Water solubility in Mg-perovskites and water storage capacity in the lower mantle

Litasov, Konstantin D.; Ohtani, Eiji; Langenhorst, F.; Yurimoto, H.; Kubo, Tomoaki; Kondo, Tadashi

doi:10.1016/s0012-821x(03)00200-0

Cited by 137 publications

(115 citation statements)

References 41 publications

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“…Hence, H 2 O is expected to be incorporated in bridgmanite as MgHAlO 3 in the lower mantle because of high pressures. Murakami et al (2002) and Litasov et al (2003) reported that synthetic Al-Fe-bearing bridgmanite in mantle peridotite can contain 1000-2000 ppm water at 26 GPa and 1500-1923 o K, which is significantly higher than that in synthetic MgSiO 3 bridgmanite at 24-25 GPa and 1573-1873 o K (Bolfan-Casanova et al, 2000; Geochemical Perspectives Letters Letter Litasov et al, 2003). Following Equation 2, the amount of 2.2 mol.…”

Section: Geochemical Implicationsmentioning

confidence: 99%

Rapid decrease of MgAlO2.5 component in bridgmanite with pressure

Liu¹,

Ishii²,

Katsura³

2017

Geochem. Persp. Let.

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The solubility of the MgAlO 2.5 component in bridgmanite was measured at pressures of 27, 35 and 40 GPa and a temperature of 2000 o K using an ultra-high pressure multi-anvil press. Compositional analysis of recovered samples demonstrated that the MgAlO 2.5 component decreases with increasing pressure, and approaches virtually zero at 40 GPa. Above this pressure, the MgAlO 2.5 component, i.e. the oxygen-vacancy substitution, becomes negligible, and Al is incorporated in bridgmanite by the charge-coupled substitution only. These results are supported by the volume change associated with the change from the oxygen-vacancy substitution to charge-coupled substitution. The present result may explain the seismically observed slab stagnation in the mid-lower mantle. Although bridgmanite has been put forward as a potential host for water and argon in the lower mantle by trapping them in oxygen vacancies, such capabilities will rapidly decrease with depth and be lost in regions deeper than 1000 km.

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Section: Geochemical Implicationsmentioning

confidence: 99%

Rapid decrease of MgAlO2.5 component in bridgmanite with pressure

Liu¹,

Ishii²,

Katsura³

2017

Geochem. Persp. Let.

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“…Moreover, experimental Kd pe=pvk H 2 O values span a disquieting range of 0. 2-75 (Bolfan-Casanova et al, 2000;Murakami et al, 2002Murakami et al, , 2002Litasov et al, 2003;Ohtani, 2005;Inoue et al, 2010). This could be explained by relevant experimental difficulties both in performing hydrous experiments at extreme pressures and temperatures and in analysing small H 2 O concentrations in the resulting tiny crystals (Keppler and Smyth, 2006 and reference therein).…”

Section: Equilibrium Constant: Mswv Vs Mswamentioning

confidence: 99%

Lower mantle hydrogen partitioning between periclase and perovskite: A quantum chemical modelling

Merli

Bonadiman

Diella

et al. 2016

Geochimica et Cosmochimica Acta

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“…Hydration under oxidising conditions could therefore be coupled to large concentrations of Fe 3+ , such as in regions of subduction (McCammon et al, 2004a). The solubility of water in lower mantle minerals remains a controversial issue (Bolfan Casanova et al, 2000;cf., Murakami et al, 2002;Litasov et al, 2003). Navrotsky (2003) suggested that the incorporation of trivalent cations in (Mg,Fe)(Si,Al)O 3 perovskite could enhance hydrogen solubility through a vacancy mechanism, and indeed in the composition range where oxygen vacancies appear to be stabilised (x Al < ~ 0.1; Frost and Langenhorst, 2002), hydrogen solubility in (Mg,Fe)(Si,Al)O 3 perovskite is observed to be higher relative to the composition range where charge coupled substitution appears to be favoured (x Al > ~ 0.1) (Litasov et al, 2003 (McCammon et al, 1998;, OH point defect concentration may be coupled instead to cation vacancies, with corresponding implications for transport properties and rheology (Bolfan Casanova et al, 2002).…”

