globalchange  > 气候变化与战略
DOI: 10.1016/j.epsl.2019.115934
论文题名:
Magnesium partitioning between silicate melt and liquid iron using first-principles molecular dynamics: Implications for the early thermal history of the Earth's core
作者: Liu W.; Zhang Y.; Yin Q.-Z.; Zhao Y.; Zhang Z.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 531
语种: 英语
中文关键词: ab initio ; core ; geodynamo ; giant impact ; Mg ; paleomagnetism
英文关键词: Buoyancy ; Equilibrium constants ; Geomagnetism ; Iron ; Magnesia ; Magnesium ; Magnetic fields ; Silicates ; Ab initio ; core ; Geodynamo ; Giant impact ; paleomagnetism ; Molecular dynamics ; core (planetary) ; geodynamo ; iron ; magnesium ; molecular analysis ; paleomagnetism ; partitioning ; silicate melt ; thermal evolution
英文摘要: The high conductivity of the Earth's core discovered through first-principles and experimental studies requires that the core must start very hot and cool down slowly to generate the Earth's magnetic field by thermal buoyancy. The requirement is difficult to satisfy due to the fast cooling of the overlying magma ocean and consequently of the underlying core. This is in direct conflict with the early appearance of the Earth's paleomagnetic field. Recently, it was proposed that significant amount of magnesium (Mg) can be partitioned into the core through the high temperature created by the Moon-forming Giant Impact. Due to its intrinsic low solubility, subsequent cooling would cause Mg precipitation to generate compositional buoyancy to power the geodynamo in the early history of the Earth. Here we show using first-principles molecular dynamics simulations that the equilibrium constant of magnesium dissolution in molten iron depends on temperature, entirely consistent with recent experimental data. We further show that Mg partitioned into the core during giant impacts and reaching a concentration of about 2 wt% can precipitate out at around 3.5 Ga, much earlier than the onset of inner core nucleation. During the subsequent evolution of the Earth, silicon (Si) concentration of the Earth's core will remain constant while Mg and oxygen (O) concentrations decrease significantly. Consequently, the current Si concentration in the core reflects the accretion processes of the Earth while O and Mg concentrations in the core is the combined result of both accretion and the subsequent evolution of the Earth core. Forward modeling shows that for MgO precipitation to provide enough power to generate the magnetic field in the early history of the Earth, initially high silicon content of the core is preferred, which is accommodated readily in the Grand Tack accretion scenario. The geodynamo driven by MgO precipitation explains the secular decline of palaeomagnetic field intensity in the early history of the Earth. © 2019 Elsevier B.V.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165129
Appears in Collections:气候变化与战略

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作者单位: Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China; Key Laboratory of Computational Geodynamics, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China; Department of Earth and Planetary Sciences, University of California, Davis, CA 95616, United States; University of Chinese Academy of Science, Beijing, 100049, China; Innovation Academy for Earth Science, Chinese Academy of Science, Beijing, 100029, China

Recommended Citation:
Liu W.,Zhang Y.,Yin Q.-Z.,et al. Magnesium partitioning between silicate melt and liquid iron using first-principles molecular dynamics: Implications for the early thermal history of the Earth's core[J]. Earth and Planetary Science Letters,2020-01-01,531
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