Experimental determination of carbon isotope fractionation between iron carbide melt and carbon: 12C-enriched carbon in the Earth's core?

Satish-Kumar, M.; So, Hayato; Yoshino, Takashi; Kato, Mitsuhiro; Hiroi, Yoshikuni

doi:10.1016/j.epsl.2011.08.008

Cited by 40 publications

(40 citation statements)

References 49 publications

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“…In a recent study, Horita and Polyakov [14] have theoretically estimated the reduced partition function ratios (b factors) for carbon isotopes ( 13 C/ 12 C) in Fe 3 C using partial vibrational densities of states (PVDOSs) and observed that it is lowest for iron carbide phase among all possible carbon phases that may exist in the mantle. The 13 C b factors are similar to those estimated using density functional theory calculations for Fe 3 C [28].…”

Section: Carbon Isotope Fractionation At High-pressure and High-tempementioning

confidence: 99%

“…The carbon isotope fractionation between elemental carbon (graphite/diamond) and iron carbide melt were estimated in a pioneering study reported in Satish-Kumar et al [14]. We estimated the temperature dependence from high-pressure high-temperature (HPHT) experiments in the Fe-C system at 5 GPa and 10 GPa under varying temperature conditions using a Kawai-type multi-anvil high-pressure apparatus.…”

Section: Carbon Isotope Fractionation At High-pressure and High-tempementioning

confidence: 99%

“…Equilibrium fractionation of carbon isotopes between graphite/diamond and Fe-C melt as a function of temperature (modified after Ref. [14]). For comparison the theoretical computation of fractionation between diamond and iron carbide is also shown (after Ref.…”

Section: Carbon Isotope Fractionation At High-pressure and High-tempementioning

confidence: 99%

“…Studies on other planetary materials in the solar system, such as howardite-eucrite-diogenite (HED) meteorites, shergottite-nakhlite-chassignite (SNC) meteorites and chondrites suggest that there is a remarkable difference in isotopic composition between these bodies and bulk silicate Earth values, the later being heavier than the former in the order of about 10 to 15 [16][17][18]. Thus, the validity of the assumption that the bulk Earth carbon isotope composition is equivalent to the carbon isotopic composition of silicate mantle is being debated recently [1,14,15]. It is therefore essential to clearly understand how far the fractionation of carbon isotopes has occurred during the segregation of core, what is going on in the present day at the core-mantle boundary and whether the carbon in the core has an impact on Earth's carbon cycle and surface processes.…”

Section: Introductionmentioning

confidence: 99%

“…Thus far, the heterogeneities in carbon isotopic composition in the upper mantle have been explained mainly by recycling process. However, recent studies have suggested the possible presence of 12 C enriched carbon in the core by fractionation processes during early accretion and segregation of metallic core [14,15]. Studies on other planetary materials in the solar system, such as howardite-eucrite-diogenite (HED) meteorites, shergottite-nakhlite-chassignite (SNC) meteorites and chondrites suggest that there is a remarkable difference in isotopic composition between these bodies and bulk silicate Earth values, the later being heavier than the former in the order of about 10 to 15 [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

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High-Pressure and High-Temperature Carbon Isotope Fractionation in the Fe-C System: Implications for Carbon Dynamics in the Deep Earth

Satish-Kumar

2017

The Review of High Pressure Science and Technology

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Section: Carbon Isotope Fractionation At High-pressure and High-tempementioning

confidence: 99%

Section: Carbon Isotope Fractionation At High-pressure and High-tempementioning

confidence: 99%

Section: Carbon Isotope Fractionation At High-pressure and High-tempementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

High-Pressure and High-Temperature Carbon Isotope Fractionation in the Fe-C System: Implications for Carbon Dynamics in the Deep Earth

Satish-Kumar

2017

The Review of High Pressure Science and Technology

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Empirical evidence for the fractionation of carbon isotopes between diamond and iron carbide from the Earth's mantle

Mikhail

Guillermier

Franchi

et al. 2014

Geochem. Geophys. Geosyst.

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We have studied two samples of mantle diamond containing iron carbide inclusions from Jagersfontein kimberlite, South Africa. Syngenetic crystal growth is inferred using morphological characteristics. These samples provide an opportunity to investigate the isotopic partitioning of 13 C in a terrestrial natural high-pressure and high-temperature (HPHT) system. The difference for the d 13 C values between the diamond and coexisting iron carbide averaged 7.2 6 1.3&. These data are consistent with available data from the literature showing iron carbide to be 13 C-depleted relative to elemental carbon (i.e., diamond). We infer that the minerals formed by crystallization of diamond and iron carbide at HPHT in the mantle beneath the Kaapvaal Craton. It is unclear whether crystallization occurred in subcratonic or sublithospheric mantle; in addition, the source of the iron is also enigmatic. Nonetheless, textural coherence between diamond and iron carbide resulted in isotopic partitioning of 13 C between these two phases. These data suggest that significant isotopic fractionation of 13 C/ 12 C (D 13 C up to >7&) can occur at HPHT in the terrestrial diamond stability field. We note that under reducing conditions at or below the iron-iron wustite redox buffer in a cratonic or deep mantle environment in Earth, the cogenesis of carbide and diamond may produce reservoirs of 13 C-depleted carbon that have conventionally been interpreted as crustal in origin. Finally, the large D 13 C for diamond-iron carbide shown here demonstrates D 13 C for silicate-metallic melts is a parameter that needs to be constrained to better determine the abundance of carbon within the Earth's metallic core.

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First‐principles prediction of Si‐doped Fe carbide as one of the possible constituents of Earth's inner core

Das

Chatterjee

Ghosh

et al. 2017

Geophysical Research Letters

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We perform a computational study based on first‐principles calculations to investigate the relative stability and elastic properties of the doped and undoped Fe carbide compounds at 200–364 GPa. We find that upon doping a few weight percent of Si impurities at the carbon sites in Fe7C3 carbide phases, the values of Poisson's ratio and density increase while VP, and VS decrease compared to their undoped counterparts. This leads to marked improvement in the agreement of seismic parameters such as P wave and S wave velocity, Poisson's ratio, and density with the Preliminary Reference Earth Model (PREM) data. The agreement with PREM data is found to be better for the orthorhombic phase of iron carbide (o‐Fe7C3) compared to hexagonal phase (h‐Fe7C3). Our theoretical analysis indicates that Fe carbide containing Si impurities can be a possible constituent of the Earth's inner core. Since the density of undoped Fe7C3 is low compared to that of inner core, as discussed in a recent theoretical study, our proposal of Si‐doped Fe7C3 can provide an alternative solution as an important component of the Earth's inner core.

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Experimental determination of carbon isotope fractionation between iron carbide melt and carbon: 12C-enriched carbon in the Earth's core?

Cited by 40 publications

References 49 publications

High-Pressure and High-Temperature Carbon Isotope Fractionation in the Fe-C System: Implications for Carbon Dynamics in the Deep Earth

High-Pressure and High-Temperature Carbon Isotope Fractionation in the Fe-C System: Implications for Carbon Dynamics in the Deep Earth

Empirical evidence for the fractionation of carbon isotopes between diamond and iron carbide from the Earth's mantle

First‐principles prediction of Si‐doped Fe carbide as one of the possible constituents of Earth's inner core

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