气候变化领域集成服务门户(CCPortal): Transport properties of Fe-Ni-Si alloys at Earth's core conditions: Insight into the viability of thermal and compositional convection

CCPortal

DOI	10.1016/j.epsl.2020.116614
	Transport properties of Fe-Ni-Si alloys at Earth's core conditions: Insight into the viability of thermal and compositional convection
	Zhang Y.; Hou M.; Driscoll P.; Salke N.P.; Liu J.; Greenberg E.; Prakapenka V.B.; Lin J.-F.
发表日期	2021
ISSN	0012821X
卷号	553
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.
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
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/203373
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
推荐引用方式 GB/T 7714	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],2021,553.
APA	Zhang Y..,Hou M..,Driscoll P..,Salke N.P..,Liu J..,...&Lin J.-F..(2021).Transport properties of Fe-Ni-Si alloys at Earth's core conditions: Insight into the viability of thermal and compositional convection.Earth and Planetary Science Letters,553.
MLA	Zhang Y.,et al."Transport properties of Fe-Ni-Si alloys at Earth's core conditions: Insight into the viability of thermal and compositional convection".Earth and Planetary Science Letters 553(2021).