Updated on 2024/10/18

写真a

 
YAMASHITA Shigeru
 
Organization
Institute for Planetary Materials Associate Professor
Position
Associate Professor
Homepage
http://www.misasa.okayama-u.ac.jp/~shigeru/shigeru.html
External link

Degree

  • D.Sc. ( The University of Tokyo )

  • M.S. ( Chiba University )

Research Interests

  • Experimental Petrology

  • Petrology

  • Geology

Research Areas

  • Natural Science / Solid earth sciences

Education

  • The University of Tokyo   理学系研究科   地質学

    1988.4 - 1991.3

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    Country： Japan

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  • Chiba University   理学研究科   地学科

    1986.4 - 1988.3

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    Country： Japan

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  • Chiba University   理学部   地学科

    1982.4 - 1986.3

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Research History

  • Geophysical Laboratory, Carnegie Institution of Washington   Visiting Scientist

    2009.1 - 2009.4

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  • Okayama University   Institute for Planetary Materials   Associate Professor

    2005

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  • Universitaet Hannover   Institut fuer Mineralogie   Alexander von Humboldt Research Fellow

    2001.12 - 2003.2

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  • Okayama University   Institute for Study of the Earth's Interior   Associate Professor

    1998 - 2004

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  • Okayama University   Institute for Study of the Earth's Interior   Research Associate

    1993.10 - 1998.9

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  • The University of Tokyo   Earthquake Research Institute   JSPS Postdoctoral Research Fellow

    1992.4 - 1993.9

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  • Gakushu-in College   Part-time lecturer (Earth Sciences)

    1992.4 - 1993.9

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Professional Memberships

  • Japan Society of High Pressure Science and Technology

    2006

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  • American Geophysical Union

    1991

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  • Volcanological Society of Japan

    1986

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  • Geological Society of Japan

    1985

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Committee Memberships

  • Volcanological Society of Japan   Bulletin of Volcanological Society of Japan, Associate Editor  

    2010 - 2014   

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    Committee type：Academic society

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  • Geological Society of Japan   "The Island Arc", Associate Editor  

    1998 - 2003   

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    Committee type：Academic society

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  • Volcanological Society of Japan   Bulletin of Volcanological Society of Japan, Associate Editor  

    1994 - 1995   

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    Committee type：Academic society

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Papers

  • Hydrogen incorporation mechanism in the lower-mantle bridgmanite Reviewed

    Narangoo Purevjav, Naotaka Tomioka, Shigeru Yamashita, Keiji Shinoda, Sachio Kobayashi, Kenji Shimizu, Motoo Ito, Suyu Fu, Jesse Gu, Christina Hoffmann, Jung-Fu Lin, Takuo Okuchi

    American Mineralogist   109   1036 - 1044   2024.6

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

    DOI： 10.2138/am-2022-8680

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  • Electrical conductivity of siderite and the effect of the spin transition of iron Reviewed

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

    Physics and Chemistry of Minerals   51 ( 2 )   2024.5

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    Publishing type：Research paper (scientific journal)   Publisher：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, Mg1-xFexCO3, could be stable up to the pressure-temperature condition of the lowermost mantle. The pressure-temperature range of the spin transition in Mg1-xFexCO3 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 Mg1-xFexCO3 may affect the observed heterogeneity of electrical conductivity in the mid-lower mantle.

    DOI： 10.1007/s00269-024-01283-8

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    Other Link： https://link.springer.com/article/10.1007/s00269-024-01283-8/fulltext.html

  • Modification for the matrix effect in SIMS-derived water contents of silicate glasses Reviewed

    Kenji Shimizu, Takayuki Ushikubo, Takeshi Kuritani, Naoto Hirano, Shigeru Yamashita

    GEOCHEMICAL JOURNAL   56 ( 6 )   223 - 230   2022

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geochemical Society of Japan  

    Analyses of elemental abundances by secondary ion mass spectrometry (SIMS) require matrix-matched standard samples to account for the matrix effect on correction factors. This requirement makes it difficult to obtain accurate results for geological samples of variable chemistry. In this study, we prepared 39 volcanic glasses of foiditic, basaltic, basaltic andesitic, rhyolitic and pure SiO2 compositions, including synthetic samples and natural samples collected from the deep seafloor. The measured H2O contents of these samples were in the range 0.02-4.8 wt%. We showed that calibration curves (H2O content vs. (OH-)-O-16/Si-30(SIMS)- ratio) differed according to the composition of the volcanic glasses. Our results demonstrated that for a particular (OH)-O-16/Si-30(SIMS) ratio, water content could differ by up to a factor of five, depending on the composition of the volcanic glass. Although the correction factor (the slope of the calibration curve for water [H2O/((OH-)-O-16/Si-30(-))(SIMS)]) was weakly correlated with SiO2 content, we identified a stronger correlation with the molar weight (g mol(-1), on a one-oxygen mole basis) of the silicate glasses. Our results suggest that modification of the correction factor for the matrix effect on SIMS-based H2O content of volcanic glasses according to their molar weights provides more accurate water contents of silicate glasses, regardless of their chemical composition and water content and without the need for a series of standard glasses of known water contents.

    DOI： 10.2343/geochemj.gj22019

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  • Nonlinear effects of hydration on high-pressure sound velocities of rhyolitic glasses Reviewed

    Jesse T. Gu, Suyu Fu, James E. Gardner, Shigeru Yamashita, Takuo Okuchi, Jung-Fu Lin

    American Mineralogist   106 ( 7 )   1143 - 1152   2021.7

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

    <title>Abstract</title>
    Acoustic compressional and shear wave velocities (VP, VS) of anhydrous (AHRG) and hydrous rhyolitic glasses (HRG) containing 3.28 wt% (HRG-3) and 5.90 wt% (HRG-6) total water concentration (H2Ot) have been measured using Brillouin light scattering (BLS) spectroscopy up to 3 GPa in a diamond-anvil cell at ambient temperature. In addition, Fourier-transform infrared (FTIR) spectroscopy was used to measure the speciation of H2O in the glasses up to 3 GPa. At ambient pressure, HRG-3 contains 1.58 (6) wt% hydroxyl groups (OH–) and 1.70 (7) wt% molecular water (H2Om) while HRG-6 contains 1.67 (10) wt% OH– and 4.23 (17) wt% H2Om where the numbers in parentheses are ±1σ. With increasing pressure, very little H2Om, if any, converts to OH– within uncertainties in hydrous rhyolitic glasses such that HRG-6 contains much more H2Om than HRG-3 at all experimental pressures. We observe a nonlinear relationship between high-pressure sound velocities and H2Ot, which is attributed to the distinct effects of each water species on acoustic velocities and elastic moduli of hydrous glasses. Near ambient pressure, depolymerization due to OH– reduces VS and G more than VP and KS. VP and KS in both anhydrous and hydrous glasses decrease with increasing pressure up to ~1–2 GPa before increasing with pressure. Above ~1–2 GPa, VP and KS in both hydrous glasses converge with those in AHRG. In particular, VP in HRG-6 crosses over and becomes higher than VP in AHRG. HRG-6 displays lower VS and G than HRG-3 near ambient pressure, but VS and G in these glasses converge above ~2 GPa. Our results show that hydrous rhyolitic glasses with ~2–4 wt% H2Om can be as incompressible as their anhydrous counterpart above ~1.5 GPa. The nonlinear effects of hydration on high-pressure acoustic velocities and elastic moduli of rhyolitic glasses observed here may provide some insight into the behavior of hydrous silicate melts in felsic magma chambers at depth.

    DOI： 10.2138/am-2021-7597

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  • Precometary organic matter: A hidden reservoir of water inside the snow line Reviewed

    Hideyuki Nakano, Naoki Hirakawa, Yasuhiro Matsubara, Shigeru Yamashita, Takuo Okuchi, Kenta Asahina, Ryo Tanaka, Noriyuki Suzuki, Hiroshi Naraoka, Yoshinori Takano, Shogo Tachibana, Tetsuya Hama, Yasuhiro Oba, Yuki Kimura, Naoki Watanabe, Akira Kouchi

    Scientific Reports   10 ( 1 )   2020.12

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

    <title>Abstract</title>The origin and evolution of solar system bodies, including water on the Earth, have been discussed based on the assumption that the relevant ingredients were simply silicates and ices. However, large amounts of organic matter have been found in cometary and interplanetary dust, which are recognized as remnants of interstellar/precometary grains. Precometary organic matter may therefore be a potential source of water; however, to date, there have been no experimental investigations into this possibility. Here, we experimentally demonstrate that abundant water and oil are formed via the heating of a precometary-organic-matter analog under conditions appropriate for the parent bodies of meteorites inside the snow line. This implies that H2O ice is not required as the sole source of water on planetary bodies inside the snow line. Further, we can explain the change in the oxidation state of the Earth from an initially reduced state to a final oxidized state. Our study also suggests that petroleum was present in the asteroids and is present in icy satellites and dwarf planets.

