研究者詳細 - 山下　茂

論文 - 山下　茂

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Hydrogen incorporation mechanism in the lower-mantle bridgmanite 査読

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年6月

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

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

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

GEOCHEMICAL JOURNAL 56 ( 6 ) 223 - 230 2022年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Web of Science

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

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

American Mineralogist 106 ( 7 ) 1143 - 1152 2021年7月

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

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年12月

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

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

Lithos 348-349 105197 - 105197 2019年12月

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

Takashi Sano, Shigeru Yamashita

Lithos 346-347 105143 - 105143 2019年11月

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

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年4月

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

Nadezda Chertkova, Shigeru Yamashita

Chemical Geology 409 149 - 156 2015年8月

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

Nadezda Chertkova, Shigeru Yamashita, Eiji Ito, Akira Shimojuku

Mineralogical Magazine 78 ( 7 ) 1677 - 1685 2014年12月

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

Bjorn O. Mysen, Shigeru Yamashita

Geochimica et Cosmochimica Acta 74 ( 15 ) 4577 - 4588 2010年8月

Nominally hydrous magmatism on the Moon 査読

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年6月

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

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

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

Electrical conductivity of wadsleyite as a function of temperature and water content 査読

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年5月

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

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

American Mineralogist 93 ( 11-12 ) 1760 - 1770 2008年11月

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

Harald Behrens, Shigeru Yamashita

Chemical Geology 256 ( 3-4 ) 306 - 315 2008年11月

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

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

Chemical Geology 256 ( 3-4 ) 231 - 241 2008年11月

阿蘇カルデラ西部に分布する栃ノ木溶岩中にみられる組成不均質とその成因査読

三好雅也, 長谷中利昭, 森康, 山下茂

岩石鉱物科学 36 ( 1 ) 15 - 29 2007年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：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

CiNii Article

CiNii Books

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00291363587?from=CiNii

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

Takashi Yoshino, Takuya Matsuzaki, Shigeru Yamashita, Tomoo Katsura

Nature 443 ( 7114 ) 973 - 976 2006年10月