The origin of the depletions of V, Cr and Mn in the mantles of the Earth and Moon

Geßmann, C. K.; Rubie, D. C.

doi:10.1016/s0012-821x(00)00323-x

Cited by 91 publications

(53 citation statements)

References 32 publications

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“…8 are appropriate representations of the pressure and fO 2 conditions predicted in a number of other singlestage siderophile-element based models, including those that considered Ni and Co in isolation (Li and Agee, 2001;Walter and Tronnes, 2004), and those that considered other elements as well (Righter and Drake, 1999;Gessmann and Rubie, 2000;Wade and Wood, 2005). In order for the P-fO 2 conditions predicted by the previous models to be considered consistent with our modeled partitioning behavior of W, they should lie within the field labeled "preferred solution.…”

Section: Discussion Ii: Equilibrium Core Formation In Earthmentioning

confidence: 87%

“…The region of intersection of the two bands in dark grey, labeled 'preferred solution', shows the range in pressures that satisfy the single-stage equilibrium model for carbon-free core formation in Earth examining W in isolation. Symbols indicate the model equilibrium core formation conditions predicted by previous workers (GR00 = Gessmann and Rubie, 2000;WT04=Walter and Tronnes, 2004;WW05 = Wade and Wood, 2005;RD99 = Righter and Drake, 1999;LA01 = Li and Agee, 2001). The oxygen fugacity reported by Righter and Drake (1999) of IW− 0.4 uses Fe and FeO activities to arrive at a final equilibration fO2.…”

Section: Discussion Ii: Equilibrium Core Formation In Earthmentioning

confidence: 99%

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Metal–silicate partitioning of tungsten at high pressure and temperature: Implications for equilibrium core formation in Earth

Cottrell

Walter

Walker

2009

Earth and Planetary Science Letters

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Section: Discussion Ii: Equilibrium Core Formation In Earthmentioning

confidence: 87%

Section: Discussion Ii: Equilibrium Core Formation In Earthmentioning

confidence: 99%

Metal–silicate partitioning of tungsten at high pressure and temperature: Implications for equilibrium core formation in Earth

Cottrell

Walter

Walker

2009

Earth and Planetary Science Letters

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“…Moreover, the redox conditions have changed during the Earth's history from perhaps as much as 2-3 orders of magnitude below that of the ironwü stite (IW) equilibrium during the core-forming stage (e.g., O'Neill, 1991;Righter et al, 1997;O'Neill et al, 0016-7037/$ -see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi: 10.1016/j.gca.2008.12.016 1998; Righter and Drake, 1999;Gessmann and Rubie, 2000;Chabot and Agee, 2003) to typically within 1-2 orders of magnitude of the quartz-fayalite-magnetite (QFM) buffer in current upper mantle (e.g., Mattioli and Wood, 1986;O'Neill, 1991;Canil, 2002;McCammon, 2005). Such an f O2 -evolution will result in CAOAH volatile species changes from dominantly H 2 , H 2 O, and CH 4 to dominantly H 2 O and CO 2 .…”

Section: Introductionmentioning

confidence: 99%

Solution behavior of reduced COH volatiles in silicate melts at high pressure and temperature

Mysen

Fogel

Morrill

et al. 2009

Geochimica et Cosmochimica Acta

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The solubility and solution mechanisms of reduced CAOAH volatiles in Na 2 OASiO 2 melts in equilibrium with a (H 2 + CH 4 ) fluid at the hydrogen fugacity defined by the iron-wü stite + H 2 O buffer [f H2 (IW)] have been determined as a function of pressure (1-2.5 GPa) and silicate melt polymerization (NBO/Si: nonbridging oxygen per silicon) at 1400°C. The solubility, calculated as CH 4 , increases from $0.2 wt% to $0.5 wt% in the melt NBO/Si-range $0.4 to $1.0. The solubility is not significantly pressure-dependent, probably because f H2 (IW) in the 1-2.5 GPa range does not vary greatly with pressure. Carbon isotope fractionation between methane-saturated melts and (H 2 + CH 4 ) fluid varied by $14& in the NBO/Si-range of these melts. The (C..H) and (O..H) speciation in the quenched melts was determined with Raman and 1 H MAS NMR spectroscopy. The dominant (C..H)-bearing complexes are molecular methane, CH 4 , and a complex or functional group that includes entities with C"CAH bonding. Minor abundance of complexes that include SiAOACH 3 bonding is tentatively identified in some melts. There is no spectroscopic evidence for SiAC or SiACH 3 . Raman spectra indicate silicate melt depolymerization (increasing NBO/Si). The [CH 4 /C"CAH] melt abundance ratio is positively correlated with NBO/Si, which is interpreted to suggest that the (C"CAH)-containing structural entity is bonded to the silicate melt network structure via its nonbridging oxygen. The $14& carbon isotope fractionation change between fluid and melt is because of the speciation changes of carbon in the melt.

