A sulfur-poor terrestrial core inferred from metal–silicate partitioning experiments

Suer, Terry‐Ann; Siebert, J.; Rémusat, Laurent; Menguy, Nicolas; Fiquet, G.

doi:10.1016/j.epsl.2017.04.016

Cited by 80 publications

(119 citation statements)

References 66 publications

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“…Of course, some scientific achievements opposed S as the main light elements of Earth's core. For example, some geochemical and cosmochemical constraints placed the S content in the core at 2–3 wt% (e.g., Dreibus & Palme, ; McDonough, ; Suer et al, ). Assuming the remainder light element is sulfur, the composition of Earth's core might be Fe‐S‐Si.…”

Section: Results and Geophysical Implicationmentioning

confidence: 99%

Equation of State for Shocked Fe‐8.6 wt% Si up to 240 GPa and 4,670 K

et al. 2019

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Using dynamic compression technique, the equation of state for Fe‐8.6 wt% Si was measured up to 240 GPa and 4,670 K. A least squares fit to the experimental data yields the Hugoniot parameters C0 = 4.603±0.101 km/s and λ = 1.505±0.037 with initial density ρ0=7.386±0.021 g/cm3. Based on the Hugoniot data, the calculated isothermal equation of state is consistent with static compression data when the lattice Grüneisen parameter γl =1.65(7.578/ρ) and electronic Grüneisen parameter γe=1.83. The calculated pressure‐density data at 300 K were fitted to a third‐order Birch‐Murnaghan equation of state with zero pressure the parameters K0=192.1±6.3 GPa, K0'=4.71±0.27 with fixed ρ0ε =7.578±0.050 g/cm3. Under the conditions of Earth's core, the densities of Fe‐8.6±2.0 wt% Si and Fe‐3.8±2.9 wt% Si agree with preliminary reference Earth mode (PREM) data of the outer and the inner core, respectively. These are the upper limits for Si in the core assuming Si is the only light element. Simultaneously considering the geophysical and geochemical constraints for a Si‐S‐bearing core, the outer core may contain 3.8±2.9 wt% Si and 5.6±3.0 wt% S.

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Section: Results and Geophysical Implicationmentioning

confidence: 99%

Equation of State for Shocked Fe‐8.6 wt% Si up to 240 GPa and 4,670 K

et al. 2019

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“…Numerous lines of evidence indicate that the S content of Earth's core can be no more than ~2 wt. % (e.g., Badro et al, , ; Dreibus & Palme, ), including the partitioning behavior of S at high pressure and temperature (Suer et al, ), which largely prohibits values above this, and as such all model results herein yield S contents in the Earth's core at or below 2 wt. %.…”

Section: Discussionmentioning

confidence: 98%

Investigating Earth's Formation History Through Copper and Sulfur Metal‐Silicate Partitioning During Core‐Mantle Differentiation

et al. 2018

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Identifying extant materials that act as compositional proxies for Earth is key to understanding its accretion. Copper and sulfur are both moderately volatile elements; however, they display different geochemical behavior (e.g., phase affinities). Thus, individually and together, these elements provide constraints on the source material and conditions of Earth's accretion, as well as on the timing and evolution of volatile delivery to Earth. Here we present laser‐heated diamond anvil cell experiments at pressures up to 81 GPa and temperatures up to 4,100 K aimed at characterizing Cu metal‐silicate partitioning at conditions relevant to core‐mantle differentiation in Earth. Partitioning results have been combined with literature results for S in Earth formation modeling to constrain accretion scenarios that can arrive at present‐day mantle Cu and S contents. These modeling results indicate that the distribution of Cu and S in Earth may be the result of accretion largely from material(s) with Cu contents at or above chondritic values and S contents that are strongly depleted, such as that in bulk CH chondrites, and that the majority of Earth's mass (~3/4) accreted incrementally via pebble and/or planetesimal accretion.

