Thermal equation of state of MgSiO4H2 phase H determined by in situ X-ray diffraction and a multianvil apparatus

Nishi, Masayuki; Tsuchiya, Jun; Arimoto, Takeshi; Kakizawa, Sho; Kunimoto, Takehiro; Tange, Yoshinori; Higo, Yuji; Irifune, Tetsuo

doi:10.1007/s00269-018-0980-z

Cited by 13 publications

(29 citation statements)

References 39 publications

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“…We calculated the pressure based on the unit cell volume of gold (Tsuchiya, ). The cell assembly was almost the same as that reported by Nishi et al ().…”

Section: Methodssupporting

confidence: 81%

Solid Solution and Compression Behavior of Hydroxides in the Lower Mantle

et al. 2019

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The high-pressure solid solution and compression behavior of hydroxides in the ternary MgSiO 4 H 2 -AlOOH-FeOOH system were studied at pressures of 16-60 GPa and temperatures of 300-1513 K. We applied in situ X-ray measurements in conjunction with a multianvil apparatus using sintered diamond anvils to achieve homogeneous temperature distributions within large sample volumes. Our results show that CaCl 2 -type hydroxides form solid solutions over a wide composition range. We also observed the volume reductions in the solid solutions accompanied by a spin transition of iron at~50 GPa, and the wide compositional ranges are maintained through this process. Consequently, water may be transported into the deep lower mantle by the hydrous CaCl 2 -type solid solution with changing its composition depending on the chemical and thermal environments.Plain Language Summary A significant amount of water has been transported into the Earth's interior via subduction of hydrous phases in cold plates since plate tectonics started to operate billions of years ago. Recent theoretical and experimental studies revealed that hydrous phases with compositions of MgSiO 4 H 2 , AlOOH, and FeOOH are stable at the high pressures occurring in the lower mantle, suggesting that a certain amount of water may be delivered to the core-mantle boundary (~2,900-km depth). However, hydroxides in multicomponent systems relevant to the actual mantle and subducting slabs are not well studied. Here we compressed multicomponent hydroxides in the ternary MgSiO 4 H 2 -AlOOH-FeOOH system using multianvil technology and found that hydroxide subducted into the lower mantle can retain Earth's major elements, such as Mg, Si, Al, Fe, and O. Key Points:• The solid solution and compression behavior of hydroxides were studied by in situ X-ray measurements and a multianvil press • CaCl 2 -type hydroxides form solid solutions over a wide composition range in the MgSiO 4 H 2 -AlOOH-FeOOH system • The volume of CaCl 2 -type hydroxides decreases due to a spin transition of iron at~50 GPa Supporting Information:• Supporting Information S1Correspondence to: M. Nishi,

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“…We calculated the pressure based on the unit cell volume of gold (Tsuchiya, ). The cell assembly was almost the same as that reported by Nishi et al ().…”

Section: Methodssupporting

confidence: 81%

Solid Solution and Compression Behavior of Hydroxides in the Lower Mantle

et al. 2019

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“…However, the values of a and b are larger than those in the results as the use of GGA causes under-binding in the calculations. At the same time, the calculated changes in the lattice constants with pressure are consistent with the experimental results [Nishi et al, 2018].…”

Section: Crystal Structures Of Phase H Under High Pressuresupporting

confidence: 86%

“…Thus, the effect of Al on the lattice constant is smaller compared to that of Fe. Nishi et al [2018] measured the lattice constant of pure-Mg phase H using the multi-anvil apparatus under 300-1300K temperature and 34-60 GPa pressure. The comparative results at a temperature of 300K are listed in Figure 1.…”

Section: Crystal Structures Of Phase H Under High Pressurementioning

confidence: 99%

“…Water plays an important role in the evolution and dynamics of Earth due to its strong influence on the physical and chemical characteristics of the Earth materials. The phase H and the solid solution formed by phase H with -phase AlOOH (phase H+-AlOOH) are considered to be the most potential hydrous phases present under the deep lower mantle conditions [Ohtani et al, 2014;Ghosh and Schmidt, 2014;Nishi et al, 2018Nishi et al, , 2019. Iron is abundantly found in the mantle, usually as the substitute for magnesium in mantle minerals.…”