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“…The simplest approach to estimating the conditions of core formation is to assume an oxygen fugacity consistent with the current Fe contents of mantle and core and to use experimental data to calculate pressure and temperature at which the core and mantle would, at equilibrium, generate the partition coefficients of table 1. The result, at the current composition of the mantle, is a pressure of ca 40 GPa and temperature of approximately 3800 K (Gessmann & Rubie 2000;Chabot & Agee 2003;Wade & Wood 2005). The observation that high pressures are needed to explain the Ni and Co concentrations in the mantle led to the 'deep magma ocean' hypothesis that, at its simplest, is interpreted as core-mantle equilibration at a single pressure, temperature and mantle composition (Li & Agee 1996;Righter & Drake 1997).…”

Section: Introductionmentioning

confidence: 99%

Accretion and core formation: constraints from metal–silicate partitioning

Wood

2008

Phil. Trans. R. Soc. A.

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Experimental metal-silicate partitioning data for Ni, Co, V, Cr, Nb, Mn, Si and W were used to investigate the geochemical consequences of a range of models for accretion and core formation on Earth. The starting assumptions were chondritic ratios of refractory elements in the Earth and the segregation of metal at the bottom of a magma ocean, which deepened as the planet grew and which had, at its base, a temperature close to the liquidus of the silicate. The models examined were as follows. (i) Continuous segregation from a mantle which is chemically homogeneous and which has a fixed oxidation state, corresponding to 6.26 per cent oxidized Fe. Although Ni, Co and W partitioning is consistent with chondritic ratios, the current V content of the silicate Earth cannot be reconciled with core segregation under these conditions of fixed oxidation state.(ii) Continuous segregation from a mantle which is chemically homogeneous but in which the Earth became more oxidized as it grew. In this case, the Ni, Co, W, V, Cr and Nb contents of core and mantle are easily matched to those calculated from the chondritic ratios of refractory elements. The magma ocean is calculated to maintain a thickness approximately 35 per cent of the depth to the core-mantle boundary in the accreting Earth, yielding a maximum pressure of 44 GPa. This model yields a Si content of the core of 5.7 per cent, in good agreement with cosmochemical estimates and with recent isotopic data. (iii) Continuous segregation from a mantle which is not homogeneous and in which the core equilibrates with a restricted volume of mantle at the base of the magma ocean. This is found to increase depth of the magma ocean by approximately 50 per cent. All of the other elements (except Mn) have partitioning consistent with chondritic abundances in the Earth, provided the Earth became, as before, progressively oxidized during accretion. (iv) Continuous segregation of metal from a crystal-melt mush. In this case, pressures decrease to a maximum of 31 GPa and it is extremely difficult to match the calculated mantle contents of the highly incompatible elements Nb and W to those observed. Progressive oxidation is required to fit the observed mantle contents of vanadium. All of the scenarios discussed above point to progressive oxidation having occurred as the Earth grew. The Earth appears to be depleted in Mn relative to the chondritic reference.

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The origin of the depletions of V, Cr and Mn in the mantles of the Earth and Moon

Cited by 91 publications

References 32 publications

Metal–silicate partitioning of tungsten at high pressure and temperature: Implications for equilibrium core formation in Earth

Metal–silicate partitioning of tungsten at high pressure and temperature: Implications for equilibrium core formation in Earth

Solution behavior of reduced COH volatiles in silicate melts at high pressure and temperature

Accretion and core formation: constraints from metal–silicate partitioning

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