研究者詳細 - 芳野　極

論文 - 芳野　極

分割表示 162 件中 1 - 20 件目／全件表示 >>

Valence/Spin States of Iron in Peridotite Glass to Megabar Pressure Implications for Dense Iron‐Rich Silicate Melt at the Bottom of the Mantle 査読

Izumi Mashino, Takashi Yoshino, Takaya Mitsui, Kosuke Fujiwara, Sayako Inoué, Takeshi Sakai

Geophysical Research Letters 52 ( 7 ) 1 - 11 2025年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Geophysical Union (AGU)

Abstract

We have conducted high‐pressure electrical conductivity and Mössbauer spectroscopic measurements of peridotite glass as an analog of silicate melts. We observed the shoulder feature in the Mössbauer spectra above 60 GPa due to the emergence of the new Fe²⁺ component, which could be associated with the change of the iron partitioning coefficient between solid and melt observed in previous melting experiments. The change in the trend of the electrical conductivity profile has been observed at around ∼83 GPa, suggesting the increase of the relative abundance of the new component. The pressure dependence of hyperfine parameters indicates the spin transitions of both Fe²⁺ and Fe³⁺ occur above 100 GPa, which is likely related to the structural change of the glass. Our results suggest that the spin state changes of iron lead to further densification of the silicate melts at the bottom of the mantle.

DOI： 10.1029/2024gl113106

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Low melt viscosity enables melt doublets above the 410-km discontinuity 査読

Longjian Xie, Denis Andrault, Takashi Yoshino, Cunrui Han, James O. S. Hammond, Fang Xu, Bin Zhao, Oliver T. Lord, Yingwei Fei, Simon Falvard, Sho Kakizawa, Noriyoshi Tsujino, Yuji Higo, Laura Henry, Nicolas Guignot, David P. Dobson

Nature Communications 16 ( 1 ) 2025年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Science and Business Media LLC

Abstract

Seismic and magnetotelluric studies suggest hydrous silicate melts atop the 410 km discontinuity form 30–100 km thick layers. Importantly, in some regions, two layers are observed. These stagnant layers are related to their comparable density to the surrounding mantle, but their formation mechanisms and detailed structures remain unclear. Here we report a large decrease of silicate melt viscosity at ~14 GPa, from 96(5) to 11.7(6) mPa⋅s, as water content increases from 15.5 to 31.8 mol% H₂O. Such low viscosities facilitate rapid segregation of melt, which would typically prevent thick layer accumulation. Our 1D finite element simulations show that continuous dehydration melting of upwelling mantle material produces a primary melt layer above 410 km and a secondary layer at the depth of equal mantle-melt densities. These layers can merge into a single thick layer under low density contrasts or high upwelling rates, explaining both melt doublets and thick single layers.

DOI： 10.1038/s41467-025-58518-7

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その他リンク： https://www.nature.com/articles/s41467-025-58518-7

Grain boundary diffusion cannot explain the W isotope heterogeneities of the deep mantle 査読

Yihang Peng, Takashi Yoshino, Jie Deng

Nature Communications 16 ( 1 ) 2025年2月

Aluminum and Iron Effects on the Electrical Conductivity of the Dense Hydrous Magnesium Silicate Phase E 査読

Bin Zhao, Izumi Mashino, Takashi Yoshino

Journal of Geophysical Research: Solid Earth 129 ( 10 ) 2024年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Geophysical Union (AGU)

Abstract

The electrical conductivity of pure and Al/Fe‐bearing phase E was measured up to 950 K at 15 GPa using a complex impedance spectroscopy. Pure phase E shows comparable conductivity to that of phase D, and a few orders of magnitude higher than that of phase A and super‐hydrous phase B. Al‐bearing phase E does not exhibit a conductivity difference, while a certain amount of incorporated Fe prominently increases its electrical conductivity by a factor of 4. Unlike the sole substitution 2Al³⁺→Mg²⁺+Si⁴⁺ in phase D and H, H⁺ is likely involved in the substitution. Proton conduction is the dominant conduction mechanism, while small polaron conduction becomes dominant with increasing Fe content. Phase E in subducted slabs at depth of the upper transition zone cannot explain the high electrical conductivity anomalies beneath the Philippine Sea or Northeast China. Other mechanisms such as dehydration of hydrous minerals is needed to account for them.

