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Article type: Photogravure
1988 Volume 33 Issue 4 Pages
App6-
Published: December 28, 1988
Released on J-STAGE: January 15, 2018
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Setsuya NAKADA, Hiroki KAMATA
Article type: Article
1988 Volume 33 Issue 4 Pages
273-289
Published: December 28, 1988
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Volcanism and deposition of volcaniclastic materials within a graben in the Shimabara area, western Kyushu, started in early Pliocene and have continued up to the present. The volcanic products comprise alkalic to high-alkali tholeiitic basalts in addition to calc-alkalic andesites. The basalts are of a member of magmas erupted extensively in NW Kyushu from late Miocene to Recent. Their incompatible-element patterns in spider gram, in which the abundances of Rb, Ba, K, Nb, Zr and Y are normalized to those of MORB, are uniform independently of their eruption-ages, and show positive Ba and Nb anomalies strongly indicative of the marked affinity with ocean-island basalts. These patterns are clearly different from those of island-arc basalts which have negative Nb anomaly, as represented by the Quaternary high-alumina basalts in central Kyushu, and from those of back-arc basin basalts usually showing the same anomaly. It is concluded that basaltic magmas in NW Kyushu were derived from partial melt of fertile mantle with high Nb/Zr. Most of the andesites in the Shimabara area have phenocryst assemblages showing co-existence of magmas with different compositions. This fact and the spidergram pattern without Nb anomaly of the andesites lead us to a magmatic model; the andesite magma originated from mixing of positive-Nb-anomaly basaltic melt with negative-Nb-anomaly acidic partial melt of lower-crust materials which were presumably heated by the former melt. The graben in the Shimabara area seems to have developed in southern periphery of the region under which fertile mantle materials have been rising up from the depth and the subducted oceanic slab has not reached, like the “hot region”.
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Takeshi KOIZUMI, Keiichi FUKUI, Tetsuo HASHIMOTO, Mitsuyuki HOSHIBA, M ...
Article type: Article
1988 Volume 33 Issue 4 Pages
291-303
Published: December 28, 1988
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During the period from Nov. 1985 to May 1988, the Izu-Oshima Volcano erupted in Nov. 15-20, 1986 (called phase-I), Nov. 21, 1986 (phase-II), (Dec. 1986 (trivial)), Nov. 16, 1987, and Nov. 18, 1987. Phase-I was the summit eruption from the pit crater of Mt. Mihara and phase-II was the fissure eruption having the NW-SE strike. One year after the phase-II eruption, the Izu-Oshima Volcano erupted again, and the lava head of the pit crater fell down about 100 meters on the morning of Nov. 18, 1987. In this period, we carried out ten sets of precise gravity survey in Izu-Oshima Island using the LaCoste & Romberg Model D gravity meter No. 109. The measurements were made on the bench marks of the leveling route rounding the island which was established by the Geographical Survey Institute (GSI) in 1979 and on gravity points by the Earthquake Research Institute and GSI. We discuss the changes in gravity differences referred to the Oshima First Gravity Station (FGS). We observed the increase in gravity values which might be caused by the charge of the magma reservoir during the period from Nov. 1985 to Nov. 15, 1986 (The beginning of the phase-I eruption). We also observed the decrease in gravity values which was caused by the phase-II eruption. In this period, except for the north and southwest stations, the relation between elevation and gravity changes did not show Bouguer gradient nor free air gradient. This fact suggests the occurrence of mass defect under the ground with the phase-II eruption. After the end of phase-II eruption, the gravity values in Izu-Oshima Island decreased gradually, and increased again in November 18, 1987. We suppose that this step-like increase was caused by the drain back of lava from the pit crater to the magma reservoir. We estimated a center of gravity increase using a point source model. The estimated center is at northwest rim of the Izu-Oshima caldera, 0.5 kilometers below the sea level.
