Updated on 2024/03/13

写真a

 
Ishii Takayuki
 
Organization
Institute for Planetary Materials Associate Professor
Position
Associate Professor
Contact information
メールアドレス
External link

Degree

  • Ph.D. of Science ( 2015.3   Gakushuin University )

  • M.S. of Science ( 2012.3   Gakushuin University )

Research Interests

  • high-pressure phase transition

  • Kawai-type multi-anvil high-pressure apparatus

  • high pressure-temperature phase relations

  • crystal chemistry

  • mantle

  • high pressure experiment

Research Areas

  • Natural Science / Biogeosciences

Education

  • Gakushuin University   自然科学研究科  

    2012.4 - 2015.3

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    Country: Japan

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  • Gakushuin University   自然科学研究科  

    2010.4 - 2012.3

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    Country: Japan

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  • Gakushuin University   理学部   化学科

    2006.4 - 2010.3

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    Country: Japan

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Research History

  • Okayama University   The Institute for Planetary Materials   Associate Professor

    2023.4

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    Country:Japan

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  • Center for High Pressure Science & Technology Advanced Research   Staff scientist

    2021.1 - 2023.3

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    Country:China

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  • University of Bayreuth   Bayerisches Geoinstitut   Principal investigator granted by German Research Foundation

    2019.4 - 2020.12

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    Country:Germany

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  • University of Bayreuth   Bayerisches Geoinstitut   Alexander von Humboldt research fellow

    2017.4 - 2019.3

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    Country:Germany

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  • University of Bayreuth   Bayerisches Geoinstitut   Japan Society for the Promotion of Science overseas research fellow

    2016.4 - 2017.3

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    Country:Germany

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  • Ehime University   Institute for Promotion of Science and Technology Geodynamics Research Center   Postdoctoral Research Fellow for Young Scientists

    2015.4 - 2016.3

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  • Gakushuin University   Graduate School of Natural Science Graduate Course in Chemistry   Predoctoral Research Fellow for Young Scientists

    2012.4 - 2015.3

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    Country:Japan

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Professional Memberships

  • Japan Association

    2022

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  • International Association for the Advancement of High Pressure Science and Technology

    2017

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  • European High Pressure Research Group

    2016

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  • American geophysical union

    2015

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  • Japan Geoscience Union

    2011

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  • International Mineralogical Association

    2011

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  • Japan Society of High Pressure Science and Technology

    2011

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Papers

  • Hydrogen partitioning between stishovite and hydrous phase δ: implications for water cycle and distribution in the lower mantle Reviewed

    Takayuki Ishii, Giacomo Criniti, Narangoo Purevjav, Tomoo Katsura, Eiji Ohtani

    Progress in Earth and Planetary Science   2024.2

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1186/s40645-024-00615-0

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  • Temperature Dependence of H2O Solubility in Al‐Free Stishovite Reviewed

    Narangoo Purevjav, Hongzhan Fei, Takayuki Ishii, Giacomo Criniti, Yanhao Lin, Ho‐Kwang Mao, Tomoo Katsura

    Geophysical Research Letters   51 ( 3 )   2024.2

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    Publishing type:Research paper (scientific journal)   Publisher:American Geophysical Union (AGU)  

    Abstract

    The role of stishovite in transporting water in subducting slabs has been a subject of debate for several decades. Here we investigated stishovite's water solubility and its potential role in water transportation as a function of temperature from 1300 to 2100°C at 22 GPa. Under water‐saturated conditions, high‐quality, Al‐free stishovite single crystals were synthesized with multi‐anvil press, and their water contents were measured using infrared spectroscopy. The H2O solubility in stishovite increases from 128(20) to 521(47) wt. ppm with increasing temperature from 1300 to 1700°C and decreased to 145(26) wt. ppm at 2100°C. The maximum H2O content was about seven times larger than earlier high‐temperature multi‐anvil studies but significantly lower than recent laser‐heated diamond anvil cell and low‐temperature multi‐anvil studies. We suggest that Al‐free stishovite may not be a significant H2O carrier in subducting slabs, at least at the topmost lower mantle corresponding to our experimental conditions.

    DOI: 10.1029/2023gl104029

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  • Crystal chemistry and compressibility of Fe0.5Mg0.5Al0.5Si0.5O3 and FeMg0.5Si0.5O3 silicate perovskites at pressures up to 95 GPa Reviewed

    Iuliia Koemets, Biao Wang, Egor Koemets, Takayuki Ishii, Zhaodong Liu, Catherine McCammon, Artem Chanyshev, Tomo Katsura, Michael Hanfland, Alexander Chumakov, Leonid Dubrovinsky

    Frontiers in Chemistry   11   2023.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Frontiers Media SA  

    Silicate perovskite, with the mineral name bridgmanite, is the most abundant mineral in the Earth’s lower mantle. We investigated crystal structures and equations of state of two perovskite-type Fe3+-rich phases, FeMg0.5Si0.5O3 and Fe0.5Mg0.5Al0.5Si0.5O3, at high pressures, employing single-crystal X-ray diffraction and synchrotron Mössbauer spectroscopy. We solved their crystal structures at high pressures and found that the FeMg0.5Si0.5O3 phase adopts a novel monoclinic double-perovskite structure with the space group of P21/n at pressures above 12 GPa, whereas the Fe0.5Mg0.5Al0.5Si0.5O3 phase adopts an orthorhombic perovskite structure with the space group of Pnma at pressures above 8 GPa. The pressure induces an iron spin transition for Fe3+ in a (Fe0.7,Mg0.3)O6 octahedral site of the FeMg0.5Si0.5O3 phase at pressures higher than 40 GPa. No iron spin transition was observed for the Fe0.5Mg0.5Al0.5Si0.5O3 phase as all Fe3+ ions are located in bicapped prism sites, which have larger volumes than an octahedral site of (Al0.5,Si0.5)O6.

    DOI: 10.3389/fchem.2023.1258389

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  • Structure and compressibility of Fe-bearing Al-phase D Reviewed

    Giacomo Criniti, Takayuki Ishii, Alexander Kurnosov, Konstantin Glazyrin, Rachel J. Husband, Tiziana Boffa Ballaran

    American Mineralogist   108 ( 9 )   1764 - 1772   2023.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Mineralogical Society of America  

    Abstract

    Due to its large thermal stability, Al-phase D, the (Al,Fe3+)2SiO6H2 member of the dense hydrous magnesium silicate (DHMS) phase D, may survive along hot subduction geotherms or even at ambient mantle temperatures in the Earth’s transition zone and lower mantle, therefore potentially playing a major role as a water reservoir and carrier in the Earth’s interior. We have investigated the crystal structure and high-pressure behavior of Fe-bearing Al-phase D with a composition of Al1.53(2)Fe0.22(1) Si0.86(1)O6H3.33(9) by means of single-crystal X-ray diffraction. While the structure of pure Al-phase D (Al2SiO6H2) has space group P63/mcm and consists of equally populated and half-occupied (Al,Si)O6 octahedra, Fe-incorporation in Al-phase D seems to induce partial ordering of the cations over the octahedral sites, resulting in a change of the space group from P63/mcm to P6322 and in well-resolved diffuse scattering streaks observed in X-ray images. The evolution of the unit-cell volume of Fe-bearing Al-phase D between room pressure and 38 GPa, determined by means of synchrotron X-ray diffraction in a diamond anvil cell, is well described by a third-order Birch-Murnaghan equation of state having an isothermal bulk modulus KT0 = 166.3(15) GPa and first pressure derivative KT0′ = 4.46(12). Above 38 GPa, a change in the compression behavior is observed, likely related to the high-to-low spin crossover of octahedrally coordinated Fe3+. The evolution of the unit-cell volume across the spin crossover was modeled using a recently proposed formalism based on crystal-field theory, which shows that the spin crossover region extends from approximately 30 to 65 GPa. Given the absence of abrupt changes in the compression mechanism of Fe-bearing Al-phase D before the spin crossover, we show that the strength of H-bonds and likely their symmetrization do not greatly affect the elastic properties of phase D solid solutions, independently of their compositions.

