Elasticity and Anisotropy of the Pyrite-Type FeO2H-FeO2 System in Earth’s Lowermost Mantle

Huang, Shengxuan; Qin, Shan; Wu, Xiang

doi:10.1007/s12583-018-0836-y

Cited by 9 publications

(28 citation statements)

References 55 publications

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“…The FeO 2 H densities from these studies differ by less than 2% and the sound velocities of our study are in reasonable agreement with the V P and V S differing by 8%-9% and 1%-8%, respectively. However, the previously reported V P and V S pressure trends reported by Huang et al (2019) exhibit slightly higher positive pressure dependencies than this study (Figure 6). These velocity differences can be attributed to the different input parameters of these studies including the use of fixed U and J values by the Huang et al (2019) study versus the internally consistent U eff of this study.…”

Section: Sound Velocitiescontrasting

confidence: 82%

“…10.1029/2021GC009703 6 of 13 Note. In both this study and Huang et al (2019), the equation of state parameters was fit to data in the pressure range of 60-140 GPa. Values in parentheses are uncertainties on the last digit.…”

Section: Structure and Equation Of Statementioning

confidence: 99%

“…The ϵ-FeOOH and δ-AlOOH data are fromThompson et al (2017) andTsuchiya and Tsuchiya (2011), respectively. The AV S of pyrite-type FeO 2 H calculated byHuang et al (2019) is included as red crosses.…”

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confidence: 99%

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Elastic Properties of the Pyrite‐Type FeOOH‐AlOOH System From First‐Principles Calculations

Thompson

Campbell

Tsuchiya

2021

Geochem Geophys Geosyst

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Hydrogen storage and cycling in the deep Earth have important implications on the chemistry and dynamics of Earth's mantle. Recent results suggest a likely carrier of hydrogen into the Earth's lower mantle is the solid solution formed by the isostructural series ϵ-FeOOH, δ-AlOOH, and phase H (MgSiO 4 H 2 ) (Kawazoe et al., 2017;Nishi et al., 2017;Ohira et al., 2014). At higher pressure, CaCl 2 -type δ-AlOOH is predicted to transform into a pyrite structure (Tsuchiya & Tsuchiya, 2011) consisting of an AlO 2 framework with symmetrically bonded interstitial hydrogen. An analogous, high-pressure phase transition from CaCl 2 -type ϵ-FeOOH (Figure 1a) to pyrite-type FeO 2 H (Figure 1b) was discovered by high-pressure experimentalists in the past few years, but the stoichiometry and properties of this phase remain contested (

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Section: Sound Velocitiescontrasting

confidence: 82%

Section: Structure and Equation Of Statementioning

confidence: 99%

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Elastic Properties of the Pyrite‐Type FeOOH‐AlOOH System From First‐Principles Calculations

Thompson

Campbell

Tsuchiya

2021

Geochem Geophys Geosyst

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“…Our V ϕ of pyrite‐type FeO 2 H at 300 and 3,000 K agrees well with Liu et al () within uncertainties, considering x of 0.5–0.7 in Liu et al (). An increase in x has been suggested to increase the sound velocity of P phase (Huang et al, ; Liu et al, ). Similar to density, the sound velocity of liquid FeO 2 H is much lower than that of its solid counterpart.…”

Section: Resultsmentioning

confidence: 99%

“…Its V ϕ is much lower than the velocity of the isochemical solid and the ambient mantle (Figure b). As a result, assuming the Voigt average, a mixture of ~20% (by volume) liquid FeO 2 H and the ambient mantle can reproduce the seismic observations in ULVZs, while for pyrite‐type FeO 2 H ~60%–70% of P phase is required (Huang et al, ). Given that FeO 2 H x is a minor mineral in the subducted slabs and also may be partly consumed during the course of subduction by reacting with other volatiles such as CO 2 (Boulard et al, ), a smaller demand on the amount of delivered FeO 2 H x favors the hypothesis of FeO 2 H x ‐induced ULVZs.…”

Section: Implications For Ulvzsmentioning

confidence: 99%

First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

et al. 2019

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Pyrite-type FeO 2 H x (P phase) has recently been suggested as a possible alternative to explain ultralow-velocity zones due to its low seismic velocity and high density. Here we report the results on the congruent melting temperature and melt properties of P phase at high pressures from first-principles molecular dynamics simulations. The results show that P phase would likely be melted near the core-mantle boundary. Liquid FeO 2 H x has smaller density and smaller bulk sound velocity compared to the isochemical P phase. As such, relatively small amounts of liquid FeO 2 H x could account for the observed seismic anomaly of ultralow-velocity zones. However, to maintain the liquid FeO 2 H x within the ultralow-velocity zones against compaction requires special physical conditions, such as relatively high viscosity of the solid matrix and/or vigorous convection of the overlying mantle.Plain Language Summary Ultralow-velocity zones (ULVZs) are 5-40-km-thick patches lying above Earth's core-mantle boundary. They are characterized with anomalously low seismic velocities compared with the ambient mantle and may contain important clues on the thermochemical evolution of the Earth. A recent experimental study argued that ULVZs may be caused by the accumulation of pyrite-type FeO 2 H x (P phase) at the bottom of the mantle. Here for the first time, we systematically study the thermoelastic properties of both FeO 2 H x solid and liquid phases. We find that P phase is likely melted near the core-mantle boundary and thus cannot be the source of ULVZs. Furthermore, in order for the molten product of P phase to cause ULVZs, the dense and nearly inviscid melts must be dynamically stable and confined within the ULVZs, which requires that the mantle is highly viscous and/or convects vigorously.

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Thermal Equation of State of Natural F-Rich Topaz up to 29 GPa and 750 K

Liu

Song

et al. 2023

J. Earth Sci.

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Elasticity and Anisotropy of the Pyrite-Type FeO2H-FeO2 System in Earth’s Lowermost Mantle

Cited by 9 publications

References 55 publications

Elastic Properties of the Pyrite‐Type FeOOH‐AlOOH System From First‐Principles Calculations

Elastic Properties of the Pyrite‐Type FeOOH‐AlOOH System From First‐Principles Calculations

First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

Thermal Equation of State of Natural F-Rich Topaz up to 29 GPa and 750 K

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Elasticity and Anisotropy of the Pyrite-Type FeO2H-FeO2 System in Earth’s Lowermost Mantle

Cited by 9 publications

References 55 publications

Elastic Properties of the Pyrite‐Type FeOOH‐AlOOH System From First‐Principles Calculations

Elastic Properties of the Pyrite‐Type FeOOH‐AlOOH System From First‐Principles Calculations

First‐Principles Study of FeO2Hx Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

Thermal Equation of State of Natural F-Rich Topaz up to 29 GPa and 750 K

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First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones