Pressure‐temperature range of reactions between liquid iron in the outer core and mantle silicates

Song, Xi J.; Ahrens, Thomas J.

doi:10.1029/93gl03262

Cited by 31 publications

(12 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Liquid iron also reacts with Al 2 O 3 at CMB pressures (Dubrovinsky et al, 2001) but not with silica (Dubrovinsky et al, 2003). Using thermodynamic calculations, Song and Ahrens (1994) determined that the observed reactions are thermodynamically possible. Thus, core-mantle reactions are expected from an experimental standpoint, although it is possible that the presence of water inhibits them (Boehler et al, 1995;Poirier et al, 1998).…”

Section: Origin Of Heterogeneitiesmentioning

confidence: 99%

Mantle Geochemical Geodynamics

Tackley

2007

Treatise on Geophysics

View full text Add to dashboard Cite

Section: Origin Of Heterogeneitiesmentioning

confidence: 99%

Mantle Geochemical Geodynamics

Tackley

2007

Treatise on Geophysics

View full text Add to dashboard Cite

“…The mechanisms by which such dense material could be introduced into DЉ involve either interactions with the underlying core or descent of denser material from the overlying mantle. Chemical reactions between iron alloys and silicates have been shown to occur at high pressures from both experimental and thermodynamic perspectives 16,[68][69][70] : such reactions are of the form…”

Section: Core-mantle Chemical Reactionsmentioning

confidence: 99%

The core–mantle boundary layer and deep Earth dynamics

Lay

Williams

Garnero

1998

Nature

367

185

View full text Add to dashboard Cite

Recent seismological work has revealed new structures in the boundary layer between the Earth's core and mantle that are altering and expanding perspectives of the role this region plays in both core and mantle dynamics. Clear challenges for future research in seismological, experimental, theoretical and computational geophysics have emerged, holding the key to understanding both this dynamic system and geological phenomena observed at the Earth's surface.The Earth acquired its primary layered structure-consisting of a molten metallic alloy core overlain by a thick shell of silicates and oxides-very early in its history, and the region near the coremantle boundary (CMB) surface has undoubtedly played a significant role in both the core and mantle dynamic systems throughout their subsequent 4.5-Gyr evolution. The CMB has a density contrast exceeding that found at the surface of the Earth, has contrasts in viscosity and physical state comparable to those at the ocean floor, and has much hotter ambient temperatures than found near the surface 1,2 . These factors, together with the requirement that significant heat be flowing from the core into the mantle in order to sustain the geodynamo (the core magnetohydrodynamic flow regime that produces the Earth's magnetic field), provide the basis for the conventional view that a significant thermal boundary layer exists at the base of the mantle, with a temperature contrast of 1;000 Ϯ 500 K (refs 2-4). With ambient temperatures averaging around 3,000 K, this hot thermal boundary layer is a likely source of boundary-layer instabilities, and it has been speculated that upwelling thermal plumes ascend from the CMB to produce surface hotspot volcanism such as at Hawaii and Iceland, transporting about 10-15% of the surface heat flux 5-7 . The large CMB density contrast favours a mantle-side accumulation of chemical heterogeneities derived from initial and continuing chemical differentiation of the mantle, possibly including downwelling subducted slabs of former oceanic lithosphere; distinctive chemical signatures of these heterogeneities may eventually be entrained into thermal plumes, resulting in unique hotspot chemistry 8,9 . There may also be a core-side chemical and thermal boundary layer, but the low seismic velocities and molten state of the core make it much harder to analyse any structure in the outermost core 2 .In the past decade, seismic tomography has provided steadily improving images of deep mantle elastic velocity heterogeneity, revealing the presence of significant large-scale (Ͼ2,000 km) patterns of coherent high-and low-velocity regions at all depths 10-12 , with enhanced lateral variations in the lowermost 300 km. Attributing the seismological variations to lateral thermal and chemical heterogeneity in the boundary layer suggests several mechanisms of coupling between the core and mantle, influencing the core flow regime as well as irregularities in rotation of the planet 2,13-15 . An experimental demonstration that chemical reactions may be continuing betwee...

show abstract

“…Chemical reaction studies between liquid iron and lower mantle perovskite or oxide have produced a wide range of results, leading to interpretations ranging from production of FeSi and FeO [ Knittle and Jeanloz , 1991; Song and Ahrens , 1994] to dissolution of oxygen into liquid iron [ Takafuji et al , 2005; Frost et al , 2010], respectively. Further investigations exploring the dependence of these reactions on CMB fugacity and chemistry may address these discrepancies, which could be complicated by the possibility of disequilibria.…”

Section: Ultra‐low Velocity Zonesmentioning

confidence: 99%

“…An enhanced iron content and subsequent oxidative uptake by (Mg,Fe)O could result in a iron‐rich composition of (Mg,Fe)O distinct from that normally in equilibrium with the rest of the mantle. It has been shown that liquid iron can react with ferrous iron‐bearing perovskite to produce perovskite, FeSi, and FeO [ Knittle and Jeanloz , 1991; Song and Ahrens , 1994]. Additionally, recent experimental results, based on analyses of quenched phase assemblages from P ∼ 100 GPa and T ∼1800 K, suggest that iron preferentially partitions into (Mg,Fe)O in the presence of Pv‐ and PPv‐structured silicates [ Murakami et al , 2005; Auzende et al , 2008; Sinmyo et al , 2008].…”

Section: Introductionmentioning

confidence: 99%

Very low sound velocities in iron‐rich (Mg,Fe)O: Implications for the core‐mantle boundary region

Wicks

Jackson

Sturhahn

2010

Geophysical Research Letters

156

139

View full text Add to dashboard Cite

[1] The sound velocities of (Mg .16 Fe .84 )O have been measured to 121 GPa at ambient temperature using nuclear resonant inelastic x-ray scattering. The effect of electronic environment of the iron sites on the sound velocities were tracked in situ using synchrotron Mössbauer spectroscopy. We found the sound velocities of (Mg .16 Fe .84 )O to be much lower than those in other presumed mantle phases at similar conditions, most notably at very high pressures. Conservative estimates of the effect of temperature and dilution on aggregate sound velocities show that only a small amount of iron-rich (Mg,Fe)O can greatly reduce the average sound velocity of an assemblage. We propose that iron-rich (Mg,Fe)O be a source of ultra-low velocity zones. Other properties of this phase, such as enhanced density and dynamic stability, strongly support the presence of iron-rich (Mg,Fe)O in localized patches above the core-mantle boundary. Citation: Wicks, J. K., J. M. Jackson, and W. Sturhahn (2010), Very low sound velocities in iron-rich (Mg,Fe)O: Implications for the core-mantle boundary region, Geophys. Res. Lett., 37, L15304,

show abstract

Pressure‐temperature range of reactions between liquid iron in the outer core and mantle silicates

Cited by 31 publications

References 23 publications

Mantle Geochemical Geodynamics

Mantle Geochemical Geodynamics

The core–mantle boundary layer and deep Earth dynamics

Very low sound velocities in iron‐rich (Mg,Fe)O: Implications for the core‐mantle boundary region

Contact Info

Product

Resources

About