    DOI： 10.1038/s41598-020-64815-6

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    Other Link： http://www.nature.com/articles/s41598-020-64815-6

  • Magma generation conditions at the Akita-Komagatake volcano, Northeast Japan arc: Implications of across-arc variations in mantle melting parameters Reviewed

    Kuritani, T, Kanai, C, Yamashita, S, Nakagawa, M

    Lithos   348-349   105197 - 105197   2019.12

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

    Akita-Komagatake is an active volcano in the Northeast Japan arc with a slab depth (H) of ~110 km. In this study, magma generation conditions were estimated for basaltic products from the volcano to examine the thermal structure of the sub-arc mantle and the across-arc variations in the parameters related to magma genesis. The studied basalts have the highest MgO content (~6 wt%) among the products from the volcano and contain ~15% plagioclase phenocrysts, ~5% olivine phenocrysts, and <1% pyroxene phenocrysts. The water content of the melt was estimated to be ~4 wt% by melt inclusions in the phenocrysts using plagioclase–melt hygrometry. Multi-component thermodynamic analyses suggest that the primary magma was generated by ~14% melting of the source mantle with ~0.5 wt% H O at ~1275 °C and ~1.3 GPa. The estimated pressure condition of ~1.3 GPa coincides well with the low-velocity anomaly observed in the mantle at ~40 km depth beneath the volcano. By comparing the results from Akita-Komagatake to the published results of the frontal-arc Iwate volcano (H = ~90 km) and the rear-arc Sannome-gata volcano (H = ~150 km), which are arranged along a cross-arc line in the Northeast Japan arc, we found that the pressure conditions of the magma generation are ~1.3 GPa at both Iwate and Akita-Komagatake, which are significantly lower than the ~1.8 GPa at the rear-arc Sannome-gata volcano. The source mantle temperature of ~1275 °C at ~1.3 GPa beneath Akita-Komagatake is higher than the ~1250 °C at ~1.3 GPa beneath Iwate, which suggests that the ascending flow of the mantle wedge corner flow may reach the shallowest levels beneath Akita-Komagatake. It was also demonstrated that the depth at which fluid was released from the subducting slab tends to increase for the volcanoes with increasing H. 2

    DOI： 10.1016/j.lithos.2019.105197

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  • Evolution, hydrothermal assimilation, and ascent of magma inferred from volatile contents in MORB glasses: An example from thick lava pile at IODP Site 1256 Reviewed

    Takashi Sano, Shigeru Yamashita

    Lithos   346-347   105143 - 105143   2019.11

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

    A continuous section through an 811 m-thick lava pile of mid-ocean ridge basalts at Integrated Ocean Drilling Program Site 1256 provides important constraints on the variation with depth of volatile element (H2O, CO2, S and Cl) contents in fresh matrix glasses to understand evolution of magma, condition of magma ascent, and degree of hydrothermal assimilation. The lava pile is divided into two groups based on eruption location: off-axis basalts of upper portion (250-534 m beneath seafloor, mbsf) and on-axis basalts of lower portion (534-1061 mbsf). The lava pile is composed of pillow, sheet, and massive lavas that include thin (<2 m) hyaloclastite intervals.Variations of H2O and major element contents in Site 1256 matrix glasses can be explained by fractional crystallization of one primitive basalt (MgO, 7.7 wt%) at the pressure of a melt lens (top of axial magma chamber). CO2/Nb and S/Dy in a large majority of fresh matrix glasses are lower than undegassed ratios, and these facts indicate that CO2 and S losses occurred during differentiation within the melt lens and/or magma transport to the seafloor. Saturation pressures calculated from dissolved CO2 and H2O contents give a wide range of pressures from sea floor (similar to 25 MPa) to axial magma chamber (similar to 60 MPa). Many off-axis glasses have saturation pressures of seafloor, but on-axis glasses have high saturation pressures up to axial magma chamber depths. The saturation pressures of off-axis glasses decrease with decreasing depth (i.e., with increasing distance from the axis). These observations indicate that the many off-axis glasses were highly degassed because their source magmas travelled for long rime periods from melt lens to off-axis seafloor locations. On the other hand, on-axis glasses were less degassed because magma transport times to on-axis locations were shorter than those for off-axis locations. The most distinctive characteristic for the Site 1256 glasses is their higher Cl/Nb than any other mid-ocean ridge basalt glasses. The strong Cl enrichment is explained by assimilation of hydrothermal brines. Beneath Site 1256, the melt lens was very shallow (<1.2 km) and hydrothermal circulation of high-salinity brines with variable salinities would reach easily to the melt lens. (C) 2019 Elsevier B.V. All rights reserved.

    DOI： 10.1016/j.lithos.2019.07.010

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  • An automated laser fluorination technique for high-precision analysis of three oxygen isotopes in silicates Reviewed

    Nak Kyu Kim, Minoru Kusakabe, Changkun Park, Jong Ik Lee, Keisuke Nagao, Yuma Enokido, Shigeru Yamashita, Sun Young Park

    Rapid Communications in Mass Spectrometry   33 ( 7 )   641 - 649   2019.4

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

    RationaleThe three oxygen isotopes in terrestrial/extraterrestrial silicates can provide geochemical and cosmochemical information about their origin and secondary processes that result from isotopic exchange. A laser fluorination technique has been widely used to extract oxygen from silicates for O-17 and O-18 measurements by isotope ratio mass spectrometry. Continued improvement of the techniques is still important for high-precision measurement of oxygen-isotopic ratios.MethodsWe adopted an automated lasing technique to obtain reproducible fluorination of silicates using a CO2 laser-BrF5 fluorination system connected online to an isotope ratio mass spectrometer. The automated lasing technique enables us to perform high-precision analysis of the three oxygen isotopes of typical reference materials (e.g., UWG2 garnet, NBS28 quartz and San Carlos olivine) and in-house references (mid-ocean ridge basalt glass and obsidian). The technique uses a built-in application of laser control with which the laser power can be varied in a programmed manner with a defocused beam which is in a fixed position.ResultsThe oxygen isotope ratios of some international reference materials analyzed by the manual lasing technique were found to be isotopically lighter with wider variations in O-18 values, whereas those measured by the automated lasing technique gave better reproducibility (less than 0.2, 2SD). The O-17 values, an excess of the O-17 value relative to the fractionation line, also showed high reproducibility (+/- 0.02 parts per thousand, 2SD).ConclusionsThe system described herein provides high-precision O-17 and O-18 measurements of silicate materials. The use of the automated lasing technique followed by careful and controlled purification procedures is preferred to achieve satisfactory isotopic ratio results.

    DOI： 10.1002/rcm.8389

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  • In situ spectroscopic study of water speciation in the depolymerized Na2Si2O5 melt Reviewed

    Nadezda Chertkova, Shigeru Yamashita

    Chemical Geology   409   149 - 156   2015.8

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    DOI： 10.1016/j.chemgeo.2015.05.012

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  • High-pressure synthesis and application of a 13C diamond pressure sensor for experiments in a hydrothermal diamond anvil cell Reviewed

    Nadezda Chertkova, Shigeru Yamashita, Eiji Ito, Akira Shimojuku

    Mineralogical Magazine   78 ( 7 )   1677 - 1685   2014.12

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

    <title>Abstract</title>Polycrystalline, cubic 13C diamond was synthesized from amorphous carbon in the Kawai-type multianvil apparatus at 21 GPa and at a temperature greater than 2350ºC. The polycrystalline diamond was homogeneous with a small grain size (10–20 μm) and a sharp Raman peak, and thereby was suitable as a pressure sensor for the experiments in a hydrothermal diamond anvil cell. Pressure- and temperature-dependence of the Raman shift of the synthesized 13C diamond was investigated in situ at simultaneous high pressures and high temperatures in the hydrothermal diamond anvil cell, using the ruby fluorescence line, quartz Raman shift and H2O phase transitions as pressure references. It was observed that the frequency shift with pressure is independent of temperature and <italic>vice versa</italic> up to 500ºC and 4.2 GPa. The present study indicates that the 13C diamond Raman shift can be used for pressure determination with an accuracy better than ±0.3 GPa under the conditions examined.

    DOI： 10.1180/minmag.2014.078.7.11

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  • Speciation of reduced C–O–H volatiles in coexisting fluids and silicate melts determined in-situ to ∼1.4GPa and 800°C Reviewed

    Bjorn O. Mysen, Shigeru Yamashita

    Geochimica et Cosmochimica Acta   74 ( 15 )   4577 - 4588   2010.8

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

    DOI： 10.1016/j.gca.2010.05.004

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  • Nominally hydrous magmatism on the Moon Reviewed

    F. M. McCubbin, A. Steele, E. H. Hauri, H. Nekvasil, S. Yamashita, R. J. Hemley

    Proceedings of the National Academy of Sciences   107 ( 25 )   11223 - 11228   2010.6

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of the National Academy of Sciences  

    DOI： 10.1073/pnas.1006677107

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  • Strength contrast between plagioclase and olivine at water-rich Moho depths Reviewed

    Shintaro AZUMA, Ikuo KATAYAMA, Ken-ichi HIRAUCHI, Shigeru YAMASHITA

    Journal of Mineralogical and Petrological Sciences   105 ( 5 )   286 - 290   2010

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

    DOI： 10.2465/jmps.100618b

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  • Electrical conductivity of wadsleyite as a function of temperature and water content Reviewed

    M.A.G.M. Manthilake, Takuya Matsuzaki, Takashi Yoshino, Shigeru Yamashita, Eiji Ito, Tomoo Katsura

    Physics of the Earth and Planetary Interiors   174 ( 1-4 )   10 - 18   2009.5

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

    DOI： 10.1016/j.pepi.2008.06.001

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  • Solubility and solution mechanisms of NOH volatiles in silicate melts at high pressure and temperature - amine groups and hydrogen fugacity Reviewed

    B. O. Mysen, S. Yamashita, N. Chertkova

    American Mineralogist   93 ( 11-12 )   1760 - 1770   2008.11

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

    DOI： 10.2138/am.2008.2879

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  • Water speciation in sodium silicate glasses based on NIR and NMR spectroscopy Reviewed

    Shigeru Yamashita, Harald Behrens, Burkhard C. Schmidt, Ray Dupree

    Chemical Geology   256 ( 3-4 )   231 - 241   2008.11

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

    DOI： 10.1016/j.chemgeo.2008.06.029

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  • Water speciation in hydrous sodium tetrasilicate and hexasilicate melts: Constraint from high temperature NIR spectroscopy Reviewed

    Harald Behrens, Shigeru Yamashita

    Chemical Geology   256 ( 3-4 )   306 - 315   2008.11

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    DOI： 10.1016/j.chemgeo.2008.06.053

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  • Origin of compositional heterogeneity within Tochinoki andesitic lava flow from the western part of Aso caldera Reviewed

    MIYOSHI Masaya, HASENAKA Toshiaki, MORI Yasushi, YAMASHITA Shigeru

    Japanese Magazine of Mineralogical and Petrological Sciences   36 ( 1 )   15 - 29   2007

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    Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

    A composite lava flow is found in core samples of Tochinoki lava unit, one of the post-caldera volcanic products distributed in the western part of Aso caldera. Including core and surface outcrop samples, Tochinoki lava shows two compositionally different lava types. One is silicic (SiO2 63-66 wt%) and phenocryst-rich (8-16 vol%), and the other is mafic (SiO2 60-62 wt%) and phenocryst-poor (< 7 vol%). Mass balance calculation and trace element modeling show that the compositional variation found among Tochinoki core samples are explained by the fractional crystallization of plagioclase, clinopyroxene, orthopyroxene and magnetite phenocrysts from the most mafic lava. Tochinoki composite lava flow is probably produced by the viscous segregation of compositionally distinct magmas ascending simultaneously in the conduit as proposed by Inyo Obsidian Dome drilling project. Bulk rock composition and mineral chemistry indicate that mafic-silicic pairs observed in Tochinoki core samples are different from those in outcrop samples. This difference probably suggests the existence of contemporaneous multiple flow units in the Tochinoki lava unit.

