Partitioning of oxygen during core formation on the Earth and Mars

Rubie, D. C.; Geßmann, C. K.; Frost, Daniel J.

doi:10.1038/nature02473

Cited by 157 publications

(80 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The partitioning of oxygen during core-mantle equilibration could have also influenced the redox state of the mantle in addition to potentially contributing at least part of the light element budget of the core (Ringwood 1977;Rubie et al 2004). The solubility of oxygen in liquid Fe metal is relatively low at room pressure.…”

Section: Oxygen Partitioning and Its Effect On The Feo/mgo Ratio Of Tmentioning

confidence: 99%

“…More complex models could be based on the determinations of oxygen activities in Fe metal assessed from the miscibility gap in the Fe-FeO system. Rubie et al (2004) proposed that the mantles of both the Earth and Mars, which have low and high FeO contents, respectively, could have been produced from material with an identical bulk composition (particularly in terms of bulk O/Fe ratio), as long as core-mantle equilibration occurred at conditions that promoted more oxygen to partition into the core of the Earth in comparison with that of Mars. Higher oxygen partitioning into the Earth's core would have depleted the mantle of FeO, whereas if relatively little oxygen partitioned into the Martian core its mantle would have retained a higher FeO content.…”

Section: Oxygen Partitioning and Its Effect On The Feo/mgo Ratio Of Tmentioning

confidence: 99%

“…To date, the partitioning of oxygen has been studied mainly between liquid Fe alloy and magnesiowüstite (Ohtani & Ringwood 1984;Rubie et al 2004;Asahara et al 2007), although some data also exist for partitioning between Fe metal and silicate perovskite Kawazoe & Ohtani 2006). Experiments on magnesiowüstite or perovskite are technically much easier to perform than those on silicate melts, which are hard to encapsulate at very high temperatures and generally react with any capsule material that does not react with liquid metal.…”

Section: Oxygen Partitioning and Its Effect On The Feo/mgo Ratio Of Tmentioning

confidence: 99%

“…Integral to most 'homogeneous' accretion models is the concept that changes in metal-silicate partition coefficients at high pressures and temperatures may negate the necessity for changing f O 2 during core formation (Li & Agee 1996;Chabot & Agee 2003;Wade & Wood 2005). In addition, however, several fractionation processes involving Fe, O and Si have been identified, which could have changed the oxidation state of the mantle, even if the redox state of accreting material remained essentially constant (Javoy 1995;Frost et al 2004;Rubie et al 2004;Galimov 2005). It is, therefore, important to determine the effectiveness of these processes and the conditions under which they may have operated.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The redox state of the mantle during and just after core formation

Frost

Mann

Asahara

et al. 2008

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

Siderophile elements are depleted in the Earth's mantle, relative to chondritic meteorites, as a result of equilibration with core-forming Fe-rich metal. Measurements of metal-silicate partition coefficients show that mantle depletions of slightly siderophile elements (e.g. Cr, V ) must have occurred at more reducing conditions than those inferred from the current mantle FeO content. This implies that the oxidation state (i.e. FeO content) of the mantle increased with time as accretion proceeded. The oxygen fugacity of the present-day upper mantle is several orders of magnitude higher than the level imposed by equilibrium with core-forming Fe metal. This results from an increase in the Fe 2 O 3 content of the mantle that probably occurred in the first 1 Ga of the Earth's history. Here we explore fractionation mechanisms that could have caused mantle FeO and Fe 2 O 3 contents to increase while the oxidation state of accreting material remained constant (homogeneous accretion). Using measured metal-silicate partition coefficients for O and Si, we have modelled core-mantle equilibration in a magma ocean that became progressively deeper as accretion proceeded. The model indicates that the mantle would have become gradually oxidized as a result of Si entering the core. However, the increase in mantle FeO content and oxygen fugacity is limited by the fact that O also partitions into the core at high temperatures, which lowers the FeO content of the mantle. (Mg,Fe)(Al,Si)O 3 perovskite, the dominant lower mantle mineral, has a strong affinity for Fe 2 O 3 even in the presence of metallic Fe. As the upper mantle would have been poor in Fe 2 O 3 during core formation, FeO would have disproportionated to produce Fe 2 O 3 (in perovskite) and Fe metal. Loss of some disproportionated Fe metal to the core would have enriched the remaining mantle in Fe 2 O 3 and, if the entire mantle was then homogenized, the oxygen fugacity of the upper mantle would have been raised to its present-day level.

