Search results for: Toshitsugu Fujii

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Progressive enrichment of arc magmas caused by the subduction of seamounts under Nishinoshima volcano, Izu–Bonin Arc, Japan

Takashi Sano, Motomaro Shirao, Kenichiro Tani, Yukiyasu Tsutsumi, more

Journal of Volcanology and Geothermal Research > 2016 > 319 > C > 52-65

The chemical composition of intraplate seamounts is distinct from normal seafloor material, meaning that the subduction of seamounts at a convergent margin can cause a change in the chemistry of the mantle wedge and associated arc magmas. Nishinoshima, a volcanic island in the Izu–Bonin Arc of Japan, has been erupting continuously over the past 2years, providing an ideal opportunity to examine the...

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Estimation of ballistic block landing energy during 2014 Mount Ontake eruption

Kae Tsunematsu, Yasuhiro Ishimine, Takayuki Kaneko, Mitsuhiro Yoshimoto, more

Earth, Planets and Space > 2016 > 68 > 1 > 1-11

The 2014 Mount Ontake eruption started just before noon on September 27, 2014. It killed 58 people, and five are still missing (as of January 1, 2016). The casualties were mainly caused by the impact of ballistic blocks around the summit area. It is necessary to know the magnitude of the block velocity and energy to construct a hazard map of ballistic projectiles and design effective shelters and...

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Polybaric crystallization differentiation of H₂O-saturated island arc low-K tholeiite magmas: a case study of the Izu-Oshima volcano in the Izu arc

Morihisa Hamada, Yuko Okayama, Takayuki Kaneko, Atsushi Yasuda, more

Earth, Planets and Space > 2014 > 66 > 1 > 1-10

Island arc low-K tholeiites are basaltic magmas erupting from frontal arc volcanoes of juvenile arcs associated with the subduction of old and cold plates. We investigated the origins of geochemical variation in volcanic rocks having multiple phase saturated liquid compositions from the Izu-Oshima volcano in the northern Izu arc. The geochemical variations in the liquids fall between two endmember...

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Syneruptive deep magma transfer and shallow magma remobilization during the 2011 eruption of Shinmoe-dake, Japan—Constraints from melt inclusions and phase equilibria experiments

Yuki Suzuki, Atsushi Yasuda, Natsumi Hokanishi, Takayuki Kaneko, more

Journal of Volcanology and Geothermal Research > 2013 > 257 > Complete > 184-204

The 2011 Shinmoe-dake eruption started with a phreatomagmatic eruption (Jan 19), followed by climax sub-Plinian events and subsequent explosions (Jan 26–28), lava accumulation in the crater (end of January), and vulcanian eruptions (February–April). We have studied a suite of ejecta to investigate the magmatic system beneath the volcano and remobilization processes in the silicic magma mush. Most...

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Hydrogen concentration in plagioclase as a hygrometer of arc basaltic melts: Approaches from melt inclusion analyses and hydrous melting experiments

Morihisa Hamada, Masashi Ushioda, Toshitsugu Fujii, Eiichi Takahashi

Earth and Planetary Science Letters > 2013 > 365 > Complete > 253-262

The partition coefficients of hydrogen between plagioclase and basaltic melt were determined by two approaches. For the first part of this study, plagioclase-hosted melt inclusions in mid-ocean ridge basalt (MORB) from the Rodriguez Triple Junction in the Indian Ocean were analyzed. The hydrogen concentration in plagioclase is less than 60wtppm water, and the average H ₂ O concentration in...

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Polybaric degassing of island arc low-K tholeiitic basalt magma recorded by OH concentrations in Ca-rich plagioclase

Morihisa Hamada, Tatsuhiko Kawamoto, Eiichi Takahashi, Toshitsugu Fujii

Earth and Planetary Science Letters > 2011 > 308 > 1-2 > 259-266

Hydrogen in nominally anhydrous minerals (NAMs) in volcanic rocks can be used as a proxy for dissolved H ₂ O in melt prior to eruption. Plagioclase is a NAM that accommodates hydrogen in concentrations of up to hundreds of wt. ppm H ₂ O. The species of hydrogen in volcanic plagioclase is structural OH. We report the analytical results of OH concentrations in Ca-rich plagioclase from...

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Effect of syneruptive decompression path on shifting intensity in basaltic sub-Plinian eruption: Implication of microlites in Yufune-2 scoria from Fuji volcano, Japan

Yuki Suzuki, Toshitsugu Fujii

Journal of Volcanology and Geothermal Research > 2010 > 198 > 1-2 > 158-176

To constrain the timing and conditions of syneruptive magma ascent that are responsible for shifting eruption intensity, we have investigated a basaltic sub-Plinian eruption that produced Yufune-2 scoria in Fuji volcano 2200years ago. We deduced magmatic decompression conditions from groundmass microlite textures, including decompression path (i.e. evolution in decompression rate) and approximate...