    DOI： 10.2465/gkk.36.15

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    Other Link： https://jlc.jst.go.jp/DN/JALC/00291363587?from=CiNii

  • Hydrous olivine unable to account for conductivity anomaly at the top of the asthenosphere Reviewed

    Takashi Yoshino, Takuya Matsuzaki, Shigeru Yamashita, Tomoo Katsura

    Nature   443 ( 7114 )   973 - 976   2006.10

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

    DOI： 10.1038/nature05223

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    Other Link： http://www.nature.com/articles/nature05223

  • Melt inclusion analysis of the Unzen 1991–1995 dacite: implications for crystallization processes of dacite magma Reviewed

    Koshi Nishimura, Tatsuhiko Kawamoto, Tetsuo Kobayashi, Takeshi Sugimoto, Shigeru Yamashita

    Bulletin of Volcanology   67 ( 7 )   648 - 662   2005.8

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

    DOI： 10.1007/s00445-004-0400-8

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    Other Link： http://link.springer.com/article/10.1007/s00445-004-0400-8/fulltext.html

  • Experimental petrology of basement lavas from Ocean Drilling Program Leg 192: implications for differentiation processes in Ontong Java Plateau magmas Reviewed

    Takashi Sano, Shigeru Yamashita

    Geological Society, London, Special Publications   229 ( 1 )   185 - 218   2004

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geological Society of London  

    <title>Abstract</title>Melting relations of the basement lavas drilled from the Ontong Java Plateau during ODP Leg 192 were experimentally determined at 1150–1250°C and 0.1–190 MPa under the oxygen fugacity along the fayalite-magnetite-quartz (FMQ) and cobalt-cobalt oxide (CCO) buffers. The basement lavas were classified into two types according to phenocryst assemblage and whole-rock composition: one type is low in MgO (&lt;8 wt%) and olivine + plagioclase + augite-phyric (Kwaimbaita type); and the other is rich in MgO (&gt;8 wt%) and olivine-phyric (Kroenke type). One sample was chosen from each type as a starting material of the melting experiments. The experimental results demonstrate that the variations in phenocryst assemblage and whole-rock composition in the basement lavas can be modelled adequately by fractional crystallization processes in a shallow magma chamber (&lt;6 km in depth). The experimentally determined mineral-melt equilibria, in combination with detailed petrographical investigation, revealed that the vast majority of phenocrysts are in equilibrium with their host magma composition, but some are not. The latter include unusually An-rich parts of plagioclase phenocrysts in the Kwaimbaita-type lavas. These An-rich parts probably crystallized in a mushy boundary layer along the wall of the magma chamber where the melt was relatively rich in H2O. Some olivine phenocrysts in the Kroenke-type lavas show reverse zoning, with core compositions that can be in equilibrium with the Kwaimbaita-type magmas. The cores of these olivine phenocrysts were most probably assimilated from a solidified pile of the Kwaimbaita-type lavas when the Kroenke-type magmas ascended through it.

    DOI： 10.1144/gsl.sp.2004.229.01.12

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  • Mid infrared throughput with 5 um aperture for H2O determination of an andesitic glass: Comparison of synchrotron radiation source at SPring-8 with conventional light sources. Reviewed

    Tatsuhiko Kawamoto, Hiroyuki Kagi, Shigeru Yamashita, Tomoko Handa, Kyoko Matsukage, Yuka Ikemoto, Taro Moriwaki, Hiroaki Kimura

    GEOCHEMICAL JOURNAL   37 ( 2 )   253 - 259   2003

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geochemical Society of Japan  

    DOI： 10.2343/geochemj.37.253

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  • Experimental Study of the Effect of Temperature on Water Solubility in Natural Rhyolite Melt to 100 MPa Reviewed

    S. Yamashita

    Journal of Petrology   40 ( 10 )   1497 - 1507   1999.10

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    Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

    DOI： 10.1093/petroj/40.10.1497

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  • Preparation of thin glass wafer for infrared spectroscopy Reviewed

    Ogo, Y, Yamashita, S

    Bulletin of the Volcanological Society of Japan   44 ( 5 )   251 - 254   1999

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    Language：Japanese   Publisher：Volcanological Society of Japan  

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  • Infrared spectroscopy of hydrous glasses of arc magma compositions. Reviewed

    Shigeru Yamashita, Toshihiro Kitamura, Minoru Kusakabe

    GEOCHEMICAL JOURNAL   31 ( 3 )   169 - 174   1997

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    Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geochemical Society of Japan  

    DOI： 10.2343/geochemj.31.169

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  • Temporal variation in primary magma compositions in the northeast Japan Arc Reviewed

    Shigeru Yamashita, Yoshiyljki Tatsumi, Susumu Nohda

    The Island Arc   5 ( 3 )   276 - 288   1996.9

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

    DOI： 10.1111/j.1440-1738.1996.tb00032.x

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  • Thermal and geochemical evolution of the mantle wedge in the northeast Japan arc: 2. Contribution from geochemistry Reviewed

    Shigeru Yamashita, Yoshiyuki Tatsumi

    Journal of Geophysical Research: Solid Earth   99 ( B11 )   22285 - 22293   1994.11

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    Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

    DOI： 10.1029/94jb00282

    CiNii Article

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  • Thermal and geochemical evolution of the mantle wedge in the northeast Japan arc: 1. Contribution from experimental petrology Reviewed

    Yoshiyuki Tatsumi, Yoshitsugu Furukawa, Shigeru Yamashita

    Journal of Geophysical Research: Solid Earth   99 ( B11 )   22275 - 22283   1994.11

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

    DOI： 10.1029/94jb00283

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  • Experimental petrology of basement basaltic rocks from ODP Leg127/128 Sites 794 and 797, Japan Sea Reviewed

    Yamashita, S, Fujii, T

    Proceedings of the Ocean Drilling Program, Scientific Results   127/128 ( Pt.2 )   891 - 898   1992

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

    CiNii Article

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  • 40Ar-39Ar analyses of volcanic rocks recovered from the Japan Sea floor by Leg127/128: constraint on the formation age of the Japan Sea Reviewed

    Kaneoka, I, Takigami, Y, Takaoka, N, Yamashita, S, Tamaki, K

    Proceedings of the Ocean Drilling Program, Scientific Results   127/128 ( Pt.2 )   819 - 836   1992

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  • Geochemistry of Leg127 basalts: implication for the evolutionary history of the Japan Sea backarc basin Reviewed

    Nohda, S, Tatsumi, Y, Yamashita, S, Fujii, T

    Proceedings of the Ocean Drilling Program, Scientific Results   127/128 ( Pt.2 )   899 - 904   1992

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    Language：English   Publishing type：Research paper (scientific journal)  

    CiNii Article

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  • Origin of felsic magmas at Meiyo-Daini seamount in Yamato backarc basin, Japan Sea Reviewed

    Shigeru Yamashita

    Bulletin of Volcanological Society of Japan   36 ( 4 )   431 - 441   1991

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    Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Volcanological Society of Japan  

    Detailed petrological study was made on the felsic volcanic rocks dredged from the Meiyo-Daini seamount in the Yamato backarc basin, Japan Sea. The Meiyo-Daini seamount was created as a subaqueous volcanic edifice together with the other seamounts in the basin at the latest stage of backarc rifting. The issued felsic volcanic rocks contain mafic inclusions with varying sizes and textures. Mass balance calculation suggests that the host felsic magmas were differentiated from the mafic parent by fractionation of amphibole and plagioclase feldspar. On the other hand, the derivative felsic magmas have phenocryst assemblages which are different from that expected from the fractional crystallization model. These puzzling phenocryst assemblages are probable reflection of the following magma plumbing system; the felsic magmas were produced in deep-seated magma reservoir(s) (>2 kbar;>ca. 7 km below surface), and then ascent to crystallize the present phenocryst assemblages consuming the crystals relevant to the differentiation. The mafic inclusions could be less differentiated portion of the deep-seated magma reservoir(s). The inferred magma plumbing system is consistent with the fact that the Yamato backarc basin is underlain by anomalously deep seismic Moho.