DOI： 10.1029/2024jb029659

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Probing Deep Hydrogen Using Electrical Conductivity 招待査読

Takashi Yoshino, Geeth Manthilake, Anne Pommier

Elements 20 ( 4 ) 247 - 252 2024年8月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Mineralogical Society of America

Electrical conductivity is perhaps the physical property of rocks that is most sensitive to the presence of hydrogen. Hydrogen enhances conductivity via proton conduction in minerals or by stabilizing highly conductive phases, such as hydrous silicate melts or aqueous fluids. Hydrogen might also be stored in the metallic core. Electrical conductivity measurements in the laboratory can be used to interpret magnetotelluric maps of the mantle in terms of hydrogen content and distribution. In active tectonic settings like subduction zones, anomalously high conductivities have revealed the distribution and migration pathways of H-bearing melts and fluids, illuminating the transport of hydrogen in our planet’s interior.

DOI： 10.2138/gselements.20.4.247

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Electrical conductivity of siderite and the effect of the spin transition of iron 査読

Izumi Mashino, Takashi Yoshino, Takaya Mitsui, Kosuke Fujiwara, Máté Garai, Shigeru Yamashita

Physics and Chemistry of Minerals 51 ( 2 ) 2024年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Science and Business Media LLC

Abstract

We have conducted electrical conductivity measurements of FeCO₃ siderite under high pressure up to 63 GPa in order to understand the nature and effect of iron spin transition and its influence on the geophysical properties of siderite, which is an end-member of major carbonate minerals. The results from Raman and Mössbauer spectroscopic measurements show that the high- to low-spin transition of iron occurs at around 50 GPa in agreement with previous studies. A sharp decrease of the electrical conductivity was also observed at around 50 GP, which is associated with the spin transition in iron. Although the stability of FeCO₃ siderite may be limited under high-temperature conditions along with the mantle geotherm, solid solutions in the MgCO₃-FeCO₃ system, Mg_1-xFe_xCO₃, could be stable up to the pressure-temperature condition of the lowermost mantle. The pressure-temperature range of the spin transition in Mg_1-xFe_xCO₃ is narrower than those of the major lower mantle minerals, ferropericlase and bridgmanite, and thus the drop of the electrical conductivity induced by the spin transition could be clearer under lower mantle conditions. Therefore, the existence of Mg_1-xFe_xCO₃ may affect the observed heterogeneity of electrical conductivity in the mid-lower mantle.

DOI： 10.1007/s00269-024-01283-8

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その他リンク： https://link.springer.com/article/10.1007/s00269-024-01283-8/fulltext.html

A thermally conductive Martian core and implications for its dynamo cessation 査読

Wen-Pin Hsieh, Frédéric Deschamps, Yi-Chi Tsao, Takashi Yoshino, Jung-Fu Lin

Science Advances 10 ( 12 ) 2024年3月

掲載種別：研究論文（学術雑誌）出版者・発行元：American Association for the Advancement of Science (AAAS)

Mars experienced a dynamo process that generated a global magnetic field ~4.3 (or earlier) to 3.6 billion years ago (Ga). The cessation of this dynamo strongly affected Mars’ history and is expected to be linked to thermochemical evolution of Mars’ iron-rich liquid core, which is strongly influenced by its thermal conductivity. Here, we directly measured thermal conductivities of solid iron-sulfur alloys to pressures relevant to the Martian core and temperatures to 1023 Kelvin. Our results show that a Martian core with 16 weight % sulfur has a thermal conductivity of ~19 to 32 Watt meter ⁻¹ Kelvin ⁻¹ from its top to the center, much higher than previously inferred from electrical resistivity measurements. Our modeled thermal conductivity profile throughout the Martian deep-mantle and core indicates a ~4- to 6-fold discontinuity across the core-mantle boundary. The core’s efficient cooling resulting from the depth-dependent, high conductivity diminishes thermal convection and forms thermal stratification, substantially contributing to cessation of Martian dynamo.

