TOHOKU UNIVERSITY Researchers

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Satoshi Okumura

Section

Graduate School of Science

Job title

Associate Professor

Degree

博士（理学）（東京工業大学）
修士（理学）（東京工業大学）

researchmap

https://researchmap.jp/satoshiokumura

J-GLOBAL ID

201801004655178140

Professional Memberships 5

International Association of Volcanology and Chemistry of the Earth's Interior
American Geophysical Union
Japan Association of Mineralogical Sciences
THE VOLCANOLOGICAL SOCIETY OF JAPAN
JAPAN GEOSCIENCE UNION

Research Interests 3

マグマ学
火山学
実験岩石学

Research Areas 1

Natural sciences / Solid earth science /

Awards 3

優秀学術賞

2018　日本火山学会
研究奨励賞

2015　日本鉱物科学会
研究奨励賞

2007　日本火山学会

Papers 75

Experimental constraints on serpentinite carbonation in the presence of a H2O–CO2–NaCl fluid

Yongsheng Huang, Satoshi Okumura, Kazuhisa Matsumoto, Naoko Takahashi, Hong Tang, Guoji Wu, Tatsuki Tsujimori, Michihiko Nakamura, Atsushi Okamoto, Yuan Li

Contributions to Mineralogy and Petrology　179　(11)　2024/10/08
Publisher: Springer Science and Business Media LLC
DOI： 10.1007/s00410-024-02175-4 　

ISSN： 0010-7999

eISSN： 1432-0967
Time‐Resolved Trigger Processes Leading to the Plinian Eruptions at Sakurajima Volcano, Japan

Naoki Araya, Michihiko Nakamura, Keiko Matsumoto, Satoshi Okumura

Journal of Geophysical Research: Solid Earth　129　(9)　2024/08/27
Publisher: American Geophysical Union (AGU)
DOI： 10.1029/2023jb028558 　

ISSN： 2169-9313

eISSN： 2169-9356

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Abstract Mafic magma recharge of crustal reservoirs and subsequent magma mixing has been considered a direct trigger of volcanic eruptions. However, although recharge frequently occurs in many active volcanoes, it rarely leads to an eruption immediately, making its role as a trigger ambiguous. Sakurajima volcano, Japan, has vigorously erupted three times since the 15th century following a common process; mixed magmas after recharge were once stored in a shallow, thick conduit before each eruption (conduit pre‐charge). We reconstructed the magma migration with a high time resolution by diffusion modeling on orthopyroxene and magnetite. Orthopyroxene phenocrysts recorded prolonged diffusive re‐equilibration timescales of years or more after recharge‐and‐mixing. Magnetite, which has the fastest elemental diffusivity among the phenocrysts examined, predominantly lacks zoning. This demonstrates that the mineral phase was re‐equilibrated with surrounding magma and homogenized via elemental diffusion after the final magmatic perturbation, implying the final repose of the shallow pre‐charged magma body for more than several tens of days. After this shallow stagnation period, the Plinian magmas began to ascend and reached the surface within 55 hr. Mass balance calculations show that crystallization‐driven vesiculation upon pre‐charge can produce overpressure sufficient to cause an eruption. The Sakurajima cases demonstrate the hierarchical timescales of trigger processes leading to the explosive eruptions.
The influence of chondrules on sub-mm fragment shape distributions in Allende impact experiments

Tatsuhiro Michikami, Axel Hagermann, Akira Tsuchiyama, Yushi Otsuka, Michihiko Nakamura, Satoshi Okumura, Harumasa Kano, Junya Matsuno, Sunao Hasegawa

Icarus　116068-116068　2024/04
Publisher: Elsevier BV
DOI： 10.1016/j.icarus.2024.116068 　

ISSN： 0019-1035
Vapor-phase crystallization from a hydrous silicate melt: an experimental simulation of diktytaxitic texture

Ryosuke Sakurai, Michihiko Nakamura, Satoshi Okumura, Mayumi Mujin, Takayuki Nakatani

Contributions to Mineralogy and Petrology　179　(3)　2024/03/06
Publisher: Springer Science and Business Media LLC
DOI： 10.1007/s00410-024-02105-4 　

ISSN： 0010-7999

eISSN： 1432-0967

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Abstract Groundmass textures of volcanic rocks provide valuable insights into the processes of magma ascent, crystallization, and eruption. The diktytaxitic texture, characterized by a lath-shaped arrangement of feldspar microlites forming glass-free and angular pores, is commonly observed in silicic dome-forming rocks and Vulcanian ashfall deposits. This texture has the potential to control the explosivity of volcanic eruptions because its micropore network allows pervasive degassing during the final stages of magma ascent and eruption. However, the exact conditions and kinetics of the formation of diktytaxitic textures, which are often accompanied by vapor-phase cristobalite, remain largely unknown. Here, we show that the diktytaxitic texture and vapor-phase minerals, cristobalite and alkali feldspar, can be produced from bulk-andesitic magma with rhyolitic glass under water-saturated, near-solidus conditions (± ~10 MPa and ± ~20 °C within the solidus; 10–20 MPa and 850 °C for our starting pumices). Such crystallization proceeds through the partial evaporation of the supercooled melt, followed by the deposition of cristobalite and alkali feldspar as a result of the system selecting the fastest crystallization pathway with the lowest activation energy. The previously proposed mechanisms of halogen-induced corrosion or melt segregation by gas-driven filter pressing are not particularly necessary, although they may occur concurrently. Diktytaxitic groundmass formation is completed within 4–8 days, irrespective of the presence or composition of the halogen. These findings constrain the outgassing of lava domes and shallow magma intrusions and provide new insights into the final stages of hydrous magma crystallization on Earth.
A new method for quantitative analysis of total water contents and estimating molecular water and hydroxyl contents in rhyolitic glasses by SIMS

Akimasa Suzumura, Satoshi Okumura, Chikashi Yoshimoto, Shoichi Itoh

Geochemical Journal　58　(3)　e1-e7　2024

DOI： 10.11263/geochemj.GJ24008 　

ISSN： 0016-7002
A Molecular‐Scale Origin of Shear Thinning and Brittle Failure of Silicate Melt

S. Okumura, K. Uesugi, A. Goto, K. Matsumoto, T. Sakamaki

Geophysical Research Letters　2023/08/28

DOI： 10.1029/2023GL104083 　
Redox state of magma recorded in volcanic glass from an ash-forming eruption at Bromo volcano, Indonesia: Insights into the degassing process

Takahiro Miwa, Hidemi Ishibashi, Ryunosuke Kazahaya, Satoshi Okumura, Masato Iguchi, Genji Saito, Atsushi Yasuda, Nobuo Geshi, Hiroyuki Kagi

Bulletin of Volcanology　85　(9)　2023/08/15
Publisher: Springer Science and Business Media LLC
DOI： 10.1007/s00445-023-01660-1 　

eISSN： 1432-0819
Oxidation-induced nanolite crystallization triggered the 2021 eruption of Fukutoku-Oka-no-Ba, Japan

Kenta Yoshida, Akira Miyake, Shota H. Okumura, Hidemi Ishibashi, Satoshi Okumura, Atsushi Okamoto, Yasuhiro Niwa, Masao Kimura, Tomoki Sato, Yoshihiko Tamura, Shigeaki Ono

Scientific Reports　13　(1)　2023/05/09
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s41598-023-34301-w 　

eISSN： 2045-2322

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Abstract Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting the viscosity of magmas and inducing bubble nucleation. We present detailed microscopic and nanoscopic petrographic analyses of nanolite-bearing and nanolite-free pumice from the 2021 eruption of Fukutoku-Oka-no-Ba, Japan. The nanolite mineral assemblage includes biotite, which is absent from the phenocryst mineral assemblage, and magnetite and clinopyroxene, which are observed as phenocrysts. The boundary between the nanolite-bearing brown glass and nanolite-free colorless glass is either sharp or gradational, and the sharp boundaries also appear sharp under the transmitted electron microscope. X-ray absorption fine structure (XAFS) analysis of the volcanic glass revealed that the nanolite-free colorless glass records an oxygen fugacity of QFM + 0.98 (log units), whereas the nanolite-bearing brown glass records a higher apparent oxygen fugacity (~ QFM + 2). Thermodynamic modelling using MELTS indicates that higher oxygen fugacities increase the liquidus temperature and thus induced the crystallization of magnetite nanolites. The hydrous nanolite mineral assemblage and glass oxygen fugacity estimates suggest that an oxidizing fluid supplied by a hot mafic magma induced nanolite crystallization in the magma reservoir, before the magma fragmentation. The oxidation-induced nanolite crystallization then enhanced heterogeneous bubble nucleation, resulting in convection in the magma reservoir and triggering the eruption.
In situ observation of glass-like fragmentation of high-temperature silicate melts generating fine ashes Peer-reviewed