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▼display all

MISC

  • Micro-IR spectroscopy of water-bearing silicate glasses: an application to experimental petrology Invited

    Shigeru Yamashita

    41 ( 2 )   15 - 18   1999

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    Authorship：Lead author,　Corresponding author   Language：Japanese  

    CiNii Article

    CiNii Books

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  • Petrology of basement basaltic rocks from ODP Leg 127 sites, Japan Sea: its implication for transportation of wedge mantle materials during backarc spreading Invited

    Shigeru Yamashita

    Chikyu   6   229 - 232   1992

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    Authorship：Lead author,　Corresponding author   Language：Japanese  

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  • Petrology of volcanic rocks from seamounts in Yamato backarc basin, Japan Sea Invited

    Shigeru Yamashita

    Kaiyo Kagaku   20   664 - 669   1988

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    Authorship：Lead author,　Corresponding author   Language：Japanese  

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Presentations

  • Comparative analysis of natural jarosite and alunite-bearing rocks: exploring mineralogical, textural, and spectral insights into diverse geological settings

    F. Cao, R.L. Flemming, M.R.M. Izawa, T. Yokoyama, S. Yamashita, Y. Masuda, I. Gautam

    55th Lunar and Planetary Science Conference 

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    Event date： 2024.3.11 - 2024.3.15

    Language：English   Presentation type：Poster presentation  

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  • Pressure insensitive speciation of water in albitic melts determined in-situ at high pressures and high temperatures Invited

    Shigeru Yamashita

    Bjorn Mysen’s Retirement Symposium  2023.11.3 

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    Event date： 2023.11.2 - 2023.11.3

    Language：English   Presentation type：Oral presentation (invited, special)  

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  • 花崗岩の非平衡溶融に伴うアルカリ長石の組織・組成変化

    川畑 博, 山下 茂

    日本鉱物科学会2023年年会  2023 

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    Event date： 2023.9.14 - 2023.9.16

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • Pressure dependence of water speciation in albitic melts determined in-situ at high pressures and high temperatures International conference

    Shigeru Yamashita

    Japan Geoscience Union Meeting 2022  2022.5.31  Japan Geoscience Union

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    Event date： 2022.5.22 - 2022.6.3

    Language：English   Presentation type：Poster presentation  

    Venue：Makuhari, Chiba   Country：Japan  

  • Pressure dependence of water speciation in albitic melts determined in-situ at high pressures and high temperatures

    Shigeru Yamashita

    Japan Geoscience Union Meeting 2022  2022.5.31 

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    Event date： 2022.5.22 - 2022.6.3

    Language：English   Presentation type：Poster presentation  

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  • Organic compounds as fluid sources in the DAC experiments involving volatiles International conference

    Nadezda Chertkova, Tadashi Kondo, Shigeru Yamashita

    Japan Geoscience Union Meeting 2022  2022.5.29  Japan Geoscience Union

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    Event date： 2022.5.22 - 2022.6.3

    Language：English   Presentation type：Poster presentation  

    Venue：Makuhari, Chiba   Country：Japan  

  • Organic compounds as fluid sources in the DAC experiments involving volatiles

    Nadezda Chertokova, Takashi Kondo, Shigeru Yamashita

    Japan Geoscience Union Meeting 2022  2022.5.29 

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    Event date： 2022.5.22 - 2022.6.3

    Language：English   Presentation type：Poster presentation  

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  • Hydrothermal ammoniation of chondrites: Implications for Ceres

    Izawa, M.R.M, Koutoula, E, Stancu, M.-N, Yamashita, S, Okuchi, T, Cloutis, E. A, Jephcoat, A. P, Reddy, V

    52nd Lunar and Planetary Science Conference  2021.3 

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    Event date： 2021.3.15 - 2021.3.19

    Language：English   Presentation type：Poster presentation  

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  • Verification and correction of matrix effect on water concentration of volcanic glasses by SIMS

    Shimizu, K, Ushikubo, T, Kuritani, T, Hirano, N, Yamashita, S

    Goldschmidt Virtual 2020  2020.6.24 

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    Event date： 2020.6.21 - 2020.6.26

    Language：English   Presentation type：Poster presentation  

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  • Anomalous elasticity of dry and hydrous rhyolitic glasses up to 3 GPa

    Jesse Gu, Suyu Fu, James E. Gardner, Shigeru Yamashita, Takuo Okuchi, Jung-Fu Lin

    American Geophysical Union 2019 Fall Meeting  2019.12.12 

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    Event date： 2019.12.9 - 2019.12.13

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  • 揮発性元素から推測した中央海嶺玄武岩マグマの分化と上昇過程

    佐野貴司, 山下茂

    日本火山学会2019年度秋季大会  2019.9.26 

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    Event date： 2019.9.25 - 2019.9.27

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • Experimental study of the effect of composition on water solubility in natural silicate melts

    Shigeru Yamashita

    Japan Geoscience Union Meeting 2019  2019.5 

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    Event date： 2019.5.25 - 2019.5.30

    Language：English   Presentation type：Oral presentation (general)  

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  • Experimental modeling of eclogite and C-O-H fluid interaction in the subduction zones

    Nadezda Chertkova, Shigeru Yamashita, Hiroaki Ohfuji, Tetsuo Irifune, Hirokazu Kadobayashi, Yoshitaka Yamamoto

    Japan Geoscience Union Meeting 2019  2019.5 

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    Event date： 2019.5.25 - 2019.5.30

    Language：English   Presentation type：Oral presentation (general)  

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  • Electrical Conductivity Measurement of rhyolite and andesite glasses

    Haraguchi, Y, Yoshino, T, Yamashita, S, Nakamoto, M, Suzuki, M, Fuji-ta, K, Tanaka, T

    Joint Symposium of Misasa 2019 and CMC  2019.3.21 

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    Event date： 2019.3.18 - 2019.3.21

    Language：English   Presentation type：Oral presentation (general)  

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  • Probing basalt–5.75H2O–CH4 system by in situ vibrational spectroscopy

    Chertkova, N, Yamashita, S, Ohfuji, H, Irifune, T, Kadobayashi, H, Yamamoto, Y

    Joint Symposium of Misasa 2019 and CMC  2019.3.20 

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    Event date： 2019.3.18 - 2019.3.21

    Language：English   Presentation type：Oral presentation (general)  

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  • In situ vibrational spectroscopy of the dehydration of talc in the system MgO-SiO2-H2O

    Shigeru Yamashita

    Joint Symposium of Misasa 2019 and CMC  2019.3.19 

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    Event date： 2019.3.18 - 2019.3.21

    Language：English   Presentation type：Oral presentation (general)  

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  • Dehydration kinetics of talc in the system MgO-SiO2-H2O probed in-situ by vibrational spectroscopy at high pressure and hight temperature

    Shigeru Yamashita

    Japan Geoscience Union Meeting 2018  2018.5.20 

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    Event date： 2018.5.20 - 2018.5.24

    Language：English   Presentation type：Oral presentation (general)  

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  • Determination of water content of natural talc: application to a recipe for hydrogen manometry

    Shigeru Yamashita

    JpGU-AGU joint meeting 2017  2017.5.22 

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    Event date： 2017.5.20 - 2017.5.24

    Language：English   Presentation type：Poster presentation  

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  • The effect of magma density, assimilation, and eruption location on volatile and halogen contents in MORB glasses: an example from IODP site 1256

    Takashi Sano, Shigeru Yamashita

    Japan Geoscience Union Meeting 2016  2016.5 

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    Event date： 2016.5.22 - 2016.5.26

    Language：English   Presentation type：Oral presentation (general)  

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  • Solution mechanism of water in depolymerized silicate melts

    Nadezda Chertkova, Shigeru Yamashita

    Japan Geoscience Union Meeting 2014  2014.5 

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    Event date： 2014.4.28 - 2014.5.2

    Language：English   Presentation type：Poster presentation  

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  • Determination of water speciation in hydrous Na2Si2O5 melt at high temperature and high pressure

    Nadezda Chertkova, Shigeru Yamashita

    IAVCEI 2013 Scientific Assembly  2013.7 

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    Event date： 2013.7.20 - 2013.7.24

    Language：English   Presentation type：Poster presentation  

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  • Experimental determinations of water solubility in the Shinmoe-dake 2011 dacite melt to 150 MPa

    山下茂, Chertkova, N.

    Japan Geoscience Union Meeting 2013  2013.5 

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    Event date： 2013.5.19 - 2013.5.24

    Language：Japanese   Presentation type：Poster presentation  

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  • Speciation of N-O-H volatiles in coexisting fluids and silicate melts determined in-situ at high pressures and high temperatures under reducing conditions

    Yamashita, S, Mysen, B.O

    Joint Symposium of Misasa-2012 and Geofluid-2  2012.3 

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    Event date： 2012.3.17 - 2012.3.21

    Language：English   Presentation type：Poster presentation  

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  • Synthesis of 13C diamond pressure marker for in-situ experiment

    Chertkova, N, Yamashita, S, Ito, E, Shimojuku, A

    Joint Symposium of Misasa-2012 and Geofluid-2  2012.3 

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    Event date： 2012.3.17 - 2012.3.21

    Language：English   Presentation type：Poster presentation  

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  • Optical pressure sensors for DAC experiment: application in high-pressure studies

    Chertkova, N, Yamashita, S

    Japan Geoscience Union Meeting 2011  2011.5 

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    Event date： 2011.5.22 - 2011.5.27

    Language：English   Presentation type：Poster presentation  

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  • Pressure and temperature dependence of 13C diamond Raman shift determined in-situ to 1.27GPa and 800°C: application to pressure sensor for high temperature diamond anvil cell experiments

    Yamashita, S, Mysen, B.O.

    Japan Geoscience Union Meeting 2011  2011.5 

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    Event date： 2011.5.21 - 2011.5.27

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • Speciation and solubility behaviors of C-O-H-N volatiles in coexisting melts and fluids at high pressure and temperature with controlled hydrogen fugacity. Invited

    Mysen, B.O, Fogel, M, Yamashita, S

    2010 Western Pacific Geophysics Meeting  2010.6 

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    Event date： 2010.6.22 - 2010.6.25

    Language：English   Presentation type：Oral presentation (invited, special)  

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  • Speciation of N-O-H Volatiles in Coexisting Fluids and Silicate Melts Determined In-situ at High Pressures and High Temperatures Under Reducing Conditions. Invited

    Yamashita, S, Mysen, B.O

    2010 Western Pacific Geophysics Meeting  2010.6 

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    Event date： 2010.6.22 - 2010.6.25

    Language：English   Presentation type：Oral presentation (invited, special)  

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  • Speciation and solubility of reduced C-O-H fluids in coexisting fluids and silicate melts determined in-situ to 1.45 GPa and 800˚C.

