globalchange  > 气候变化与战略
DOI: 10.1016/j.epsl.2020.116614
论文题名:
Transport properties of Fe-Ni-Si alloys at Earth's core conditions: Insight into the viability of thermal and compositional convection
作者: Zhang Y.; Hou M.; Driscoll P.; Salke N.P.; Liu J.; Greenberg E.; Prakapenka V.B.; Lin J.-F.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 553
语种: 英语
中文关键词: Earth's core ; electrical resistivity ; Fe alloys ; geodynamo ; high pressure-temperature experiments ; thermal conductivity
英文关键词: Acoustic wave velocity ; Binary alloys ; Chemical elements ; Electric variables measurement ; Experimental mineralogy ; Heat convection ; Nickel alloys ; Silicon alloys ; Temperature distribution ; Thermal conductivity of solids ; Core-mantle boundary ; Inner core boundary ; Inner core growth ; Laser-heated diamond anvil cells ; Thermal convections ; Thermal transport properties ; Van der Pauw method ; Wiedemann-Franz law ; Iron alloys ; alloy ; electrical resistivity ; geodynamo ; high pressure ; high temperature ; iron ; nickel ; silicon ; thermal conductivity ; thermal convection ; Calluna vulgaris
英文摘要: Thermal and compositional convection in Earth's core are thought to be the main power sources driving geodynamo. The viability and strength of thermally and compositionally-driven convection over Earth's history depend on the adiabatic heat flow across the core-mantle boundary (CMB) which is governed by the thermal conductivity of a constituent Fe-Ni-light element alloy at the pressure-temperature (P-T) conditions relevant to the core. Silicon is often proposed to be an abundant light element alloyed with Fe along with ∼5 wt% Ni, but the thermal transport properties of Fe-Ni-Si alloys at high P-T remain largely uncertain. Here we measured the electrical resistivities of Fe-10wt%Ni and Fe-1.8wt%Si alloys up to ∼142 GPa and ∼3400 K using four-probe van der Pauw method in laser-heated diamond anvil cell experiments. Our results show that the resistivities of hcp-Fe-1.8Si and Fe-10Ni display quasi-linear temperature dependence from ∼1500 to 3400 K at each given high pressure. Addition of ∼2 wt% Si in hcp-Fe significantly increases its resistivity by ∼25% at ∼138 GPa and 4000 K, but Fe-10wt%Ni has similar resistivity to pure hcp-Fe at near CMB P-T conditions. Using our measured values of electrical resistivities, we model thermal conductivities via the Wiedemann-Franz law, giving a nominal thermal conductivity of ∼50 W m−1 K−1 for liquid Fe-5Ni-8Si alloy at the topmost outer core, implying an adiabatic (conductive) core heat flow of ∼8.0 TW. The outer core has a much lower thermal conductivity than the inner core due to light-element differentiation across the solidifying inner-core boundary. Our studies imply that the adiabatic core heat flow is low enough to enable thermal convection to drive the geodynamo over most and possibly all of Earth's history, while the strength of compositional convection increases with the inner-core growth and accounts for ∼83% of the buoyancy flux to the present-day geodynamo. © 2020 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/165751
Appears in Collections:气候变化与战略

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作者单位: Institute of Atomic and Molecular Physics, Sichuan University, Chengdu, 610065, China; Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, United States; Center for High Pressure Science and Technology Advanced Research, Beijing, 100094, China; Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road N.W., Washington, DC, 20015, United States; Center for Advanced Radiation Sources, University of ChicagoIL 60637, United States; Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, United States

Recommended Citation:
Zhang Y.,Hou M.,Driscoll P.,et al. Transport properties of Fe-Ni-Si alloys at Earth's core conditions: Insight into the viability of thermal and compositional convection[J]. Earth and Planetary Science Letters,2021-01-01,553
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