Atsuko Namiki, Satoshi Okumura, Akio Goto, Tsutomu Yamada

Communications Earth & Environment　2023/05/05

DOI： 10.1038/s43247-023-00816-3 　
Molecular-scale structural changes of silicate melts under tension revealed by time-resolved X-ray diffraction Peer-reviewed

Satoshi Okumura, Kentaro Uesugi, Akio Goto, Atsuko Namiki, Kazuhisa Matsumoto, Tatsuya Sakamaki

Chemical Geology　621　121372-121372　2023/03
Publisher: Elsevier {BV}
DOI： 10.1016/j.chemgeo.2023.121372 　

ISSN： 0009-2541
Constraints on magma properties at fragmentation during the 2011 sub‐Plinian eruptions of Kirishima Shinmoe‐dake volcano, Japan

Tomofumi Kozono, Satoshi Okumura

Journal of Geophysical Research: Solid Earth　2022/11/22
Publisher: American Geophysical Union (AGU)
DOI： 10.1029/2022jb025183 　

ISSN： 2169-9313

eISSN： 2169-9356
Three-dimensional imaging of high-velocity-impact induced crack growth in carbonaceous meteorites

Tatsuhiro Michikami, Akira Tsuchiyama, Axel Hagermann, Akio Takeda, Katsuki Shishido, Yushi Otsuka, Osamu Sasaki, Michihiko Nakamura, Satoshi Okumura, Harumasa Kano, Sunao Hasegawa

Icarus　392　115371-115371　2022/11
Publisher: Elsevier BV
DOI： 10.1016/j.icarus.2022.115371 　

ISSN： 0019-1035
Rheology of nanocrystal-bearing andesite magma and its roles in explosive volcanism

Satoshi Okumura, Kentaro Uesugi, Akio Goto, Tatsuya Sakamaki, Kazuhisa Matsumoto, Akihisa Takeuchi, Akira Miyake

COMMUNICATIONS EARTH & ENVIRONMENT　3　(1)　2022/10

DOI： 10.1038/s43247-022-00573-9 　

eISSN： 2662-4435
Conduit Flow Dynamics During the 1986 Sub-Plinian Eruption at Izu-Oshima Volcano

Tomofumi Kozono, Hidemi Ishibashi, Satoshi Okumura, Takahiro Miwa

Journal of Disaster Research　17　(5)　754-767　2022/08/01
Publisher: Fuji Technology Press Ltd.
DOI： 10.20965/jdr.2022.p0754 　

ISSN： 1881-2473

eISSN： 1883-8030

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We investigated conduit flow dynamics during the 1986 sub-Plinian eruption of Izu-Oshima volcano, Japan, using a 1-D steady conduit flow model. Following observations that the magma plumbing system beneath Izu-Oshima, characterized by the feeding of a dyke, generated a fissure-type sub-Plinian eruption, we considered a dyke-like conduit geometry by applying a pseudo-dyke conduit with an ellipsoidal horizontal cross-section. Under appropriate parameter settings constrained by geological, petrological, and geophysical observations, we identified a conduit geometry that enables steady solutions of a conduit flow that generates the sub-Plinian eruption. A dyke-like conduit geometry allows us to widen the range of geometric parameters of the solution. We found that the distribution of magma overpressure in the conduit strongly depends on conduit geometry. When the conduit geometry is composed of deeper and shallower dykes with large and small aspect ratios, respectively, localized overpressurization occurs in the region before magma fragmentation. This overpressurization in the dyke-like conduit may induce a characteristic crustal deformation similar to that caused by a vertical tensile fault. It is crucial to consider the effects of conduit flow with a dyke-like geometry on deformation for precise monitoring of eruption sequences based on geodetic signals in future eruptions at Izu-Oshima volcano.
Amorphous silica coating on flank deposits of the 1783 CE eruption at Asama volcano

Takayuki Nakatani, Sarina Sugaya, Maya Yasui, Satoshi Okumura, Michihiko Nakamura

Journal of Volcanology and Geothermal Research　411　107149-107149　2021/03
Publisher: Elsevier BV
DOI： 10.1016/j.jvolgeores.2020.107149 　

ISSN： 0377-0273
Decompression experiments for sulfur-bearing hydrous rhyolite magma: Redox evolution during magma decompression Peer-reviewed

Satoshi Okumura, Hidemi Ishibashi, Shoichi Itoh, Akimasa Suzumura, Yoshihiro Furukawa, Takahiro Miwa, Hiroyuki Kagi

AMERICAN MINERALOGIST　106　(2)　216-225　2021/02

DOI： 10.2138/am-2020-7535 　

ISSN： 0003-004X

eISSN： 1945-3027
An experimental system for time-resolved x-ray diffraction of deforming silicate melt at high temperature Peer-reviewed

Satoshi Okumura, Kentaro Uesugi, Tatsuya Sakamaki, Akio Goto, Masayuki Uesugi, Akihisa Takeuchi

REVIEW OF SCIENTIFIC INSTRUMENTS　91　(9)　2020/09

DOI： 10.1063/5.0009769 　

ISSN： 0034-6748

eISSN： 1089-7623
Combined numerical and experimental study of microstructure and permeability in porous granular media Peer-reviewed

Philipp Eichheimer, Marcel Thielmann, Wakana Fujita, Gregor J. Golabek, Michihiko Nakamura, Satoshi Okumura, Takayuki Nakatani, Maximilian O. Kottwitz

Journal of Geophysical Research, Solid Earth　2020/03/23
Publisher: Copernicus GmbH
DOI： 10.5194/egusphere-egu2020-2992 　

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&lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;p&gt;Fluid flow on different scales is of interest for several Earth science disciplines like petrophysics, hydrogeology and volcanology. To parameterize fluid flow in large-scale numerical simulations (e.g. groundwater and volcanic systems), flow properties on the microscale need to be considered. For this purpose experimental and numerical investigations of flow through porous media over a wide range of porosities are necessary. In the present study we sinter glass bead media with&amp;#160;various porosities, representing shallow depth crustal sediments.&amp;#160;The microstructure, namely effective porosity and effective specific surface, is investigated using image processing. We furthermore determine flow properties like hydraulic tortuosity and permeability using both experimental measurements and numerical simulations. By fitting microstructural and flow properties to porosity, we obtain a modified Kozeny-Carman equation for isotropic low-porosity media, that can be used to simulate permeability in large-scale numerical models. To verify the modified Kozeny-Carman equation we compare it to the numerically computed and experimentally measured permeability values.&lt;/p&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt;
Space Weathering Simulation with Low-energy Laser Irradiation of Murchison CM Chondrite for Reproducing Micrometeoroid Bombardments on C-type Asteroids Peer-reviewed

Moe Matsuoka, Tomoki Nakamura, Takahiro Hiroi, Satoshi Okumura, Sho Sasaki

Astrophysical Journal Letters　890　(2)　2020/02/20

DOI： 10.3847/2041-8213/ab72a4 　

ISSN： 2041-8205

eISSN： 2041-8213
Fragility and an extremely low shear modulus of high porosity silicic magma Peer-reviewed

Atsuko Namiki, Yukie Tanaka, Satoshi Okumura, Osamu Sasaki, Kyohei Sano, Shingo Takeuchi

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH　392　2020/02

DOI： 10.1016/j.jvolgeores.2019.106760 　

ISSN： 0377-0273

eISSN： 1872-6097
Space Weathering Simulation with Low-energy Laser Irradiation of Murchison CM Chondrite for Reproducing Micrometeoroid Bombardments on C-type Asteroids Peer-reviewed

Moe Matsuoka, Tomoki Nakamura, Takahiro Hiroi, Satoshi Okumura, Sho Sasaki

ASTROPHYSICAL JOURNAL LETTERS　890　(2)　2020/02

DOI： 10.3847/2041-8213/ab72a4 　

ISSN： 2041-8205

eISSN： 2041-8213
Caldera-forming eruptions of mushy magma modulated by feedbacks between ascent rate, gas retention/loss and bubble/crystal framework interaction Peer-reviewed