    Mysen, B.O, Yamashita, S, Fogel, M

    Goldschmidt Conference 2010  2010.6 

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    Event date： 2010.6.13 - 2010.6.18

    Language：English   Presentation type：Oral presentation (general)  

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  • Structure and Properties of Silicate-Saturated Fluids in the System Na2O-Al2O3-SiO2-H2O Determined in situ at High Temperature and Pressure.

    Mysen, B.O, Yamashita, S

    Goldschmidt Conference 2010  2010.6 

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    Event date： 2010.6.13 - 2010.6.18

    Language：English   Presentation type：Oral presentation (general)  

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  • Speciation of N-O-H volatiles in coexisting fluids and silicate melts determined in-situ under reduced conditions

    Yamashita, S, Mysen, B.O

    Japan Geoscience Union Meeting 2010  2010.5 

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    Event date： 2010.5.23 - 2010.5.28

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  • From N2 to NHx groups in silicate melts governed by fH2 at high pressure and temperature.

    Mysen, B.O, Yamashita, S, Chertkova, N

    Goldschmidt Conference 2008  2008.6 

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    Event date： 2008.6.13 - 2008.6.18

    Language：English   Presentation type：Oral presentation (general)  

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  • In situ observation of liquids at high temperature and high pressure.

    Yamashita, S, Kanzaki, M, Mysen, B. O

    International Symposium MISASA-3, Origin, Evolution and Dynamics of the Earth  2008.3 

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    Event date： 2008.3.22 - 2008.3.23

    Language：English   Presentation type：Poster presentation  

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  • Water speciation in silicate glasses and melts - an overview.

    Behrens, H, Yamashita, S, Schmidt, B

    8th SILICATE MELT WORKSHOP  2007.10 

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    Event date： 2007.10.1 - 2007.10.5

    Language：English   Presentation type：Oral presentation (general)  

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  • Evidence for dry mantle transition zone from the electrical conductivity wadsleyite

    M. A. G. M. Manthilake, T. Matsuzaki, T. Yoshino, S. Yamashita, E. Ito, T. Katsura

    GEOCHIMICA ET COSMOCHIMICA ACTA  2007.8  PERGAMON-ELSEVIER SCIENCE LTD

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    Event date： 2007.8

    Language：English  

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  • Electrical conductivity of wadsleyite

    Geeth, M, Yoshino, T, Matsuzaki, T, Yamashita, S, Ito, E, Katsura., T

    Japan Geoscience Union Meeting 2007  2007.5.24 

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    Event date： 2007.5.19 - 2007.5.24

    Language：English   Presentation type：Oral presentation (general)  

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  • In situ observation of silicate speciation in liquids in the system K2Si4O9-H2O at high temperature and high pressure.

    Yamashita, S, Kanzaki, M, Mysen, B. O

    Japan Geoscience Union Meeting 2007  2007.5.22 

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    Event date： 2007.5.19 - 2007.5.24

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  • Energetic property of magma degassing: a thermodynamic model.

    Yamashita, S

    International Seminar AASPP-Misasa, Magmatic gases, their trip from the mantle to the surface of the Earth.  2006.2.27 

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    Event date： 2006.2.27

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  • Composition dependence of molar absorption coefficient of mid-infrared water species band.

    Yamashita, S

    Misasa International Symposium MISASA-2, The Evolution of Early Stage of Earth and Solar System.  2006.2 

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    Event date： 2006.2.25 - 2006.2.26

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  • 流紋岩メルトへの水の溶解反応の潜熱

    山下茂

    地球惑星関連学会2005年合同大会  2005.5 

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    Event date： 2005.5.22 - 2005.5.25

    Language：Japanese   Presentation type：Poster presentation  

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  • Melting experiments with the control of oxygen fugacity under dry conditions at high pressure: implication for evolution of magmas on the Ontong Java Plateau.

    Sano, T, Yamashita, S

    International Symposium MISASA "Origin, Evolution and Dynamics of the Earth - Present & Future Research - "  2004.3 

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    Event date： 2004.3.5 - 2004.3.6

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  • Heat of water dissolution in rhyolite melt.

    Yamashita, S

    International Symposium MISASA "Origin, evolution and dynamics of the Earth - Present & Future Research"  2004.3 

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    Event date： 2004.3.5 - 2004.3.6

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  • Water speciation in sodium silicate melts: Constraints from high temperature IR spectroscopy.

    Yamashita, S, Behrens, H, Holtz, F

    13th Goldschimdt Conference  2003.9 

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    Event date： 2003.9.7 - 2003.9.12

    Language：English   Presentation type：Oral presentation (general)  

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  • 岩石溶融実験による超巨大玄武岩火山（オントンジャワ海台）のマグマ分化作用の研究

    佐野貴司, 山下茂

    日本火山学会2002年秋季大会  2002.10 

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    Event date： 2002.10.22 - 2002.10.24

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • Water speciation in basaltic melts determined by high-temperature infrared spectroscopy

    Yamashita, S

    International symposium on experimental mineralogy, petrology and geochemistry  2002.3 

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    Event date： 2002.3.24 - 2002.3.27

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  • Water speciation in basaltic melts: Constraints from water solubility measurements.

    Yamashita, S

    International Symposium Transport of Materials in the Dynamic Earth  2001.10 

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    Event date： 2001.10.2 - 2001.10.5

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  • Heat of solution of water in rhyolite melt: Constraints from water solubility measurements.

    Yamashita, S

    American Geophysical Union Spring Meeting 2000  2000.6 

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    Event date： 2000.5.31 - 2000.6.4

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  • Experimental study of the effect of temperature on water solubility in rhyolite melt.

    Yamashita, S

    ALFRED-WEGENER CONFERENCE, Processes and Censequences of Deep Subduction  1999.9 

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    Event date： 1999.9.5 - 1999.9.11

    Language：English   Presentation type：Poster presentation  

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  • 流紋岩メルトへの水の溶解度の温度依存性

    山下茂

    地球惑星科学関連学会1998年合同大会  1998.5 

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    Event date： 1998.5.26 - 1998.5.29

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • Experimental determination of water solubility in rhyolite melt at low pressures and 850 to 1200℃

    Yamashita, S

    American Geophysical Union Fall Meeting 1997  1997.12 

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    Event date： 1997.12.8 - 1997.12.12

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  • Production of arc basalt magmas: an insight from temporal change in major element compositions of the NE Japan arc basalts

    Yamashita, S

    Misasa Seminar on Evolutionary Processes of Earth and Planetary Materials  1996.6 

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    Event date： 1996.6

    Language：English   Presentation type：Oral presentation (general)  

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  • 顕微赤外分光分析による玄武岩ガラス中の水の定量

    山下茂, 北村俊博, 日下部実

    地球惑星科学関連学会1996年合同大会  1996.3 

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    Event date： 1996.3.26 - 1996.3.29

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  • 比較的低い圧力領域における玄武岩メルトへの水の溶解度

    1996.3 

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    Event date： 1996.3.22 - 1996.3.29

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • Spatial variation in magmatic processes at the Rodriguez triple junction in the Indian Ocean

    Yamashita, S, Fujii, T, Hirose, K

    American Geophysical Union Fall Meeting 1994  1994.12 

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    Event date： 1994.12.5 - 1994.12.9

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  • インド洋ロドリゲス三重点周辺の海嶺軸における玄武岩高密度サンプリング

    藤井敏嗣, 山下茂, 石井輝明, 田結床良昭, Langmuir, C.H, 中田節也, 松本哲志, 原田靖, 高橋成実, 広瀬敬

    地球惑星科学関連学会1994年合同大会  1994.3 

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    Event date： 1994.3.20 - 1994.3.23

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  • 富士山1707年噴出物の含水量と水素同位体比からみたマグマの脱ガス過程、地球惑星科学関連学会合同大会

    北村俊博, 日下部実, 山下茂, 佐藤博明

    地球惑星科学関連学会1994年合同大会  1994.3 

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    Event date： 1994.3.20 - 1994.3.23

    Language：Japanese   Presentation type：Poster presentation  

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  • Geochemical evolution of mantle wedge during Japan Sea opening I: Contribution from isotope geochemistry

    Nohda, S, Tatsumi, Y. Yamashita, S, Fujii, T

    American Geophysical Union Fall Meeting 1991  1991.12 

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    Event date： 1991.12.9 - 1991.12.13

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  • Geochemical evolution of mantle wedge during Japan Sea opening II: Contribution from experimental petrology

    Yamashita, S, Fujii, T, Tatsumi, Y, Nohda, S

    American Geophysical Union Fall Meeting 1991  1991.12 

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    Event date： 1991.12.9 - 1991.12.13

    Language：English   Presentation type：Poster presentation  

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  • Constraints on the formation period of the Japan Sea based on 40Ar-39Ar ages of ODP Leg127/128 samples

    Kaneoka, I, Takigami, Y, Takaoka, N, Yamashita, S, Tamaki, K

    地球惑星科学関連学会1991年合同大会  1991.4 

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    Event date： 1991.4.2 - 1991.4.5

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • 本海より掘削された玄武岩試料のSr、Nd同位体比—日本海の形成とマントルの進化

    能田成, 巽好幸, 山下茂, 藤井敏嗣

    球惑星科学関連学会1991年合同大会  1991.4 

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    Event date： 1991.4.2 - 1991.4.5

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • ODP Leg127で掘削された日本海の音響基盤を構成する玄武岩類〜記載岩石学的特徴

    山下茂, Allan, J., Stewart, K., Thy, P., Leg 127 shipboard scientific party

    地球惑星科学関連学会1990年合同大会  1990.4 

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    Event date： 1990.4.5 - 1990.4.8

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • ODP Leg127で掘削された日本海の音響基盤を構成する玄武岩類〜初生高アルミナ玄武岩質マグマの存在？

    山下茂, Leg 127 shipboard scientific party

    地球惑星科学関連学会1990年合同大会  1990.4 

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    Event date： 1990.4.5 - 1990.4.8