    DOI: 10.2138/am-2022-8559

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  • Buoyancy of slabs and plumes enhanced by curved post-garnet phase boundary Reviewed

    Takayuki Ishii, Daniel J. Frost, Eun Jeong Kim, Artem Chanyshev, Keisuke Nishida, Biao Wang, Rintaro Ban, Jianing Xu, Jin Liu, Xiaowan Su, Yuji Higo, Yoshinori Tange, Ho-kwang Mao, Tomoo Katsura

    Nature Geoscience   2023.9

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)  

    DOI: 10.1038/s41561-023-01244-w

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

    Giacomo Criniti, Takayuki Ishii, Alexander Kurnosov, Konstantin Glazyrin, Tiziana Boffa Ballaran

    American Mineralogist   108 ( 8 )   1558 - 1568   2023.8

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    Publishing type:Research paper (scientific journal)   Publisher:Mineralogical Society of America  

    DOI: 10.2138/am-2022-8546

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  • Iron and aluminum substitution mechanism in the perovskite phase in the system MgSiO3-FeAlO3-MgO Reviewed

    Takayuki Ishii, Catherine McCammon, Tomoo Katsura

    American Mineralogist   108 ( 4 )   738 - 743   2023.4

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:Mineralogical Society of America  

    Abstract

    Fe,Al-bearing MgSiO3 perovskite (bridgmanite) is considered to be the most abundant mineral in Earth’s lower mantle, hosting ferric iron in its structure as charge-coupled (Fe2O3 and FeAlO3) and vacancy components (MgFeO2.5 and Fe2/3SiO3). We examined concentrations of ferric iron and aluminum in the perovskite phase as a function of temperature (1700–2300 K) in the MgSiO3-FeAlO3-MgO system at 27 GPa using a multi-anvil high-pressure apparatus. We found a LiNbO3-structured phase in the quenched run product, which was the perovskite phase under high pressures and high temperatures. The perovskite phase coexists with corundum and a phase with (Mg,Fe3+,☐)(Al,Fe3+)2O4 composition (☐ = vacancy). The FeAlO3 component in the perovskite phase decreases from 69 to 65 mol% with increasing temperature. The Fe2O3 component in the perovskite phase remains unchanged at ~1 mol% with temperature. The A-site vacancy component of Fe2/3SiO3 in the perovskite phase exists as 1–2 mol% at 1700–2000 K, whereas 1 mol% of the oxygen vacancy component of MgFeO2.5 appears at higher temperatures, although the analytical errors prevent definite conclusions. The A-site vacancy component might be more important than the oxygen vacancy component for the defect chemistry of bridgmanite in slabs and for average mantle conditions when the FeAlO3 charge-coupled component is dominant.

    DOI: 10.2138/am-2022-8457

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  • Equation of State and Spin Crossover of (Al, Fe)‐Phase H Reviewed

    Benjamin Strozewski, Johannes Buchen, Wolfgang Sturhahn, Takayuki Ishii, Itaru Ohira, Stella Chariton, Barbara Lavina, Jiyong Zhao, Thomas S. Toellner, Jennifer M. Jackson

    Journal of Geophysical Research: Solid Earth   128 ( 4 )   2023.4

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    Publishing type:Research paper (scientific journal)   Publisher:American Geophysical Union (AGU)  

    DOI: 10.1029/2022jb026291

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    Other Link: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2022JB026291

  • Ferric Iron Substitution Mechanism in Bridgmanite under SiO2-Saturated Conditions at 27 GPa Reviewed

    Artem Chanyshev, Hongzhan Fei, Dmitry Bondar, Biao Wang, Zhaodong Liu, Takayuki Ishii, Robert Farla, Catherine McCammon, Tomoo Katsura

    ACS Earth and Space Chemistry   7 ( 2 )   471 - 478   2023.2

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    Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    DOI: 10.1021/acsearthspacechem.2c00326

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  • Stability of Fe5O6 and its relation to other Fe-Mg-oxides at high pressures and temperatures Reviewed

    Alan B. Woodland, Laura Uenver-Thiele, Tiziana Boffa Ballaran, Nobuyoshi Miyajima, Kevin Rosbach, Takayuki Ishii

    American Mineralogist   108 ( 1 )   140 - 149   2023.1

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    Authorship:Last author   Publishing type:Research paper (scientific journal)   Publisher:Mineralogical Society of America  

    Abstract

    The stability of Fe5O6 has been experimentally determined under pressure-temperature conditions relevant for the Earth’s deeper upper mantle down to the upper portion of the lower mantle (to 28 GPa). In addition, we investigated the incorporation of Mg into Fe5O6 and its systematics, which allows us to discuss the relevance of this phase for the mantle. Experiments were performed from 8–28 GPa and 900–1600 °C. Additional oxide phases may appear if the bulk composition does not maintain the Fe32+Fe23+O6 stoichiometry during the experiment, including coexisting Fe4O5 or Fe9O11. Unfortunately, the similarities in Raman spectra between several high-pressure Fe-oxide phases make this method unsuitable for distinguishing which phase is present in a given sample. The stability field for Fe5O6 extends from ~9 to at least 28 GPa but is truncated at lower temperatures by the assemblage Fe4O5 + wüstite. Refined thermodynamic properties for Fe5O6 are presented. The range of redox stability of Fe5O6 appears to be more limited than that of Fe4O5.

    Solid solution along the Fe5O6-Mg3Fe2O6 binary is quite limited, reaching a maximum Mg content of ~0.82 cations per formula unit (i.e., XMg3Fe2O6 ≈ 0.27) at 1400 °C and 10 GPa. The observed sharp decrease in molar volume of the O6-phase with Mg content could be a possible explanation for the limited range of solid solution. A phase diagram has been constructed for a composition of approximately Mg0.5Fe2.52+Fe23+O6 stoichiometry. This small amount of Mg causes a significant change in the relations between the O6-structured phase and the assemblage O5-structured phase + (Mg,Fe)O. Several experiments were performed to test whether the O6-phase can coexist with mantle silicates like wadsleyite and ringwoodite. In all cases, the run products contained (Mg,Fe)2Fe2O5 rather than the O6-phase, further underlining the limited ability of Fe5O6 to accommodate enough Mg to be stable in a mantle assemblage.

    The large stability field of Fe5O6 implies that this phase could likely occur in locally Fe-rich environments, like those sampled by some “deep” diamonds. However, the limited solubility of Mg in the O6-phase leads us to conclude that the O5-phase should be of much more relevance as an accessory phase in a peridotitic mantle assemblage.

    DOI: 10.2138/am-2022-8370

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

    Takayuki Ishii, Giacomo Criniti, Xiaoyu Wang, Konstantin Glazyrin, Tiziana Boffa Ballaran

    American Mineralogist   108 ( 1 )   217 - 221   2023.1

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:Mineralogical Society of America  

    Abstract

    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 a few percent of vacancies in the eightfold-coordinated site with Na, Mg, and Fe2+ and partially disordered Al and Si in the octahedral sites. Iron-bearing Cf-type phases have 32–34% Fe3+ that is hosted both in the octahedral sites and in the eightfold-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 the formation of hydrous Na-rich melt and Al-rich oxides or hydroxides, suggesting the possible absence of Cf-type phase in the hydrous basaltic crust. The single-crystal syntheses of Cf-type phases will be useful for investigating their physical properties, potentially improving models of lower mantle structure and dynamics.

    DOI: 10.2138/am-2022-8748

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  • The influence of Al2O3 on the structural properties of MgSiO3 akimotoite Reviewed

    Nicki C. Siersch, Giacomo Criniti, Alexander Kurnosov, Tiziana Boffa Ballaran, Zhaodong Liu, Takayuki Ishii, Daniel J. Frost, Tony Yu, Yanbin Wang

    American Mineralogist   108 ( 1 )   100 - 109   2023.1

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    Publishing type:Research paper (scientific journal)   Publisher:Mineralogical Society of America  

    Abstract

    Akimotoite, a MgSiO3 polymorph present in the lower transition zone within ultramafic portions of subducting slabs and potentially also in the ambient mantle, will partition some amount of Al, raising the question of how this will affect its crystal structure and properties. In this study, a series of samples along the MgSiO3-Al2O3 (akimotoite-corundum) solid solution have been investigated by means of single-crystal X-ray diffraction to examine their crystal chemistry. Results show a strong nonlinear behavior of the a- and c-axes as a function of Al content, which arises from fundamentally different accommodation mechanisms in the akimotoite and corundum structures. Furthermore, two Al2O3-bearing akimotoite samples were investigated at high pressure to determine the different compression mechanisms associated with Al substitution. Al2O3-bearing akimotoite becomes more compressible at least up to 20 mol% Al2O3, due likely to an increase in compressibility as the Al cation is incorporated into the SiO6 octahedron. This observation is in strong contrast to the stiffer corundum end-member having a KT = 250 GPa, which is larger than that of the akimotoite end-member [KT = 205(1) GPa]. These findings have implications for mineral physics models of elastic properties, which have in the past assumed linear mixing behavior between the MgSiO3 akimotoite and Al2O3 corundum end-members to calculate sound wave velocities for Al-bearing akimotoite at high pressure and temperature.

    DOI: 10.2138/am-2022-8257

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  • Superhydrous aluminous silica phases as major water hosts in high-temperature lower mantle Reviewed

    Takayuki Ishii, Giacomo Criniti, Eiji Ohtani, Narangoo Purevjav, Hongzhan Fei, Tomoo Katsura, Ho-kwang Mao

    Proceedings of the National Academy of Sciences   119 ( 44 )   2022.10

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of the National Academy of Sciences  

    Water transported by subducted oceanic plates changes mineral and rock properties at high pressures and temperatures, affecting the dynamics and evolution of the Earth’s interior. Although geochemical observations imply that water should be stored in the lower mantle, the limited amounts of water incorporation in pyrolitic lower-mantle minerals suggest that water in the lower mantle may be stored in the basaltic fragments of subducted slabs. Here, we performed multianvil experiments to investigate the stability and water solubility of aluminous stishovite and CaCl 2 -structured silica, referred to as poststishovite, in the SiO 2 -Al 2 O 3 -H 2 O systems at 24 to 28 GPa and 1,000 to 2,000 °C, representing the pressure–temperature conditions of cold subducting slabs to hot upwelling plumes in the top lower mantle. The results indicate that both alumina and water contents in these silica minerals increase with increasing temperature under hydrous conditions due to the strong Al 3+ -H + charge coupling substitution, resulting in the storage of water up to 1.1 wt %. The increase of water solubility in these hydrous aluminous silica phases at high temperatures is opposite of that of other nominally anhydrous minerals and of the stability of the hydrous minerals. This feature prevents the releasing of water from the subducting slabs and enhances the transport water into the deep lower mantle, allowing significant amounts of water storage in the high-temperature lower mantle and circulating water between the upper mantle and the lower mantle through subduction and plume upwelling. The shallower depths of midmantle seismic scatterers than expected from the pure SiO 2 stishovite–poststishovite transition pressure support this scenario.

