气候变化领域集成服务门户(CCPortal): SW Pacific arc and backarc lavas and the role of slab-bend serpentinites in the global halogen cycle

CCPortal

DOI	10.1016/j.epsl.2019.115921
	SW Pacific arc and backarc lavas and the role of slab-bend serpentinites in the global halogen cycle
	Kendrick M.A.; Danyushevsky L.V.; Falloon T.J.; Woodhead J.D.; Arculus R.J.; Ireland T.
发表日期	2020
ISSN	0012821X
卷号	530
英文摘要	In order to better understand the global halogen cycle and the behaviour of halogens during subduction, we investigated the concentrations of F, Cl, Br and I in suites of rare submarine glasses formed during subduction initiation on the Hunter Ridge (N. Fiji Basin) and from the northernmost part of the Tonga Arc. Additional submarine glasses from mature arcs and backarcs including the Tonga arc (Volcano A), North Fiji, Lau, Manus and Woodlark Basins were also investigated. The aim was to constrain the relative abundances of all four halogens (F/Cl, Br/Cl and I/Cl) in subducted components in proto-arc, arc and backarc lavas for the first time. This enables an assessment of slab-fluid evolution from incipient arcs to mature backarcs, and a comparison of halogens in slab-fluids with possible subduction inputs and other mantle outputs. The various arc and backarc lavas investigated are strongly enriched in Cl, Br and I relative to Nb, and weakly enriched in F compared to Pr, demonstrating metasomatism of incipient sub-arc mantle and sub-arc/backarc mantle by slab-components with strikingly similar ranges of F/Cl (0.11 ± 0.09), Br/Cl (0.0028 ± 0.0008) and I/Cl (0.000013-0.001) (2 standard deviations). The F/Cl ratio, which is much higher than seawater and other surface fluids, is attributed to enhanced mobility of F in saline fluids in sub-arc environments, with slab-melts ascribed an additional minor role. The slab-fluid Br/Cl and I/Cl ratios are strikingly similar to altered oceanic crust and seafloor serpentinites, and distinctly different from sediment pore waters, sediments and most forearc serpentinites. The median Br/Cl and I/Cl ratios of slab fluids in sub-arc and sub-backarcs are also indistinguishable from median mid-ocean ridge and ocean island basalt values, which have I/Cl ratios lower than estimated for the primitive mantle. The data are interpreted to indicate that sedimentary volatile components present in sediments and forearc serpentinites are efficiently returned to the surface through forearc regions. In contrast, halogens in altered ocean crust and lithospheric serpentinites are recycled through magmatic arcs and into the deeper mantle with the result that the mantle's I/Cl ratio has decreased over time. Mass balance considerations suggest that serpentinisation of the lithospheric mantle at the slab-bend immediately prior to subduction is more significant than estimated previously and is driven by seawater-derived fluids without sedimentary components. Lithospheric serpentinites are likely to represent a dominant source of halogens and other volatiles, including noble gases, in the Earth's mantle. © 2019 Elsevier B.V.
关键词	adakite boninite bromine chlorine fluorine iodine
英文关键词	Chlorine; Fluorine; Glass; Inert gases; Iodine; Seawater; Sedimentology; Sediments; Structural geology; Submarines; Adakites; Altered oceanic crusts; Boninites; Lithospheric mantle; Mass balance considerations; Ocean island basalts; Sediment pore water; Subduction initiation; Bromine; adakite; boninite; bromine; chlorine; concentration (composition); fluorine; halogen; iodine; lava; serpentinite; slab; subduction; Pacific Ocean; Pacific Ocean (Southwest)
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202696
作者单位	Research School of Earth Sciences, Australian National University, ACT, Acton, 2601, Australia; CODES and Earth Sciences, School of Natural Sciences, University of Tasmania, Hobart, TAS 7001, Australia; School of Earth Sciences, University of MelbourneVIC 3010, Australia
推荐引用方式 GB/T 7714	Kendrick M.A.,Danyushevsky L.V.,Falloon T.J.,et al. SW Pacific arc and backarc lavas and the role of slab-bend serpentinites in the global halogen cycle[J],2020,530.
APA	Kendrick M.A.,Danyushevsky L.V.,Falloon T.J.,Woodhead J.D.,Arculus R.J.,&Ireland T..(2020).SW Pacific arc and backarc lavas and the role of slab-bend serpentinites in the global halogen cycle.Earth and Planetary Science Letters,530.
MLA	Kendrick M.A.,et al."SW Pacific arc and backarc lavas and the role of slab-bend serpentinites in the global halogen cycle".Earth and Planetary Science Letters 530(2020).