Satoshi Okumura, Shanaka L. de Silva, Michihiko Nakamura, Osamu Sasaki

SCIENTIFIC REPORTS　9　2019/11

DOI： 10.1038/s41598-019-52272-9 　

ISSN： 2045-2322
Three-dimensional imaging of crack growth in L chondrites after high-velocity impact experiments. Peer-reviewed

Tatsuhiro Michikami, Axel Hagermann, Akira Tsuchiyama, Hirotaka Yamaguchi, Terunori Irie, Keita Nomura, Osamu Sasaki, Michihiko Nakamura, Satoshi Okumura, Sunao Hasegawa

Planetary and Space Science　177　(104690 (14pp.))　104690-104690　2019/11
Publisher: Elsevier BV
DOI： 10.1016/j.pss.2019.07.005 　

ISSN： 0032-0633
Shallow magma pre-charge during repeated Plinian eruptions at Sakurajima volcano Peer-reviewed

Naoki Araya, Michihiko Nakamura, Atsushi Yasuda, Satoshi Okumura, Tomoki Sato, Masato Iguchi, Daisuke Miki, Nobuo Geshi

SCIENTIFIC REPORTS　9　(1979)　2019/02

DOI： 10.1038/s41598-019-38494-x 　

ISSN： 2045-2322
Evaluation of Caldera Hosted Geothermal Potential during Volcanism and Magmatism in Subduction System, NE Japan Peer-reviewed

Fajar F. Amanda, Ryoichi Yamada, Masaoki Uno, Satoshi Okumura, Noriyoshi Tsuchiya

GEOFLUIDS　2019　2019/01

DOI： 10.1155/2019/3031586 　

ISSN： 1468-8115

eISSN： 1468-8123
Water diffusion in silica glass through pathways formed by hydroxyls

Minami Kuroda, Shogo Tachibana, Naoya Sakamoto, Satoshi Okumura, Michihiko Nakamura, Hisayoshi Yurimoto

American Mineralogist　103　(3)　412-417　2018/03/26
Publisher: Walter de Gruyter GmbH
DOI： 10.2138/am-2018-6208 　

ISSN： 1945-3027 0003-004X

eISSN： 1945-3027
Advancement of magma fragmentation by inhomogeneous bubble distribution

M. Kameda, M. Ichihara, S. Maruyama, N. Kurokawa, Y. Aoki, S. Okumura, K. Uesugi

SCIENTIFIC REPORTS　7　2017/12

DOI： 10.1038/s41598-017-16941-x 　

ISSN： 2045-2322
Rheology of basaltic ash from Stromboli volcano inferred froth intermittent compression experiments

Aika K. Kurokawa, Takahiro Miwa, Satoshi Okumura, Kentaro Uesugi

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH　343　211-219　2017/09

DOI： 10.1016/j.jvolgeores.2017.07.002 　

ISSN： 0377-0273

eISSN： 1872-6097
Silicic lava effusion controlled by the transition from viscous magma flow to friction controlled flow

S. Okumura, T. Kozono

GEOPHYSICAL RESEARCH LETTERS　44　(8)　3608-3614　2017/04

DOI： 10.1002/2017GL072875 　

ISSN： 0094-8276

eISSN： 1944-8007
Differentiation of eruptive magma in the late Miocene Shirasawa Caldera and present geothermal reservoir

Taku Suzuki, Masaoki Uno, Satoshi Okumura, Ryoichi Yamada, Noriyoshi Tsuchiya

Journal of the Geothermal Research Society of Japan　39　(1)　25-37　2017
Publisher: Geothermal Research Society of Japan
DOI： 10.11367/grsj.39.25 　

ISSN： 1883-5775 0388-6735
Rheology of crystal-bearing natural magmas: Torsional deformation experiments at 800 degrees C and 100 MPa

Satoshi Okumura, Alexandra R. L. Kushnir, Caroline Martel, Remi Champallier, Quentin Thibault, Shingo Takeuchi

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH　328　237-246　2016/12

DOI： 10.1016/j.jvolgeores.2016.11.009 　

ISSN： 0377-0273

eISSN： 1872-6097
Tracking bubble evolution inside a silicic dike

Antonio M. Alvarez-Valero, Satoshi Okumura, Fabio Arzilli, Javier Borrajo, Clemente Recio, Masao Ban, Juan C. Gonzalo, Jose M. Benitez, Madison Douglas, Osamu Sasaki, Piedad Franco, Juan Gomez-Barreiro, Asuncion Carnicero

LITHOS　262　668-676　2016/10

DOI： 10.1016/j.lithos.2016.08.012 　

ISSN： 0024-4937

eISSN： 1872-6143
Mineralogical Record of the Mechanism of Mt. Fuji 1707 Eruption

Aruga T., Nakamura M., Okumura S., Yoshimoto M.

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2016　5-5　2016
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2016.0_5 　
Rheology of basaltic ash from Stromboli volcano revealed by cyclic compression experiment

K. Kurokawa A., Miwa T., Okumura S., Uesugi K.

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2016　11-11　2016
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2016.0_11 　
Magma outgassing and rheology control the explosivity of volcanic eruptions

Satoshi Okumura

Japanese Magazine of Mineralogical and Petrological Sciences　45　(1)　13-20　2016
Publisher: Japanese Association of Mineralogists Petrologists and Economic Geologists
DOI： 10.2465/GKK.151214 　

ISSN： 1349-7979 1345-630X
Interfacial tension-driven relaxation of magma foam: An experimental study

Shizuka Otsuki, Michihiko Nakamura, Satoshi Okumura, Osamu Sasaki

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH　120　(11)　7403-7424　2015/11

DOI： 10.1002/2015JB012391 　

ISSN： 2169-9313

eISSN： 2169-9356
Pulse-laser irradiation experiments of Murchison CM2 chondrite for reproducing space weathering on C-type asteroids

Moe Matsuoka, Tomoki Nakamura, Yuki Kimura, Takahiro Hiroi, Ryosuke Nakamura, Satoshi Okumura, Sho Sasaki

ICARUS　254　135-143　2015/07

DOI： 10.1016/j.icarus.2015.02.029 　

ISSN： 0019-1035

eISSN： 1090-2643
Rheological transitions in high-temperature volcanic fault zones

Satoshi Okumura, Kentaro Uesugi, Michihiko Nakamura, Osamu Sasaki

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH　120　(5)　2974-2987　2015/05

DOI： 10.1002/2014JB011532 　

ISSN： 2169-9313

eISSN： 2169-9356
B1-06 Vesiculation and lubrication of crystal-rich magma

Okumura Satoshi, Iwamoto Masaaki, Sasaki Osamu

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2015　52-52　2015
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2015.0_52 　
Major and trace element analyses of igneous rocks by polarizing energy dispersive X-ray fluorescence spectrometry (EDXRF)

Toshio Miyazaki, Shin-Ichi Yamasaki, Noriyoshi Tsuchiya, Satoshi Okumura, Ryoichi Yamada, Michihiko Nakamura, Yoshitaka Nagahashi, Takeyoshi Yoshida

Japanese Magazine of Mineralogical and Petrological Sciences　43　(2)　47-53　2015
Publisher: Japanese Association of Mineralogists Petrologists and Economic Geologists
DOI： 10.2465/gkk.131224 　

ISSN： 1349-7979 1345-630X
Permeability reduction of fractured rhyolite in volcanic conduits and its control on eruption cyclicity

Satoshi Okumura, Osamu Sasaki

GEOLOGY　42　(10)　843-846　2014/10

DOI： 10.1130/G35855.1 　

ISSN： 0091-7613

eISSN： 1943-2682
Carbon dioxide emission to Earth's surface by deep-sea volcanism

Satoshi Okumura, Naoto Hirano

GEOLOGY　41　(11)　1167-1170　2013/11

DOI： 10.1130/G34620.1 　

ISSN： 0091-7613

eISSN： 1943-2682
Coupled effect of magma degassing and rtheology on silicic volcanism

Satoshi Okumura, Michihiko Nakamura, Kentaro Uesugi, Tsukasa Nakano, Takuma Fujioka

EARTH AND PLANETARY SCIENCE LETTERS　362　163-170　2013/01

DOI： 10.1016/j.epsl.2012.11.056 　

ISSN： 0012-821X

eISSN： 1385-013X
Experimental constraints on permeable gas transport in crystalline silicic magmas

Satoshi Okumura, Michihiko Nakamura, Tsukasa Nakano, Kentaro Uesugi, Akira Tsuchiyama

