Boron, arsenic and antimony recycling in subduction zones: New insights from interactions between forearc serpentinites and CO2-rich fluids at the slab-mantle interface

doi:10.1016/j.gca.2021.01.039

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	Boron, arsenic and antimony recycling in subduction zones: New insights from interactions between forearc serpentinites and CO2-rich fluids at the slab-mantle interface
	Wu, Kai 4; Zhang, Lipeng 1,3; Yuan, Honglin 4; Sun, Weidong 1,3; Deng, Jianghong 1,3; Zartman, Robert E.3; Guo, Jia 2; Bao, Zhian 4; Zong, Chunlei 4
刊名	GEOCHIMICA ET COSMOCHIMICA ACTA
	2021-04-01
卷号	298 页码:21-42
关键词	Serpentinite Fe-poor antigorite Slab-mantle interface Fluid mobile elements
ISSN号	0016-7037
DOI	10.1016/j.gca.2021.01.039
通讯作者	Yuan, Honglin(hlyuan@nwu.edu.cn) ; Sun, Weidong(weidongsun@qdio.ac.cn)
英文摘要	Hydrous minerals in the hybridized zone at the slab-mantle interface play a critical role in retaining and transporting fluid mobile elements in subduction zones. The observed high B and As concentrations and high delta(11) B values in arc magmas were previously thought to have been resulted from the mechanical transport of forearc serpentinites down to subarc depths by mantle corner flows or through subduction channels because B, As, and Sb are mostly released during early stages of subduction. This study provides new insights into the recycling of B, As, and Sb in subduction zones via an in-situ study on a set of carbonate-bearing serpentinite samples from the Mianlue me ' lange complex in the Qinling Orogen. Petrological observations and bulk-rock Sr-Pb isotopes reveal that the Jianchaling serpentinites were formed by interactions between forearc peridotites and sediment-derived fluids at a shallow depth in the subduction channel. Some Jianchaling serpentinites experienced the lizardite to antigorite transition at 300-400 degrees C with infiltrations of CO2-rich fluids. In contrast, the Liangyazi antigorite serpentinites were produced at a greater depth. Antigorite grains in the Jianchaling serpentinites have lower Fe-apfu than those in the Liangyazi serpentinites and most antigorite with geochemical data in the literature. Meanwhile, B, As, and Sb concentrations of Fe-poor antigorite from the Jianchaling serpentines (385-653 ppm B, 198-334 ppm As, and 6.24-8.01 ppm Sb) are not only higher than those of the Fe-rich antigorite from the Liangyazi serpentinites but also 2-3.5 times higher than those of the surrounding lizardite. The lower modal percentage of spinel and ferritchromite in antigorite veinlets, together with the lower bulk-rock FeO content of antigorite-lizardite serpentinites than that of lizardite serpentinites from the Jianchaling region, indicates that some FeO might be lost during the lizardite to antigorite transition. The presence of carbonate minerals in the antigorite veinlets and the remarkably high B, As, and Sb concentrations in the Jianchaling antigorite indicate that the penetrating fluids during the lizardite to antigorite transition are most likely derived from sediment and metabasite decarbonations at <350 degrees C. Infiltrations of CO2-rich fluids at the slab-mantle interface could buffer a relatively low pH to significantly enhance the mobility of Fe2+, which is produced by reduction of the cronstedtite component in lizardite or Fe3+ in magnetite during the lizardite to antigorite transition, and facilitate the formation of Fe-poor antigorite at the slab-mantle interface. The oxygen fugacity in such a CO2-rich water-rock system is also high enough for the occurrence of As5+ in the surrounding fluids. Therefore, once Fe-IV(3+) is lost from the serpentine lattice structure during the lizardite to antigorite transition, B3+, As5+, and Sb5+ in the surrounding fluids can occupy the tetrahedral sites in the newly formed Fe-poor antigorite. The formation of Fe-poor antigorite at the slab-mantle interface is therefore made available to transport shallow slab-derived B, As, and Sb to a greater depth, where destabilization of antigorite at 600-700 degrees C liberates these elements into the arc magma source. (C) 2021 Elsevier Ltd. All rights reserved.
资助项目	National Natural Science Foundation of China[41903009] ; National Natural Science Foundation of China[41825007] ; National Natural Science Foundation of China[41703027] ; National Natural Science Foundation of China[41503004] ; Strategic Priority Research Program (B) of the Chinese Academy of Sciences[XDB18020102] ; China Postdoctoral Science Foundation[2018M643711] ; MOST Special Fund from the State Key Laboratory of Continental Dynamics ; National Demonstration Center for Experimental Geology Education (Northwest University)
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	PERGAMON-ELSEVIER SCIENCE LTD
WOS记录号	WOS:000627882600002
内容类型	期刊论文
源URL	[http://ir.qdio.ac.cn/handle/337002/170356]
专题	海洋研究所_深海极端环境与生命过程研究中心
通讯作者	Yuan, Honglin; Sun, Weidong
作者单位	1.Chinese Acad Sci, Ctr Deep Sea Res, Ctr Ocean Megasci, Inst Oceanol, Qingdao 266071, Peoples R China 2.Chengdu Univ Technol, Coll Earth Sci, Chengdu 610059, Peoples R China 3.Pilot Natl Lab Marine Sci & Technol Qingdao, Lab Marine Mineral Resources, Qingdao 266237, Peoples R China 4.Northwest Univ, Dept Geol, State Key Lab Continental Dynam, Xian 710069, Peoples R China
推荐引用方式 GB/T 7714	Wu, Kai,Zhang, Lipeng,Yuan, Honglin,et al. Boron, arsenic and antimony recycling in subduction zones: New insights from interactions between forearc serpentinites and CO2-rich fluids at the slab-mantle interface[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2021,298:21-42.
APA	Wu, Kai.,Zhang, Lipeng.,Yuan, Honglin.,Sun, Weidong.,Deng, Jianghong.,...&Zong, Chunlei.(2021).Boron, arsenic and antimony recycling in subduction zones: New insights from interactions between forearc serpentinites and CO2-rich fluids at the slab-mantle interface.GEOCHIMICA ET COSMOCHIMICA ACTA,298,21-42.
MLA	Wu, Kai,et al."Boron, arsenic and antimony recycling in subduction zones: New insights from interactions between forearc serpentinites and CO2-rich fluids at the slab-mantle interface".GEOCHIMICA ET COSMOCHIMICA ACTA 298(2021):21-42.