Experimental determination of carbon solubility in Fe-Ni-S melts

Zhang, Zhou; Hastings, Patrick; Handt, Anette von der; Hirschmann, M. M.

doi:10.1016/j.gca.2018.01.009

Cited by 22 publications

(15 citation statements)

References 56 publications

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“…In some experimental charges, vermicular intergrowths of graphite in metal were also present. These textures are similar to superliquidus metals produced by Zhang et al (2018) when quenched to room temperature.…”

Section: Resultssupporting

confidence: 80%

“…The experimental results from Malavergne et al (2014) support a decrease in C content (2.8 to 0.1 wt%) with increasing Si (6.04 to 23.66 wt%) in the metal phases, complimentary to the results in this study. Zhang et al (2018, and references therein) showed a similar effect in the Fe‐Ni‐S system conducted from 2–7 GPa and 1200–1600°C. These observations coupled with our own indicate that there are likely structural controls on the incorporation of C in metallic melts that are consistent with a paucity of bonds between C and non‐Fe metallic melt components (Elardo & Shahar, 2017; Hume‐Rothery, 1966).…”

Section: Discussionmentioning

confidence: 60%

“…Consequently, we infer that Mercury's core has an Fe/Ni weight ratio of 17 (Lodders & Fegley, 1998). Li et al (2015) showed that the addition of S in an Fe‐rich metal alloy does not have a considerable effect on carbon solubility in the alloy melt, although Zhang et al (2018, and references therein) showed that C solubility diminishes with increasing S content, similar to the results of Bouchard and Bale (1995). Furthermore, Chabot et al (2014) showed that even up to 5 wt% S in the core of Mercury allows for more than 8 wt% Si in the metal.…”

Section: Discussionmentioning

confidence: 65%

“…With respect to the estimated abundances of carbon in Mercury's core, the chondritic models all assume a simplified core composition in the Fe‐Ni‐Si‐C system with a chondritic Fe/Ni ratio of 17 (Lodders & Fegley, 1998); however, the core of Mercury is likely to have additional major or minor components, in particular, S. Previous studies have demonstrated that the addition of S and Ni to the Fe‐Si‐C system will further diminish the solubility of C (Dasgupta et al, 2013; Kim et al, 2014; Li et al, 2015; Zhang et al, 2018). Furthermore, we do not have sufficient evidence to rule out the possibility that Mercury has a superchondritic abundance of C, which could have been attained contemporaneously with a superchondritic Fe/Si resulting from a giant impact.…”

Section: Discussionmentioning

confidence: 99%

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Constraints on the Abundances of Carbon and Silicon in Mercury's Core From Experiments in the Fe‐Si‐C System

et al. 2020

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The composition of a planet's core has important implications for the thermal and magmatic evolution of that planet. Here, we conducted carbon (C) solubility experiments on iron-silicon (Fe-Si) metal mixtures (up to 35 wt% [~52 atom%] Si) at 1 GPa and 800-1800°C to determine the carbon concentration at graphite saturation (CCGS) in metallic melt and crystalline metal with varying proportions of Fe and Si to constrain the C content of Mercury's core. Our results, combined with those in the literature, show that composition is the major controlling factor for carbon solubility in Fe-rich metal with minimal effects from temperature and pressure. Moreover, there is a strong anticorrelation between the abundances of carbon and silicon in iron-rich metallic systems. Based on the previous estimates of <1-25 wt% Si in Mercury's core, our results indicate that a carbon-saturated Mercurian core has 0.5-6.4 wt% C, with 6.4 wt% C corresponding to an Si-free, Fe core and 0.5 wt% C corresponding to an Fe-rich core with 25 wt% Si. The upper end of estimated FeO abundances in the mantle (up to 2.2 wt%) are consistent with a core that has <1 wt% Si and up to 6.4 wt% C, which would imply that bulk Mercury has a superchondritic Fe/Si ratio. However, the lower end of estimated FeO (≤0.05 wt%) supports CB chondrite-like bulk compositions of Mercury with core Si abundances in the range of 5-18.5 wt% and C abundances in the range of 0.8-4.0 wt%. Plain Language SummaryThe composition of a planet's core can provide clues as to how the planet has changed over time. In this study, we conducted experiments at high pressures and temperatures to investigate potential carbon and silicon abundances in the core of Mercury. We utilized a variety of iron-silicon metal mixtures (up to 35 wt% silicon) and graphite capsules in order to examine the concentration of carbon in metallic melts and crystalline metals at graphite saturation with the intention of constraining the carbon and silicon content of Mercury's core. Combining the results of this study with those in the literature, we found that composition is the major controlling factor of carbon solubility in silicon-bearing, iron-rich metal, with minimal effects from temperature. More importantly, our results showed a strong anticorrelation between the abundances of carbon and silicon in iron-rich metallic systems. Since Mercury may have formed in a region of the solar system with less oxygen available, it is likely that some silicon partitioned into Mercury's core as silicon becomes more siderophile under reducing conditions. These findings, when combined with other elemental data, can be used to place constraints on the bulk composition of Mercury, which could help to constrain its origin.

