DOI: 10.1016/j.epsl.2018.01.018
Scopus记录号: 2-s2.0-85044321510
论文题名: Earth's inner core nucleation paradox
作者: Huguet L. ; Van Orman J.A. ; Hauck S.A. ; II ; Willard M.A.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 487 起始页码: 9
结束页码: 20
语种: 英语
英文关键词: inner core
; nucleation
; outer core
; solidification
; supercooling
; thermal evolution
Scopus关键词: Energy barriers
; Geomagnetism
; Iron alloys
; Solidification
; Substrates
; Supercooling
; Complete dissolution
; Heterogeneous nucleation
; Homogeneous liquids
; Inner core
; outer core
; Plausible mechanisms
; Spontaneous crystallization
; Thermal evolution
; Nucleation
英文摘要: The conventional view of Earth's inner core is that it began to crystallize at Earth's center when the temperature dropped below the melting point of the iron alloy and has grown steadily since that time as the core continued to cool. However, this model neglects the energy barrier to the formation of the first stable crystal nucleus, which is commonly represented in terms of the critical supercooling required to overcome the barrier. Using constraints from experiments, simulations, and theory, we show that spontaneous crystallization in a homogeneous liquid iron alloy at Earth's core pressures requires a critical supercooling of order 1000 K, which is too large to be a plausible mechanism for the origin of Earth's inner core. We consider mechanisms that can lower the nucleation barrier substantially. Each has caveats, yet the inner core exists: this is the nucleation paradox. Heterogeneous nucleation on a solid metallic substrate tends to have a low energy barrier and offers the most straightforward solution to the paradox, but solid metal would probably have to be delivered from the mantle and such events are unlikely to have been common. A delay in nucleation, whether due to a substantial nucleation energy barrier, or late introduction of a low energy substrate, would lead to an initial phase of rapid inner core growth from a supercooled state. Such rapid growth may lead to distinctive crystallization texturing that might be observable seismically. It would also generate a spike in chemical and thermal buoyancy that could affect the geomagnetic field significantly. Solid metal introduced to Earth's center before it reached saturation could also provide a nucleation substrate, if large enough to escape complete dissolution. Inner core growth, in this case, could begin earlier and start more slowly than standard thermal models predict. © 2018 The Author(s) Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/110015
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Department of Earth, Environmental, and Planetary Sciences, Case Western Reserve University, Cleveland, OH 44106, United States; Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106, United States
Recommended Citation:
Huguet L.,Van Orman J.A.,Hauck S.A.,et al. Earth's inner core nucleation paradox[J]. Earth and Planetary Science Letters,2018-01-01,487