Fe–FeO and Fe–Fe3C melting relations at Earth's core–mantle boundary conditions: Implications for a volatile-rich or oxygen-rich core

Morard, Guillaume; Andrault, Denis; Antonangeli, Daniele; Nakajima, Yoichi; Auzende, Anne-Line; Boulard, E.; Cervera, S.; Clark, A. N.; Lord, O. T.; Siebert, J.; Svitlyk, Volodymyr; Garbarino, Gastón; Mézouar, M.

doi:10.1016/j.epsl.2017.05.024

Cited by 85 publications

(150 citation statements)

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“…Assuming a linear relation between the two end‐members, as supported by the existence of solid solution in the Fe‐Ni binary system Kuwayama et al (), we obtain an increase of 2 K/wt % Ni of the melting temperature of pure Fe; therefore, the effect of Ni may be to increase the melting temperature of the Earth's core of ∼10–20 K (Ni content ∼5–10 wt %). This is 1 order of magnitude lower than the effect of light element such as S, C, or O Morard et al () at 90 GPa and in the opposite direction.…”

Section: Resultsmentioning

confidence: 65%

“…Linear interpolation in the Fe‐Ni solid solution gives an increase of 10–20 K for Fe melting temperature due to the addition of Ni in the Earth's core, 1 order of magnitude lower than the effect of light elements (Morard et al, ) and in the opposite direction. Nickel could then be neglected during discussion of temperature profile and melting relations under Earth's core conditions.…”

Section: Discussionmentioning

confidence: 97%

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The Melting Curve of Nickel Up to 100 GPa Explored by XAS

et al. 2017

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Precise knowledge of the melting temperatures of iron, nickel, and their alloys at pressures of the deep Earth would allow us to better constrain the parameters used for the Earth's heat budget and dynamics. However, melting curves of transition metals at pressures approaching 100 GPa and above are still controversial. To address this issue, we report new data on the melting temperature of nickel in a laser‐heated diamond anvil cell up to 100 GPa obtained by X‐ray absorption spectroscopy (XAS), a technique rarely used at such conditions. We couple this for the first time to ex situ analysis of the sample, providing a further validation of the melting criterion adopted here. Finally, a Simon‐Glatzel fit to the melting data obtained in this work, combined with those obtained in the most recent X‐ray diffraction experiments, gives TM(K)=1727×[]PM17±3+112.5±0.1, defining the most up‐to‐date X‐ray‐determined melting curve for Ni. This result confirms that Ni could be ignored in the discussion on melting properties and thermal profile of the Earth's core, as it should affect the Fe melting point by only 10–20 K at 90 GPa.

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Section: Resultsmentioning

confidence: 65%

Section: Discussionmentioning

confidence: 97%

The Melting Curve of Nickel Up to 100 GPa Explored by XAS

et al. 2017

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“…Experiments to collect diffuse X‐ray scattering of liquid Fe‐C alloys were performed in situ at high pressures and temperatures by angle dispersive X‐ray diffraction measurements in the Paris‐Edinburgh press (PEP) below 10 GPa and the double‐sided laser‐heated diamond anvil cell (LH‐DAC) above 40 GPa (Beamline ID27 of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France (Mezouar et al, )). For the LH‐DAC experiments, starting materials with initial composition of Fe + 1.5 wt % C (6.6 at % C) were synthesized by an ultrarapid quench method at the Institut de Chimie et des Matériaux de Paris‐Est (ICMPE), Paris, France (Morard et al, ), whereas for the PEP experiments the starting material was composed of a mixture of pure Fe (Alfa Aesar, 99.9%) and graphite powders.…”

Section: Methodsmentioning

confidence: 99%

Structure and Density of Fe‐C Liquid Alloys Under High Pressure

et al. 2017

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The density and structure of liquid Fe‐C alloys have been measured up to 58 GPa and 3,200 K by in situ X‐ray diffraction using a Paris‐Edinburgh press and laser‐heated diamond anvil cell. Study of the pressure evolution of the local structure inferred by X‐ray diffraction measurements is important to understand the compression mechanism of the liquid. Obtained data show that the degree of compression is greater for the first coordination sphere than the second and third coordination spheres. The extrapolation of the measured density suggests that carbon cannot be the only light element alloyed to iron in the Earth's core, as 8–16 at % C (1.8–3.7 wt % C) would be necessary to explain the density deficit of the outer core relative to pure Fe. This concentration is too high to account for outer core velocity. The presence of other light elements (e.g., O, Si, S, and H) is thus required.

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“…We use pressure and temperature conditions for the ICB to determine the adiabatic geotherm. However, it is likely that temperatures at ICB are lower than the melting temperature of pure iron due to the presence of light elements and associated depression in melting temperatures (Fischer, 2016;Morard et al, 2017). However, it is likely that temperatures at ICB are lower than the melting temperature of pure iron due to the presence of light elements and associated depression in melting temperatures (Fischer, 2016;Morard et al, 2017).…”

Section: Resultsmentioning

confidence: 99%

“…Estimates on the nitrogen in the liquid outer core could be obtained by examining its effect on the structure, density, elasticity, and bulk sound velocity and comparing such effects with the effects of other light elements such as Si, O, S, C, and H from literature (silicon: Badro et al, 2015;Sanloup et al, 2004;Yu & Secco, 2008;oxygen: Badro et al, 2014;Huang et al, 2011;sulfur: Jing et al, 2014;Sanloup et al, 2000;Umemoto et al, 2014;carbon: Kuwabara et al, 2016;Liu et al, 2016;Morard et al, 2017;Nakajima et al, 2015;Shimoyama et al, 2016;hydrogen: Umemoto & Hirose, 2015). Previous experimental studies showed that the solid iron-nitrides could possibly explain the geophysically observed density and sound velocities at the Earth's inner core (Adler & Williams, 2005;Litasov et al, 2017;Minobe et al, 2015;Niewa et al, 2009;Popov et al, 2015;Schwarz et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen Content in the Earth's Outer Core

Bajgain

Mookherjee

Dasgupta

et al. 2019

Geophysical Research Letters

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Using first principles molecular dynamic simulations, we explore the effects of nitrogen (N) on the density and sound velocity of liquid iron and evaluate its potential as a light element in the Earth's outer core. Our results suggest that Fe‐N melt cannot simultaneously explain the density and seismic velocity of the Earth's outer core. Although ~2.0 wt.% N can explain the bulk sound velocity of the outer core, such N content only lowers the density of liquid Fe by ~3%. Matching both the velocity and density by the other light elements limits the N in the core to ≪2.0 wt.%. Our finding suggests that nitrogen is a minor to trace element in the Earth's core and is consistent with the geochemical mass balance with terrestrial abundance of N and alloy‐silicate partitioning data, which suggest that there cannot be significant N in the core.

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Fe–FeO and Fe–Fe3C melting relations at Earth's core–mantle boundary conditions: Implications for a volatile-rich or oxygen-rich core

Cited by 85 publications

References 50 publications

The Melting Curve of Nickel Up to 100 GPa Explored by XAS

The Melting Curve of Nickel Up to 100 GPa Explored by XAS

Structure and Density of Fe‐C Liquid Alloys Under High Pressure

Nitrogen Content in the Earth's Outer Core

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