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Section: Resultssupporting

confidence: 80%

Section: Discussionmentioning

confidence: 60%

Section: Discussionmentioning

confidence: 65%

Section: Discussionmentioning

confidence: 99%

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Constraints on the Abundances of Carbon and Silicon in Mercury's Core From Experiments in the Fe‐Si‐C System

et al. 2020

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“…The Fe 3 C starting material was synthesized from Fe and high purity graphite powder in an MgO capsule held at 2.0 GPa and 1473 K for 24 hours, in a piston cylinder apparatus at The University of Edinburgh. The molar ratio of Fe:C for the starting powders was 2.9701:1, slightly enriched in C, in order to ensure the run product was not in the Fe−Fe 3 C stability field upon minor volatilization of carbon (Zhang et al 2018). The Fe 3 C sample was ground into a powder under acetone, and phase purity was confirmed by X-ray diffraction.…”

Section: Methodsmentioning

confidence: 99%

P-V-Tmeasurements of Fe3C to 117 GPa and 2100 K: Implications for stability of Fe3C phase at core conditions

McGuire

Komabayashi

Thompson

et al. 2021

American Mineralogist

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The Geochemical Legacy of Low-Temperature, Percolation-Driven Core Formation in Planetesimals

Bromiley

2023

Earth Moon Planets

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Mechanisms for core formation in differentiated bodies in the early solar system are poorly constrained. At temperatures below those required to extensively melt planetesimals, core formation could have proceeded via percolation of metallic liquids. Although there is some geochemical data to support such ‘low-temperature’ segregation, experimental studies and simulations suggest that percolation-driven segregation might have only contributed to core formation in a proportion of fully-differentiated bodies. Here, the effects low-temperature core-formation on elemental compositions of planetesimal cores and mantles are explored. Immiscibility of Fe-rich and FeS-rich liquids will occur in all core-formation models, including those involving large fraction silicate melting. Light element content of cores (Si, O, C, P, S) depends on conditions under which Fe-rich and FeS-rich liquids segregated, especially pressure and oxygen fugacity. The S contents of FeS-rich liquids significantly exceed eutectic compositions in Fe–Ni–S systems and cannot be reconciled with S-contents of parent bodies to magmatic iron meteorites. Furthermore, there is limited data on trace element partitioning between FeS-rich and Fe-rich phases, and solid/melt partitioning models cannot be readily applied to FeS-rich liquids. Interaction of metallic liquids with minor phases stable up to low fraction silicate melting could provide a means for determining the extent of silicate melting prior to initiation of core-formation. However, element partitioning in most core-formation models remains poorly constrained, and it is likely that conditions under which segregation of metallic liquid occurred, especially oxygen fugacity and pressure, had as significant a control on planetesimal composition as segregation mechanisms and extent of silicate melting.

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Experimental determination of carbon solubility in Fe-Ni-S melts

Cited by 22 publications

References 56 publications

Constraints on the Abundances of Carbon and Silicon in Mercury's Core From Experiments in the Fe‐Si‐C System

Constraints on the Abundances of Carbon and Silicon in Mercury's Core From Experiments in the Fe‐Si‐C System

P-V-Tmeasurements of Fe3C to 117 GPa and 2100 K: Implications for stability of Fe3C phase at core conditions

The Geochemical Legacy of Low-Temperature, Percolation-Driven Core Formation in Planetesimals

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