Resistivity saturation of hcp Fe-Si alloys in an internally heated diamond anvil cell: A key to assessing the Earth's core conductivity

Inoue, Hisahiro; Sugitani, Suehiro; Ohta, Kenji; Hirose, Kei; Ohishi, Yasuo

doi:10.1016/j.epsl.2020.116357

Cited by 33 publications

(47 citation statements)

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“…The discrepancy [30,31] between the thermal conductivity and resistivity measurements may arise from temperature gradients in the laser-heated samples, sample deformation and textures, probe geometry, and the breakdown of ideal Wiedemann-Franz law (see Supplemental Material [18], which includes Refs. [7,8,14,17,20,[32][33][34]). Uncertain thermal conductivity of the core may result in a big difference in our understanding of the thermal history of the core and its geodynamo [35,36].…”

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confidence: 99%

Reconciliation of Experiments and Theory on Transport Properties of Iron and the Geodynamo

et al. 2020

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We measure the electrical resistivity of hcp iron up to ∼170 GPa and ∼3000 K using a four-probe van der Pauw method coupled with homogeneous flattop laser heating in a DAC, and compute its electrical and thermal conductivity by first-principles molecular dynamics including electron-phonon and electronelectron scattering. We find that the measured resistivity of hcp iron increases almost linearly with temperature, and is consistent with our computations. The results constrain the resistivity and thermal conductivity of hcp iron to ∼80 AE 5 μΩ cm and ∼100 AE 10 Wm −1 K −1 , respectively, at conditions near the core-mantle boundary. Our results indicate an adiabatic heat flow of ∼10 AE 1 TW out of the core, supporting a present-day geodynamo driven by thermal and compositional convection.

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confidence: 99%

Reconciliation of Experiments and Theory on Transport Properties of Iron and the Geodynamo

et al. 2020

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“…A detailed comparison of different methodologies for determining k is both beyond the scope of this article and the expertise of the authors and so we refer the reader to Williams (2018), Zhang et al (2020) and Pourovskii et al (2020) for recent discussions. We consider experimental studies comprising direct determinations of k in hcp iron (Konôpková et al, 2016) and solid Fe-Si alloys (Hsieh et al, 2020) and inferences of k based on measured electrical conductivity σ of hcp iron (Ohta et al, 2016;Xu et al, 2018;Zhang et al, 2020) and hcp Fe-Si alloys (Inoue et al, 2020) using the Wiedemann-Franz Law…”

Section: Core Thermal Conductivitymentioning

confidence: 99%

“…Pressure: Pozzo and Alfè (2016) provide the pressure-dependence of electrical conductivity of pure iron at 4350 K. Inoue et al (2020) show P -dependence of a 4…”

Section: Core Thermal Conductivitymentioning

confidence: 99%

“…Colours distinguish studies: open/closed symbols denote the method employed (experiment, calculation); shape denotes the material (square=solid, circle=liquid), stars distinguish alloys with the Si molar concentration denoted as a number inside the symbol. The considered studies are: P12 (Pozzo et al, 2012); D12 (de Koker et al, 2012); P13 (Pozzo et al, 2013); K16 (Konôpková et al, 2016); O16 (Ohta et al, 2016); P16 (Pozzo and Alfè, 2016); X18 (Xu et al, 2018); Z20 (Zhang et al, 2020); I20 (Inoue et al, 2020); H20 (Hsieh et al, 2020).…”

Section: Core Thermal Conductivitymentioning

confidence: 99%

“…Converting to k values using equation ( 12) with L = L 0 yields mean dk/dP values of 0.4 W m −1 K −1 GPa −1 for Pozzo and Alfè (2016) and 0.13 W m −1 K −1 GPa −1 and 0.5 W m −1 K −1 GPa −1 for Inoue et al (2020) corresponding to an increase in k of 15−20 W m −1 K −1 from 95 GPa to 135 GPa. We use dk/dP = 0.4 W m −1 K −1 GPa −1 below.…”

Section: Core Thermal Conductivitymentioning

confidence: 99%

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Thermo-Chemical Dynamics in Earth's Core Arising from Interactions with the Mantle

Davies¹,

Greenwood²

2021

Preprint

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Thermo-chemical interactions at the core-mantle boundary (CMB) play an integral role in determining the dynamics and evolution Earth's deep interior. This review considers the processes in the core that arise from heat and mass transfer at the CMB, with particular focus on thermo-chemical stratification and the precipitation of oxides. A fundamental parameter is the thermal conductivity of the core, which we estimate as k = 70 − 110 W m −1 K −1 at CMB conditions based on consistent extrapolation from a number of recent studies. These high conductivity values imply the existence of an early basal magma ocean (BMO) overlying a hot core and rapid cooling potentially leading to a loss of power to the dynamo before the inner core formed around 0.5 − 1 Gyrs ago, the so-called "new core paradox". Coupling core thermal evolution modelling and calculations of chemical equilibrium between liquid iron and silicate melts suggests that FeO dissolved into the core after its formation, creating a stably stratified chemical layer below the CMB, while precipitation of MgO and SiO 2 was delayed until the last 2−3 Gyrs and was therefore not available to power the early dynamo; however, once initiated, precipitation supplied ample power for field generation. We also present a possible solution to the new core paradox without requiring precipitation or radiogenic heating using k = 70 W m −1 K −1 . The model matches the present inner core size and heat flow and temperature at the top of the

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Dynamics in Earth's Core Arising from Thermo‐Chemical Interactions with the Mantle

Davies

Greenwood

2023

Geophysical Monograph Series

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Resistivity saturation of hcp Fe-Si alloys in an internally heated diamond anvil cell: A key to assessing the Earth's core conductivity

Cited by 33 publications

References 47 publications

Reconciliation of Experiments and Theory on Transport Properties of Iron and the Geodynamo

Reconciliation of Experiments and Theory on Transport Properties of Iron and the Geodynamo

Thermo-Chemical Dynamics in Earth's Core Arising from Interactions with the Mantle

Dynamics in Earth's Core Arising from Thermo‐Chemical Interactions with the Mantle

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