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DOI	10.1016/j.epsl.2019.115934
	Magnesium partitioning between silicate melt and liquid iron using first-principles molecular dynamics: Implications for the early thermal history of the Earth's core
	Liu W.; Zhang Y.; Yin Q.-Z.; Zhao Y.; Zhang Z.
发表日期	2020
ISSN	0012821X
卷号	531
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.
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
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/202751
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
推荐引用方式 GB/T 7714	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],2020,531.
APA	Liu W.,Zhang Y.,Yin Q.-Z.,Zhao Y.,&Zhang Z..(2020).Magnesium partitioning between silicate melt and liquid iron using first-principles molecular dynamics: Implications for the early thermal history of the Earth's core.Earth and Planetary Science Letters,531.
MLA	Liu W.,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".Earth and Planetary Science Letters 531(2020).