    DOI: 10.1073/pnas.2211243119

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  • Sound Velocity Measurements of B2‐Fe‐Ni‐Si Alloy Under High Pressure by Inelastic X‐Ray Scattering: Implications for the Composition of Earth's Core Reviewed

    S. Dominijanni, C. A. McCammon, E. Ohtani, D. Ikuta, T. Sakamaki, T. Ishii, G. Criniti, L. S. Dubrovinsky, S. Khandarkhaeva, T. Fedotenko, K. Glazyrin, H. Uchiyama, H. Fukui, A. Q. R. Baron

    Geophysical Research Letters   49 ( 15 )   2022.8

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    Publishing type:Research paper (scientific journal)   Publisher:American Geophysical Union (AGU)  

    Abstract

    Elastic properties of B2‐Fe0.67Ni0.06Si0.27 (15 wt.% Si) alloy have been investigated by combined high‐resolution inelastic X‐ray scattering and powder X‐ray diffraction in diamond anvil cells up to 100 GPa at room temperature. Densities (ρ), compressional (VP) and shear (VS) wave velocities were extrapolated to inner core conditions to enable comparison with the preliminary reference Earth model. The modeled aggregate compressional and shear wave velocities and densities of the two‐phase mixture of B2‐Fe0.67Ni0.06Si0.27 and hcp‐Fe‐Ni are consistent with inner core PREM values of VP,VS, and ρ based on a linear mixing model with 30(5) vol % B2‐Fe0.67Ni0.06Si0.27 and 70(5) vol % hcp Fe‐Ni, which corresponds to ∼3–5 wt.% Si and ∼5–12 wt.% Ni.

    DOI: 10.1029/2021gl096405

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    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021GL096405

  • 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 Invited Reviewed

    Takayuki Ishii, Artem Chanyshev, Tomoo Katsura

    Minerals   12 ( 7 )   820 - 820   2022.6

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:MDPI AG  

    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.

    DOI: 10.3390/min12070820

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  • Low Thermal Conductivity of Hydrous Phase D Leads to a Self‐Preservation Effect Within a Subducting Slab Reviewed

    Wen‐Pin Hsieh, Enrico Marzotto, Takayuki Ishii, Leonid Dubrovinsky, Alena A. Aslandukova, Giacomo Criniti, Yi‐Chi Tsao, Chun‐Hung Lin, Jun Tsuchiya, Eiji Ohtani

    Journal of Geophysical Research: Solid Earth   127 ( 6 )   2022.6

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    Publishing type:Research paper (scientific journal)   Publisher:American Geophysical Union (AGU)  

    DOI: 10.1029/2022jb024556

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    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2022JB024556

  • Structural independence of hydrogen-bond symmetrisation dynamics at extreme pressure conditions Reviewed

    Thomas Meier, Florian Trybel, Saiana Khandarkhaeva, Dominique Laniel, Takayuki Ishii, Alena Aslandukova, Natalia Dubrovinskaia, Leonid Dubrovinsky

    Nature Communications   13 ( 1 )   2022.6

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    Abstract

    The experimental study of hydrogen-bonds and their symmetrization under extreme conditions is predominantly driven by diffraction methods, despite challenges of localising or probing the hydrogen subsystems directly. Until recently, H-bond symmetrization has been addressed in terms of either nuclear quantum effects, spin crossovers or direct structural transitions; often leading to contradictory interpretations when combined. Here, we present high-resolution in-situ 1H-NMR experiments in diamond anvil cells investigating a range of systems containing linear O-H ⋯  O units at pressure ranges of up to 90 GPa covering their respective H-bond symmetrization. We found pronounced minima in the pressure dependence of the NMR resonance line-widths associated with a maximum in hydrogen mobility, precursor to a localisation of hydrogen atoms. These minima, independent of the chemical environment of the O-H ⋯  O unit, can be found in a narrow range of oxygen oxygen distances between 2.44 and 2.45 Å, leading to an average critical oxygen-oxygen distance of $${\bar{r } }_{ { { { { { { { \rm{OO } } } } } } } } }^{ { { { { { { { \rm{crit } } } } } } } } }=2.443(1)$$ Å.

    DOI: 10.1038/s41467-022-30662-4

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    Other Link: https://www.nature.com/articles/s41467-022-30662-4

  • The electrical conductivity of Fe4O5, Fe5O6, and Fe7O9 up to 60 GPa Reviewed

    Shuhou Maitani, Ryosuke Sinmyo, Takayuki Ishii, Saori I. Kawaguchi, Naohisa Hirao

    Physics and Chemistry of Minerals   49 ( 5 )   2022.5

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1007/s00269-022-01188-4

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    Other Link: https://link.springer.com/article/10.1007/s00269-022-01188-4/fulltext.html

  • Equations of state of α-SiC (6H) and βʹ-Mg2Si1.1 from single-crystal X-ray diffraction data and novel high-pressure magnesium silicide Mg2Si7 Reviewed

    Iuliia Koemets, Takayuki Ishii, Michael Hanfland, Leonid Dubrovinsky

    Physics and Chemistry of Minerals   49 ( 5 )   2022.5

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    Abstract

    SiC and (Fe, Mg)-silicide are candidate phases forming under reducing conditions in the Earth and planetary interiors. However, structural studies of SiC and Mg2Si at high pressure and their thermal stability are presently lacking. In this work, we applied single-crystal X-ray diffraction in a diamond anvil cell at high pressure and determined the equations of state of α-SiC (6H) and βʹ-Mg2Si1.1 up to 60 and 40 GPa, respectively, yielding bulk moduli of 226.0(4) and 56(1) GPa. We also report the formation of a novel orthorhombic Mg2Si7 phase upon laser heating βʹ-Mg2Si1.1 at ~ 45 GPa and 2000 °C [Pbam, a = 7.16(1) Å, b = 12.490(3) Å, c = 2.6545(3) Å, V = 237.5(3) Å3]. The structure of this compound contains layers formed by irregular 12-member silicon rings, which are arranged in channels filled with both Mg and Si atoms. No signs of the Mg2Si7 phase were detected upon releasing the pressure in the DAC, which suggests that this phase is unstable under ambient conditions.

    DOI: 10.1007/s00269-022-01189-3

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    Other Link: https://link.springer.com/article/10.1007/s00269-022-01189-3/fulltext.html

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

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

    Earth and Planetary Science Letters   584   117472 - 117472   2022.4

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.epsl.2022.117472

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  • Aluminum and hydrogen partitioning between bridgmanite and high-pressure hydrous phases: Implications for water storage in the lower mantle Reviewed

    Takayuki Ishii, Eiji Ohtani, Anton Shatskiy

    Earth and Planetary Science Letters   583   117441 - 117441   2022.4

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    DOI: 10.1016/j.epsl.2022.117441

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  • Extreme conditions research using the large-volume press at the P61B endstation, PETRA III Reviewed

    Robert Farla, Shrikant Bhat, Stefan Sonntag, Artem Chanyshev, Shuailing Ma, Takayuki Ishii, Zhaodong Liu, Adrien Néri, Norimasa Nishiyama, Guilherme Abreu Faria, Thomas Wroblewski, Horst Schulte-Schrepping, Wolfgang Drube, Oliver Seeck, Tomoo Katsura

    Journal of Synchrotron Radiation   29 ( 2 )   409 - 423   2022.2

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    Publishing type:Research paper (scientific journal)   Publisher:International Union of Crystallography (IUCr)  

    Penetrating, high-energy synchrotron X-rays are in strong demand, particularly for high-pressure research in physics, chemistry and geosciences, and for materials engineering research under less extreme conditions. A new high-energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front-end components and beam characteristics. The second part describes the performance of the instrumentation and the latest developments at the P61B endstation. Particular attention is given to the unprecedented high-energy photon flux delivered by the ten wigglers of the PETRA III storage ring and the challenges faced in harnessing this amount of flux and heat load in the beam. Furthermore, the distinctiveness of the world's first six-ram Hall-type large-volume press, Aster-15, at a synchrotron facility is described for research with synchrotron X-rays. Additionally, detection schemes, experimental strategies and preliminary data acquired using energy-dispersive X-ray diffraction and radiography techniques are presented.