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • 日本海・大和海盆の中期中新世火成活動—大和海盆の下には何があるか？

    山下茂

    日本火山学会1989年春季大会  1989.4 

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    Event date： 1989.4.6 - 1989.4.8

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • 背弧海盆拡大時における火成活動（予察）—日本海・大和海盆の例—

    山下茂

    日本火山学会1988年秋季大会  1988.11 

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    Event date： 1988.11.29 - 1988.12.1

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • 大和海山列の中新世火山岩類の岩石学

    山下茂

    日本火山学会1988年春季大会  1988.7 

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    Event date： 1988.7.16 - 1988.7.18

    Language：Japanese   Presentation type：Oral presentation (general)  

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Research Projects

  • Experimental study of water solubility in andesitic magmas

    Grant number：20K04130  2020.04 - 2023.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    Shigeru Yamashita

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    Authorship：Principal investigator 

    Grant amount：\3510000 （ Direct expense: \2700000 、 Indirect expense：\810000 ）

    マグマにどのくらいの水が溶け込めるのか（溶解度）についての実験データが玄武岩や流紋岩といった極端な組成のマグマに偏っており、中間的な組成である安山岩マグマの実験データがほとんどないことに問題意識を持ち、そのデータギャップを埋めるべくこの研究を始めた。マグマへの水の溶解度はマグマの浮力や過剰圧といった噴火に関わる過程を考える上で必須のパラメータであり、本邦のようなプレート沈み込み帯の火山弧で大量に噴出している安山岩マグマのデータ拡充は社会的意義が大きい。
    前年度までの溶解度実験で、安山岩マグマへの水の溶解度は同じ圧力温度条件の流紋岩マグマに対して10~20%（相対）程度大きいことが明らかになった。令和3年度は、この溶解度の違いが生じる原因について手がかりを得るために、マグマ中の水の溶解種間平衡（マグマに溶け込んだ水の一部がマグマの構造を作っている酸素と反応して水酸基になる）を安山岩マグマと流紋岩マグマのあいだで比較した。マグマの構造緩和理論に基づけば、この溶解種間平衡は急冷時のガラス転移温度で凍結されるとみなすことができる。そこで、既存のマグマ粘性率モデルを利用して、装置固有の急冷速度10°C/secオーダーに対応するガラス転移温度をそれぞれの急冷ガラスについて求め、安山岩マグマと流紋岩マグマそれぞれについて水の溶解種間平衡を温度の関数として整理した。その結果、安山岩マグマ中の水の溶解種間平衡の平衡定数は、同じ温度条件の流紋岩マグマと測定誤差の範囲内で一致することが明らかになった。このことは、溶解度の違いが溶解種間平衡ではなく、マグマと水のあいだの不均一系平衡に駆動されていることを示唆している。平行して、前年度までの実験よりも還元的な状態で溶解度実験を行い、天然の安山岩マグマに普遍的な酸化還元状態の範囲では、マグマの酸化還元状態は水の溶解度に影響しないことも確かめた。

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  • Thermodynamic model for volumetric property of hydrous magmas

    Grant number：17K05707  2017.04 - 2020.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    Yamashita Shigeru

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    Authorship：Principal investigator 

    Grant amount：\4160000 （ Direct expense: \3200000 、 Indirect expense：\960000 ）

    The speciation of water in an albitic melt was studied in-situ at high pressure and high temperature using micro FTIR-Raman spectroscopy. The water speciation in the hydrous melt was found to be independent of pressure. This indicates that the standard volume change of the water speciation equilibrium is negligibly small, and hence the volumetric property of hydrous melts is independent of water speciation.

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  • Quantitavie analysis of hydrogen sites and occupancies in deep-mantle hydrous minerals by time of flight single crystal neutron diffraction

    Grant number：26287135  2014.04 - 2017.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    Okuchi Takuo, YAMASHITA Shigeru, KURIBAYASHI Takahiro

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    Grant amount：\15080000 （ Direct expense: \11600000 、 Indirect expense：\3480000 ）

    Water in the Earth has been transported from the oceans into its deep interior, where it forms hydrous deep mantle minerals. Wadsleyite and ringwoodite have been considered as the two most important host minerals incorporating this type of water as hydroxyl groups. To constrain the capacity of water in their structures and also to understand the effect of such water on their physical properties, it is essential to quantitatively determine the sites and occupancies of hydrogen in their structures. We thus conducted neutron time-of-flight Laue single crystal diffraction studies of synthetic crystals of them. Single crystals, which have size and quality suitable for the method, were synthesized by a newly-developed slow-cooling method at the relevant high pressure and temperature conditions. The structures of two hydrous minerals have been successfully determined in very high resolution in space.

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  • 顕微FTIR反射分光法の応用と高度化：含水量データ10倍増計画

    2014.04 - 2015.03

    東京大学地震研究所  特定共同研究(B) 

    安田敦、山下茂ほか

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    Authorship：Coinvestigator(s) 

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  • In situ observation of magma at upper mantle conditions

    Grant number：24540514  2012.04 - 2015.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    YAMASHITA Shigeru, CHERTKOVA Nadezda

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    Authorship：Principal investigator 

    Grant amount：\4940000 （ Direct expense: \3800000 、 Indirect expense：\1140000 ）

    Feasibility of in situ observation of magmatic substance was assessed at high pressure and high temperature using an externally heated optical anvil cell. Moissanite was tested as possible high-temperature resistant anvil but no advantage of the moissanite to the regular diamond anvil was found under the controlled reduction-oxidation state near upper mantle conditions. In situ observation of an upper mantle magma analogue was performed using the regular diamond anvil, and the water speciation equilibrium in the melt state was successfully determined as function of pressure and temperature.

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  • Hydrogen in earth and planetary materials observed by high-pressure diamond anvil cell NMR

    Grant number：23340161  2011.04 - 2015.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    OKUCHI Takuo, YOSHINO Takashi, SASAKI Shigeo, YAMASHITA Shigeru

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    Grant amount：\18200000 （ Direct expense: \14000000 、 Indirect expense：\4200000 ）

    Chemcial bonding state and microscopic dynamics of hydrogen in minerals, ices and gas hydrates at high pressure are important problems in earth and planetary material sciences. Diamond anvil cell nuclear magnetic resonance spectroscopy is an unique probe to determine microscopic structure and dynamics of hydrogenous materials confined at high pressures. Here we successfully applied this technique to observe hydrogen's dynamics in hydrogen hydrate and in fluid hydogen in situ at high pressures to 5 GPa. In addition to this achievement, we have also determined hydrogen diffusion coefficients in brucite at high pressure and temperature conditions. We also newly developed a technique to observe neutron diffraction of methane hydrate at a few gigapascals of pressures.

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  • In-situ spectroscopic observation of magma and water fluid at high temperature and high pressure

    Grant number：21340161  2009.04 - 2012.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    YAMASHITA Shigeru, KANZAKI Masami

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    Authorship：Principal investigator 

    Grant amount：\17810000 （ Direct expense: \13700000 、 Indirect expense：\4110000 ）

    Speciation reaction equilibria in silicate melts and multi-component fluids were investigated in-situ at high temperature and high pressure using an externally heated diamond anvil cell. FTIR/Raman spectroscopy was used as a probe. The spectrometers were modified to have a common optical axis near and in the sample chamber of the cell, which renders quasi-simultaneous FTIR/Raman measurements. This, in combination with a newly established C^<13> diamond Raman pressure scale, provides a new development of in-situ spectroscopic study of magma-fluid systems.

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  • In situ observation of silicate melts and fluids at high temperature and high pressure

    2009.01 - 2009.04

    Visiting Scientist 

    Shigeru Yamashita, Bjorn Mysen

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    Authorship：Principal investigator 

    平成21年1月8日〜平成21年4月8日のあいだ，米国カーネギー研究機構地球物理学研究所（Geophysical Laboratory, Carnegie Institution of Washington）にvisiting scientistとして滞在し， 同研究所のBjorn Mysenとともに実験／研究を行った．特に，初期地球に相当する酸化還元状態におけるN-O-H流体のケイ酸塩メルトへの溶解反応を，高温高圧その場分光観察によってはじめて直接に明らかにすることができた．これは，マグマオーシャンからの脱ガスと初期地球大気の形成，さらには有機物の前駆物質の生成を考えるうえで重要な成果である．

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  • マグマ再現実験における酸化還元状態制御法の検討（その2）

    2008.04 - 2009.03

    東京大学地震研究所  一般共同研究 

    山下茂

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    Authorship：Principal investigator 

    Grant amount：\470000

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  • マグマ再現実験における酸化還元状態制御法の検討

    2007.04 - 2008.03

    東京大学地震研究所  一般共同研究 

    山下茂

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    Authorship：Principal investigator 

    Grant amount：\417000

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  • ケイ酸塩ガラス中の溶存水種の顕微赤外分光分析法の確立

    2005.04 - 2006.03

    東京大学地震研究所  一般共同研究 

    山下茂

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    Authorship：Principal investigator 

    Grant amount：\312000

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  • 超高圧高温下での水流体の状態方程式の決定

    Grant number：17654104  2005 - 2006

    日本学術振興会  科学研究費助成事業  萌芽研究

    桂 智男, 福井 宏之, 山下 茂

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    Grant amount：\3300000 （ Direct expense: \3300000 ）

