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Article type: Photogravure
1989 Volume 34 Issue 2 Pages
App1-
Published: July 25, 1989
Released on J-STAGE: January 15, 2018
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Keiji WADA
Article type: Article
1989 Volume 34 Issue 2 Pages
89-104
Published: July 25, 1989
Released on J-STAGE: January 15, 2018
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Simultaneous eruptions of basaltic andesite, andesite, and dacite magmas took place during the somma-building stage (about 13 ka) of Meakan volcano, eastern Hokkaido. Pyroclastic materials consist of scoriae and pumices with essential lithics and bombs, and are characterized by heterogeneous texture such as banded structure, blob-like inclusion, and branched form. This mode of occurrence and eruptive sequence suggest that the basaltic andesite magma were injected into the dacite magma. Morphology of the heterogeneous texture shows a fractal structure with a dimension of 1.6, that is identical to the theoretical value of fractal dimension for turbulence diffusion. Mixing mechanism in a volcanic conduit is dicussed, based on the turbulence model and recent fluid dynamical experiments. During one eruption event, turbulent flow of the basaltic andesite magma with incorporation of the dacite magma in the central part of the conduit could produce the heterogeneous and macroscopically homogeneous mixed-ejecta, whereas homogeneous dacite pumice may be derived from outer flow near the vertical wall of the conduit. Turbulent magmatic flow facilitates blending of mafic and felsic magmas. However, mixed-ejecta reserves small-scale heterogeneity, i.e., the scoriaceous groundmass has glass of various compositions, and the phenocrysts originally derived from the dacite magma contact with both felsic and mafic groundmass. One possible idea to explain this feature is that ascending rate of heterogeneous magmas through the conduit was greater than the homogenizing rate of magma mixing.
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Hikaru IWAMORI
Article type: Article
1989 Volume 34 Issue 2 Pages
105-123
Published: July 25, 1989
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Cenozoic olivine-bearing basaltic lavas in the central Chugoku district form eight distributional provinces, each having 20 to 30 km diameter. Lavas in each province have similarities in chemical composition and mode of occurrence. Moreover, these provinces can be grouped into three zones almost parallel to the SW Japan arc on the basis of the differences in chemical composition and eruption volume of volcanics; the San-yo zone (the nearest to the Nankai trough), the Sekiryo zone, and the San-in zone (along the Japan Sea coast) from the south to the north. The eruption volume including both basalts and andesites exponentially increases northward, in other words, towards the back-arc side. The chemical compositions of the relatively undifferentiated basalts show systematic across-arc variations. SiO
2 and Al
2O
3 increase, and FeO
*, MgO and CaO decrease toward the back-arc side (44 to 54, 13 to 18, 11 to 6, 13 to 7 and 12 to 8 wt. % at FeO
*/MgO=0.85, respectively). The above compositional difference can be explained by a difference in the depth of magma segregation; the depth of magma segregation decreases towards the back-arc side. These across-arc variations of the basalts in the central Chugoku district has opposite polarity compared with that in the NE Japan arc, and cannot be explained by the process related to subduction of the oceanic lithosphere from the Nankai trough or the Japan trench. Taking into account the timing of volcanism which started at 12 Ma, the volcanism could have been caused by the upwelling of mantle materials associated with the opening of the Japan Sea.
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Izumi YOKOYAMA
Article type: Scientific Communication
1989 Volume 34 Issue 2 Pages
125-126
Published: July 25, 1989
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I. Moriya
Article type: Abstract
1989 Volume 34 Issue 2 Pages
127-
Published: July 25, 1989
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T. Hasenaka
Article type: Abstract
1989 Volume 34 Issue 2 Pages
127-128
Published: July 25, 1989
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H. Hamaguchi, S. Tanaka
Article type: Abstract
1989 Volume 34 Issue 2 Pages
128-
Published: July 25, 1989
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S. Tamanyu
Article type: Abstract
1989 Volume 34 Issue 2 Pages
128-
Published: July 25, 1989
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H. Hoshizumi
Article type: Abstract
1989 Volume 34 Issue 2 Pages
128-129
Published: July 25, 1989
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R. Imura
Article type: Abstract
1989 Volume 34 Issue 2 Pages
129-
Published: July 25, 1989
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K. Sakaguchi, T. Kobayashi
Article type: Abstract
1989 Volume 34 Issue 2 Pages
129-130
Published: July 25, 1989
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T. Kobayashi
Article type: Abstract
1989 Volume 34 Issue 2 Pages
130-
Published: July 25, 1989
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J. Ishibashi, T. Gamo, H. Sakai, Y. Sano, H. Wakita, Y. Nojiri
Article type: Abstract
1989 Volume 34 Issue 2 Pages
130-
Published: July 25, 1989
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M. Tsuchide, F. Kuwakino, K. Shimizu, K. Kusunoki
Article type: Abstract
1989 Volume 34 Issue 2 Pages
131-
Published: July 25, 1989
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M. Yuasa, F. Murakami
Article type: Abstract
1989 Volume 34 Issue 2 Pages
131-
Published: July 25, 1989
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T. Miyazaki, S. Sakashita, E. Koyama, M. Sawada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
131-132
Published: July 25, 1989