    DOI: 10.1107/s1600577522001047

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  • Depressed 660-km discontinuity caused by akimotoite–bridgmanite transition Reviewed

    Artem Chanyshev, Takayuki Ishii, Dmitry Bondar, Shrikant Bhat, Eun Jeong Kim, Robert Farla, Keisuke Nishida, Zhaodong Liu, Lin Wang, Ayano Nakajima, Bingmin Yan, Hu Tang, Zhen Chen, Yuji Higo, Yoshinori Tange, Tomoo Katsura

    Nature   601 ( 7891 )   69 - 73   2022.1

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    Abstract

    The 660-kilometre seismic discontinuity is the boundary between the Earth’s lower mantle and transition zone and is commonly interpreted as being due to the dissociation of ringwoodite to bridgmanite plus ferropericlase (post-spinel transition)1–3. A distinct feature of the 660-kilometre discontinuity is its depression to 750 kilometres beneath subduction zones4–10. However, in situ X-ray diffraction studies using multi-anvil techniques have demonstrated negative but gentle Clapeyron slopes (that is,  the ratio between pressure and temperature changes) of the post-spinel transition that do not allow a significant depression11–13. On the other hand, conventional high-pressure experiments face difficulties in accurate phase identification due to inevitable pressure changes during heating and the persistent presence of metastable phases1,3. Here we determine the post-spinel and akimotoite–bridgmanite transition boundaries by multi-anvil experiments using in situ X-ray diffraction, with the boundaries strictly based on the definition of phase equilibrium. The post-spinel boundary has almost no temperature dependence, whereas the akimotoite–bridgmanite transition has a very steep negative boundary slope at temperatures lower than ambient mantle geotherms. The large depressions of the 660-kilometre discontinuity in cold subduction zones are thus interpreted as the akimotoite–bridgmanite transition. The steep negative boundary of the akimotoite–bridgmanite transition will cause slab stagnation (a stalling of the slab’s descent) due to significant upward buoyancy14,15.

    DOI: 10.1038/s41586-021-04157-z

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  • High‐Pressure Elasticity of δ‐(Al,Fe)OOH Single Crystals and Seismic Detectability of Hydrous MORB in the Shallow Lower Mantle Reviewed

    Niccolò Satta, Giacomo Criniti, Alexander Kurnosov, Tiziana Boffa Ballaran, Takayuki Ishii, Hauke Marquardt

    Geophysical Research Letters   48 ( 23 )   2021.12

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    DOI: 10.1029/2021gl094185

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  • Synthesis of paracrystalline diamond Reviewed

    Hu Tang, Xiaohong Yuan, Yong Cheng, Hongzhan Fei, Fuyang Liu, Tao Liang, Zhidan Zeng, Takayuki Ishii, Ming-Sheng Wang, Tomoo Katsura, Howard Sheng, Huiyang Gou

    Nature   599 ( 7886 )   605 - 610   2021.11

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    DOI: 10.1038/s41586-021-04122-w

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  • A simplified rapid-quench multi-anvil technique Reviewed

    Dmitry Bondar, Hongzhan Fei, Anthony C. Withers, Takayuki Ishii, Artem Chanyshev, Tomoo Katsura

    Review of Scientific Instruments   92 ( 11 )   113902 - 113902   2021.11

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    DOI: 10.1063/5.0062525

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  • Spectroscopic evidence for the Fe3+ spin transition in iron-bearing δ-AlOOH at high pressure Reviewed

    Xiaowan Su, Chaoshuai Zhao, Liangxu Xu, Chaojia Lv, Xitong Song, Takayuki Ishii, Yuming Xiao, Paul Chow, Qiang Sun, Jin Liu

    American Mineralogist   106 ( 11 )   1709 - 1716   2021.11

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    Abstract

    δ-AlOOH has emerged as a promising candidate for water storage in the lower mantle and could have delivered water into the bottom of the mantle. To date, it still remains unclear how the presence of iron affects its elastic, rheological, vibrational, and transport properties, especially across the spin crossover. Here, we conducted high-pressure X-ray emission spectroscopy experiments on a δ-(Al0.85Fe0.15) OOH sample up to 53 GPa using silicone oil as the pressure transmitting medium in a diamond-anvil cell. We also carried out laser Raman measurements on δ-(Al0.85Fe0.15)OOH and δ-(Al0.52Fe0.48)OOH up to 57 and 62 GPa, respectively, using neon as the pressure-transmitting medium. Evolution of Raman spectra of δ-(Al0.85Fe0.15)OOH with pressure shows two new bands at 226 and 632 cm−1 at 6.0 GPa, in agreement with the transition from an ordered (P21nm) to a disordered hydrogen bonding structure (Pnnm) for δ-AlOOH. Similarly, the two new Raman bands at 155 and 539 cm−1 appear in δ-(Al0.52Fe0.48)OOH between 8.5 and 15.8 GPa, indicating that the incorporation of 48 mol% FeOOH could postpone the order-disorder transition upon compression. On the other hand, the satellite peak (Kβ′) intensity of δ-(Al0.85Fe0.15)OOH starts to decrease at ~30 GPa and it disappears completely at 42 GPa. That is, δ-(Al0.85Fe0.15)OOH undergoes a gradual electronic spin-pairing transition at 30–42 GPa. Furthermore, the pressure dependence of Raman shifts of δ-(Al0.85Fe0.15)OOH discontinuously decreases at 32–37 GPa, suggesting that the improved hydrostaticity by the use of neon pressure medium could lead to a relatively narrow spin crossover. Notably, the pressure dependence of Raman shifts and optical color of δ-(Al0.52Fe0.48)OOH dramatically change at 41–45 GPa, suggesting that it probably undergoes a relatively sharp spin transition in the neon pressure medium. Together with literature data on the solid solutions between δ-AlOOH and ε-FeOOH, we found that the onset pressure of the spin transition in δ-(Al,Fe)OOH increases with increasing FeOOH content. These results shed new insights into the effects of iron on the structural evolution and vibrational properties of δ-AlOOH. The presence of FeOOH in δ-AlOOH can substantially influence its high-pressure behavior and stability at the deep mantle conditions and play an important role in the deep-water cycle.

    DOI: 10.2138/am-2021-7541

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  • In situ high-pressure nuclear magnetic resonance crystallography in one and two dimensions Reviewed

    Thomas Meier, Alena Aslandukova, Florian Trybel, Dominique Laniel, Takayuki Ishii, Saiana Khandarkhaeva, Natalia Dubrovinskaia, Leonid Dubrovinsky

    Matter and Radiation at Extremes   6 ( 6 )   068402 - 068402   2021.11

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    DOI: 10.1063/5.0065879

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  • The elastic properties and anisotropic behavior of MgSiO3 akimotoite at transition zone pressures Reviewed

    Nicki C. Siersch, Alexander Kurnosov, Giacomo Criniti, Takayuki Ishii, Tiziana Boffa Ballaran, Daniel J. Frost

    Physics of the Earth and Planetary Interiors   320   106786 - 106786   2021.11

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    DOI: 10.1016/j.pepi.2021.106786

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  • Simultaneous generation of ultrahigh pressure and temperature to 50 GPa and 3300 K in multi-anvil apparatus Reviewed

    Longjian Xie, Artem Chanyshev, Takayuki Ishii, Dmitry Bondar, Keisuke Nishida, Zhen Chen, Shrikant Bhat, Robert Farla, Yuji Higo, Yoshinori Tange, Xiaowan Su, BingMin Yan, Shuailin Ma, Tomoo Katsura

    Review of Scientific Instruments   92 ( 10 )   103902 - 103902   2021.10

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    DOI: 10.1063/5.0059279

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  • Determination of phase relations of the olivine–ahrensite transition in the Mg2SiO4–Fe2SiO4 system at 1740 K using modern multi-anvil techniques Reviewed

    Artem Chanyshev, Dmitry Bondar, Hongzhan Fei, Narangoo Purevjav, Takayuki Ishii, Keisuke Nishida, Shrikant Bhat, Robert Farla, Tomoo Katsura

    Contributions to Mineralogy and Petrology   176 ( 10 )   2021.9

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    Abstract

    The phase relations of iron-rich olivine and its high-pressure polymorphs are important for planetary science and meteoritics because these minerals are the main constituents of terrestrial mantles and meteorites. The olivine–ahrensite binary loop was previously determined by thermochemical calculations in combination with high-pressure experiments; however, the transition pressures contained significant uncertainties. Here we determined the binary loop of the olivine–ahrensite transition in the (Mg,Fe)2SiO4 system at 1740 K in the pressure range of 7.5–11.2 GPa using a multi-anvil apparatus with the pressure determined using in situ X-ray diffraction, compositional analysis of quenched run products, and thermochemical calculation. Based on the determined binary loop, a user-friendly software was developed to calculate pressure from the coexisting olivine and ahrensite compositions. The software is used to estimate the shock conditions of several L6-type chondrites. The obtained olivine–ahrensite phase relations can also be applied for precise in-house multi-anvil pressure calibration at high temperatures.

    DOI: 10.1007/s00410-021-01829-x

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  • Vibrational anisotropy of δ-(Al,Fe)OOH single crystals as probed by nuclear resonant inelastic X-ray scattering Reviewed

    Johannes Buchen, Wolfgang Sturhahn, Takayuki Ishii, Jennifer M. Jackson

    European Journal of Mineralogy   33 ( 4 )   485 - 502   2021.8

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    Abstract. The formation of high-pressure oxyhydroxide phases spanned by the components AlOOH–FeOOH–MgSiO2(OH)2 in experiments suggests their capability to retain hydrogen in Earth's lower mantle. Understanding the vibrational properties of high-pressure phases provides the basis for assessing their thermal properties, which are required to compute phase diagrams and physical properties. Vibrational properties can be highly anisotropic, in particular for materials with crystal structures of low symmetry that contain directed structural groups or components. We used nuclear resonant inelastic X-ray scattering (NRIXS) to probe lattice vibrations that involve motions of 57Fe atoms in δ-(Al0.87Fe0.13)OOH single crystals. From the recorded single-crystal NRIXS spectra, we calculated projections of the partial phonon density of states along different crystallographic directions. To describe the anisotropy of central vibrational properties, we define and derive tensors for the partial phonon density of states, the Lamb–Mössbauer factor, the mean kinetic energy per vibrational mode, and the mean force constant of 57Fe atoms. We further show how the anisotropy of the Lamb–Mössbauer factor can be translated into anisotropic displacement parameters for 57Fe atoms and relate our findings on vibrational anisotropy to the crystal structure of δ-(Al,Fe)OOH. As a potential application of single-crystal NRIXS at high pressures, we discuss the evaluation of anisotropic thermal stresses in the context of elastic geobarometry for mineral inclusions. Our results on single crystals of δ-(Al,Fe)OOH demonstrate the sensitivity of NRIXS to vibrational anisotropy and provide an in-depth description of the vibrational behavior of Fe3+ cations in a crystal structure that may motivate future applications of NRIXS to study anisotropic vibrational properties of minerals.