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Evolution of Mount Fuji, Japan: Inference from drilling into the subaerial oldest volcano, pre‐Komitake

Mitsuhiro Yoshimoto, Toshitsugu Fujii, Takayuki Kaneko, Atsushi Yasuda, more

Island Arc > 19 > 3 > 470 - 488

A buried, old volcanic body (pre‐Komitake Volcano) was discovered during drilling into the northeastern flank of Mount Fuji. The pre‐Komitake Volcano is characterized by hornblende‐bearing andesite and dacite, in contrast to the porphyritic basaltic rocks of Komitake Volcano and to the olivine‐bearing basaltic rocks of Fuji Volcano. K‐Ar age determinations and geological analysis of drilling cores...

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Crypto-magma chambers beneath Mt. Fuji

Takayuki Kaneko, Atsushi Yasuda, Toshitsugu Fujii, Mitsuhiro Yoshimoto

Journal of Volcanology and Geothermal Research > 2010 > 193 > 3-4 > 161-170

Mt. Fuji consists dominantly of basalt. A study of olivine-hosted melt-inclusions from layers of air-fall scoria, however, shows clear evidence of andesitic liquids. Whole rock compositions show a narrow range of SiO ₂ , but a wide range of FeO*/MgO and incompatible elements. Phenocrystic plagioclase generally shows bi-modal distributions in compositional frequency, while most olivine phenocrysts...

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Experimental constraints on the effects of pressure and H₂O on the fractional crystallization of high-Mg island arc basalt

Morihisa Hamada, Toshitsugu Fujii

Contributions to Mineralogy and Petrology > 2008 > 155 > 6 > 767-790

H₂O-undersaturated melting experiments of synthesized basalt (SiO₂ = 50.7 wt.%, MgO = 8.3 wt.%, Mg# = 60) were conducted at fO₂ corresponding to NNO+1 and NNO−1 to clarify the effects of pressure (2–7 kbar) and H₂O on fractional crystallization in island arcs. H₂O content was ranged from nominally anhydrous to 4.4 wt.%. Differentiation trends, namely the liquid lines of descent, change sensitively...

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Mg–Fe partitioning between olivine and ultramafic melts at high pressures

Kenji Mibe, Toshitsugu Fujii, Atsushi Yasuda, Shigeaki Ono

Geochimica et Cosmochimica Acta > 2006 > 70 > 3 > 757-766

Precise determination of the partitioning of Mg and Fe ²⁺ between olivine and ultramafic melt has been made at pressures from 5 to 13GPa using a MA-8 type multi-anvil high-pressure apparatus (PREM) installed at Earthquake Research Institute, University of Tokyo. A very short rhenium capsule (<100μm sample thickness) was adopted to minimize temperature variation within the sample container...

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Submarine flank eruption preceding caldera subsidence during the 2000 eruption of Miyakejima Volcano, Japan

Takayuki Kaneko, Atsushi Yasuda, Taketo Shimano, Setsuya Nakada, more

Bulletin of Volcanology > 2005 > 67 > 3 > 243-253

During the early part of a seismic swarm preceding eruption and caldera formation at Miyakejima Volcano, discoloured sea surfaces were observed ∼1.5 km off the western coast of Miyakejima on 27 June 2000. A later survey of the area using a multi-beam side scan sonar and a remotely operated small submarine revealed four craters of 20–30 m diameter aligned east-west in a 100×10–30 m area on the seafloor,...

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Response to the comment by R. Stalder on ''composition of aqueous fluid coexisting with mantle minerals at high pressure and its bearing on the differentiation of the earth's mantle''

Kenji Mibe, Toshitsugu Fujii, Atsushi Yasuda

Geochimica et Cosmochimica Acta > 2004 > 68 > 4 > 929-930

article

Composition of aqueous fluid coexisting with mantle minerals at high pressure and its bearing on the differentiation of the Earth's mantle

Kenji Mibe, Toshitsugu Fujii, Atsushi Yasuda

Geochimica et Cosmochimica Acta > 2002 > 66 > 12 > 2273-2285

In order to understand the role of aqueous fluid on the differentiation of the mantle, the compositions of aqueous fluids coexisting with mantle minerals were investigated in the system MgO-SiO ₂ -H ₂ O at pressures of 3 to 10 GPa and temperatures of 1000 to 1500 ^o C with an MA8-type multianvil apparatus. Phase boundaries between the stability fields of forsterite + aqueous...

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Fresh pumice from the Central Indian Basin: a Krakatau 1883 signature

Abhay Mudholkar, Toshitsugu Fujii

Marine Geology > 1995 > 125 > 1-2 > 143-151

The occurrence of pumice in the Central Indian Basin (CIB) has been a controversy. Some are of the opinion that these pumices are erupted from a volcano along the Ninetyeast ridge while others suggest the Indonesian arc volcanism as their probable source. Recently, it is also suggested that the pumice are the products of in-situ silicic volcanism in the CIB. This study was initiated in order to resolve...

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