, Weidong(weidongsun@qdio.ac.cn)
摘要	Subduction related metasomatism has been proposed to be one of the most important processes that may cause Ca isotopic heterogeneities in the mantle. Back-arc basin basalts (BABBs) affected by different contributions of subducted materials have various geochemical compositions ranging from MORB-like to arc-like, so that they are ideal media to investigate the behavior of Ca isotopes during plate subduction. Here we report Ca isotopic compositions of a series of BABBs from the Lau Basin, Woodlark Basin and Coriolis Troughs in the southwestern Pacific. Our results show that delta Ca-44/40 of all the BABBs exhibit a narrow range of 0.73 +/- 0.07 to 0.89 +/- 0.06 parts per thousand with an average of 0.80 +/- 0.08 parts per thousand (2SD, N = 21), which are lower than the estimated value of the Bulk Silicate Earth (BSE, 0.94 +/- 0.05 parts per thousand), but are similar to that of MORBs reported in the literature (0.83 +/- 0.11 parts per thousand, 2SD, N = 21). Even though the mantle sources of BABBs studied here have been influenced by various amounts of slab-derived fluids and/or sediments, there is no systematic variation of delta Ca-44/40 with indicators of subduction contributions (e.g., Ce/Pb, Nb/U, Ba/La, Th/Yb, Sr-87/Sr-86 and Nd-143/Nd-144). This suggests that either there is no Ca isotopic discrepancy between subducted components and mantle, and/or the amount of Ca that is transferred from the subducting Pacific slab to the studied BABB mantle sources is insignificant. Water depths at which subducting sediments were deposited control the components of marine sediments that may be subducted, which in turn determine how subduction affects Ca isotopic composition of the mantle. Because the southwestern Pacific has deeper water depths than the carbonate compensation depth, pelagic clays dominate the contribution from the subducted slab rather than carbonates, which leads to the negligible Ca isotopic fractionation during subduction along these trenches. The lack of correlations of delta Ca-44/40 with geochemical indicators of magma differentiation (e.g., MgO, CaO/Al2O3, Sr/Nd, Eu/Eu*) suggests that intermediate-mafic magma differentiation has insignificant effects on Ca isotopic compositions of BABBs. Therefore, we conclude that the observed offset of delta Ca-44/40 (similar to 0.14 parts per thousand) between the mantle and BABBs studied here should be primarily controlled by Ca isotopic fractionation during partial melting without significant contributions from subducted materials. (C) 2019 Elsevier Ltd. All rights reserved.
关键词	Ca isotopes Back-arc basin basalts (BABBs) Subduction Mantle melting Magma differentiation
DOI	10.1016/j.gca.2019.12.004
收录类别	SCI
语种	英语
资助项目	National Natural Science Foundation of China[41873002] ; National Natural Science Foundation of China[41773009] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDB18000000] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDA22050103] ; National Key P&D Program of China[2016YFC0600408] ; Taishan Scholar Program of Shandong[ts201712075] ; AoShan Talents Cultivation Program - Qingdao National Laboratory for Marine Science and Technology[2017ASTCP-OS07] ; China Postdoctoral Science Foundation[2018M640660] ; National Natural Science Foundation of China[41873002] ; National Natural Science Foundation of China[41773009] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDB18000000] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDA22050103] ; National Key P&D Program of China[2016YFC0600408] ; Taishan Scholar Program of Shandong[ts201712075] ; AoShan Talents Cultivation Program - Qingdao National Laboratory for Marine Science and Technology[2017ASTCP-OS07] ; China Postdoctoral Science Foundation[2018M640660]
WOS研究方向	Geochemistry & Geophysics
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:000506666300021
出版者	PERGAMON-ELSEVIER SCIENCE LTD
引用统计	被引频次：33[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/164449
专题	深海极端环境与生命过程研究中心
通讯作者	Zhang, Zhaofeng; Sun, Weidong
作者单位	1.Chinese Acad Sci, Ctr Deep Sea Res, Inst Oceanog, Qingdao 266071, Peoples R China 2.Qingdao Natl Lab Marine Sci & Technol, Lab Marine Mineral Resources, Qingdao 266237, Peoples R China 3.Chinese Acad Sci, Ctr Ocean Megasci, Qingdao 266071, Peoples R China 4.Shandong Univ Sci & Technol, Coll Earth Sci & Engn, Qingdao 266590, Peoples R China 5.Chinese Acad Sci, Guangzhou Inst Geochem, State Key Lab Isotope Geochem, Guangzhou 510640, Peoples R China 6.Univ Chinese Acad Sci, Beijing 100094, Peoples R China
第一作者单位	中国科学院海洋大科学研究中心
通讯作者单位	中国科学院海洋大科学研究中心
推荐引用方式 GB/T 7714	Zhu, Hongli,Du, Long,Li, Xin,et al. Calcium isotopic fractionation during plate subduction: Constraints from back-arc basin basalts[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2020,270:379-393.
APA	Zhu, Hongli,Du, Long,Li, Xin,Zhang, Zhaofeng,&Sun, Weidong.(2020).Calcium isotopic fractionation during plate subduction: Constraints from back-arc basin basalts.GEOCHIMICA ET COSMOCHIMICA ACTA,270,379-393.
MLA	Zhu, Hongli,et al."Calcium isotopic fractionation during plate subduction: Constraints from back-arc basin basalts".GEOCHIMICA ET COSMOCHIMICA ACTA 270(2020):379-393.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
Calcium isotopic fra（1031KB）	期刊论文	出版稿	限制开放	CC BY-NC-SA	浏览