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Hiroki KAMATA, Kozo UTO, Shigeru UCHIUMI
Article type: Article
1988 Volume 33 Issue 4 Pages
305-320
Published: December 28, 1988
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Andesitic volcano groups were emplaced during middle Pleistocene around the Waitasan area in the center of the Hohi volcanic zone, Kyushu, Japan. These andesitic volcanoes formed on the buried Shishimuta caldera, after eruption of the Yabakei pyroclastic flow in an extensional stress field. Stratigraphic successions, radiometric ages, volumes and compositions of the volcanic rocks in the Waitasan area are investigated in order to clarify the evolution of the post-Shishimuta caldera activity. The characteristics of volcanic activity, which took place during 1.0-0.3 Ma, changed at about 0.7 Ma from predominance of large-volume pyroxene andesite lavas to that of small-volume hornblende andesite lavas, suggesting that the magma beneath Shishimuta caldera decreased its temperature. At about 0.7 Ma, the dominant volcanic edifice changed from lava plateau to lava domes accompanied by a few stratovolcanoes. The appearance of stratovolcanoes can be accounted for by the occurrence of local compressional stress field which initiated at about 0.7 Ma and started to overlap the previously dominant N-S extensional stress field.
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H. Muraoka, Suwijanto, Suharyono Kardi, Y. Miyazaki, R. Kouda
Article type: Abstract
1988 Volume 33 Issue 4 Pages
321-
Published: December 28, 1988
Released on J-STAGE: February 13, 2018
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H. Sawatari, H. Shimizu, Y. Kawata, A. Masuda
Article type: Abstract
1988 Volume 33 Issue 4 Pages
321-322
Published: December 28, 1988
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J. Matsuda, T. Ui, K. Notsu, K. Nagao, T. Kita, T. Fujitani, T. Ercan
Article type: Abstract
1988 Volume 33 Issue 4 Pages
322-
Published: December 28, 1988
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T. Nishimura, H. Hamaguchi, N. Zana
Article type: Abstract
1988 Volume 33 Issue 4 Pages
322-323
Published: December 28, 1988
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T. Hasenaka
Article type: Abstract
1988 Volume 33 Issue 4 Pages
323-
Published: December 28, 1988
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A. Kubotera
Article type: Abstract
1988 Volume 33 Issue 4 Pages
323-324
Published: December 28, 1988
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H. Hamaguchi
Article type: Abstract
1988 Volume 33 Issue 4 Pages
324-
Published: December 28, 1988
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Y. Nishida, H. Mori, Y. Matsushima, M. Michiwaki, R. Ichikawa, K. Yama ...
Article type: Abstract
1988 Volume 33 Issue 4 Pages
324-
Published: December 28, 1988
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Y. Takigami, K. Niida
Article type: Abstract
1988 Volume 33 Issue 4 Pages
324-325
Published: December 28, 1988
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T. Nakano, N. Fujii
Article type: Abstract
1988 Volume 33 Issue 4 Pages
325-
Published: December 28, 1988
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J. Oikawa, Y. Ida, T. Watanabe
Article type: Abstract
1988 Volume 33 Issue 4 Pages
325-326
Published: December 28, 1988
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Y. Ida
Article type: Abstract
1988 Volume 33 Issue 4 Pages
326-
Published: December 28, 1988
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A. Toramaru
Article type: Abstract
1988 Volume 33 Issue 4 Pages
326-
Published: December 28, 1988
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S. Sato
Article type: Abstract
1988 Volume 33 Issue 4 Pages
326-327
Published: December 28, 1988
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K. Ito
Article type: Abstract
1988 Volume 33 Issue 4 Pages
327-
Published: December 28, 1988
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K. Ono
Article type: Abstract
1988 Volume 33 Issue 4 Pages
327-328
Published: December 28, 1988
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Y. Wada
Article type: Abstract
1988 Volume 33 Issue 4 Pages
328-
Published: December 28, 1988
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A. Takada
Article type: Abstract
1988 Volume 33 Issue 4 Pages
328-
Published: December 28, 1988
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K. Anazawa, M. Yoshida
Article type: Abstract
1988 Volume 33 Issue 4 Pages
328-329
Published: December 28, 1988