    DOI: 10.5194/ejm-33-485-2021

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  • P-V-Tmeasurements of Fe3C to 117 GPa and 2100 K: Implications for stability of Fe3C phase at core conditions Reviewed

    Chris McGuire, Tetsuya Komabayashi, Samuel Thompson, Geoffrey Bromiley, Takayuki Ishii, Eran Greenberg, Vitali B. Prakapenka

    American Mineralogist   106 ( 8 )   1349 - 1359   2021.8

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    Abstract

    We report the thermal Equation of State (EoS) of the non-magnetic Fe3C phase based on in situ X-ray diffraction (XRD) experiments to 117 GPa and 2100 K. High-pressure and temperature unit-cell volume measurements of Fe3C were conducted in a laser-heated diamond-anvil cell. Our pressure-volume-temperature (P-V-T) data together with existing data were fit to the Vinet equation of state with the Mie-Grüneisen-Debye thermal pressure model, yielding V0 = 151.6(12) Å3, K0 = 232(24) GPa, K0′= 5.09(46), γ0 = 2.3(3), and q = 3.4 (9) with θ0 = 407 K (fixed). The high-T data were also fit to the thermal pressure model with a constant αKT term, PTh = αKT(ΔT), and there is no observable pressure or temperature dependence, which implies minor contributions from the anharmonic and electronic terms. Using the established EoS for Fe3C, we made thermodynamic calculations on the P-T locations of the breakdown reaction of Fe3C into Fe7C3 and Fe. The reaction is located at 87 GPa and 300 K and 251 GPa and 3000 K. An invariant point occurs where Fe, Fe3C, Fe7C3, and liquid are stable, which places constraints on the liquidus temperature of the outer core, namely inner core crystallization temperature, as the inner core would be comprised by the liquidus phase. Two possible P-T locations for the invariant point were predicted from existing experimental data and the reaction calculated in this study. The two models result in different liquidus “phases” at the outer core-inner core boundary pressure: Fe3C at 5300 K and Fe7C3 at 3700 K. The Fe7C3 inner core can account for the density, as observed by seismology, while the Fe3C inner core cannot. The relevance of the system Fe-C to Earth’s core can be resolved by constructing a thermodynamic model for melting relations under core conditions as the two models predict very different liquidus temperatures.

    DOI: 10.2138/am-2021-7581

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  • High-pressure syntheses and crystal structure analyses of a new low-density CaFe2O4-related and CaTi2O4-type MgAl2O4 phases Reviewed

    Takayuki Ishii, Giacomo Criniti, Elena Bykova, Leonid Dubrovinsky, Tomoo Katsura, Hidekazu Arii, Hiroshi Kojitani, Masaki Akaogi

    American Mineralogist   106 ( 7 )   1105 - 1112   2021.7

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    Abstract

    Three single crystals of CaTi2O4 (CT)-type, CaFe2O4 (CF)-type, and new low-density CaFe2O4 (LD-CF) related MgAl2O4 were synthesized at 27 GPa and 2500 °C and also CT-type MgAl2O4 at 45 GPa and 1727 °C using conventional and advanced multi-anvil technologies, respectively. The structures of CT-type and LD-CF related MgAl2O4 were analyzed by single-crystal X-ray diffraction. The lattice parameters of the CT-type phases synthesized at 27 and 45 GPa were a = 2.7903(4), b = 9.2132(10), and c = 9.3968(12) Å, and a = 2.7982(6), b = 9.2532(15), and c = 9.4461(16) Å, respectively, (Z = 4, space group: Cmcm) at ambient conditions. This phase has an AlO6 octahedral site and an MgO8 bicapped trigonal prism with two longer cation-oxygen bonds. The LD-CF related phase has a novel structure with orthorhombic symmetry (space group: Pnma), and lattice parameters of a = 9.207(2), b = 3.0118(6), and c = 9.739(2) Å (Z = 4). The structural framework comprises tunnel-shaped spaces constructed by edge- and corner-sharing of AlO6 and a 4+1 AlO5 trigonal bipyramid, in which MgO5 trigonal bipyramids are accommodated. The CF-type MgAl2O4 also has the same space group of Pnma but a slightly different atomic arrangement, with Mg and Al coordination numbers of 8 and 6, respectively. The LD-CF related phase has the lowest density of 3.50 g/cm3 among MgAl2O4 polymorphs, despite its high-pressure synthesis from the spinel-type phase (3.58 g/cm3), indicating that the LD-CF related phase formed via back-transformation from a high-pressure phase during the recovery. Combined with the previously determined phase relations, the phase transition between CF-and CT-type MgAl2O4 is expected to have a steep Clapeyron slope. Therefore, CT-type phase may be stable in basaltic- and continental-crust compositions at higher temperatures than the average mantle geotherm in the wide pressure range of the lower mantle. The LD-CF related phase could be found in shocked meteorites and used for estimating shock conditions.

    DOI: 10.2138/am-2021-7619

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  • Dry metastable olivine and slab deformation in a wet subducting slab Reviewed

    Takayuki Ishii, Eiji Ohtani

    Nature Geoscience   14 ( 7 )   526 - 530   2021.5

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    DOI: 10.1038/s41561-021-00756-7

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  • Effect of Water on Lattice Thermal Conductivity of Ringwoodite and Its Implications for the Thermal Evolution of Descending Slabs Reviewed

    Enrico Marzotto, Wen‐Pin Hsieh, Takayuki Ishii, Keng‐Hsien Chao, Gregor J. Golabek, Marcel Thielmann, Eiji Ohtani

    Geophysical Research Letters   47 ( 13 )   2020.7

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    DOI: 10.1029/2020gl087607

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  • Discovery of New‐Structured Post‐Spinel MgFe 2 O 4 : Crystal Structure and High‐Pressure Phase Relations Reviewed

    Takayuki Ishii, Nobuyoshi Miyajima, Ryosuke Sinmyo, Hiroshi Kojitani, Daisuke Mori, Yoshiyuki Inaguma, Masaki Akaogi

    Geophysical Research Letters   47 ( 6 )   2020.3

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    DOI: 10.1029/2020gl087490

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  • Spin Transition of Iron in δ‐(Al,Fe)OOH Induces Thermal Anomalies in Earth's Lower Mantle Reviewed

    Wen‐Pin Hsieh, Takayuki Ishii, Keng‐Hsien Chao, Jun Tsuchiya, Frédéric Deschamps, Eiji Ohtani

    Geophysical Research Letters   47 ( 4 )   2020.2

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    DOI: 10.1029/2020gl087036

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  • Stability and Solubility of the FeAlO 3 Component in Bridgmanite at Uppermost Lower Mantle Conditions Reviewed

    Zhaodong Liu, Catherine McCammon, Biao Wang, Leonid Dubrovinsky, Takayuki Ishii, Dmitry Bondar, Ayano Nakajima, Yoshinori Tange, Yuji Higo, Tian Cui, Bingbing Liu, Tomoo Katsura

    Journal of Geophysical Research: Solid Earth   125 ( 2 )   2020.2

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    DOI: 10.1029/2019jb018447

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  • Development of High-Pressure Technology with Kawai-Type Multi-Anvil Presses and its Application to Geoscience Invited Reviewed

    Takayuki ISHII

    The Review of High Pressure Science and Technology   30 ( 2 )   156 - 165   2020

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of High Pressure Science and Technology  

    DOI: 10.4131/jshpreview.30.156

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  • Crystal Structure of a Novel Fe-Mg Oxide and Deep Earth Science Invited Reviewed

    Takayuki ISHII

    Nihon Kessho Gakkaishi   61 ( 4 )   205 - 206   2019.12

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:The Crystallographic Society of Japan  

    DOI: 10.5940/jcrsj.61.205

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  • Sharp 660-km discontinuity controlled by extremely narrow binary post-spinel transition Reviewed

    Takayuki Ishii, Rong Huang, Robert Myhill, Hongzhan Fei, Iuliia Koemets, Zhaodong Liu, Fumiya Maeda, Liang Yuan, Lin Wang, Dmitry Druzhbin, Takafumi Yamamoto, Shrikant Bhat, Robert Farla, Takaaki Kawazoe, Noriyoshi Tsujino, Eleonora Kulik, Yuji Higo, Yoshinori Tange, Tomoo Katsura

    Nature Geoscience   12 ( 10 )   869 - 872   2019.9

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    DOI: 10.1038/s41561-019-0452-1