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“…Indeed, seismic data indicate that the core is well mixed (Davies et al, ; Labrosse, ; Nimmo, ). However, compositional convection is still not fully resolved as there is significant uncertainty in terms of light element composition in the core (Morard et al, ; Mori et al, ; Ozawa et al, ; Shibazaki & Kono, ; Suehiro et al, ; Suer et al, ; Tateno et al, ). For example, it was recently proposed that the exsolution of Mg at the CMB is sufficient to drive compositional convection (O'Rourke et al, ; O'Rourke & Stevenson, ) from the top down.…”

Section: Discussionmentioning

confidence: 99%

“…A variety of light elements, such as S, C, and O, is expected to be in the liquid OC in relatively small quantities of a few percent (e.g., McDonough, ; Morard et al, ; Tateno et al, ; Zhang, Sekine, et al, ). It was established recently (e.g., Zhang, Sekine, et al, ) that the OC is unlikely to contain just a single light element, since it has been demonstrated that no one light element can satisfy the combined compositional, cosmochemical, and geophysical constraints in the OC near ICB (Morard et al, ; Mori et al, ; Ozawa et al, ; Shibazaki & Kono, ; Suehiro et al, ; Suer et al, ; Tateno et al, ). Even with the unknown compositional makeup of the light elements in the core, our study leads to the conclusion that the electrical resistivity and thermal conductivity of liquid Fe alloy will remain the same at ICB and likely at CMB, regardless of the light element identity for small contents.…”

Section: Discussionmentioning

confidence: 99%

“…However, the challenge of better constraining the transport properties of the liquid Fe alloy in the core is multifaceted. The uncertainty in evaluation of both thermal conductivity and electrical resistivity of the Fe alloy in the OC is caused by (i) the unresolved compositional makeup and proportions of light elements in the liquid OC (e.g., Litasov & Shatskiy, ) although the consensus tilts toward Si as the major light element in the OC (e.g., Suer et al, ; Zhang, Sekine, et al, ), (ii) the exact effects of light element alloying on the transport properties of the liquid Fe (e.g., Shibazaki & Kono, ; Zhang, Sekine, et al, ), (iii) the amount of heat flow across the CMB (e.g., Ammann et al, ; Nimmo, ), and (iv) a large spread of estimated temperatures at the CMB and ICB (e.g., Andrault et al, ; Anzellini et al, ; Sakairi et al, ; Zhang, Sekine, et al, ). Lastly, from the experimental perspective, reaching and maintaining the core temperatures ( T ) and pressures ( P ) for sufficiently long time, while maintaining liquid sample geometry and purity to collect resistivity data, are still not experimentally achievable (e.g., Williams, ).…”

Section: Introductionmentioning

confidence: 99%

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Heat Flow in Earth's Core From Invariant Electrical Resistivity of Fe‐Si on the Melting Boundary to 9 GPa: Do Light Elements Matter?

et al. 2019

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The electrical resistivity and thermal conductivity of liquid Fe alloys are the least constrained parameters in Earth's outer core (OC). These parameters are important as they modulate energy budget available for the geodynamo and affect the spatiotemporal evolution of the core. We report results of electrical resistivity measurements on solid and liquid Fe‐4.5 wt%Si from 3–9 GPa using a large volume multianvil press. The internally modified 18/11 octahedron cell was used to maintain the geometry of the liquid sample and to delay the onset of contamination. Electrical resistivity of solid Fe‐4.5Si decreases steadily with pressure and is very sensitive to increasing temperature‐driven onset of phase transitions. Along the melting boundary and within error, electrical resistivity remains constant and assumes the same value of 120 μΩcm as observed in pure liquid Fe. The results are interpreted in the context of icosahedral short‐range order (ISRO) structures that exhibit higher concentration with increasing pressure. Along the melting line, the increasing concentration of ISROs reduces charge carrier mean free path and prevents decrease of electrical resistivity with increasing pressure as seen in liquid metals, Cu, Ag, and Au, which do not have ISROs. In light of recent developments in understanding of the structure and dynamics of liquid transition metals and alloys, we postulate that our findings are applicable to other Fe alloys in the OC with small light element (C, S, and O) content. We calculated an adiabatic heat flow of 9.4–12 TW at the OC‐CMB interface, which admits thermal convection.

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A sulfur-poor terrestrial core inferred from metal–silicate partitioning experiments

Cited by 80 publications

References 66 publications

Equation of State for Shocked Fe‐8.6 wt% Si up to 240 GPa and 4,670 K

Equation of State for Shocked Fe‐8.6 wt% Si up to 240 GPa and 4,670 K

Investigating Earth's Formation History Through Copper and Sulfur Metal‐Silicate Partitioning During Core‐Mantle Differentiation

Heat Flow in Earth's Core From Invariant Electrical Resistivity of Fe‐Si on the Melting Boundary to 9 GPa: Do Light Elements Matter?

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