show abstract

Section: Oxygen Partitioning and Its Effect On The Feo/mgo Ratio Of Tmentioning

confidence: 99%

Section: Oxygen Partitioning and Its Effect On The Feo/mgo Ratio Of Tmentioning

confidence: 99%

Section: Oxygen Partitioning and Its Effect On The Feo/mgo Ratio Of Tmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The redox state of the mantle during and just after core formation

Frost

Mann

Asahara

et al. 2008

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

show abstract

“…Similarly, significant amount of O is found in liquid iron in equilibrium with another major lower mantle mineral ferropericlase [Rubie et al, 2004;Ozawa et al, 2008]. These higher values of light-element solubility hint at the possibility that significant amount of O and Si could dissolve into liquid iron simultaneously if temperature and pressure are high enough.…”

Section: Resultsmentioning

confidence: 91%

Partitioning of Si and O between liquid iron and silicate melt: A two‐phase ab‐initio molecular dynamics study

Zhang

Guo

2009

Geophysical Research Letters

View full text Add to dashboard Cite

The magma ocean process in the early history of the Earth has a great influence on the light element identities and contents of the core which subsequently affect the energy of the geodynamo provided by the compositional convection and the inner core growth through their effect on the phase diagram of iron alloy. In the present work, a two‐phase ab‐initio molecular dynamics method is established to study the solubility of silicon and oxygen in liquid iron in equilibrium with silicate melt. The ab‐initio results are found to be in close agreement with experimental data. At the base of a deep magma ocean (39 GPa and 3116 K), liquid iron contains 2.7 wt% silicon and 0.5 wt% oxygen at the current bulk Earth composition. The oxygen content is low compared with its current estimate in the core, indicating a deeper magma ocean may need to be invoked.

show abstract

Thermodynamics of melting relations in the system Fe‐FeO at high pressure: Implications for oxygen in the Earth's core

2014

View full text Add to dashboard Cite

The thermodynamics of melting relations in the system Fe-FeO was investigated to the outer core-inner core boundary condition from a self-consistent thermodynamic database which was evaluated from the latest static high-pressure (P) and high-temperature (T) experiments. The evaluated database together with an existing nonideal mixing model for liquids reproduces experimental data on the eutectic composition and temperature to P = 50 GPa. On the other hand at the outer core pressures (136 to 330 GPa), employing an ideal solution model gives calculated eutectic temperatures of T = 2990-4330 K, which are also consistent with experimental data. Hence, the ideal solution model is applied to calculate the liquid property under outer core conditions and yields the eutectic compositions of Fe-7.2-9.1 wt % O. From the Gibbs free energy for the Fe-FeO liquids, I calculated the density, sound velocity, and isentropic temperature gradient of a hypothetical oxygen-bearing outer core. Under the outer core conditions, the addition of oxygen reduces the compressional wave velocity of iron liquid, moving it away from seismologically constrained values. An overall O-rich bulk outer core model is thus excluded. Seismological observations however suggest the presence of a low-velocity layer with a thickness of 60-70 km at the top of the outer core. The origin of such a low-velocity layer can be explained by an enrichment of oxygen which might be a consequence of chemical interactions between the core and mantle.

show abstract

Partitioning of oxygen during core formation on the Earth and Mars

Cited by 157 publications

References 26 publications

The redox state of the mantle during and just after core formation

The redox state of the mantle during and just after core formation

Partitioning of Si and O between liquid iron and silicate melt: A two‐phase ab‐initio molecular dynamics study

Thermodynamics of melting relations in the system Fe‐FeO at high pressure: Implications for oxygen in the Earth's core

Contact Info

Product

Resources

About