DOI： 10.1126/sciadv.adk1087

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Wetting property of Fe‐S melt in solid core: Implication for the core crystallization process in planetesimals 査読

Shiori Matsubara, Hidenori Terasaki, Takashi Yoshino, Satoru Urakawa, Daisuke Yumitori

Meteoritics & Planetary Science 2024年3月

掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley

Abstract

In differentiated planetesimals, the liquid core starts to crystallize during secular cooling, followed by the separation of liquid–solid phases in the core. The wetting property between liquid and solid iron alloys determines whether the core melts are trapped in the solid core or they can separate from the solid core during core crystallization. In this study, we performed high‐pressure experiments under the conditions of the interior of small bodies (0.5–3.0 GPa) to study the wetting property (dihedral angle) between solid Fe and liquid Fe‐S as a function of pressure and duration. The measured dihedral angles are approximately constant after 2 h and decrease with increasing pressure. The dihedral angles range from 30° to 48°, which are below the percolation threshold of 60° at 0.5–3.0 GPa. The oxygen content in the melt decreases with increasing pressure and there are strong positive correlations between the S + O or O content and the dihedral angle. Therefore, the change in the dihedral angle is likely controlled by the O content of the Fe‐S melt, and the dihedral angle tends to decrease with decreasing O content in the Fe‐S melt. Consequently, the Fe‐S melt can form interconnected networks in the solid core. In the obtained range of the dihedral angle, a certain amount of the Fe‐S melt can stably coexist with solid Fe, which would correspond to the “trapped melt” in iron meteorites. Excess amounts of the melt would migrate from the solid core over a long period of core crystallization in planetesimals.

DOI： 10.1111/maps.14149

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Some new insights about electrical discontinuities in the cratonic lithosphere 査読

Baohua Zhang, Hongzhan Fei, Takashi Yoshino, Qunke Xia

Earth-Science Reviews 104592 - 104592 2023年10月

Effect of water on seismic attenuation of the upper mantle: The origin of the sharp lithosphere–asthenosphere boundary 査読

Chao Liu, Takashi Yoshino, Daisuke Yamazaki, Noriyoshi Tsujino, Hitoshi Gomi, Moe Sakurai, Youyue Zhang, Ran Wang, Longli Guan, Kayan Lau, Yoshinori Tange, Yuji Higo

Proceedings of the National Academy of Sciences 120 ( 32 ) 2023年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Proceedings of the National Academy of Sciences

Oceanic lithosphere moves over a mechanically weak layer (asthenosphere) characterized by low seismic velocity and high attenuation. Near mid-ocean ridges, partial melting can produce such conditions because of the high-temperature geotherm. However, seismic observations have also shown a large and sharp velocity reduction under oceanic plates at the lithosphere–asthenosphere boundary (LAB) far from mid-ocean ridges. Here, we report the effect of water on the seismic properties of olivine aggregates in water-undersaturated conditions at 3 GPa and 1,223 to 1,373 K via in-situ X-ray observation using cyclic loading. Our results show that water substantially enhances the energy dispersion and reduces the elastic moduli over a wide range of seismic frequencies (0.5 to 1,000 s). An attenuation peak that appears at higher frequencies (1 to 5 s) becomes more pronounced as the water content increases. If water exists only in the asthenosphere, this is consistent with the observation that the attenuation in the asthenosphere is almost constant over a wide frequency range. These sharp seismic changes at the oceanic LAB far from mid-ocean ridges could be explained by the difference in water content between the lithosphere and asthenosphere.

DOI： 10.1073/pnas.2221770120

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Preliminary results from the new deformation multi-anvil press at the photon factory: Insight into the creep strength of calcium silicate perovskite 査読

Andrew R. Thomson, Yu Nishihara, Daisuke Yamazaki, Noriyoshi Tsujino, Simon A. Hunt, Yumiko Tsubokawa, Kyoko Matsukage, Takashi Yoshino, Tomoaki Kubo, David P. Dobson

