DOI: 10.1016/j.epsl.2020.116208
论文题名: Transfer of oxygen to Earth's core from a long-lived magma ocean
作者: Davies C.J. ; Pozzo M. ; Gubbins D. ; Alfè D.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 538 语种: 英语
中文关键词: chemical interactions
; Earth's core
; magma ocean
; stratified layer
英文关键词: Boundary layers
; Chromium compounds
; Mass transfer
; Oceanography
; Oxygen
; Silicates
; Structural geology
; Chemical boundary layers
; Chemical interactions
; Core-mantle boundary
; Earth's core
; Magma ocean
; Partition coefficient
; Stratified layers
; Time-dependent models
; Iron oxides
; concentration (composition)
; core-mantle boundary
; crystallization
; iron oxide
; magma
; mass transfer
; metal
; oxygen
; partition coefficient
; precipitation (chemistry)
; silicate
英文摘要: Chemical interactions between metal and silicates at the core-mantle boundary (CMB) are now thought to lead to transfer of oxygen into Earth's liquid core. Establishing the nature and extent of this transfer is important for constraining the conditions under which the core formed, the origin of a stably stratified region below the CMB and the possible precipitation of oxides within the core. Previous models of FeO transfer have considered a solid mantle; however, several lines of evidence suggest that the lowermost mantle could have remained above its solidus long after core formation was complete, which would allow much faster mass transfer. We investigate this scenario by developing a time-dependent model of FeO exchange between a diffusive stratified layer at the top of the core and a long-lived molten magma ocean. Core FeO concentration, c¯FeO c, is evolved subject to a time-dependent mass flux at the CMB, radius rcmb, which depends on the FeO concentration at the bottom (c¯FeO m(rcmb)) and top (c¯FeO m(rbulk)) of the chemical boundary layer above the CMB. Coupled core-magma ocean evolution arises because c¯FeO m(rcmb) and c¯FeO c(rcmb) are linked through the partition coefficient P=c¯FeO c(rcmb)/c¯FeO m(rcmb). c¯FeO m(rbulk) is held constant in No Crystallization (NC) models and evolves in Middle-Out Crystallization (MOC) models according to the basal magma ocean model of Labrosse et al. (2007), generalised to account for FeO loss to the core. In the first 1 Gyr, FeO transfer in all models with ≥10% FeO in the magma ocean and P≥5 produces pure FeO compositions at the CMB, stably stratified layers of 60−80 km and accounts for 15−50% of the total present-day core oxygen content. In NC models the magma ocean does not completely freeze in 4 Gyr, in which time the stable layer reaches 120−150 km and FeO transfer can account for all of the present-day O in the core. However, in MOC models FeO loss to the core causes the magma ocean to completely freeze in the first 1-3 Gyrs following core formation. Our results suggest that the present-day core composition may not provide a strong constraint on models of core formation and that FeO could have precipitated at the top of the core. © 2020 The Authors Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/164936
Appears in Collections: 气候变化与战略
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作者单位: School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom; Department of Earth Sciences, Thomas Young Centre @ UCL, UCL, Gower Street, London, WC1E 6BT, United Kingdom; Dipartimento di Fisica Ettore Pancini, Università di Napoli Federico II, Monte S. Angelo, Napoli, I-80126, Italy
Recommended Citation:
Davies C.J.,Pozzo M.,Gubbins D.,et al. Transfer of oxygen to Earth's core from a long-lived magma ocean[J]. Earth and Planetary Science Letters,2020-01-01,538