High pressure-temperature phase relations of basaltic crust up to mid-mantle conditions

Ishii, Takayuki; Miyajima, Nobuyoshi; Criniti, Giacomo; Hu, Qingyang; Glazyrin, Konstantin; Katsura, Tomoo

doi:10.1016/j.epsl.2022.117472

Cited by 29 publications

(20 citation statements)

References 52 publications

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“…Therefore, negative dv S anomalies associated with seismic scattering could be explained by the presence of hydrous stishovite with lower Al contents than our samples, but with similar or even lower Al/H ratios, thus closer to the SiO 2 -AlOOH join. Slightly lower Al content would then be in good agreement with previous experimental phase relations studies at topmost lower mantle conditions (Ono et al 2001;Litasov and Ohtani 2005;Ishii et al 2019bIshii et al , 2022. Further elasticity measurements across the structural phase transformation of hydrous Al-bearing silica will allow to pinpoint the pressure range and the extent of its elastic shear softening, enabling us to evaluate its actual geophysical relevance.…”

Section: Discussionsupporting

confidence: 83%

“…Stishovite is a high-pressure polymorph of SiO 2 with rutile-type structure (space group P4 2 /mnm) that constitutes up to 25 vol.% of metabasaltic phase assemblages at lower mantle depths (e.g. Irifune & Ringwood, 1993;Ishii et al, 2019aIshii et al, , 2022. At about 50 GPa and room temperature, SiO 2 stishovite was found to undergo a second-order ferroelastic phase transition to a poststishovite phase having CaCl 2 -type structure (space group Pnnm), with a decrease from tetragonal to orthorhombic symmetry (Kingma et al 1995;Andrault et al 1998).…”

Section: Introductionmentioning

confidence: 99%

“…DOI: https://doi.org/10.2138/am-2022-8546. http://www.minsocam.org/ component between 25 and 60 GPa (Ono et al 2001;Hirose et al 2005;Ricolleau et al 2010;Ishii et al 2019aIshii et al , 2022. In the presence of water, the solubility of Al is even higher and reaches 7 mol% AlO 1.5 component, corresponding to about 6 wt.% Al 2 O 3 (Litasov et al 2007).…”

Section: Introductionmentioning

confidence: 99%

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High-pressure phase transition and equation of state of hydrous Al-bearing silica

Criniti

Ishii

Kurnosov

et al. 2023

American Mineralogist

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Stishovite, a rutile-structured polymorph of SiO 2 , is a main component of subducted basaltic lithologies in the lower mantle. At mid lower-mantle depths, a second-order ferroelastic transition to orthorhombic CaCl 2 -type (post-stishovite) structure occurs, causing extensive elastic shear softening. Previous studies showed that Al incorporation can decrease the transition pressure, while it is still debated whether H has a similar effect. Here we report the equations of state, structural evolution, and phase transformation of Si 0.948 Al 0.052 O 1.983 H 0.018 (Al5) stishovite and Si 0.886 Al 0.114 O 1.980 H 0.074 (Al11) post-stishovite samples using diamond anvil cells in combination with synchrotron X-ray diffraction and Raman spectroscopy. The Al5 sample transformed to the orthorhombic polymorph upon compression to 16 GPa, displaying a drop of ~12% in its bulk modulus across the transformation. The Al11 sample did not undergo any phase transition in the pressure range investigated. Single-crystal structural refinements and Raman spectroscopy measurements on the Al5 sample show that the soft optic mode B 1g is decoupled from the tetragonal-to-orthorhombic structural transformation and shows a plateau in the stability field of post-stishovite, between 20 and 30 GPa. This observation indicates that the transformation is not pseudo-proper ferroelastic as in SiO 2 stishovite and that existing Landau expansions are likely not applicable to H-rich Al-bearing silica samples. Using the equation of state parameters of orthorhombic Al5 and Al11 and literature data on SiO 2 post-stishovite we then discuss the possibility of non-ideal mixing along the SiO 2 -AlOOH join.