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J. K. Murayama, M. Kumazawa, M. Tokonami
Article type: Abstract
1988 Volume 33 Issue 4 Pages
329-
Published: December 28, 1988
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T. Suzuki
Article type: Abstract
1988 Volume 33 Issue 4 Pages
329-330
Published: December 28, 1988
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T. Kobayashi, S. Aramaki
Article type: Abstract
1988 Volume 33 Issue 4 Pages
330-
Published: December 28, 1988
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R. Imura, T. Kobayashi
Article type: Abstract
1988 Volume 33 Issue 4 Pages
330-331
Published: December 28, 1988
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H. Hoshizumi, K. Mimura
Article type: Abstract
1988 Volume 33 Issue 4 Pages
331-
Published: December 28, 1988
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H. Sato
Article type: Abstract
1988 Volume 33 Issue 4 Pages
331-
Published: December 28, 1988
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Y. Tanaka, T. Sakata
Article type: Abstract
1988 Volume 33 Issue 4 Pages
331-332
Published: December 28, 1988
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K. Fujioka, K. Suga, H. Yoshida, M. Yuasa
Article type: Abstract
1988 Volume 33 Issue 4 Pages
332-
Published: December 28, 1988
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M. Sasaki
Article type: Abstract
1988 Volume 33 Issue 4 Pages
332-333
Published: December 28, 1988
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M. Ban
Article type: Abstract
1988 Volume 33 Issue 4 Pages
333-
Published: December 28, 1988
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Y. Nishimura
Article type: Abstract
1988 Volume 33 Issue 4 Pages
333-334
Published: December 28, 1988
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A. Takagi, Y. Nishimura
Article type: Abstract
1988 Volume 33 Issue 4 Pages
334-
Published: December 28, 1988
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K. Kazahaya, M. Takahashi, T. Soya, H. Endo, N. Ando, J. Kosaka, J. Hi ...
Article type: Abstract
1988 Volume 33 Issue 4 Pages
334-335
Published: December 28, 1988
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S. Arai
Article type: Abstract
1988 Volume 33 Issue 4 Pages
335-
Published: December 28, 1988
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M. Takahashi, K. Abe, T. Noda, Y. Kazahaya, N. Ando
Article type: Abstract
1988 Volume 33 Issue 4 Pages
335-
Published: December 28, 1988
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N. Takahashi, S. Arai
Article type: Abstract
1988 Volume 33 Issue 4 Pages
335-336
Published: December 28, 1988
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M. Churei, K. Yoshikawa, M. Asanuma
Article type: Abstract
1988 Volume 33 Issue 4 Pages
336-
Published: December 28, 1988
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T. Kobayashi, J. Ito
Article type: Abstract
1988 Volume 33 Issue 4 Pages
336-337
Published: December 28, 1988
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K. Yamaoka, J. Oikawa, Y. Ida
Article type: Abstract
1988 Volume 33 Issue 4 Pages
337-
Published: December 28, 1988
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H. Y. Mori, Y. Nishimura, A. Suzuki
Article type: Abstract
1988 Volume 33 Issue 4 Pages
337-
Published: December 28, 1988
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H. Okada, A. Katsuyama, H. Murakami
Article type: Abstract
1988 Volume 33 Issue 4 Pages
338-
Published: December 28, 1988
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M. Churei, J. Funasaki
Article type: Abstract
1988 Volume 33 Issue 4 Pages
338-
Published: December 28, 1988
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K. Yamaoka
Article type: Abstract
1988 Volume 33 Issue 4 Pages
338-339
Published: December 28, 1988
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E. Fukuyama
Article type: Abstract
1988 Volume 33 Issue 4 Pages
339-
Published: December 28, 1988
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M. Seino, T. Odaka, H. Yamasato
Article type: Abstract
1988 Volume 33 Issue 4 Pages
339-340
Published: December 28, 1988
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H. Watanabe, S. Okubo, S. Sakashita
Article type: Abstract
1988 Volume 33 Issue 4 Pages
340-
Published: December 28, 1988
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S. Yamashita
Article type: Abstract
1988 Volume 33 Issue 4 Pages
340-
Published: December 28, 1988
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