CONTRIBUTIONS TO MINERALOGY AND PETROLOGY　164　(3)　493-504　2012/09

DOI： 10.1007/s00410-012-0750-8 　

ISSN： 0010-7999
放射光Ｘ線を用いた流動するマグマのその場観察：火山噴火の多様性の原因解明へ向けて Peer-reviewed

奥村聡, 中村美千彦, 上杉健太郎

Laboratory simulation of volcanism : In situ observation of flowing magma by synchrotron radiation X-ray radiography and computed tomography　25　(4)　222-228　2012/07/31
Publisher:
ISSN： 0914-9287
The H2O content of andesitic magmas from three volcanoes in Japan, inferred from the infrared analysis of clinopyroxene

Satoshi Okumura

EUROPEAN JOURNAL OF MINERALOGY　23　(5)　771-778　2011/10

DOI： 10.1127/0935-1221/2011/0023-2141 　

ISSN： 0935-1221
B1-08 Magma permeability measurement at high temperature and high pressure by pore-pressure oscillation method

Okumura Satoshi, Okazaki Keishi, Katayama Ikuo

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2011　64-64　2011
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2011.0_64 　
Shear deformation experiments on vesicular rhyolite: Implications for brittle fracturing, degassing, and compaction of magmas in volcanic conduits Peer-reviewed

Satoshi Okumura, Michihiko Nakamura, Tsukasa Nakano, Kentaro Uesugi, Akira Tsuchiyama

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH　115　2010/06

DOI： 10.1029/2009JB006904 　

ISSN： 2169-9313

eISSN： 2169-9356
Incubation processes for the Taisho eruption of Sakurajima Volcano: Constraint from the mineral chemistry of magnetite

Michihiko NAKAMURA, Sho TAMURA, Yoshinori ITOH, Satoshi OKUMURA, Masato IGUCHI, Daisuke MIKI

Annuals of Dissas. Prev. Res. Inst., Kyoto Univ.　53A　(53)　261-267　2010/06
Publisher:
2-A05 Experimental study on shear-induced compaction vesicular silicic magma

Fujioka Takuma, Okumura Satoshi, Nakamura Michihiko, Uesugi Kentaro

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2010　23-23　2010
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2010.0_23 　
3-B12 Carbon emission from volcanoes

Okumura Satoshi, Hirano Naoto

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2010　84-84　2010
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2010.0_84 　
Shear deformation experiments on vesicular rhyolite: Implications for brittle fracturing, degassing, and compaction of magmas in volcanic conduits

Satoshi Okumura, Michihiko Nakamura, Tsukasa Nakano, Kentaro Uesugi, Akira Tsuchiyama

Journal of Geophysical Research: Solid Earth　115　(6)　2010
Publisher: Blackwell Publishing Ltd
DOI： 10.1029/2009JB006904 　

ISSN： 2169-9356 2169-9313
Magma deformation may induce non-explosive volcanism via degassing through bubble networks

Satoshi Okumura, Michihiko Nakamura, Shingo Takeuchi, Akira Tsuchiyama, Tsukasa Nakano, Kentaro Uesugi

EARTH AND PLANETARY SCIENCE LETTERS　281　(3-4)　267-274　2009/05

DOI： 10.1016/j.epsl.2009.02.036 　

ISSN： 0012-821X

eISSN： 1385-013X
A04 The effect of temperature and total strain on brittle failure of vesiculated rhyolite

Fujioka Takuma, Okumura Satoshi, Nakamura Michihiko

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2009　4-4　2009
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2009.0_4 　
Three differentiation stages of a single magma at Piton de la Fournaise volcano (Reunion hot spot)

Vincent Famin, Benoit Welsch, Satoshi Okumura, Patrick Bachelery, Satoru Nakashima

GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS　10　2009/01

DOI： 10.1029/2008GC002015 　

ISSN： 1525-2027
Color-change processes of a plinian pumice and experimental constraints of color-change kinetics in air of an obsidian

Mihoko Moriizumi, Satoru Nakashima, Satoshi Okumura, Yuta Yamanoi

BULLETIN OF VOLCANOLOGY　71　(1)　1-13　2009/01

DOI： 10.1007/s00445-008-0202-5 　

ISSN： 0258-8900
Color measurements of volcanic ash deposits from three different styles of summit activity at Sakurajima volcano, Japan: Conduit processes recorded in color of volcanic ash

Yuta Yamanoi, Shingo Takeuchi, Satoshi Okumura, Satoru Nakashima, Tadashi Yokoyama

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH　178　(1)　81-93　2008/11

DOI： 10.1016/j.jvolgeores.2007.11.013 　

ISSN： 0377-0273

eISSN： 1872-6097
Evolution of bubble microstructure in sheared rhyolite: Formation of a channel-like bubble network

Satoshi Okumura, Michihiko Nakamura, Akira Tsuchiyama, Tsukasa Nakano, Kentaro Uesugi

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH　113　(B7)　2008/07

DOI： 10.1029/2007JB005362 　

ISSN： 2169-9313

eISSN： 2169-9356
Microstructure of bubbles in flowing magma Invited

M. Nakamura, S. Okumura, A. Tsuchiyama

SPring-8 Research Frontier　2007　124-125　2008/05
B14 A study of mechanism and condition of peculiar bubbling in hydrated basaltic glass

IKUSE Hiroshi, SAIKI Kazuto, TSUCHIYAMA Akira, NAKANO Tsukasa, UESUGI Kentaro, OKUMURA Satoshi

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2008　66-66　2008
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2008.0_66 　
P63 Effect of relaxation of bubble shape by surface tension and magma compaction on permeable degassing of magma

Okumura Satoshi, Nakamura Michihiko

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2008　154-154　2008
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2008.0_154 　
Hydration of rhyolitic glass during weathering as characterized by IR microspectroscopy

Tadashi Yokoyama, Satoshi Okumura, Satoru Nakashima

GEOCHIMICA ET COSMOCHIMICA ACTA　72　(1)　117-125　2008/01

DOI： 10.1016/j.gca.2007.10.018 　

ISSN： 0016-7037

eISSN： 1872-9533
C03 Permeable degassing of magma : Effect of shear deformation

Okumura Satoshi, Nakamura Michihiko, Takeuchi Shingo

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2007　23-23　2007
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2007.0_23 　
Shear-induced bubble coalescence in rhyolitic melts with low vesicularity

Satoshi Okumura, Michihiko Nakamura, Akira Tsuchiyama

GEOPHYSICAL RESEARCH LETTERS　33　(20)　2006/10

DOI： 10.1029/2006GL027347 　

ISSN： 0094-8276

eISSN： 1944-8007
Pressurization processes of magmas in a shallow conduit to cause vulcanian eruption

TAKEUCHI Shingo, OKUMURA Satoshi, YAMANOI Yuta

Japanese Magazine of Mineralogical and Petrological Sciences　35　(3)　144-152　2006/05/30
Publisher: Japan Association of Mineralogical Sciences
DOI： 10.2465/gkk.35.144 　

ISSN： 1345-630X

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Vulcanian eruptions are relatively frequent eruptive phenomena in island arc volcanism. The high frequency provides us many opportunities to observe the eruptive behavior and to sample the erupted materials. Vulcanian activity of the Sakurajima volcano located at southern Kyushu in Japan has continued since 1955 and been precisely monitored by Sakurajima Volcano Observatory. Therefore, the vulcanian eruptions of Sakurajima volcano can be a common, interesting target to study the eruptive behavior from the various viewpoints of material analysis, geophysical observation and numerical modeling. Recently, many researchers have focused on pressurization processes of magmas in shallow conduits to cause vulcanian eruptions. In this paper, we review several studies on observations and models of generation of excess pressure in shallow conduit magmas just before vulcanian eruptions. We evaluate the possibility of pressurization processes by dehydration-induced crystallization and buoyancy of vesicular conduit magmas. The results of this study indicate that the dehydration-induced crystallization is not effective for excess pressure generation, if crystallizing magma in shallow conduit contains a significant amount of exsolved gas phase. Instead, excess pressure can be generated in a shallow conduit by buoyancy of vesicular conduit magma, when partially solidified magma at the vent of conduit prevents magma ascent and the conduit is filled with vesicular magmas from magma chamber located at ca. 3 km depth to the shallow conduit.
Water diffusion in silicate melts