    本年度も、水流体を高温高圧下で等体積におくため、テーパー付きサファイヤシリンダー中に水流体を封じることを試みた。昨年度は、全長6.00mmで、両端に長さ3.50mm、入り口2.0mm内部1.0mmのテーパー部をつくったサファイヤシリンダーに水流体を封じた0.9Φの白金カプセルをサファイヤカプセルに入れて、X線その場観察を行った。しかしこの場合、水流体の膨張により白金カプセルが破れ、水流体を封じることが出来なかった。本年度は、カプセルをサファイヤと白金の二重構造にすることを止めた。即ち、直径4.0mm・長さ3.1mm・擂り鉢開口径2.5mm・試料部長1.0mm、試料部系1.0mmのサファイヤシリンダーを作成し、それに適合するサイズのモリブデンのふたを作成し、そこに水流体を封じることを試みた。モリブデンのふたとサファイヤシリンダーの間には、厚さ50ミクロンの金箔を敷いて、水流体をシールした。このシールはX線その場観察実験において圧力測定にも用いられる。この試料を高圧セル(1辺25mmのMgO八面耐圧力媒体・グラファイトヒーター・窒化硼素サンプル容器・クロメルアルメル熱電対)中に入れ、高圧X線その場観察実験を行った。荷重100トンで0.64GPaまで加圧し、500Kまで加熱し、冷却した。水流体が封じられていれば、加熱によって圧力が上昇し、冷却によってもとの圧力に戻るはずであるが、加熱しても圧力は上昇せず、冷却すると圧力はゼロ付近になった。実験後、試料部を観察すると水流体は存在していなかった。このように、本研究では水流体を高温高圧下で等体積中に封じることは出来なかった。

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  • Thermodynamic properties of water in silicate melts

    2001.12 - 2003.02

    Alexander von Humboldt Stiftung  Alexander von Humboldt Foundation Research Fellow 

    Shigeru Yamashita

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    Authorship：Principal investigator 

    Grant amount：\3220000 （ Direct expense: \3220000 ）

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  • Electric conductivity measurement of the Earth's materials

    Grant number：13440164  2001 - 2003

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    KATSURA Tomoo, YAMASHITA Shigeru, YONEDA Akira, ITO Eiji, URAKAWA Satoru

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    Grant amount：\15000000 （ Direct expense: \15000000 ）

    We measured electrical conductivity of granulite from Hidaka metramorphic belt, Hokkaido, Japan. From the experimental results, we estimated the temperature of the high resistance region at depth of 10-30 km to be 600℃.
    We conducted experiments to estimate connectivity of iron-iron sulfide melts in dunite and lherzolite matrixes by means of electrical conductivity measurement. From this series of experiments, we found that iron-iron sulfide melt connects if its volume proportion is more than 5 %. Therefore, segregation of core material from mantle should have easily occurred in the early history of the Earth.
    We measured electrical conductivity of (Mg_<0.93>Fe_<0.07>)SiO_3 ilmenite at pressures of 25, 35 and 40 GPa and temperature of 500 to 1000 K. We found the pre-exponential term is constant of 3×10 S/m at all of these pressures. The activation energy at 0 GPa and activation volume are 0.69±0.04 eV and -0.90±0.10 cm^3/mol. Thus pressure dependence of ilmenite is quite large.
    We also measured electrical conductivity of (Mg_<0.93>Fe_<0.07>)SiO_3 perovskite at pressures of 35 and 40 GPa and temperature of 500 to 1100 K. We found the pre-exponential term is constant of 1×10 S/m at both of these pressures. The activation energy at 0 GPa and activation volume are 0.39±0.02 eV and -0.06±0.04 cm^3/mol. Thus pressure dependence of pervoskite is one order of magnitude smaller than that of ilmenite.

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  • 高圧X線ラジオグラフィ法によるマグマの拡散系数測定

    Grant number：12874059  2000 - 2001

    日本学術振興会  科学研究費助成事業  萌芽的研究

    神崎 正美, 山下 茂, 薛 献宇

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    Grant amount：\2300000 （ Direct expense: \2300000 ）

    今年度もSpring-8の共用ビームラインBL04B1でビームタイムを申請して認可され,高圧X線ラジオグラフィ実験をそこで行った.高温高圧実験にはSPEED1500プレスを使用した.昨年度試料のコントラストが良くなかった点を考慮し,試料にはCaSiO3/CaGeO3対を用いた.この場合メルト中のSi-Geの相互拡散を見ることになる.また高ダイナミックレンジのX線カメラを自作してコントラストの改善を図った.これは冷却カメラ,光学レンズ2式と蛍光板を組み合わせたものである.ただSpring-8設置のカメラでも静止画モードで撮影すると,ダイナミックレンジが上がり,今回作成したカメラとそれほど違いがないことも判明した.
    実験は約3GPaで行った.上記の改善により昨年のNaAlSi3O8/NaGaSi3O8対と比べて遙かによいコントラストが得られた.残念ながら熱電対が切れたため,温度は測定できなかった.加熱電力を増加させていくと試料が熔けて相互拡散が始まり,CaSiO3/CaGeO3界面のコントラストがシャープなものからなだらかなものへと変化する様子が観察された.しかし時間がたつとCaGeO3メルト中のGeが還元されて,下部に堆積する様子が見られた.Geの還元を防ぐためにFe2O3を試料容器外においてあったが,Geの還元を阻止することはできなかった.しかし最初の方はGeの還元の影響はないと考えられるため,その部分のデータの解析を現在進めているところである.またGeの還元プロセスがその場観察できたことは,この方法が地球中心核の形成に関連したケイ酸塩/金属との反応の研究に利用できることを示唆する.
    2年間の本研究により,Geの還元などのテクニカルな問題はまだ残っているが,高温高圧下におけるメルト中の相互拡散係数のその場観察法を確立した.今後この手法を使って各種メルトの相互拡散係数を高温高圧下で測定する.

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  • In situ spectroscopic study of the thermodynamic properties of water-bearing magmas

    Grant number：11640480  1999.04 - 2001.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    YAMASHITA Shigeru

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    Authorship：Principal investigator 

    Grant amount：\3500000 （ Direct expense: \3500000 ）

    The goal of this research was to quantify the thermodynamic properties of water dissolved in silicate melts. Water is a major volatile component dissolved in magma at depth, and is capable of nearly complete exsolution from the melt (but being sustained in the melt as vapor bubbles) when the magma rises to near the surface. This causes a progressive increase of the volume per unit mass of the rising magma and a modification of the cooling path. Knowledge of the thermodynamic properties of water in silicate melts is critical for modeling these effects, and thus fundamental for understanding the dynamics of magma migration and eruption. Two major advances in the quantification of the thermodynamic properties of water in silicate melts have been achieved through this research: (1) High temperature infrared absorption peaks due to OH group and H2O molecule were measured in two basalt glasses (one containing 1.3 wt% water, one containing 2.9 wt% water; the anhydrous composition remains unchanged) as a function of temperature between 〜 25℃ and 575℃. The concentrations of OH group and H2O molecule were determined using the room-temperature calibrations of the molar absorption coefficients. The results show that both OH group and H2O molecule are equilibrium species in the melts, which is consistent with the idea that water is incorporated in a silicate melt through homogeneous reaction H2O molecule + O = 2OH. The product is favored by increase of temperature above the glass transition, and the homogeneous reaction equilibria in these two melts show a good agreement with each other; an equation 1n K = -4070(±470)/T + 3.68(±0.60) reproduces both. The 1n K values obtained in the melts are not distinguishable from those obtained by previous studies in rhyolitic melts within experimental uncertainty. This suggests that there is little influence of composition on the calorimetric properties of the homogeneous reaction equilibria in natural magmatic melts. (2) Heat of solution of water in rhyolite melts was thermodynamically modeled, on the basis of the temperature dependence of water solubility in the melts obtained from infrared spectroscopy of the quenched glasses. In the model developed here, water was assumed to be dissoleved through a coupled reaction H2O molecule melt + O melt = 2OH melt (homogeneous reaction) and H2O vapor = H2O molecule melt (heterogeneous reaction), and ideal mixing of these melt components was assumed. A non-linear multiple regression to the solubility dataset converged upon ΔH° homo (P, T) = 25.8±11.8 kJ, ΔS° homo (P, T) = 6.0±8.7 J/K, and, ΔH° hetero (1bar, T) = -25.3±4.8 kJ/mol. From these optimum values, the following interpretations can be made: The heat of solution is approximately zero at 0.1 MPa, and increases with pressure below 〜 20 MPa, where the absolute value of the heat is negative. At pressures between 〜 20 MPa and 100 MPa, the heat of solution roughly levels out (〜 -7±6 kJ/mol at 850℃) as a result of the balance of the exothermic heterogeneous reaction and endothermic homogeneous reaction. Although error of estimation is large, the present results suggest that at pressures of 10 to 100 MPa (the pressure range important to closed system magma bubbling), the calorimetric effect of bubbling causes a temperature drop of only <10℃.

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  • Determination of interdiffusivity in major rock-forming minerals

    Grant number：11440161  1999 - 2001

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    OZAWA Kazuhito, TAKAHASHI Hiroko, YAMASHITA Shigeru

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    Grant amount：\13700000 （ Direct expense: \13700000 ）

    In this research project, cation diffusion in olivine and Cr-Al spinel was examined by vacuum evaporation technique. The Fe-Mg interfiffusion and Ni tracer diffusion coefficients in olivine were determined at 1300〜1500℃ with gem-quality San Carlos olivine. The composition dependence and anisotropy were determined by applying a diffusion model with moving boundary. The diffusivity was found to be largest along the c-axis, intermediate along the b-axis, and smallest along the a-axis. At 1400℃, the interfifusion coefficient is estimated to be 8.7x10^<-15>±2.8(m^2/sec) along the c-axis. The anisotropy was also significant at 1500 and 1300℃, but there is a tendency that the diffusivities along a-and b-axis become similar at lower temperatures. Elemental diffusion in Cr-Al spinel was studied on octahedral chromian spinel from the Horokanai ophiolite at 1300〜1500℃. The spinel samples were evaporated incongruently developing outer reaction zone with low iron content and inner diffusion zone. By analyzing the compositional profile, the magnetite component was selectively evaporated through rapid diffusion promoted by point defects derived from reduction of ferric iron to ferrous iron. At 1300 and 1400℃, Al shows marked uphill diffusion, which clearly indicate that the Cr diffusivity is much slower than that of Al.

