The “New Core Paradox”: Challenges and Potential Solutions

Driscoll, Peter; Davies, C. J.

doi:10.1029/2022jb025355

Cited by 14 publications

(9 citation statements)

References 97 publications

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“…This agrees with the findings of (Driscoll and Davies, 2023) who found that a present day radiogenic heat production of ≥ 2 TW and an f viscosity ≤ 10…”

Section: Potassiumsupporting

confidence: 93%

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Examining the power supplied to Earth's dynamo by magnesium precipitation and radiogenic heat production

Wilson¹,

Pozzo²,

Davies³

et al. 2023

Preprint

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We examine magnesium and potassium solubility in liquid Fe mixtures, representative of Earth’s core composition, in equilibrium with liquid silicate mixtures representative of an early magma ocean. Our study is based on the calculation of the chemical potentials of MgO and K2O in both phases, using density functional theory. For MgO, we also study stability against precipitation of the solid phase. We use thermal evolution models of the core and mantle to assess whether either radiogenic heating from 40K decay or Mg precipitation from the liquid core can resolve the new core paradox by powering the geodynamo prior to inner core formation. Our results on K show that concentrations in the core are likely to be small and the effect of 40K decay on the thermal evolution of the core is minimal, making it incapable of sustaining the early geodynamo alone. Our results also predict small concentrations of Mg in the core although these might be sufficient to power the geodynamo prior to inner core formation, depending on the process by which it is transported across the core mantle boundary.

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“…This agrees with the findings of (Driscoll and Davies, 2023) who found that a present day radiogenic heat production of ≥ 2 TW and an f viscosity ≤ 10…”

Section: Potassiumsupporting

confidence: 93%

“…All models where Q ppt = 0 fail to maintain E j > 0 prior to inner core nucleation (O'Rourke et al, 2017;Driscoll and Davies, 2023). Similarly, all models where only Mg is extracted through precipitation (O concentration only changes due to inner core growth) also fail in this regard.…”

Section: Mgomentioning

confidence: 99%

Examining the power supplied to Earth's dynamo by magnesium precipitation and radiogenic heat production

Wilson¹,

Pozzo²,

Davies³

et al. 2023

Preprint

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“…Using a less sensitive formalism such as Al'Tshuler will at least close one of the point of discussion about the validity of the results: whether or not the values of γ 0 and γ ∞ are the 'true' values, at least the error is low and if differences arise between models, then they are probably not due to the Grüneisen parameter. On the other hand, if the end goal is to best describe the entirety of the phenomenon or get a precise estimate of the core temperature (Driscoll & Davies 2023;Dobrosavljevic et al 2022), then the best formalism is the one that fits the best the data, or the values that are calculated directly within ab initio studies (Vočadlo 2007;Alfè 2009;Alfè et al 2007). If one would use a core segregation model to calculate the actual temperature at the CMB instead of highlighting the correlations between parameters, or actually deriving a precise value on those correlations, then the choice of formalism and parameters value must be driven by the quality of the data, the quality of the fit, and the range of uncertainties on the parameters as highlighted in section 6.2.…”

Section: Assessing the Uncertainties In The Output Of The Modelmentioning

confidence: 99%

Grüneisen parameter formalism in the study of the Earth's core formation: a sensitivity study

Clesi,

Deguen

2024

Preprint

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The Grüneisen parameter is an important parameter for the thermal state and evolution of the core, but its uncertainties and their implications are sometimes overlooked . Several formalisms using different parameters values have been used in different studies, making comparison between studies difficult. In this paper, we use previously published datasets to test the sensitivity of modeling the thermal state of the early core to the different formalisms and parameter values used to describe the evolution of the Grüneisen parameter with density. The temperature of the core obtained in our models is less sensitive to the uncertainties of the parameters used in Al'Tshuler et al (1987) formalism than the uncertainties of the parameters used in Anderson (1967) formalism.

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“…The intrinsic magnetic fields observed on Earth and terrestrial planets are thought to originate from the convection processes within their metallic liquid cores [1][2][3]. This convection could be driven by thermal or chemical buoyancy depending on the thermal conductivity of the core minerals and the temperature gradient across the core-mantle boundary.…”

Section: Introductionmentioning

confidence: 99%

Electrical Resistivity and Phase Evolution of Fe–N Binary System at High Pressure and High Temperature

Wang,

Yang,

Shen

et al. 2024

Minerals

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Partitioning experiments and the chemistry of iron meteorites indicate that the light element nitrogen could be sequestered into the metallic core of rocky planets during core–mantle differentiation. The thermal conductivity and the mineralogy of the Fe–N system under core conditions could therefore influence the planetary cooling, core crystallization, and evolution of the intrinsic magnetic field of rocky planets. Limited experiments have been conducted to study the thermal properties and phase relations of Fe–N components under planetary core conditions, such as those found in the Moon, Mercury, and Ganymede. In this study, we report results from high-pressure experiments involving electrical resistivity measurements of Fe–N phases at a pressure of 5 GPa and temperatures up to 1400 K. Four Fe–N compositions, including Fe–10%N, Fe–6.4%N, Fe–2%N, and Fe–1%N (by weight percent), were prepared and subjected to recovery experiments at 5 GPa and 1273 K. These experiments show that Fe–10%N and Fe–6.4%N form a single hexagonal close-packed phase (ɛ-nitrides), while Fe–2%N and Fe–1%N exhibit a face-centered cubic structure (γ-Fe). In separate experiments, the resistivity data were collected during the cooling after compressing the starting materials to 5 GPa and heating to ~1400 K. The resistivity of all compositions, similar to the pure γ-Fe, exhibits weak temperature dependence. We found that N has a strong effect on the resistivity of metallic Fe under rocky planetary core conditions compared to other potential light elements such as Si. The temperature-dependence of the resistivity also revealed high-pressure phase transition points in the Fe–N system. A congruent reaction, ε ⇌ γ’, occurs at ~673 K in Fe–6.4%N, which is ~280 K lower than that at ambient pressure. Furthermore, the resistivity data provided constraints on the high-pressure phase boundary of the polymorphic transition, γ ⇌ α, and an eutectoid equilibrium of γ’ ⇌ α + ε. The data, along with the recently reported phase equilibrium experiments at high pressures, enable construction of a phase diagram of the Fe–N binary system at 5 GPa.

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The “New Core Paradox”: Challenges and Potential Solutions

Cited by 14 publications

References 97 publications

Examining the power supplied to Earth's dynamo by magnesium precipitation and radiogenic heat production

Examining the power supplied to Earth's dynamo by magnesium precipitation and radiogenic heat production

Grüneisen parameter formalism in the study of the Earth's core formation: a sensitivity study

Electrical Resistivity and Phase Evolution of Fe–N Binary System at High Pressure and High Temperature

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