Takayuki Ishii

Zeria Pharmaceutical (Japan)

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Tomoo Katsura

University of Bayreuth

Giacomo Criniti

Carnegie Institution for Science

Hiroshi Kojitani

Gakushuin University

Masaki Akaogi

Gakushuin University

Tiziana Boffa Ballaran

Bayerisches Landesamt für Umwelt

Yuji Higo

Japan Synchrotron Radiation Research Institute

Zhaodong Liu

Fujian Medical University

Artem Chanyshev

University of Bayreuth

Leonid Dubrovinsky

University of Bayreuth

Eiji Ohtani

Tohoku University

Cooperative Institutions

University of Bayreuth

Center for High Pressure Science and Technology Advanced Research

Carnegie Institution for Science

Tohoku University

Bayer (Germany)

Deutsches Elektronen-Synchrotron DESY

The University of Tokyo

Japan Synchrotron Radiation Research Institute

Bayerisches Landesamt für Umwelt

Japan Agency for Marine-Earth Science and Technology

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Cross-ridge Fissures Appearing due to the 1995 Hyogoken-Nanbu Earthquake in the Rokko Mountains, Japan, with Special Reference to the Formation Process

Geographical Review of Japan (1999)

Takayuki Ishii Masashige Hirano Shigeki Hada

1995年1月17日未明に発生した兵庫県南部地震により,六甲山地の3カ所の尾根,すなわち摩耶山南西の学校林道と呼ばれる尾根,有馬温泉南の湯槽谷山付近の尾根ならびに六甲ケーブル山頂駅南東の寒天山道と呼ばれる尾根において,尾根を横切る地割れ系が形成された.本研究では,これら3カ所の地割れ系の性質を詳述するとともに,その形成プロセスを地盤に作用した水平加速度の推定と併せて吟味することを目的とした.ここで地震により地盤に生じた水平加速度の大きさと方向は,巨礫および墓石・献灯の中座の変位から推定した. これら3カ所の地割れ系は直線性のみならず,雁行状の配列を示しながら尾根を斜めに横切り,一部は尾根のほか地震によって形成された崩壊地の滑落崖を斜めに切っていることなどの性質を有すること,ならびに周辺に存在する巨礫などから求めた地盤に作用した推定水平加速度の大きさと方向の分布特性の吟味などから,問題とした地割れ系は地震によって発生した斜面崩壊に伴うものではなく,テクトニックなものと推定した. さらに,各調査地点周辺の推定水平加速度の大きさと方向のほか,地震による崩壊地の方位ならびに道路側溝などのオフセットの方向から判断し,地割れ系の形成プロセスに関する二つのモデルを提案した.それらは,水平加速度の作用した方向は同じであるが,その大きさが異なることによって地割れ系が形成されるタイプ(学校林道型)と,ある線を境にして水平加速度の作用した方向そのものが異なることによって地割れ系が形成されるタイプ(有馬・湯槽谷山型)である.

10.4157/grj1984a.72.10_691

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Crystal structure analysis of a new high-pressure strontium silicate

Japan Geoscience Union (2014)

K. Sekine Takayuki Ishii Hiroshi Kojitani Masaki Akaogi

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Peridotites outcropped in the southern Mariana Trench

AGUFM (2016)

Shunsuke Oya Katsuyoshi Michibayashi Yasuhiko Ohara Takayuki Ishii

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

Journal of Geophysical Research Solid Earth (2022)

Wen‐Pin Hsieh Enrico Marzotto Takayuki Ishii Leonid Dubrovinsky Alena Aslandukovа

Abstract Earth's deep water cycle impacts the physical and chemical properties and geodynamics in its deep interior. However, how dense hydrous magnesium silicates (DHMSs) influence the thermal evolution and dynamics of sinking slabs remains poorly understood. We have precisely measured thermal conductivity of phase D, an important DHMS that could carry large amounts of water from the mantle transition zone to the lower mantle, at high pressure‐temperature conditions. The thermal conductivity of (Al,Fe)‐bearing phase D is lower than those of the pyrolitic mantle and basaltic crust along slab subduction, except for the depth range of ∼800–1,100 km where a spin transition of iron occurs. Numerical simulations indicate that although the spin transition in phase D has minor effects on slab's temperature due to its small volume fraction, the poorly thermally‐conductive hydrous minerals contribute to maintain a cold hydrous layer within a sinking slab, stabilizing slab hydrous minerals and promoting water transportation to the deeper mantle.

Slab

geodynamics

10.1029/2022jb024556

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Thermal conductivity of carbonate and hydrous minerals in Earth's deep interior

AGU Fall Meeting Abstracts (2019)

Wen‐Pin Hsieh Keng‐Hsien Chao Takayuki Ishii Eiji Ohtani

Carbonate minerals

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

Nature Geoscience (2019)

Takayuki Ishii Rong Huang Robert Myhill Hongzhan Fei Iuliia Koemets

Ringwoodite

Discontinuity (linguistics)

Silicate perovskite

10.1038/s41561-019-0452-1

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Stability of the high yield MSMPR crystallizer with size‐dependent growth rate

AIChE Journal (1980)

Takayuki Ishii Alan D. Randolph

Engine department

10.1002/aic.690260324

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

American Mineralogist (2017)

Takaaki Kawazoe Itaru Ohira Takayuki Ishii Tiziana Boffa Ballaran Catherine McCammon

Single crystals of δ-AlOOH, δ-(Al0.953,Fe0.047)OOH, and δ-(Al0.878,Fe0.122)OOH with dimensions up to ~0.4–0.6 mm were synthesized by the high-pressure hydrothermal method. Synthesis experiments were performed at 21 GPa and 1470 K for 4 h using a Kawai-type multi-anvil apparatus. The crystals of δ-AlOOH, δ-(Al0.953,Fe0.047)OOH, and δ-(Al0.878,Fe0.122)OOH were colorless, yellowish green, and brown, respectively. Mössbauer spectra showed 95–100% Fe3+/∑Fe at the octahedral site in δ-(Al,Fe)OOH. Chemical compositions of δ-(Al0.953,Fe0.047)OOH and δ-(Al0.878,Fe0.122)OOH are homogeneous with Fe/(Al+Fe) of 0.0469(8) and 0.122(3), respectively. Unit-cell parameters of δ-AlOOH are consistent with those of previous studies, and they increase with Fe/(Al+Fe). These results confirm that δ-AlOOH can form a solid solution with ε-FeOOH. The crystals contained a small number of fluid inclusions. The syntheses of large single crystals of δ-(Al,Fe)OOH will facilitate investigation of their phase stability, physical properties including elasticity and elastic anisotropy, behavior of hydrogen bonding, and spin state of Fe, which will improve models of the water and oxygen cycles in the deep Earth.

10.2138/am-2017-6153

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

American Mineralogist (2022)

Alan B. Woodland Laura Uenver‐Thiele Tiziana Boffa Ballaran Nοbuyοshi Miyajima Kevin Rosbach

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.

Stoichiometry

10.2138/am-2022-8370

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

American Mineralogist (2020)

Takayuki Ishii Giacomo Criniti Elena Bykova Leonid Dubrovinsky Tomoo Katsura

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.

Orthorhombic crystal system

Lattice (music)

10.2138/am-2021-7619

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Citations (7)