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  • 珪酸塩メルト-水系の体積(密度)の実験岩石学的研究

    Grant number：09740396  1997 - 1998

    日本学術振興会  科学研究費助成事業  奨励研究(A)

    山下 茂

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    Grant amount：\1600000 （ Direct expense: \1600000 ）

    この研究の目的は、マグマのメルト相に溶解している水が気相として析出(=発泡)するときの体積・密度変化を定量化することにより、マグマの輸送現象をよりよく理解することにあった。9年度の研究ではモデルケースとして流紋岩マグマをとりあげ、そのメルト相への水の溶解度をマグマだまりに相当する温度・圧力条件で溶融実験により決定し、温度の上昇とともに溶解度が減少(発泡度は増加)することを明らかにした。さらに溶解度データを解析し、ソリダス近傍の700℃からリキダスをこえる1200℃にいたる広い温度範囲で、流紋岩マグマだまりのメルト相への水の溶解度を計算できる熱力学モデルを確立した。10年度の研究では、この溶解度の熱力学モデルを流紋岩マグマだまりの発泡現象へ応用し、適当な状態方程式を用いて、流紋岩マグマの体積・密度変化の様子を温度と発泡度の関数として計算することを試みた。この計算で新たに見い出されたことは、50〜100MPaの圧力条件(深さ約2〜4km)の流紋岩マグマだまりでは、温度の上昇にともなう発泡度の増加がそれを考慮しない場合にくらべて、マグマの高温部にかかるthermalbuoyancyforceを5〜10倍大きくするほどの体積増加(密度減少)をひきおこすことである。今回の結果は、浅所にある流紋岩マグマだまりでは、小さな温度擾乱(熱伝導による冷却や新たに注入されたマグマからの熱供給など)でも系の重力不安定を容易に誘起することを示しており、マグマの輸送現象に新たな制約を与えるものである。

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  • International Cooperative Research on the mid-Oceanic Ridges

    Grant number：08044061  1996 - 1998

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for international Scientific Research

    TAMAKI Kensaku, ISEZAKI Nobuhiro, MEVEL Catherrine, NAKANISHI Masao, OOTA Suguru, FUJIMOT Hiromi

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    Grant amount：\27800000 （ Direct expense: \27800000 ）

    This program corresponds to the InterRidge program, an international initiative of mid-oceanic ridge studies. The funds of this program are mainly used for travels of ridge researchers in Japan for participating cruises, attending workshops, program planning meetings, and society meetings. The other part of usage is transportation of instruments for the research cruises. The research cruises that the researchers of this program participated cover the global ridge system including the Juan de Fuca Ridge, the East Pacific Rise, the Mid-Atlantic Ridge, the Southwestern Indian Ridge, the Central Indian Ridge, and the western Pacific back-arc basins ridges. The major achievements were done in the studies in the Southwestern Ridge. Five research cruises were executed at the Southwestern Indian Ridge during this program. Multinarrow bathymetric survey, deep-tow sidescan sonnar survey, gravity and magnetic measurements, ocean bottom seismometer measurements, and bottom rock sampling were done. The compilation of these data sets clearly shows the unique segmentation pattern of this ridge, the ultraslow spreading system with striking heterogeneity of crustal structure and intensively focused magmatism.

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  • Magma degassing processes in view of hydrogen isotopic variations

    Grant number：08454166  1996 - 1997

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    KUSAKABE Minoru, YAMASHITA Shigeru

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    Grant amount：\5900000 （ Direct expense: \5900000 ）

    Hydrogen isotopic variation of water in volcanic eject is a good indicator to understand the degassing processes of magma, because large hydrogen isotopicfractionation between vapor and water dissolved in melt is significantly large even at magmatic temperatures (-800ﾟC). This research aimed at studying the degassing processes magmas with different chemical properties that lead to different eruption styles.
    (1) Water contents and hydrogen isotopic ratios were determined for whole rocks and mineral separates (hornblende and biotite) from lavas and bombs obtained from the 1991 eruption of Unzen volcano. The eruption was of typical dacite dome formation. The data indicated that the deep-seated magma characterized by a high initial water conten (5-6 wt.%) and hydrogen isotopic ratio (deltaD=-50) lost most of water during ascent to the Earth's surface, resulting in the low H_2O lavas (0.5 wt% or lower). The observed H_2O-deltaD relationship followed neither the closed- nor open-system degassing models, suggesting that a kinetic isotopic effect playd an important role during degassing of highly viscous magma. These results will be published shortly in Journal of Volcanology and Geothermal Research.
    (2) Water contents and hydrogen isotopic ratios were determined for basaltic scoria samples from the 1707 eruption of Mt.Fuji. It was found that the deltaD values negatively correlate with H_2O contents. The same trend was found for basaltic scoria from Kilauea volcano, Hawaii. This suggests that part of water dissolved in basaltic melt was reduced to hydrogen through reaction with abundant Fe^<2+> in the melt, resulting in the negative correlation between deltaD and H_2O.

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  • 珪酸塩メルトへの水の溶解度の圧力・温度依存性の実験的研究

    Grant number：08740417  1996

    日本学術振興会  科学研究費助成事業  奨励研究(A)

    山下 茂

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    Grant amount：\700000 （ Direct expense: \700000 ）

    この研究では流絞岩メルトと玄武岩メルトへの水の溶解度を溶融実験により決定し、特に噴火直前のマグマに相当する100MPa以下の圧力領域における珪酸塩メルトへの水の溶解度の圧力・温度依存性の基礎データを拡充することができた。実験の出発物質には無水の天然流紋岩ガラスと合成玄武岩ガラスを使用した。これらを脱イオン水とともにカプセルに封入し、内熱式ガス圧装置を用いて22〜100MPa、1000〜1200℃の条件で溶融させ、水と4〜69時間反応させた後、急冷・回収し、含水ガラスを作成した。これらの含水ガラス試料中の水を Yamashita et al.(1997)の方法で顕微赤外分光分析により定量し、それぞれの組成のメルトへの水の溶解度を決定した。出発物質を粉末状に調整すると、粘性の大きい流紋岩組成のメルトでは共存する水相(気泡)は分離せずにガラス試料中に高密度に残存してしまい、これを避けてガラス部分の溶存水を定量することは困難である。そのため今回新たな試みとして、出発物質を長さ2mm、直径2mm程度の柱状に整形し、水を拡散浸透・飽和させ、気泡の生成をふせいだ。ガラス部分の均質性からメルト-水間の平衡が確認された実験について結果を整理すると:(1)玄武岩メルトへの水の溶解度は、1200℃において、22MPaの1.5wt%から100MPaの3.0wt%まで圧力の上昇とともに増加する、(2)流紋岩メルトへの水の溶解度は、1200℃において、22MPaの1.4wt%から圧力の上昇とともに増加するが、100MPaまで昇圧しても2.3wt%にしか達しない。今回の結果は、水の溶解度の圧力依存性の程度が珪酸塩メルトの組成によって相当に変化することを示している。

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  • Experimental Study of Magma Degassing Processes

    Grant number：06403003  1994 - 1995

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for General Scientific Research (A)

    KUSAKABE Minoru, YAMASHITA Shigeru

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    Grant amount：\21800000 （ Direct expense: \21800000 ）

    (1)Infrared absorption spectroscopy of hydrous glasses of arc lava compositions
    Hydrous glasses of arc lava compositions (tholeiitic basalt, high-alumina basalt and dacite) were synthesized using a high pressure apparatus. The glasses were precisely analyzed for total water contents with hydrogen manometry, followed by FTIR analysis to obtain molar absorption coefficients of absorption bands at 2.8mum (molecular H_2O and OH stretching), 2.2mum (OH stretching and bending), and 1.9mum (stretching + bending of molecular H_2O).
    (2)Experimental determination of water solubility in basaltic melts at low pressure
    Water solubility in silicate melts is the most basic information in understanding the magma ascent and vesiculation. Using a gas-medium internal pressure apparatus, water-saturated basaltic melts of tholeiitic composition were prepared under 1200ﾟC and 10-80 MPa. The quenched glasses were analyzed for water contents to determine the water solubility. The data were combined with the literature values for higher pressures to obtain an empirical equation describing satisfactorily the water solubility in basaltic melts under a wide range of pressure, i.e., 10-1000 MPa.
    (3)Magma degassing and hydrogen isotopic variations
    Magma degassing processes for the 1991-1992 Mt.Unzen volcano and 1707 Mt.Fuji volcano were considered on the basis of water contents and hydrogen isotopic rations of the glassy rocks. The Unzen magma had lost most of its water before dome formation. Degassing of water from the dome lava and underlying magma was controlled mainly by diffusion, resulting in increase in the D/H ratio as water content decreases. The scoria samples from the 1707 Fuji eruption showed the correlation that the D/H ratio increases as the Fe^<2+>/Fe^<3+> ratio decreases. This correlation was interpreted to indicate that significant loss of hydrogen took place at the time of eruption by reaction of water with Fe^<2+> in the magma. It was shown that the correlation between water contents and hydrogen isotopic variations can be used to evaluate the magma degassing processes.

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Media Coverage

  • New insight into the origin of water on the earth Internet

    2020.5

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    Author：Other 

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  • 月の内部に予想の１００倍の水か アポロ計画で採取の石を分析 Newspaper, magazine

    共同通信  産經新聞  2010.6.15

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Academic Activities

  • Detection of magmatism beneath the Ontong Java Plateau last for ~100 million years

    Role(s)：Planning/Implementing academic research

    Japan Agency for Marine-Earth Science and Technology  2016

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    Type：Academic research 

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  • Geological and geophysical study of the Rodviguez Triple Junction, Indian Ocean

    Role(s)：Planning/Implementing academic research

    Ocean Research Institute, University of Tokyo  1993

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  • Geological and petrological study of Deccan Flood Basalt Province

    Role(s)：Planning/Implementing academic research

    Earthquake Research Institute, University of Tokyo  1993

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  • Ocean Drilling Program (ODP) Leg127

    Role(s)：Planning/Implementing academic research

    Ocean Drilling Program (ODP)  1989

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    Type：Academic research 

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