DOI: 10.1016/j.epsl.2019.115921
论文题名: SW Pacific arc and backarc lavas and the role of slab-bend serpentinites in the global halogen cycle
作者: Kendrick M.A. ; Danyushevsky L.V. ; Falloon T.J. ; Woodhead J.D. ; Arculus R.J. ; Ireland T.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 530 语种: 英语
中文关键词: 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)
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. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165074
Appears in Collections: 气候变化与战略
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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
Recommended Citation:
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]. Earth and Planetary Science Letters,2020-01-01,530