OKUMURA Satoshi

Japanese Magazine of Mineralogical and Petrological Sciences　35　(3)　119-125　2006/05/30
Publisher: Japan Association of Mineralogical Sciences
DOI： 10.2465/gkk.35.119 　

ISSN： 1345-630X

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Water diffusion in silicate melts is a controlling factor of magma ascent process in volcanic eruption, because it dominates the rates of bubble nucleation and growth in magmas and the decrease of water contents by water diffusion causes drastic changes in the physical properties of silicate melts (viscosity and density). This paper reviews experimental studies for water diffusion in rhyolitic to basaltic melts and glasses. In rhyolitic and dacitic melts (polymerized silicate melts), water mainly dissolves as hydroxyl group (OH) and molecular water (H₂O), but only H₂O is considered as the mobile species. The H₂O diffusivities in rhyolite and dacite increase with water contents and temperature. The mechanism of water diffusion in andesite to basalt (depolymerized silicate melts) is still unclear, but some studies presented the data of total water (OH + H₂O) diffusivities in andesite and basalt by assuming the diffusion of one component water. Those data show that the diffusivity of total water increases with melt depolymerization (from rhyolite to basalt) at high temperatures (e.g., > 1400 °C at 0.7 wt% water), but the magnitude relation inverts at the lower temperatures due to the difference of temperature dependences of total water diffusivity in rhyolite to basalt. Recently, a few studies explored the compositional dependence of total water diffusivity and expressed the total water diffusivity as a function of the SiO₂ content or the NBO/T value. To test and develop those models, additional experimental data are needed in the future studies, and the developed-comprehensive model for water diffusion in silicate melts and glasses will make a significant contribution to understanding of volcanic eruptions.
Water diffusion in basaltic to dacitic glasses

S Okumura, S Nakashima

CHEMICAL GEOLOGY　227　(1-2)　70-82　2006/03

DOI： 10.1016/j.chemgeo.2005.09.009 　

ISSN： 0009-2541
B32 Shear-induced bubble coalescence in rhyolitic melt with low vesicularity(THE VOLCANOLOGICAL SOCIETY OF JAPAN 2006 FALL MEETING)

Okumura Satoshi, Nakamura Michihiko, Tsuchiyama Akira

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2006　88-88　2006
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2006.0_88 　
Molar absorptivities of OH and H2O in rhyolitic glass at room temperature and at 400-600 C-degrees

S Okumura, S Nakashima

AMERICAN MINERALOGIST　90　(2-3)　441-447　2005/02

DOI： 10.2138/am.2005.1740 　

ISSN： 0003-004X
P51 Deformation experiment of bubbly rhyolitic melt(THE VOLCANOLOGICAL SOCIETY OF JAPAN 2005 FALL MEETING)

OKUMURA Satoshi, NAKAMURA Michihiko

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2005　151-151　2005
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2005.0_151 　
A25 Colors of ashes erupted by summit activities at Sakurajima volcano(THE VOLCANOLOGICAL SOCIETY OF JAPAN 2005 FALL MEETING) Peer-reviewed

Yamanoi Yuta, Takeuchi Shingo, Okumura Satoshi, Nakashima Satoru, Yokoyama Tadashi

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2005　(0)　25-25　2005
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2005.0_25 　

ISSN： 2433-5320
Water diffusivity in rhyolitic glasses as determined by in situ IR spectroscopy

S Okumura, S Nakashima

PHYSICS AND CHEMISTRY OF MINERALS　31　(3)　183-189　2004/04

DOI： 10.1007/s00269-004-0383-1 　

ISSN： 0342-1791
P64 Spectro-colorimetric study of volcanic ash : Explosive and effusive eruptions in vulcanian activities at Sakurajima volcano Peer-reviewed

Yamanoi Yuta, Takeuchi Shingo, Okumura Satoshi, Nakashima Satoru

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2004　(0)　174-174　2004
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2004.0_174 　

ISSN： 2433-5320
Determination of molar absorptivity of IR fundamental OH-stretching vibration in rhyolitic glasses

S Okumura, M Nakamura, S Nakashima

AMERICAN MINERALOGIST　88　(11-12)　1657-1662　2003/11

ISSN： 0003-004X
Analyses of pyroclasts erupted in Vulcanian eruptions at Sakurajima Volcano : Preliminary results

Takeuchi Shingo, Okumura Satoshi, Yamanoi Yuta

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2003　115-115　2003
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2003.0_115

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Misc. 23

SPECTRAL AND WATER ANALYSIS OF EXPERIMENTALLY HEATED TAGISH LAKE AND CR CARBONACEOUS CHONDRITES WITH NO EFFECTS OF ADSORBED AND REHYDRATED WATER.

Kana Amano, Kaoru Mogi, Tomoki Nakamura, Moe Matsuoka, Yoshihiro Furukawa, Satoshi Okumura

METEORITICS & PLANETARY SCIENCE　53　6309-6309　2018/08

ISSN： 1086-9379

eISSN： 1945-5100
DEHYDRATION PROCESS OF EXPERIMENTALLY HEATED MURCHISON WITHOUT ANY EFFECTS OF ADSORBED AND REHYDRATED WATER

Kaoru Mogi, Sayuri Yamashita, Tomoki Nakamura, Moe Matsuoka, Satoshi Okumura, Yoshihiro Furukawa

METEORITICS & PLANETARY SCIENCE　52　A240-A240　2017/08

ISSN： 1086-9379

eISSN： 1945-5100
ケイ酸塩ガラス中の水の拡散における含水量依存性

黒田みなみ, 橘省吾, 奥村聡, 中村美千彦, 坂本直哉, 圦本尚義

日本鉱物科学会年会講演要旨集　2015　5　2015/09/18

ISSN： 1348-6543
B2-26 Textural relaxation of melt foam due to surface tension : Sample size dependence

Otsuki Shizuka, Nakamura Michihiko, Okamura Satoshi, Sasaki Osamu

Programme and abstracts the Volcanological Society of Japan　2014　85-85　2014/11/02
Publisher: Volcanological Society of Japan
P2-10 Mechanism of transition from Plinian eruption to lava effusion inferred from petrographic study on pumice and juvenile lithic fragment from Taisho eruption of Sakurajima volcano

Shimizu Hikaru, Okumura Satoshi, Nakamura Michihiko

Programme and abstracts the Volcanological Society of Japan　2014　162-162　2014/11/02
Publisher: Volcanological Society of Japan
B1-17 Evolution of gas permeability and strength of magmatic fault

Okumura Satoshi, Sasaki Osamu

Programme and abstracts the Volcanological Society of Japan　2013　68-68　2013/09/29
Publisher: Volcanological Society of Japan
Fluidization of crystal-rich silicic magmas by gas bubbles

OKUMURA Satoshi, DE SILVA Shan, NAKAMURA Michihiko, SASAKI Osamu

2013　39-39　2013/09/05

ISSN： 1348-6543
下部地殻・最上部マントルにおける流体分布:捕獲岩のX線CT観察からの制約

中村美千彦, 奥村聡, 吉田武義, 高橋栄一, 佐々木理

日本鉱物科学会年会講演要旨集　2013　2013

ISSN： 1348-6543
流体相変化による析出シリカ鉱物の産状とき裂間隙構造の発達プロセス

山田稜, 岡本敦, 最首花恵, 中村美千彦, 奥村聡, 佐々木理, 土屋範芳

日本鉱物科学会年会講演要旨集　2013　2013

ISSN： 1348-6543
流体相変化に伴うシリカの沈殿挙動と鉱物脈形成

山田稜, 岡本敦, 最首花恵, 中村美千彦, 奥村聡, 佐々木理, 土屋範芳

日本地質学会学術大会講演要旨　120th　2013

ISSN： 1348-3935
B1-21 Crystallization process of nanolites in erupted materials of the 2011 eruption of Shinmoedake, Kirishima volcanoes

Mujin Mayumi, Nakamura Michihiko, Okumura Satoshi

Programme and abstracts the Volcanological Society of Japan　2012　67-67　2012/10/14
Publisher: Volcanological Society of Japan
A3-10 Experimental study on shear fracturing and frictional sliding of magma

Okumura Satoshi

Programme and abstracts the Volcanological Society of Japan　2012　43-43　2012/10/14
Publisher: Volcanological Society of Japan
In situ observation of brittle fracturing and gas transport in silicic magma

OKUMURA Satoshi, NAKAMURA Michihiko, UESUGI Kentaro, NAKANO Tsukasa

2011　88-88　2011/09/05

ISSN： 1348-6543
Open-system degassing from silicic arc magmas

OKUMURA Satoshi, NAKAMURA Michihiko, TSUCHIYAMA Akira, NAKANO Tsukasa, TAKEUCHI Shingo, UESUGI Kentaro

2010　16-16　2010/09/23

ISSN： 1348-6543
Experimental Studies of Dehydration and Open-System Degassing of Magma

OKUMURA Satoshi

Bulletin of the Volcanological Society of Japan　53　(6)　207-213　2008/12/29
Publisher: Volcanological Society of Japan
ISSN： 0453-4360
Water diffusion in silicate melts

OKUMURA Satoshi

2007　66-66　2007/09/22

ISSN： 1348-6543
Shear deformation experiments on vesiculated rhyolitic melts : Evolution of bubble structure

OKUMURA Satoshi, NAKAMURA Michihiko, TSUCHIYAMA Akira, NAKANO Tsukasa, UESUGI Kentaro

2007　57-57　2007/09/22

ISSN： 1348-6543
4-dimensional observation on bubble growth in hydrous silicate glass using synchrotron radiation microtomography

TSUCHIYAMA A., SAIKI K., OKUMURA S., NAKANO T., UESUGI K.