Section: Introductionmentioning

confidence: 99%

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The effect of Fe on crystal structure and elasticity superhydous Phase H under high pressure by First-principles calculations

Liu¹,

Yang²,

Yang³

et al. 2020

Annals of Geophysics

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Being one of the potentially important hydrous phases of the lower mantle, it is important to study the properties of phase H to understand the structure and composition of the mantle. The crystal structure, elastic modulus, and seismic wave velocity of phase H under different Fe concentrations (0, 12.5, 25, 100 at%) at 16–60 GPa were calculated by the first-principles simulation. The density of phase H linearly increases with increasing Fe concentration. The iron concentrations of 35.5–84.3 at% lead to densities matching the mantle density profile at different depths of the Earth. The effects of Fe on different elastic constants show varying tendencies. The K value increases with the Fe concentration, while the G value decreases. The values for Vp and Vs increase almost linearly with the rise in pressure. The Vp and Vs values decrease with increasing Fe content. The wave velocities of the pure-Mg phase H and Fe-bearing phase H are close to the typical velocity of the Earth at 500–1400 km depth. The FeOOH-AlOOH-MgSiH2O4-FeSiH2O4 system may be responsible for the observed seismic properties of LLSVP in the Earth’s lower mantle. The quantitative effect of Fe on the density, elastic moduli (K and G), and wave velocities (Vp and Vs) are listed as fitted equations. These results help to infer the Fe concentration and structure of the deep Earth.

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“…Several experimental studies reported the existence of phase H up to around 60 GPa (Nishi et al, ; Ohtani et al, ; Walter et al, ). However, it is usually difficult to determine precise thermodynamic phase boundaries by experiments, as the transition is often restricted at low temperature because sufficient thermal energy required for the reaction to proceed is unavailable.…”

Section: Resultsmentioning

confidence: 99%

First‐Principles Determination of the Dissociation Phase Boundary of Phase H MgSiO₄H₂

Tsuchiya

Umemoto

2019

Geophysical Research Letters

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Phase H (MgSiO4H2) is considered an important carrier of water into the lower mantle by the subduction of slabs. This phase has been reported to decompose into H2O ice VII and MgSiO3 bridgmanite under pressure. However, the dissociation phase boundary under the mantle pressure and temperature conditions has not been determined thus far. In this work, the dissociation phase boundary of phase H is determined by the calculation of Gibbs free energy of H2O ice VII. The stability field of phase H is found to be significantly extended from 52 to 62 GPa by the inclusion of zero‐point vibrational energy. Phase H decomposes into MgSiO3 bridgmanite and H2O ice VII at approximately 60 GPa (at ∼1000 K). This result indicates that the transportation of water by dense hydrous magnesium silicates may be terminated at a depth of approximately 1,500 km in the middle of the lower mantle in a pure Mg‐endmember composition.

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Thermal equation of state of MgSiO4H2 phase H determined by in situ X-ray diffraction and a multianvil apparatus

Cited by 13 publications

References 39 publications

Solid Solution and Compression Behavior of Hydroxides in the Lower Mantle

Solid Solution and Compression Behavior of Hydroxides in the Lower Mantle

The effect of Fe on crystal structure and elasticity superhydous Phase H under high pressure by First-principles calculations

First‐Principles Determination of the Dissociation Phase Boundary of Phase H MgSiO₄H₂

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Thermal equation of state of MgSiO4H2 phase H determined by in situ X-ray diffraction and a multianvil apparatus

Cited by 13 publications

References 39 publications

Solid Solution and Compression Behavior of Hydroxides in the Lower Mantle

Solid Solution and Compression Behavior of Hydroxides in the Lower Mantle

The effect of Fe on crystal structure and elasticity superhydous Phase H under high pressure by First-principles calculations

First‐Principles Determination of the Dissociation Phase Boundary of Phase H MgSiO4H2

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First‐Principles Determination of the Dissociation Phase Boundary of Phase H MgSiO₄H₂