Core-Mantle Coevolution: A Multidisciplinary Approach 59 - 73 2023年6月

掲載種別：論文集(書籍)内論文

A D111 deformation multi-anvil press, which is a larger version of the Deformation T-cup, has been installed at beamline NE7A at PF-AR, KEK, Tsukuba, Japan. Using this apparatus, controlled deformation experiments can be performed by independently moving two opposite second-stage anvils in a Kawai-type 6/8 geometry. This allows both pure and simple shear experiments with sample strain rates of 10 -6s -1 to be conducted at pressure and temperature conditions up to at least 27 GPa and 1,700 K. Here, the capabilities of the D111 press are demonstrated using experiments investigating the creep strength of calcium silicate perovskite at mantle conditions. Experiments performed at 13 GPa and 1150-1373 K with quantitative stress and strain rate measurements have allowed preliminary evaluation of the creep strength of calcium silicate perovskite. Observations indicate that under dry and wet conditions samples possess grain sizes of between 0.5 and 10 μm, and undergo deformation in a diffusion creep regime with an apparent activation energy of 364 kJ mol -1 and a stress exponent of 1.28. Qualitative comparison of preliminary results with the properties of mantle silicate minerals including bridgmanite, wadsleyite, and dry olivine indicates that calcium silicate perovskite is very weak, such that it may strongly influence the geodynamics of the deep mantle especially in regions of subduction.

DOI： 10.1002/9781119526919.ch04

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Rheology of hexagonal close‐packed(hcp) iron 査読

Yu Nishihara, Shunta Doi, Noriyoshi Tsujino, Daisuke Yamazaki, Kyoko N. Matsukage, Yumiko Tsubokawa, Takashi Yoshino, Andrew R. Thomson, Yuji Higo, Yoshinori Tange

Journal of Geophysical Research: Solid Earth 128 ( 6 ) e2022JB026165 2023年5月

Hadean mantle oxidation inferred from melting of peridotite under lower-mantle conditions 査読

Hideharu Kuwahara, Ryoichi Nakada, Shintaro Kadoya, Takashi Yoshino, Tetsuo Irifune

Nature Geoscience https://doi.org/10.1038/s41561-023-01169-4 2023年5月

Investigation of Solid‐Solid Transition in Ti and Zr at High Pressure by Electrical Resistivity 査読

Innocent C. Ezenwa, Takashi Yoshino

physica status solidi (b) 2023年4月

Effect of Iron Content on Thermal Conductivity of Ferropericlase: Implications for Planetary Mantle Dynamics 査読

Youyue Zhang, Takashi Yoshino, Masahiro Osako

Geophysical Research Letters 50 ( 7 ) 2023年3月

Interaction of carbonates with peridotite containing iron metal: Implications for carbon speciation in the upper mantle 査読

N.S. Martirosyan, A. Shatskiy, K.D. Litasov, I.S. Sharygin, T. Yoshino

Lithos 428-429 106817 - 106817 2022年11月

Editorial: Water in the Earth’s interior 査読

Hongzhan Fei, Baohua Zhang, Jia Liu, Takashi Yoshino

Frontiers in Earth Science 10 2022年10月

Viscosity of bridgmanite determined by in situ stress and strain measurements in uniaxial deformation experiments 査読

Noriyoshi Tsujino, Daisuke Yamazaki, Yu Nishihara, Takashi Yoshino, Yuji Higo, Yoshinori Tange

Science Advances 8 ( 13 ) 2022年4月

掲載種別：研究論文（学術雑誌）出版者・発行元：American Association for the Advancement of Science (AAAS)

To understand mantle dynamics, it is important to determine the rheological properties of bridgmanite, the dominant mineral in Earth’s mantle. Nevertheless, experimental data on the viscosity of bridgmanite are quite limited due to experimental difficulties. Here, we report viscosity and deformation mechanism maps of bridgmanite at the uppermost lower mantle conditions obtained through in situ stress-strain measurements of bridgmanite using deformation apparatuses with the Kawai-type cell. Bridgmanite would be the hardest among mantle constituent minerals even under nominally dry conditions in the dislocation creep region, consistent with the observation that the lower mantle is the hardest layer. Deformation mechanism maps of bridgmanite indicate that grain size of bridgmanite and stress conditions at top of the lower mantle would be several millimeters and ~10 ⁵ Pa to realize viscosity of 10 ^21–22 Pa·s, respectively. This grain size of bridgmanite suggests that the main part of the lower mantle is isolated from the convecting mantle as primordial reservoirs.

DOI： 10.1126/sciadv.abm1821

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Partial dehydration of brucite and its implications for water distribution in the subducting oceanic slab 査読

Xinzhuan Guo, Takashi Yoshino, Sibo Chen, Xiang Wu, Junfeng Zhang

Geoscience Frontiers 13 ( 2 ) 101342 - 101342 2022年3月