Section: Chemical and Physical Propertiesmentioning

confidence: 99%

“…The solubility of water in lower mantle minerals remains a controversial issue (Bolfan Casanova et al, 2000;cf., Murakami et al, 2002;Litasov et al, 2003). Navrotsky (2003) suggested that the incorporation of trivalent cations in (Mg,Fe)(Si,Al)O 3 perovskite could enhance hydrogen solubility through a vacancy mechanism, and indeed in the composition range where oxygen vacancies appear to be stabilised (x Al < ~ 0.1; Frost and Langenhorst, 2002), hydrogen solubility in (Mg,Fe)(Si,Al)O 3 perovskite is observed to be higher relative to the composition range where charge coupled substitution appears to be favoured (x Al > ~ 0.1) (Litasov et al, 2003 (McCammon et al, 1998;, OH point defect concentration may be coupled instead to cation vacancies, with corresponding implications for transport properties and rheology (Bolfan Casanova et al, 2002). While there are no direct experiments on hydrogen solubility in the ppv phase, first principles calculations have shown that the substitution Si 4+ → Al 3+ + H + stabilises MgSiO 3 in the ppv phase relative to the perovskite structure (Akber Knutson et al, 2005), suggesting that hydrogen solubility may be composition dependent, and different for the two phases.…”

Section: Chemical and Physical Propertiesmentioning

confidence: 99%

Microscopic properties to macroscopic behaviour: The influence of iron electronic state

McCammon

2006

Journal of Mineralogical and Petrological Sciences

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Iron is the only major element in the Earth with multiple electronic configurations (oxidation and spin state). In the upper mantle and transition zone iron is predominantly Fe 2+ , but the small amount of Fe 3+ that is present significantly affects properties that are sensitive to defect chemistry, including electrical conductivity, diffusivity and hydrogen solubility. Fe 3+ also determines the oxygen fugacity, where the upper mantle is relatively oxidised due to the high Fe 3+ /ΣFe ratio in spinel, even though the overall Fe 3+ concentration in the upper mantle is low due to its concentration in modally minor phases. The transition zone contains a similar amount of Fe 3+ , but its distribution among all the major phases results in a significantly lower oxygen fugacity, near metal saturation. In the lower mantle the transition to (Mg,Fe)(Si,Al)O 3 perovskite involves the creation of significant Fe 3+(approximately 50% of available iron), even at reducing conditions, which is likely balanced in the bulk lower mantle by disproportionation of Fe 2+ to form Fe 3+ and metallic iron, and potentially in subducting slabs through reduction of oxidised species in the slab. The nature of Fe 3+ charge balance in (Mg,Fe)(Si,Al)O 3 perovskite largely determines the influence on physical and chemical properties, where electrical conductivity is enhanced, diffusivity is reduced, and elasticity and hydrogen solubility vary depending on the substitution mechanism. If Fe 2+ is more stable in the post perovskite phase relative to (Mg,Fe)(Si,Al)O 3 perovskite as suggested by experiments, both Fe 3+ /ΣFe and the nature of its influence on physical and chemical properties may be different in the post perovskite phase. The influence of spin crossover on mantle properties remains unclear. Recent models show that the growth of an (Mg,Fe)(Si,Al)O 3 perovskite rich lower mantle during core formation would progressively oxidise the mantle to present levels as a portion of the disproportionated iron rich metal phase became incorporated into the core, and the increase in oxygen fugacity during the later stages of Earth accretion would alter the partitioning behaviour of elements between mantle and core, resolving puzzles such as the siderophile element anomaly and the discrepancy between U-Pb and Hf-W systematics in the early Earth. Redox reactions involved in the movement of material across the lower mantle boundary could be related to the formation of deep diamonds, and potentially the rise of atmospheric oxygen through a mantle avalanche in the late Archean that disturbed the balance of volatile element cycles.

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Water solubility in Mg-perovskites and water storage capacity in the lower mantle

Cited by 137 publications

References 41 publications

Rapid decrease of MgAlO2.5 component in bridgmanite with pressure

Rapid decrease of MgAlO2.5 component in bridgmanite with pressure

Lower mantle hydrogen partitioning between periclase and perovskite: A quantum chemical modelling

Microscopic properties to macroscopic behaviour: The influence of iron electronic state

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