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  • The stability of Fe5O6 and Fe4O5 at high pressure and temperature Reviewed

    Koutaro Hikosaka, Ryosuke Sinmyo, Kei Hirose, Takayuki Ishii, Yasuo Ohishi

    American Mineralogist   104 ( 9 )   1356 - 1359   2019.9

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    Abstract

    The oxygen fugacity in the interior of the Earth is largely controlled by iron-bearing minerals. Recent studies have reported various iron oxides with chemical compositions between FeO and Fe3O4 above ~10 GPa. However, the stabilities of these high-pressure iron oxides remain mostly uninvestigated. In this study, we performed in situ X-ray diffraction (XRD) measurements in a laser-heated diamond-anvil cell (DAC) to determine the phase relations in both Fe5O6 and Fe4O5 bulk compositions to 61 GPa and to 2720 K. The results show that Fe5O6 is a high-temperature phase stable above 1600 K and ~10 GPa, while FeO + Fe4O5 are formed at relatively low temperatures. We observed the decomposition of Fe5O6 into 2FeO + Fe3O4 above 38 GPa and the decomposition of Fe4O5 into FeO + h-Fe3O4 at a similar pressure range. The coexistence of FeO and Fe3O4 indicates that none of the recently discovered compounds between FeO and Fe3O4 (i.e., Fe5O6, Fe9O11, Fe4O5, and Fe7O9) are formed beyond ~40 GPa at 1800 K, corresponding to conditions in the shallow lower mantle. Additionally, as some superdeep diamonds have genetic links with these high-pressure iron oxides, our results give constraints on pressure and temperature conditions of their formation.

    DOI: 10.2138/am-2019-7097

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  • A Breakthrough in Pressure Generation by a Kawai-Type Multi-Anvil Apparatus with Tungsten Carbide Anvils Invited Reviewed

    Takayuki Ishii, Zhaodong Liu, Tomoo Katsura

    Engineering   5 ( 3 )   434 - 440   2019.6

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    DOI: 10.1016/j.eng.2019.01.013

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  • Phase Relations of Harzburgite and MORB up to the Uppermost Lower Mantle Conditions: Precise Comparison With Pyrolite by Multisample Cell High‐Pressure Experiments With Implication to Dynamics of Subducted Slabs Reviewed

    Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi

    Journal of Geophysical Research: Solid Earth   124 ( 4 )   3491 - 3507   2019.4

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    DOI: 10.1029/2018jb016749

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  • High-Pressure Phase Relations and Crystal Structures of Postspinel Phases in MgV2O4, FeV2O4, and MnCr2O4: Crystal Chemistry of AB2O4 Postspinel Compounds Reviewed

    Takayuki Ishii, Tsubasa Sakai, Hiroshi Kojitani, Daisuke Mori, Yoshiyuki Inaguma, Yoshitaka Matsushita, Kazunari Yamaura, Masaki Akaogi

    Inorganic Chemistry   57 ( 11 )   6648 - 6657   2018.5

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    DOI: 10.1021/acs.inorgchem.8b00810

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  • Complete agreement of the post-spinel transition with the 660-km seismic discontinuity Reviewed

    Takayuki Ishii, Rong Huang, Hongzhan Fei, Iuliia Koemets, Zhaodong Liu, Fumiya Maeda, Liang Yuan, Lin Wang, Dmitry Druzhbin, Takafumi Yamamoto, Shrikant Bhat, Robert Farla, Takaaki Kawazoe, Noriyoshi Tsujino, Eleonora Kulik, Yuji Higo, Yoshinori Tange, Tomoo Katsura

    Scientific Reports   8 ( 1 )   2018.4

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    Abstract

    The 660-km seismic discontinuity, which is a significant structure in the Earth’s mantle, is generally interpreted as the post-spinel transition, as indicated by the decomposition of ringwoodite to bridgmanite + ferropericlase. All precise high-pressure and high-temperature experiments nevertheless report 0.5–2 GPa lower transition pressures than those expected at the discontinuity depth (i.e. 23.4 GPa). These results are inconsistent with the post-spinel transition hypothesis and, therefore, do not support widely accepted models of mantle composition such as the pyrolite and CI chondrite models. Here, we present new experimental data showing post-spinel transition pressures in complete agreement with the 660-km discontinuity depth obtained by high-resolution in situ X-ray diffraction in a large-volume high-pressure apparatus with a tightly controlled sample pressure. These data affirm the applicability of the prevailing mantle models. We infer that the apparently lower pressures reported by previous studies are experimental artefacts due to the pressure drop upon heating. The present results indicate the necessity of reinvestigating the position of mantle mineral phase boundaries previously obtained by in situ X-ray diffraction in high-pressure–temperature apparatuses.

    DOI: 10.1038/s41598-018-24832-y

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  • High-pressure phase transitions in MgCr2O4·Mg2SiO4 composition: Reactions between olivine and chromite with implications for ultrahigh-pressure chromitites Reviewed

    Masaki Akaogi, Airi Kawahara, Hiroshi Kojitani, Kazuaki Yoshida, Yuki Anegawa, Takayuki Ishii

    American Mineralogist   103 ( 1 )   161 - 170   2018.1

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    DOI: 10.2138/am-2018-6135

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  • Phase relations and mineral chemistry in pyrolitic mantle at 1600–2200 °C under pressures up to the uppermost lower mantle: Phase transitions around the 660-km discontinuity and dynamics of upwelling hot plumes Reviewed

    Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi

    Physics of the Earth and Planetary Interiors   274   127 - 137   2018.1

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    DOI: 10.1016/j.pepi.2017.10.005

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  • Synthesis and crystal structure of Mg-bearing Fe9O11: New insight in the complexity of Fe-Mg oxides at conditions of the deep upper mantle Reviewed

    American Mineralogist   2018

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    DOI: 10.2138/am-2018-6646

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  • Phase Relations in the System MgSiO3 -Al2 O3 up to 2300 K at Lower Mantle Pressures Reviewed

    Zhaodong Liu, Masayuki Nishi, Takayuki Ishii, Hongzhan Fei, Nobuyoshi Miyajima, Tiziana Boffa Ballaran, Hiroaki Ohfuji, Takeshi Sakai, Lin Wang, Svyatoslav Shcheka, Takeshi Arimoto, Yoshinori Tange, Yuji Higo, Tetsuo Irifune, Tomoo Katsura

    Journal of Geophysical Research: Solid Earth   122 ( 10 )   7775 - 7788   2017.10

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    DOI: 10.1002/2017jb014579

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  • A shallow origin of so-called ultrahigh-pressure chromitites, based on single-crystal X-ray structure analysis of the high-pressure Mg2Cr2O5 phase, with modified ludwigite-type structure Reviewed

    Takayuki Ishii, Noriyoshi Tsujino, Hidekazu Arii, Kiyoshi Fujino, Nobuyoshi Miyajima, Hiroshi Kojitani, Takehiro Kunimoto, Masaki Akaogi

    American Mineralogist   102 ( 10 )   2113 - 2118   2017.10

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    DOI: 10.2138/am-2017-6050

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  • Rapid decrease of MgAlO2.5 component in bridgmanite with pressure Reviewed

    Z. Liu, T. Ishii, T. Katsura

    Geochemical Perspectives Letters   12 - 18   2017.10

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    Publishing type:Research paper (scientific journal)   Publisher:European Association of Geochemistry  

    DOI: 10.7185/geochemlet.1739

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  • Pressure generation to 65 GPa in a Kawai-type multi-anvil apparatus with tungsten carbide anvils Reviewed

    Takayuki Ishii, Daisuke Yamazaki, Noriyoshi Tsujino, Fang Xu, Zhaodong Liu, Takaaki Kawazoe, Takafumi Yamamoto, Dmitry Druzhbin, Lin Wang, Yuji Higo, Yoshinori Tange, Takashi Yoshino, Tomoo Katsura

    High Pressure Research   37 ( 4 )   507 - 515   2017.9

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:Informa UK Limited  

    DOI: 10.1080/08957959.2017.1375491

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  • Single crystal synthesis of δ-(Al,Fe)OOH Reviewed

    Takaaki Kawazoe, Itaru Ohira, Takayuki Ishii, Tiziana Boffa Ballaran, Catherine McCammon, Akio Suzuki, Eiji Ohtani

    American Mineralogist   102 ( 9 )   1953 - 1956   2017.9

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    DOI: 10.2138/am-2017-6153

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  • Synthesis and crystal structure of LiNbO3-type Mg3Al2Si3O12: A possible indicator of shock conditions of meteorites Reviewed

    Takayuki Ishii, Ryosuke Sinmyo, Tetsuya Komabayashi, Tiziana Boffa Ballaran, Takaaki Kawazoe, Nobuyoshi Miyajima, Kei Hirose, Tomoo Katsura

    American Mineralogist   102 ( 9 )   1947 - 1952   2017.9

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    DOI: 10.2138/am-2017-6027

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  • Shocked chromites in fossil L chondrites: A Raman spectroscopy and transmission electron microscopy study Reviewed

    Surya S. Rout, Philipp R. Heck, Nestor J. Zaluzec, Takayuki Ishii, Jianguo Wen, Dean J. Miller, Birger Schmitz

    Meteoritics & Planetary Science   52 ( 9 )   1776 - 1796   2017.5

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    Publishing type:Research paper (scientific journal)   Publisher:Wiley  