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T. Murakami, K. Inoue, K. Nemoto, A. Itabashi, H. Tsuji, T. Tada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
132-
Published: July 25, 1989
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T. Yabuki, M. Matsu’ura, M. Hashimoto, T. Tada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
132-133
Published: July 25, 1989
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M. Hashimoto, T. Tada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
133-
Published: July 25, 1989
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K. Yamaoka, M. Hashimoto
Article type: Abstract
1989 Volume 34 Issue 2 Pages
133-
Published: July 25, 1989
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E. Fukuyama, M. Takeo
Article type: Abstract
1989 Volume 34 Issue 2 Pages
133-134
Published: July 25, 1989
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K. Fukui, Y. Sawada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
134-
Published: July 25, 1989
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H. Watanabe
Article type: Abstract
1989 Volume 34 Issue 2 Pages
134-
Published: July 25, 1989
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K. Katoh, M. Takahashi, K. Kazahaya, K. Ando
Article type: Abstract
1989 Volume 34 Issue 2 Pages
134-135
Published: July 25, 1989
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K. Kazahaya, T. Soya, N. Ando, J. Kosaka
Article type: Abstract
1989 Volume 34 Issue 2 Pages
135-
Published: July 25, 1989
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K. Kazahaya, M. Takahashi, H. Shinohara, J. Hirabayashi
Article type: Abstract
1989 Volume 34 Issue 2 Pages
135-136
Published: July 25, 1989
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K. Notsu, Y. Sano, G. Igarashi, H. Wakita
Article type: Abstract
1989 Volume 34 Issue 2 Pages
136-
Published: July 25, 1989
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A. Takagi, M. Kasahara
Article type: Abstract
1989 Volume 34 Issue 2 Pages
136-
Published: July 25, 1989
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K. Wada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
136-137
Published: July 25, 1989
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S. Kawachi, Y. Katsui, T. Watanabe, Y. Ikeda, J. Maeda, T. Shibata, N. ...
Article type: Abstract
1989 Volume 34 Issue 2 Pages
137-
Published: July 25, 1989
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Y. Ikeda, Y. Katsui, S. Kawachi, T. Watanabe, N. Fujibayashi, J. Maeda ...
Article type: Abstract
1989 Volume 34 Issue 2 Pages
137-138
Published: July 25, 1989
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N. Miyaji, K. Kouyama, Y. Kondou, M. Sumita, T. Yamazaki, Y. Katsui
Article type: Abstract
1989 Volume 34 Issue 2 Pages
138-
Published: July 25, 1989
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Y. Nishimura, H. Miyamachi, H. Mori, T. Maekawa, A. Suzuki, H. Okada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
139-
Published: July 25, 1989
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H. Shimizu, S. Ohmi, H. Miyamachi, T. Maekawa, S. Suzuki, M. Kasahara, ...
Article type: Abstract
1989 Volume 34 Issue 2 Pages
139-
Published: July 25, 1989
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T. Nishimura, S. Ueki, H. Miyamachi, Y. Nishimura
Article type: Abstract
1989 Volume 34 Issue 2 Pages
140-
Published: July 25, 1989
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H. Mori, Y. Nishimura, A. Suzuki, M. Kasahara
Article type: Abstract
1989 Volume 34 Issue 2 Pages
140-
Published: July 25, 1989
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N. Okazaki, N. Matsushima, R. Ichikawa, M. Michiwaki
Article type: Abstract
1989 Volume 34 Issue 2 Pages
140-141
Published: July 25, 1989
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Y. Nishimura, H. Miyamachi, T. Maekawa, Hm. Okada, K. Ishihara, M. Igu ...
Article type: Abstract
1989 Volume 34 Issue 2 Pages
141-
Published: July 25, 1989
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S. Ohmi, H. Shimizu, H. Miyamachi, T. Maekawa, H. Okada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
141-142
Published: July 25, 1989
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K. Suga
Article type: Abstract
1989 Volume 34 Issue 2 Pages
142-
Published: July 25, 1989
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Y. Hirata
Article type: Abstract
1989 Volume 34 Issue 2 Pages
142-143
Published: July 25, 1989
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K. Yamaoka, H. Watanabe, H. Imai
Article type: Abstract
1989 Volume 34 Issue 2 Pages
143-
Published: July 25, 1989
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F. Masutani, M. Yamaguchi
Article type: Abstract
1989 Volume 34 Issue 2 Pages
143-
Published: July 25, 1989
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T. Hasenaka
Article type: Abstract
1989 Volume 34 Issue 2 Pages
143-144
Published: July 25, 1989
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M. Takeuchi, T. Ui
Article type: Abstract
1989 Volume 34 Issue 2 Pages
144-
Published: July 25, 1989
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S. Nagaoka, S. Kato, M. Hayashida, H. Seta, Y. Kato
Article type: Abstract
1989 Volume 34 Issue 2 Pages
144-145
Published: July 25, 1989
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T. Kagiyama, J. S. S. Pareja
Article type: Abstract
1989 Volume 34 Issue 2 Pages
145-
Published: July 25, 1989
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A. Takada
Article type: Abstract
1989 Volume 34 Issue 2 Pages
145-
Published: July 25, 1989
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T. Nakano, N. Fujii
Article type: Abstract
1989 Volume 34 Issue 2 Pages
146-
Published: July 25, 1989
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Y. Tatsumi, S. Nohda
Article type: Abstract
1989 Volume 34 Issue 2 Pages
146-
Published: July 25, 1989
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