21　(2)　206-207　2006/10/01

ISSN： 0915-6089
Color Change Measurements of a Scoria and Simulation Heating Experiments by Spectro-colorimetry

YAMANOI Yuta, NAKASHIMA Satoru, OKUMURA Satoshi, TAKEUCHI Shingo

Bulletin of the Volcanological Society of Japan　49　(6)　317-331　2004/12/25
Publisher: Volcanological Society of Japan
ISSN： 0453-4360

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In order to study quantitatively color changes of basaltic scoria erupted at Takatsukayama, North-east Izu, Japan, the scoria colors were measured by spectro-colorimetry and described m the international standard color space(CIE L^* a^* b^*)The color values [a^* (red) and b^* (yellow) values]of Takatsukayama scoria cone increase from margin to center, indicating their color change from black to red. The bulk chemical compositions of scoria, including total Fe content, remain almost unchanged despite the color variations. 0n the other hand, the FeO(Fe^<2+>) contents determined by the phenanthrolme method have a good linear relation with a^* values (red) of scoria. Under the optical microscope, the red parts are not found m the black scoria, whereas the red scoria have red parts m the groundmass and the olivine phenocryst. For dull red scoria, the red carts are observed only m the groundmass These indicate that red parts appear first m the groundmass and then in the olivine phenocryst. Visible and Raman microspectroscopy indicated the presence of hematite m these red Darts A series of heating experiments of the black scoria under an atmospheric condition at 500-1150℃ were conducted to simulate the color changes of Takatsukayama scoria. The heated scoria showed the increases in a^* and b* values (i e. red coloring). The FeO(Fe^<2+>) contents of the heated scoria had similar linear correlation with a^* values (red) as for natural ones. The presence of hematite was also found by visible and Raman microspectroscopy. These results imply that the increases m a* and b* values (red coloring) of Takatsukayama scoria can be explained by the high temperature oxidation of Fe^<2+>, resulting m the formation of hematite first in the groundmass and then m the olivine phenocryst. Since the direction of the red coloring is oblique to the depositional sequences of the cone, the high temperature oxidation process might have occurred after the scoria deposition from the center of a heat source to the outer parts.
In-situ dehydration of hydrous glasses at high temperature

S Okumura, S Nakashima

GEOCHIMICA ET COSMOCHIMICA ACTA　67　(18)　A359-A359　2003/09

ISSN： 0016-7037
Color change of a scoria and simulation heating experiments by spectro-colorimetry

Y Yamanoi, S Nakashima, S Okumura, S Takeuchi

GEOCHIMICA ET COSMOCHIMICA ACTA　67　(18)　A555-A555　2003/09

ISSN： 0016-7037
Ascent process of magma inferred from water content : In the case of 1929 Plinian eruption at Hokkaido-Komagatake

Okumura Satoshi, Takeuchi Shingo, Nakashima Satoru, Nakamura Michihiko

PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN　2002　(0)　52-52　2002
Publisher: The Volcanological Society of Japan
DOI： 10.18940/vsj.2002.2.0_52 　

ISSN： 2433-5320
顕微赤外分光法による火山ガラス中の含水量測定 (総特集水・岩石相互作用の機構と速度)

奥村聡, 佐藤泰彦, 森泉美穂子

月刊地球　22　(7)　457-462　2000/07
Publisher: 海洋出版
ISSN： 0387-3498

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Presentations 4

Gas bubble formation in crystal-rich magma and its roles on eruption dynamics Invited

Satoshi Okumura

AGU Fall Meeting 2020　2020/12
Laboratory Simulation of Shear Deformation and Outgassing of Silicic Magmas International-presentation Invited

Satoshi Okumura

Goldschmidt Conference 2016　2016/06
Outgassing of silicic magma through bubble and fracture networks International-presentation Invited

Satoshi Okumura

American Geophysical Union Fall Meeting　2013/12
Coupled effect of magma degassing and rheology on silicic volcanism International-presentation Invited

Satoshi Okumura

European Geosciences Union General Assembly　2012/04

Research Projects 22

マグマの脆性的破砕の痕跡：偏光ラマン分光法を用いた分子スケール構造からの探索

奥村聡, 宇野正起, 石橋秀巳

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 挑戦的研究(萌芽)

Institution: 東北大学

2024/06/28 - 2027/03/31
破壊実験と断層調査から解明する地震のエネルギー散逸過程

長濱裕幸, 武藤潤, 奥村聡, 河野義生, 澤燦道

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(B)

Institution: 東北大学

2024/04/01 - 2027/03/31
気泡と結晶を含むマグマの粘弾性と破壊強度の測定及び構造のその場観察

並木敦子, 星野真人, 奥村聡, 上杉健太朗

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(A)

Institution: 名古屋大学

2024/04/01 - 2027/03/31
爆発的火山噴火を引き起こすマグマの破壊現象の解明：変形するマグマの時分割構造解析

奥村聡, 坂巻竜也, 小園誠史, 上杉健太朗

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(A)

Institution: 東北大学

2022/04/01 - 2026/03/31
Crysallization process and fragmentation mechanism in the shallow conduit of mafic plinian eruption

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (C)

Institution: Shizuoka University

2022/04/01 - 2025/03/31
Catastrophic caldera forming eruption revealed by petrological and experimental study of lubrication of crystal-mush

Okumura Satoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))

Institution: Tohoku University

2021/10/07 - 2024/03/31

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This study aims to evaluate the idea that bubbles in magma lubricate crystal mash and make it possible to ascend to the surface. We performed decompression experiments to investigate bubble formation processes and their roles on magma lubrication. Based on these experiments, we found that bubbles induce magma lubrication when the decompression rate is high, while bubbles segregate when the decompression rate is low. In addition, the bubble segregation occurred when the decompression proceeds stepwise even if the decompression rate is high. By comparing these experimental results with actual caldera forming eruption conditions (decompression history and rate), it is inferred that bubble segregation does not occur during caldera-forming eruptions and hence the formation of gas bubbles cause the lubrication of crystal mush.
火山直下のマグマの状態と将来を知る方法の提案：粘弾性測定と浸透流・破砕の実験

並木敦子, 奥村聡

Offer Organization: 日本学術振興会

System: 科学研究費助成事業基盤研究(A)

Category: 基盤研究(A)

Institution: 広島大学

2019/04/01 - 2024/03/31

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本研究では大きく分けて以下の４つのプロジェクトを行っている。以下にそれぞれの進行状況を記す。１）低粘性マグマの粘弾性測定では気泡を含むマグマを1200℃に加熱し、レオメータを用いてその動的粘弾性を測定する。この計画については2019年度に玄武岩を溶かす為の炉を購入し、2020年度は測定用治具を開発した。高温炉をレオメータから離して置く必要があり、その為治具を長くする必要があり、これが測定中に偏心する為正しい粘弾性の値を得る事が難しくなっていた。特殊なアタッチメントを付ける事で偏心の問題を解決し、正しい測定値が得られるようになった。２）高粘性シリシックマグマの粘弾性測定は2022年度から着手の予定であったが、予定を繰り上げて2020年度から測定装置の設計を始めた。2021年度には発注できるよう、詳細をまとめた。３）高温高圧下でのマグマの浸透率測定は2019年度に測定装置を導入し、2020年度はキャリブレーションを行った。特に、常温では信用できる測定ができるようになった。４）溶融マグマの破砕その場観察実験は2019年度にマグマを破砕する為の引張試験の方法を策定し、2020年度は950℃まで昇温可能な炉に穴をあけ、破砕の最中を高速度カメラで観察する為の光学系と照明について方法を検討した。また、応力・歪曲線を得る為のロードセル、レーザー変位計について検討した。これらを用いて予備的実験を行い、破砕の現場を撮影するとともに、応力歪曲線を得る事ができた。
苦鉄質マグマの火道上昇に伴う物性変化とその噴火ダイナミクスへの影響の解明