    DOI: 10.1111/maps.12887

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    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1111/maps.12887

  • High-pressure high-temperature phase relations in FeTiO3 up to 35 GPa and 1600 °C Reviewed

    M. Akaogi, K. Abe, H. Yusa, T. Ishii, T. Tajima, H. Kojitani, D. Mori, Y. Inaguma

    Physics and Chemistry of Minerals   44 ( 1 )   63 - 73   2016.8

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1007/s00269-016-0836-3

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    Other Link: http://link.springer.com/article/10.1007/s00269-016-0836-3/fulltext.html

  • Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils Reviewed

    D. Druzhbin, R. Myhill

    Review of Scientific Instruments   87 ( 2 )   024501 - 024501   2016.2

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    DOI: 10.1063/1.4941716

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  • High-pressure high-temperature transitions in MgCr2O4 and crystal structures of new Mg2Cr2O5 and post-spinel MgCr2O4 phases with implications for ultrahigh-pressure chromitites in ophiolites Reviewed

    T. Ishii, H. Kojitani, K. Fujino, H. Yusa, D. Mori, Y. Inaguma, Y. Matsushita, K. Yamaura, M. Akaogi

    American Mineralogist   100 ( 1 )   59 - 65   2015.1

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    DOI: 10.2138/am-2015-4818

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  • Super structure in recovered high-pressure phase Mg2Cr2O5 Reviewed

    Fujino Kiyoshi, Ishii Takayuki, Kunimoto Takehiro, Kojitani Hiroshi, Akaogi Masaki

    Abstracts for Annual Meeting of Japan Association of Mineralogical Sciences   2015 ( 0 )   70 - 70   2015

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    Language:Japanese   Publisher:Japan Association of Mineralogical Sciences  

    XRD and TEM observations of recovered high-pressure phase Mg2Cr2O5 revealed split spots around the position of h = n + 1/2 (n: integer) in the diffraction patterns of the basic structure of this phase. It was proved that these split spots were formed by the periodic arrangement of the anti-phase boundaries in the structure. Then, the relation between the formation of these periodic anti-phase boundaries and the high-pressure phase transformation of Mg2Cr2O5 is discussed.

    DOI: 10.14824/jakoka.2015.0_70

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  • High-pressure phase transitions in FeCr2O4 and structure analysis of new post-spinel FeCr2O4 and Fe2Cr2O5 phases with meteoritical and petrological implications Reviewed

    T. Ishii, H. Kojitani, S. Tsukamoto, K. Fujino, D. Mori, Y. Inaguma, N. Tsujino, T. Yoshino, D. Yamazaki, Y. Higo, K. Funakoshi, M. Akaogi

    American Mineralogist   99 ( 8-9 )   1788 - 1797   2014.8

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    DOI: 10.2138/am.2014.4736

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  • High-pressure synthesis of the BaIrO3 perovskite: A Pauli paramagnetic metal with a Fermi liquid ground state Reviewed

    J.-G. Cheng, T. Ishii, H. Kojitani, K. Matsubayashi, A. Matsuo, X. Li, Y. Shirako, J.-S. Zhou, J. B. Goodenough, C. Q. Jin, M. Akaogi, Y. Uwatoko

    Physical Review B   88 ( 20 )   2013.11

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.88.205114

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.88.205114/fulltext

  • High-pressure phase transitions and subduction behavior of continental crust at pressure–temperature conditions up to the upper part of the lower mantle Reviewed

    Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi

    Earth and Planetary Science Letters   357-358   31 - 41   2012.12

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    Authorship:Lead author   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.epsl.2012.09.019

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  • Thermodynamic investigation on phase equilibrium boundary between calcium ferrite-type MgAl2O4 and MgO+α-Al2O3 Reviewed

    Hiroshi Kojitani, Takayuki Ishii, Masaki Akaogi

    Physics of the Earth and Planetary Interiors   212-213   100 - 105   2012.12

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    Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.pepi.2012.10.002

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  • High-pressure phase relations in the system TiO2–ZrO2 to 12 GPa: stability of αPbO2-type srilankite solid solutions of (Ti1−x , Zr x )O2 (0 ≤ x ≤ 0.6) Reviewed

    Masaki Akaogi, Nanami Horiuchi, Takayuki Ishii, Hiroshi Kojitani

    Physics and Chemistry of Minerals   39 ( 10 )   797 - 802   2012.8

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1007/s00269-012-0534-8

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    Other Link: http://link.springer.com/article/10.1007/s00269-012-0534-8/fulltext.html

  • Post-spinel transitions in pyrolite and Mg2SiO4 and akimotoite–perovskite transition in MgSiO3: Precise comparison by high-pressure high-temperature experiments with multi-sample cell technique Reviewed

    Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi

    Earth and Planetary Science Letters   309 ( 3-4 )   185 - 197   2011.9

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    DOI: 10.1016/j.epsl.2011.06.023

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MISC

  • Akimotoite-bridgmanite phase transition explains depressed 660-km seismic discontinuity in subduction zones Invited

    Artem Chanyshev, Takayuki Ishii, Tomoo Katsura

    SPring-8 Research Frontiers 2021   96 - 97   2022

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    Publishing type:Rapid communication, short report, research note, etc. (bulletin of university, research institution)  

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  • Sharp 660-km seismic discontinuity explained by extremely narrow binary post-spinel transition Invited

    Takayuki Ishii, Tomoo Katsura

    74 - 75   2020

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  • Complete agreement of the post-spinel transition pressure with the 660-km seismic discontinuity depth Invited

    Takayuki Ishii, Tomoo Katsura

    SPring-8 Research Frontiers 2018   88 - 89   2019

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Presentations

  • Dry olivine and its high-pressure polymorphs coexisting with hydrous phases in wet subducting slab

    Takayuki Ishii, Eijij Ohtani

    American Geophysical Union Fall meeting 2021  2021.12 

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    Event date: 2021.12.1 - 2021.12.17

    Language:English   Presentation type:Poster presentation  

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  • Water partitioning between olivine and its polymorphs and hydrous phases under water-undersaturated conditions

    Takayuki Ishii, Eijij Ohtani

    The 61th High Pressure Conference of Japan,  2020.12 

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    Event date: 2020.12.2 - 2020.12.4

    Presentation type:Oral presentation (general)  

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  • Water solubility of aluminous silicas at lower mantle conditions and their implication for water cycle in the deep mantle

    Takayuki Ishii, Giacomo Criniti, Eiji Ohtani, Narangoo Purevjav, Hongzhan Fei, Tomoo Katsura, Ho-kwang Mao

    American Geophysical Union Fall meeting 2023  2023.12.11 

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  • 非線形クラペイロン勾配を持つMg3Al2Si3O12系ポストガーネット相転移とそのマントルダイナミクスへの影響

    石井 貴之, FROST Daniel, KIM Eun Jeong, CHANYSHEV Artem, 西田 圭佑, WANG Biao, 坂 凛太郎, U Jianing, LIU Jin, SU Xiaowan, 肥後 祐司, 丹下 慶範, HO-KWANG Mao, 桂 智男

    第64回高圧討論会  2023.11.1 

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  • 川井型マルチアンビルプレスを用いた技術開発とその地球科学的応用 Invited

    石井貴之

    SPRUC地球惑星科学・高圧物質科学 合同サテライト研究会  2023.9.26 

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  • Developments of Kawai-type multi-anvil technology and their applications to geoscience Invited

    Takayuki Ishii

    The 2nd Conference on Physics under Synergetic Extreme Conditions held jointly with the Summer School of SECUF  2023.7.19 

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  • Water solubility of aluminous stishovite coexisting with hydrous phase δ: Implication for water cycle in the lower mantle

    Takayuki Ishii, Eiji Ohtani

    Japan Geoscience Union Meeting 2023  2023.5.25 

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  • A new approach determining an accurate and precise phase transition boundary strictly based on a definition of phase equilibrium by means of in-situ multi-anvil technique Invited

    Takayuki Ishii, Artem Chanyshev, Tomoo Katsura

    American Geophysical Union Fall meeting 2022  2022.12.15 

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  • A new approach to determine high pressure-temperature phase boundary strictly based on the definition of phase equilibrium

    Takayuki Ishii, Artem Chanyshev, Tomoo Katsura

    2022 Japan Association of Mineralogical Science Annual Meeting  2022.9.18 

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  • A new approach determining a phase transition boundary strictly based on a definition of phase equilibrium by means of in-situ multi-anvil technique Invited

    Takayuki Ishii, Artem Chanyshev, Dmitry Bondar, Shrikant Bha, Eun Jeong Kim, Robert Farla, Keisuke Nishida, Zhaodong Liu, Lin Wang, Ayano Nakajima, Bimbing Yan, Hu Tang, Z. Chen, Yuji Higo, Yoshinori Tange, Tomoo Katsura

    1st International Conference on Physics under Synergetic Extreme Conditions  2022.7.18 

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  • Crystal chemistry and compressibility of Fe2+- and oxygen vacancy-rich aluminous bridgmanite: Implications for lower mantle structure and dynamics Invited

    Takayuki Ishii, Giacomo Criniti, Nobuyoshi Miyajima, Alexander Kurnosov, Nicki Siersch, Konstantin Glazyrin, Tiziana Boffa Ballaran

    2022 Japan Geoscience Union Meeting  2022.5 

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  • Water solubility of aluminous post-stishovite at top lower mantle conditions: Implications for water cycle in the deep mantle

    Takayuki Ishii, Giacomo Criniti, Eiji Ohtani, Narangoo Purevjav, Hongzhan Fei, Tomoo Katsura, Hokwang Mao

    2022 Japan Geoscience Union Meeting  2022.5 

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  • Water content in olivine and its polymorphs coexisting with hydrous phases under water undersaturated conditions

    Takayuki Ishii, Eijij Ohtani

    2021 Japan Geoscience Union Meeting  2021.6 

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  • Phase relations of basaltic crust determined by simultaneous pressure-temperature generation techniques to 52 GPa and 2000 K using a multi-anvil press with tungsten carbide anvils.

