DOI: 10.1016/j.epsl.2019.116030
论文题名: Precipitation of multiple light elements to power Earth's early dynamo
作者: Mittal T. ; Knezek N. ; Arveson S.M. ; McGuire C.P. ; Williams C.D. ; Jones T.D. ; Li J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 532 语种: 英语
中文关键词: core formation
; core-mantle evolution
; light-element precipitation
; paleomagnetic field
; thermo-chemical evolution
英文关键词: Entropy
; Equilibrium constants
; Interactive devices
; Iron alloys
; Iron oxides
; Magnesia
; Magnetic fields
; Nucleation
; Oxygen
; Silica
; Silicon oxides
; Core formation
; Core-mantle
; Light elements
; Paleomagnetic field
; Thermo-chemical
; Precipitation (chemical)
; core-mantle boundary
; geodynamo
; magnetic field
; mantle convection
; nucleation
; paleomagnetism
; Paleozoic
; precipitation (chemistry)
; thermochemistry
; Mya
英文摘要: Earth has had a global magnetic field for at least 3.5 billion years, but if the iron-alloy in the core has high conductivity, it is difficult to explain this duration with energy from cooling and inner-core growth alone. Precipitation of light elements (e.g., magnesium, silicon, and oxygen) from Earth's core is a potential alternative energy source to power the dynamo. We develop a new framework of coupled thermo-chemical evolution of the Earth to consider precipitation of multiple light components from the core and their interaction with the overlying mantle layer. The precipitated material accumulates in a layer at the base of the mantle which is then continuously eroded by mantle convection. We allow the precipitation of three species (MgO, FeO, and SiO2), including their interactions not considered by most previous studies. We find that MgO, SiO2, and FeO precipitation may each dominate entropy production depending on the choice of equilibrium constants and initial model states and that the three species together can explain the duration of Earth's magnetic field across a range of plausible scenarios. Over the Earth's history, we find that the core can lose ∼1–2 wt% silicon and oxygen suggesting that light precipitation is potentially an important process for the core compositional evolution and core-mantle chemical exchange. Additionally, our results show that precipitation does not, in most cases, have a systematic influence on the timing of inner-core nucleation or magnitude of the resulting paleomagnetic signal with inner-core nucleation typically around 550 Mya. However, the onset of precipitation of individual species could produce additional sharp increases in paleomagnetic intensity at various points through Earth's history besides the inner-core nucleation event. © 2019 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165169
Appears in Collections: 气候变化与战略
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作者单位: Earth and Planetary Science Department, University of California, Berkeley, Berkeley, CA, United States; Department of Geology & Geophysics, Yale University, New Haven, CT, United States; School of GeoSciences, University of EdinburghEH9 3FE, United Kingdom; Earth and Planetary Science Department, University of California, Davis, Davis, CA, United States; Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, United States; Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC, United States
Recommended Citation:
Mittal T.,Knezek N.,Arveson S.M.,et al. Precipitation of multiple light elements to power Earth's early dynamo[J]. Earth and Planetary Science Letters,2020-01-01,532