石橋秀巳, 奥村聡, 安田敦

Offer Organization: 日本学術振興会

System: 科学研究費助成事業基盤研究(C)

Category: 基盤研究(C)

Institution: 静岡大学

2019/04/01 - 2022/03/31

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何故、脱ガスしやすいはずの苦鉄質マグマが激しい爆発的噴火をおこすのか？そのメカニズムを解明することが本研究の目的である。近年の研究より、火道浅部での脱ガスに駆動されたマイクロライト結晶作用（以後、脱ガス結晶作用とよぶ）によって引き起こされる苦鉄質マグマの粘性-脆性遷移が、苦鉄質マグマが爆発的噴火を発生するうえで重要な役割を担っていることがわかってきた。したがって、今明らかにすべきことは、「火道上昇中のマグマは、どのように脱ガス結晶作用が進行するか」であろう。そこで本研究では、火道浅部での脱ガス結晶作用プロセスを明らかにすることを目指し、天然の苦鉄質スコリアの石基について組織解析と化学分析を行っている。減圧結晶作用のプロセスが明らかにできれば、苦鉄質マグマの火道上昇過程でマグマの物性がどのように変化し、その結果噴火ダイナミクスにどのように影響を及ぼしたかがわかると期待できる。 3カ年の研究期間の初年度にあたる2019年度では、サブプリニ―式噴火（伊豆大島1986年B噴火）とストロンボリ式噴火（伊豆大室山噴火）の異なる噴火様式を代表する苦鉄質スコリアについて、電子顕微鏡による石基組織の組織解析と石基ガラスの化学分析を行い、両者について火道浅部における脱ガス結晶作用のプロセスを検討した。その結果，(1)ストロンボリ式噴火では、火道浅部の高結晶度・高粘性プラグが重要な役割を果たしていること、(2)苦鉄質サブプリニ―式噴火では、およそ600mより浅部で破砕がおこっていることなどが明らかとなった。
Magma fragmentation mechanism inducing explosive volcanic eruptions and a predicition model for volcanic eruptions

Okumura Satoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2018/04/01 - 2022/03/31

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The explosive volcanism is controlled by magma fragmentation during its ascent. The fragmentation of magma causes explosive eruptions by changing the flow type from viscous flow to a low-viscous gas flow with magma fragments. In order to clarify the mechanism of magma fragmentation, we analyzed pyroclastic materials, and performed decompression experiments. We also conducted numerical simulation based on a physical model for magma flow in a volcanic conduit. Finally, we could determine magma fragmentation mechanism, and then the relationship between magma fragmentation conditions and eruption transition was also discussed.
Structure and brittle failure of magma under deformation revealed by time-resolved X-ray diffraction

Satoshi Okumura

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Challenging Research (Exploratory)

Institution: Tohoku University

2019/06/28 - 2021/03/31

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Magma mainly consists of silicate melt (liquid), which results from the melting of rock, but it shows the transition from liquid- to solid-like behavior under deformation. This transition is a key mechanism for the cause of explosive volcanism. The transition occurs when magma deforms rapidly; however, the relationship between the transition and the atomic- and nanometer-scale structure of magma is unclear yet. In this study, we constructed an experimental system for time-resolved X-ray diffraction and small-angle scattering for deforming magma. Using this experimental system, we demonstrated that the atomic-scale structure of magma may not change during the transition from liquid- to solid-like behavior under deformation.
Development of near-real time volcanology based on in-situ observation experiments of shallow magmatic processes

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (S)

Category: Grant-in-Aid for Scientific Research (S)

Institution: Tohoku University

2016/05/31 - 2021/03/31
A mechanism of explosive eruption of low-viscosity mafic magma

Ishibashi Hidemi, Yasuda Atsushi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

Category: Grant-in-Aid for Scientific Research (C)

Institution: Shizuoka University

2016/04/01 - 2019/03/31

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We performed thermodynamic simulation of degassing-driven crystallization of mafic melts. The results suggest that the behaviors of crystallization are primarily controlled by the temperature of melt and the temperature-dependent change of crystallization behavior is responsible for the variation of eruption style of mafic magmas. In addition, we analyzed run samples of cooling-driven crystallization experiments of a high-Al basaltic melt from Hawaii. The results suggest that kinetic delay of crystallization induces the change of liquid line of descent and overestimation of melt-plagioclase geothermometers against quenched temperatures whereas melt-plagioclase partition coefficient of anorthite component does not depend on substantial cooling rate. Therefore, plagioclase-melt thermmeters can be applied to estimate temperature of natural mafic magmas if kinetic delay is minimum due to the effects of shear flow and/or H2O in melt.
Initiation and eruption style of silicic volcanism: Roles of outgassing and rheology of crystal- and bubble-bearing magmas

Okumura Satoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2015/04/01 - 2018/03/31

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Crystal-rich magmas with high viscosity often cause explosive volcanism. To ascend rapidly to the surface, the magma must be lubricated during the eruption. We performed decompression experiments for bubble- and crystal-bearing magmas to simulate magma ascent process. We also measured the viscosity of magmas with gas bubbles and crystals. Based on these experiments, we found that crystal-rich magma can lubricate due to the breakage of crystal network with gas bubble formation under high decompression rates. In contrast, gas bubbles escaped under low decompression rates. Thus, we infer that explosive volcanism by crystal-rich magmas can cause when high decompression rate is achieved by some mechanisms such as large overpressure in a magma reservoir.
高温変形実験による浅所貫入マグマ物性の研究

中村美千彦, 奥村聡, 三宅亮, 下司信夫, 小園誠史

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(A)

Institution: 東北大学

2016/04/01 - 2017/03/31

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火山の火道浅部まで上昇したマグマは、減圧により発泡して上昇の駆動力を得ると同時に、脱水して大きな過冷却状態に置かれ、微細な結晶が晶出して粘性が急上昇する。その両者がいかにバランスするかで、噴火の発生や噴火様式が決定される。本研究ではこれまで未解明のままである、安山岩～玄武岩質マグマの脱ガス機構、特に流動・変形の効果を高温変形実験により調べるとともに、マグマの粘性に対する減圧脱水結晶作用の影響を明らかにする。そしてこの両者を火道流物理モデルに組み込み、実際のマグマ貫入事例の圧力―時間履歴に即したマグマ挙動の時間発展を予測可能とすることを可能とし、さらにこの予測を、実際の活動推移や噴出物と比較し、モデルの検証や現象の解釈を行うことで、火山噴火メカニズムの解明に貢献することを目指した。初年度は、まず独自の流紋岩質マグマの変形その場観察装置開発の実績と経験を基に、より高温に対応した改良型の製作を目指し、その設計に着手した。 Anton Paar社の粘弾性精密粘性測定ユニット（レオメーターヘッド）を組み込み、幅広い範囲の粘性と同時に、振動測定法により弾性の測定を可能とする計画に基づき。高温電気炉部分の、より詳細な装置設計を行うため、先にレオメーターヘッドの制御ソフトウェアを購入し、制御ソフトの構成や、設定可能パラメターを調べるとともに、物性データの取得手順などを確認した。その結果、本実験試料のように、時々刻々と物性が変化する場合には、一部の手順で通常用いる自動制御が使えない可能性があり、模擬試料によるマニュアル制御法のキャリブレーションを行うための試料ユニットを用意するのがよいことがわかった。また自作した加熱装置に応じて、ソフトウェアを書き換えることができることもわかった。本研究の内容は基盤研究Sに含まれ、継続して実施される。
Sulfur partition among gas, melt, and crystal during magma decompression