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High-pressure phase transition and equation of state of hydrous Al-bearing silica

Criniti

Ishii

Kurnosov

et al. 2023

American Mineralogist

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“…Although electrical conduction mechanism and element diffusion rates in the Cf phase have not been investigated yet, the Cf phase may have relatively high electrical conductivity and low viscosity compared with other mantle minerals due to some A-site vacancies. In this case, these properties can contribute to electrical conductivity increase and viscosity decrease at least below 660 km depth (e.g., Civet et al Ishii et al, 2022). Our single-crystal structural analyses also suggested that not all of Fe 3+ is in octahedral coordination.…”

Section: Discussionsupporting

confidence: 58%

Synthesis and structural analysis of CaFe2O4-type single crystals in the NaAlSiO4-MgAl2O4-Fe3O4 system

Ishii

Criniti

Wang

et al. 2023

American Mineralogist

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Orthorhombic CaFe2O4-structured (Cf) Na-rich aluminous silicate (space group Pbnm) is a major mineral of metabasaltic rocks at lower mantle conditions and can therefore significantly affect the physical properties of subducted oceanic crusts. We attempted to synthesize single crystals of Cf-type phases in the systems NaAlSiO4, NaAlSiO4-MgAl2O4, NaAlSiO4-MgAl2O4-Fe3O4, and NaAlSiO4-MgAl2O4-Fe3O4-H2O at 23-26 GPa and 1100-2200 °C. Under dry conditions, single-crystals of Cf-type phase up to 100-150 μm in size were recovered from 23 GPa and 2000-2200 °C. Single-crystal X-ray diffraction and composition analyses suggest that the synthesized Cf-type phases have few percent of vacancies in the 8fold coordinated site with Na, Mg, and Fe 2+ and partially disordered Al and Si in the octahedral sites. Iron-bearing Cf-type phases have 32-34% Fe 3+ that is hosted both in the octahedral sites and in the 8-fold coordinated site. In NaAlSiO4-MgAl2O4-Fe3O4-H2O system, no formation of Cf-type phase was observed at 24 GPa and 1100-2000 °C, due to formation of hydrous Na-rich melt and Al-rich oxides or hydroxides, suggesting possible absence of Cf-type phase in hydrous basaltic crust. The single crystal syntheses of Cf-type phases will be useful to investigate their physical properties, improving models of lower mantle structure and dynamics.

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“…The starting material of the in situ experiment was a bridgmanite + periclase aggregate synthesized from forsterite powder at a pressure of 27 GPa and a temperature of 1200 K. Since the stability field of bridgmanite is 23-110 GPa [18,29], and the ultrahigh-pressure multi-anvil technology can generate pressure over 50 GPa [30][31][32], we can synthesize bridgmanite + periclase at 50 GPa and probably at a much lower temperature than 1200 K because of larger excess Gibbs energy caused by significant excess pressure. However, the product amount in 50 GPa multi-anvil experiments is limited, whereas we need a much larger amount of the starting material from a practical viewpoint, we limited the synthesis pressure to 27 GPa.…”

Section: Preparation Of Highly Reactive Starting Materialsmentioning

confidence: 99%

A New Approach Determining a Phase Transition Boundary Strictly Following a Definition of Phase Equilibrium: An Example of the Post-Spinel Transition in Mg2SiO4 System

2022

Self Cite

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The Clapeyron slope is the slope of a phase boundary in P–T space and is essential for understanding mantle dynamics and evolution. The phase boundary is delineating instead of balancing a phase transition’s normal and reverse reactions. Many previous high pressure–temperature experiments determining the phase boundaries of major mantle minerals experienced severe problems due to instantaneous pressure increase by thermal pressure, pressure drop during heating, and sluggish transition kinetics. These complex pressure changes underestimate the transition pressure, while the sluggish kinetics require excess pressures to initiate or proceed with the transition, misinterpreting the phase stability and preventing tight bracketing of the phase boundary. Our recent study developed a novel approach to strictly determine phase stability based on the phase equilibrium definition. Here, we explain the details of this technique, using the post-spinel transition in Mg2SiO4 determined by our recent work as an example. An essential technique is to observe the change in X-ray diffraction intensity between ringwoodite and bridgmanite + periclase during the spontaneous pressure drop at a constant temperature and press load with the coexistence of both phases. This observation removes the complicated pressure change upon heating and kinetic problem, providing an accurate and precise phase boundary.

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High pressure-temperature phase relations of basaltic crust up to mid-mantle conditions

Cited by 29 publications

References 52 publications

High-pressure phase transition and equation of state of hydrous Al-bearing silica

High-pressure phase transition and equation of state of hydrous Al-bearing silica

Synthesis and structural analysis of CaFe2O4-type single crystals in the NaAlSiO4-MgAl2O4-Fe3O4 system

A New Approach Determining a Phase Transition Boundary Strictly Following a Definition of Phase Equilibrium: An Example of the Post-Spinel Transition in Mg2SiO4 System

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