    Takayuki Ishii, Nobuyoshi Miyajima, Tomoo Katsura

    American Geophysical Union Fall meeting 2020  2020.12.9 

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  • Non-linear temperature dependence of the post-garnet transition boundary in Mg3Al2Si3O12 revealed by accurate equilibrium experiment in a multi-anvil press with in-situ X-ray diffraction

    T. Ishii, D. J. Fros, A. Chanyshev, K. Nishida, R. Ban, X. Su, Y. Higo, Y. Tange, T. Katsura

    American Geophysical Union Fall meeting 2019  2019.12 

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  • Development of high-pressure experimental techniques using multianvil presses and their applications to Earth science Invited

    Takayuki Ishii

    The 60th High Pressure Conference of Japan,  2019.11 

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  • Crystal structure of Mg-bearing Fe9O11: New insight in the complexity of Fe-Mg oxides at conditions of the deep upper mantle

    T. Ishii, L. Uenver-Thiele, A. B. Woodland, E. Alig, T. B. Ballaran

    2019 Japan Geoscience Union Meeting  2019.5 

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  • Experimental redetermination of the post-spinel transition boundary in Mg2SiO4 by means of in-situ X-ray diffraction in a multi-anvil press

    T. Ishii, Z. Liu, D. Bonder, A. Nakajima, B. Yang, H. Tang, Y. Higo, Y. Tange, T. Katsura

    American Geophysical Union Fall meeting 2018  2018.12 

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  • The pressure and thickness of the post-spinel transition in (Mg,Fe)2SiO4 explaining the sharp 660-km seismic discontinuity Invited

    Takayuk Ishii

    Academy Commission Business Meeting at Bayerisches Geoinstitut  2018.4 

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  • The pressure and thickness of the post-spinel transition in (Mg,Fe)2SiO4 explaining the sharp 660-km discontinuity

    T. Ishii, R. Huang, H. Fei, I. Koemets, Z. Liu, F. Maeda, L. Yuan, L. Wang, D. Druzhbin, T. Yamamoto, S. Bha, R. Farla, T. Kawazoe, N. Tsujino, E. Kulik, Y. Higo, Y. Tange, T. Katsura

    European Geophysical Union General Assembly 2018  2018.4 

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  • The pressure and thickness of the post-spinel transition in (Mg,Fe)2SiO4 explaining the sharp 660-km discontinuity

    T. Ishii, R. Huang, H. Fei, I. Koemets, Z. Liu, F. Maeda, L. Yuan, L. Wang, D. Druzhbin, T. Yamamoto, S. Bha, R. Farla, T. Kawazoe, T. Noriyoshi, E. Kulik, Y. Higo, Y. Tange, T. Katsura

    American Geophysical Union Fall Meeting  2017.12 

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  • Precise determination of post-spinel transition in MgO-FeO-SiO2 system

    T. Ishii, R. Huang, H. Fei, I. Koemets, Z. Liu, F. Maeda, L. Yuan, L. Wang, D. Druzhbin, T. Yamamoto, S. Bha, R. Farla, T. Kawazoe, T. Noriyoshi, E. Kulik, Y. Higo, Y. Tange, T. Katsura

    The 26th International conference on High Pressure Science and Technology  2017.8 

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Awards

  • Mineral and Rock Physics Early Career Award

    2021.12   American Geophysical Union  

    Takayuki Ishii

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  • The Encouragement Prize

    2019.10   The Japan Society of High Pressure Science and Technology  

    Takayuki Ishii

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Research Projects

  • National Key Research Major Research Plan on West-Pacific Earth System Multispheric Interactions

    2022 - 2026

    National Natural Science Foundation of China 

    Renbbiao Tao, Takayuki Ishii

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  • High-pressure-temperature phase relations of basaltic crust under lower-mantle conditions: implications for chemical heterogeneity in the lower mantle

    2019.04 - 2021.12

    German Research Foundation  Research Grant  Research Grant

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  • High-pressure phase transitions of slab-constituent minerals under lower-mantle conditions

    2017.04 - 2019.03

    Alexander von Humboldt Foundation  Humboldt Research Fellowship for Postdoctoral Researcher  Humboldt Research Fellowship for Postdoctoral Researcher

    Takayuki Ishii

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  • High-pressure phase transitions and stabilities of hydrous lower mantle model minerals

    2016.04 - 2017.03

    Japan Society for the Promotion of Science  Overseas Research Fellowship 

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  • 下部マントル物質の含水条件下における高圧相転移と高圧物性

    Grant number:15J06233  2015.04 - 2016.03

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    石井 貴之

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    Grant amount:\2730000 ( Direct expense: \2100000 、 Indirect expense:\630000 )

    この1年間はドイツバイロイト大学バイエルン地球科学研究所に滞在し、1年目の研究課題である①川井型マルチアンビルプレスを用いた50 GPa以上の圧力発生技術の開発と②40 GPa以上、2000 Kにおける新規圧力定点の確立を主な目的に研究を行ってきた。
    ①に関しては、2段目アンビルに斜面付きタングステンカーバイドアンビルを採用し、高圧セル、ガスケットの最適化を行い、室温で63 GPa、2000 Kで45 GPaの圧力発生に成功した。この結果は国内・国際学会で発表し、また国際誌で公表されている。また、発生圧力の見積もりに用いていたMg3Al2Si3O12組成試料の高圧相転移について、同組成のブリッジマナイトを合成した際、減圧過程でリチウムニオベート構造へ相転移することが解った。この相の結晶構造解析を放射光X線回折測定と組み合わせて行い、現在国際誌への投稿論文を準備している。
    この高圧発生技術を②に応用して、パイロープ(Mg3Al2Si3O12)-アルマンディン(Fe3Al2Si3O12)系高温高圧相関係を決定し、この系中で合成されるブリッジマナイト相の化学組成の圧力依存性を現在決定中である。現在までに、両者の中間組成である(Mg,Fe)Al2Si3O12組成の2000 Kにおける高圧相関係を40 GPaまで決定した。40 GPaで同組成を持つリチウムニオベート相が合成されることが解り、この相についても結晶構造解析を行っていく予定である。

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  • マントル物質の高圧相転移・ダイナミックスの解明と新規ポストスピネル相の探索と物性

    Grant number:12J09330  2012.04 - 2015.03

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    石井 貴之

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    Grant amount:\2700000 ( Direct expense: \2700000 )

    研究課題のAB2O4新規ポストスピネル相の探索に関して、合成に成功した未知相であるMgFe2O4高圧相について、バイロイト大学バイエルン地球科学研究所で透過型電子顕微鏡を用いて、格子定数、空間群の決定を行った。その結果、格子定数、空間群は粉末X線回折から得られた結果と一致していることが分かった。現在、粉末X線回折データから結晶構造の決定を試みている。その他に、新たにCaFe2O4型MnCr2O4、CaTi2O4型FeV2O4新規高圧相の合成に成功した。以上の結果は、ポストスピネル相の安定性を理解する上で重要な結果である。これらの結果について国際誌に論文投稿する予定である。また、MgCr2O4の高圧相として本研究により発見されたMg2Cr2O5の結晶構造解析を透過型電子顕微鏡(TEM)法と単結晶X線回折法から行った。高分解能TEM像から微細構造モデルを立て、そのモデル構造が特異な制限視野電子線回折パターンを良く説明することができることを明らかにした。単結晶X線回折からは、平均的な構造が粉末X線回折から得られる構造と同じであることを確かめ、粉末X線回折よりも精密に結晶構造に関するパラメーターを決定した。この結果は、結晶化学的に珍しい発見であり、この内容に関して国内の学会で発表するとともに、現在国際誌への投稿の為、論文を執筆中である。
    また、前年度に明らかにしたマントル岩石であるパイロライト、ハルツバージャイト、中央海嶺玄武岩の1600~2200℃でのマントル660 km不連続面付近の高温高圧相関係について、新たに約12~20 GPaでの高温高圧相関係を決定した。この結果は、沈み込むプレート、マントル上昇流中の鉱物組み合わせを下部マントル最上部まで明らかにした点で重要である。この内容に関して、国内の学会において発表を行い、現在論文を執筆中である。
    上記の内容とこの3年間で得られた結果を総括し、博士論文を執筆した。

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  • Guidance in Planetary Physics (2023academic year) Prophase  - その他

  • Introduction to Earth and Planetary Materials Science (2023academic year) Prophase  - 月3~4

  • Advanced Research in Experimental Planetary Physics (2023academic year) Year-round  - その他

  • Introduction to Mineral Physics (2023academic year) Late  - 月3~4