Okumura Satoshi, SUMINO Hirochika

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

Category: Grant-in-Aid for Challenging Exploratory Research

Institution: Tohoku University

2015/04/01 - 2017/03/31

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Magmatic sulfur is released to the surface as a volcanic gas and it has a large impact on atmospheric chemistry and climate. Therefore, it is necessary to determine the partition of sulfur among gas, melt, and crystal. In this study, we investigated the partition of sulfur by performing decompression experiments. The decompression experiments were conducted at decompression rates of 1 to 900 MP/h that simulate a part of magma ascent during explosive to effusive eruptions. The experiments demonstrated that rapid decompression causes the oxidation of magma, resulting in sulfide breakdown. The partition between melt and crystal shows the dependence of decompression rate and hence we conclude that the composition of volcanic gas is controlled by the decompression rate.
Mechanism of fragmentation of inhomogeneous porous viscoelastic liquid in solid/fluid transition regime

KAMEDA Masaharu, YAMANAKA Akinori, ICHIHARA Mie, OKUMURA Satoshi, UESUGI Kentaro

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

Category: Grant-in-Aid for Challenging Exploratory Research

Institution: Tokyo University of Agriculture and Technology

2014/04/01 - 2016/03/31

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We conducted laboratory experiment and numerical simulation for fragmentation of vesicular magma, which is a trigger of explosive eruption. We observed the fragmentation of vesicular magma analog whose three-dimensional (3D) pore structure was determined by X-ray tomography. We simulated 3D internal stress distribution of the analog by finite-element analysis (FEM). By combined analysis of experimental observation and FEM analysis, we found that the location of crack initiation is coincide with the maximum stress concentration point around the pore. We simulated crack propagation in Maxwell fluid based on a continuum approach using the phase-field method coupled with FEM. We successfully captured the difference in crack propagation in a two-dimensional plate under the different viscoelasticity.
Creation of Interface Petrology with a New Grain Liberation Method and X-ray CT Imaging

NAKAMURA MICHIHIKO, TANI Kenichirou, OKUMURA Satoshi, YOSHIDA Takeyoshi, SASAKI Osamu

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

Category: Grant-in-Aid for Challenging Exploratory Research

Institution: Tohoku University

2013/04/01 - 2016/03/31

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We have investigated mafic and ultramafic xenoliths from lower continental crust and upper mantle from various localities in the world by using a high voltage pulse power fragmentation method and X-ray CT imaging. Most of the xenoliths samples included intergranular pores that should have been filled with aqueous fluids at high pressure and temperature. The local volume fraction of the pores was at most 5 %.The three-dimensional shape of the pores were polyhedral - oblate spheroidal. Based on these volume fraction and shapes of the fluids, the relative decrease of dlnVs to dlnVp, the Rsp value, was estimated to be 0.9.The dihedral angles between mantle xenoliths and isolated intergranular fluids were variable, dependent on the localities of the xenoliths samples. This means that shapes of the intergranular fluids may represent the carbon dioxide content in the fluids.
Strain localization in magma and its roles in volcanic eruptions

OKUMURA Satoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

Category: Grant-in-Aid for Young Scientists (B)

Institution: Tohoku University

2012/04/01 - 2015/03/31

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The explosivity of volcanic eruptions is controlled by magma vesiculation and outgassing. The rate of outgassing that releases gas phase to the outside is enhanced by magma deformation via the formation of bubble networks. In this study, we observed in-situ magma deformation under high temperature and pressure condition using a synchrotron radiation X-ray imaging, and determined the criterion for the onset of strain localization for vesicular rhyolite. Based on this result, we can predict the change of outgassing rate during magma ascent. We also found that the formation and healing of shear-localized zone in magma depend on magma temperature, pressure, and deformation rate.
A study on the mechanism of shallow-level degassing of conduit magmas as a controlling factor of eruption styles

NAKAMURA Michihiko, KURITANI Takesi, YASUI Maya, OKUMURA Satoshi, YOSHIA Takeyoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2009 - 2012

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We examined the crystal size distribution (CSD) of ground crystals in the erupted materials of the 2011 Shinmoe-dake volcano. We found that magma residence time in the shallow conduit in the explosive subplinian phase is shorter than in the less-explosive vulcanian and lava dome phases. We also conducted textural relaxation experiments of andesitic pumices in shallow conduit conditions and clarified the vapor pressure dependence of the relaxation and bubble coagulation. We conclude that the textural relaxation enhances formation of “gas pockets" via compaction of shallow melt foam.
Mechanism and rate of magma degassing : Toward an understanding of bifurcation of explosive-effusive silicic volcanism

OKUMURA Satoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)

Category: Grant-in-Aid for Young Scientists (A)

Institution: Tohoku University

2009 - 2011

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A factor controlling the style and explosivity of volcanic eruptions is magma degassing during its ascent in a volcanic conduit. To understand the mechanism of the degasing and determine the degassing rate, we experimentally simulated magma ascent and observed in situ the deformation of magma by using originally developed deformation apparatus which was built up on synchrotron radiation X-ray imaging system in SPring-8. The experimental results demonstrated that the degassing rate from flowing magma was high. This result implies that some unknown mechanisms inhibit the degassing for explosive volcanism.
火山噴火の様式を支配する脱ガス率の定量化:マグマ中の気泡の変形とその効果

奥村聡

Offer Organization: 日本学術振興会

System: 科学研究費助成事業特別研究員奨励費

Category: 特別研究員奨励費

Institution: 東北大学

2006 - 2008

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マグマの上昇中に起こる脱ガス率を決定することは,火山噴火の多様性の原因を解明するために重要である.これまでに,天然試料を用いた研究が行われてきたが,それらはマグマの変形や圧密など様々なプロセスを経た結果を表わしていて,マグマ上昇中の情報だけを引き出すことは原理的に難しい.一方で,マグマの上昇を模擬した実験から得られている結果は,地球化学的・地球物理学的な観測研究の結果と一致しない点が挙げられている.特に,マグマが脱ガスを開始する予想深度について不一致が見られる.これらの問題点を解決すべく,申請者はマグマが流動しているという事実に着目し,これまでほとんど検討されていないせん断応力下における気泡組織の進化に注目した. 過去2年間の実験,分析と考察の結果から,せん断変形によりマグマ中の気泡合体が促進され,それに伴いマグマの脱ガス率が上昇する可能性が示された.今年度は主に,浸透率の実測とその結果を用いた物理モデルの構築,そしてマグマの脱ガスと噴火様式の多様性の関係について考察した.まず浸透率の測定結果から,せん断変形により浸透率が2-4桁程度も上昇する可能性が見出された.そして,この結果を組み込んだ物理モデルからは,噴火様式を支配する要因の一つとして火道の形状(火道半径と長さ)が挙げられた.つまり,半径が大きく長さの短い火道ほど爆発的噴火になりやすく,半径が小さく長い火道では比較的穏やかな噴火になると予想される.これらの結果からは,噴火様式を予測する方法の一つとして,地球物理学的な方法などを用いて火道形状を計測する方法が提案される.
マグマの脱水速度論に基づくマグマ上昇時間スケールの定量化

奥村聡

Offer Organization: 日本学術振興会

System: 科学研究費助成事業特別研究員奨励費

Category: 特別研究員奨励費

2004 - 2005

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マグマの脱水速度を決定しマグマ上昇の時間スケールを考察することは,火山噴火のダイナミクスを理解し火山噴火の様式を予測するために重要である.本研究は,マグマの脱水速度を定量化し,マグマ上昇の時間スケールを考察することを目的とした. 本年度の主要な成果として次の3点が挙げられる.まず,第一に多様な化学組成をもつシリケイトメルト中の水の拡散係数を決定し,その化学組成依存性をモデル化した点である.この研究により多様な化学組成を持つマグマについて,噴火時の脱水をモデル化することが可能になった.この研究成果は,国際雑誌に発表した.また,関連成果を国内誌に投稿中である.第二は,シリケイトメルトの脱水機構としての拡散・反応モデルを構築した点である.この研究では,脱水機構を詳細に調べるため申請者が確立したシリケイトメルトの脱水その場観測実験を行った.また,拡散・反応モデルを構築し,そのモデルを基に数値実験を行った。この研究により,流紋岩質メルトの脱水はH_2O分子の拡散と2段階の反応モデル(H_2O分子⇔OHペアとOHペアの形成)で説明可能であることが示された.また,モデルに含まれる速度論的パラメーターの決定に成功した.この研究成果は,国際雑誌に投稿中である.最後に,これまでに決定された脱水速度と火山噴出物中に残る脱水の痕跡からマグマの上昇スケールについて考察を行った.そして,爆発的な噴火であるプリニー式噴火のマグマ上昇の時間スケールが〜1000秒程度であることを示した.

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