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Hatao MATSUMOTO, Tadaiti MATUMOTO, Takehiko TSUNETOMI
Article type: Article
1972 Volume 17 Issue 2 Pages
59-65
Published: October 01, 1972
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Tateishi-yama pumice flow covers an area of about 1.5km in the N-S and 3km in the E-W, on the north slope of Tateishi-yama, being covered by the Tateishi-yama lava flow. The pumice flow is similar to the nearby Kuju pumice flow. But the Tateishi-yama pumice flow contains more lithic fragments, less hornblende phenocrysts and shows lighter colour. Banded pumice is frequently found in the upper part of the pumice flow with less felsic bread crust bombs. Dark and pale coloured parts of the banded pumice consist of augite-hypersthene-hornblende dacite. Pale part is richer in SiO
2, Na
2O and K
2O and poorer in FeO, Fe
2O
3, MnO, CaO and TiO
2 as compared with the dark part. The banded structure may have resulted from the mechanical mixing of two different magmas in the process of rising through the narrow volcanic pipe from the reservoir.
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Daisuke SHIMOZURU, Noboru OSADA, Kazuo HORIGOME, Munehisa SAWADA, Atus ...
Article type: Article
1972 Volume 17 Issue 2 Pages
66-87
Published: October 01, 1972
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Results of seismic and geodetic observations at Izu Islands, south of Tokyo, during 1966-1971 are briefly summarized. Izu Islands are situated at the northern part of Huzi Volcanic Belt and are composed of several active and dormant volcanoes. Among them, O-sima and Miyake-zima are basaltic volcanoes which showed frequent eruptions in the past. Hatizyo-zima, a basaltic volcano, is located southern extremity of Izu Islands of which last eruption is recorded as 1606. Beside these basaltic volcanoes arranged as the step-stones in NS direction, rhyolitic volcanoes such as Nii-zima and Kozu-sima are situated at the western part of the chain of basaltic volcanoes. These rhyolitic volcanoes are located on the marked ridge which extends NE-SW direction. In August 1965, an intense earthquake swarm occurred near Kozu-sima. Since then, we set up an acceleration seismograph at Kozu-sima and carried out temporal seismic observations at Kozu-sima, Nii-zima, O-sima, Miyake-zima and at Hatizyo-zima successively. According to our continuing observation at Kozu-sima, seismic energy liberated from off coast of Kozu-sima during 1966-1969 was estimated to be 3.2×10
20 ergs. Precise levelling survey was carried out in O-sima and we found subsidence of the summit region between 1958 and 1967. Study of deformation of the O-sima caldera was made by AGA Model 6 geodimeter. It was found that the direction of the axis of principal strain being roughly parallel to the direction of regional horizontal compression as inferred from earthquake mechanism. It is markedly characterized that epicentral regions of earthquake swarms are roughly located at W/NW part or off coast of the individual volcanic islands. For interpretation of these observational evidences, an argument for a possible model is presented. 1. Izu Islands are located at the northern extremity of Philippine Sea plate and the direction of compression within the plate is shown in Fig.26. 2. Sea bottom topography shows lineament roughly perpendicular to the direction of the compression. 3. Earthquake mechanism of the concerned region shows the small amount of dip component. It implies that the lithosphere of the said region is largely suffered by horizontal compressive stress. 4. The ridge on which rhyolitic volcanoes are located was caused by buckling of the upper part of the lithosphere as the consequence of horizontal compression. 5. Buckling of the upper lithosphere produces pressure decrease at its lower boundary which may yield the melting of the crustal material. Thus, the rhyolitic volcanism is very likely possible. 6. Supposing the vertical gradient of horizontal flow velocity within the lithosphere, volcanoes are left eastward from the location of magmatic foci as shown in Fig. 27. 7. Stress concentration is expected above the magmatic foci (Fig.28) due to horizontal compression which produces earthquake swarms. The above proposed model is nothing but a speculation and we hope further detailed investigation, especially geodetic observation, may be done in future.
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Sadakatu TANEDA, Kazuyo KINOSHITA
Article type: Article
1972 Volume 17 Issue 2 Pages
88-97
Published: October 01, 1972
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An alkaline intrusive rock body with peculiar occurrence and petrographic character is found in the Tanegashima island, south Kyushu, Japan. It is exposed as an extraordinary thin dyke intruded into the Paleogene Kumage group, and overlain by the Pliocene-Pleistocene Kaminaka group. It is only about 10m or less in thickness but as long as 20km or more in length, in a NNE-SSW direction which may be concerned with the “Peri-Tunghai tectonic movement”. It is composed of albite-oligoclase, anorthoclase, “kaersutite”, biotite, opaque minerals and some accessories such as chlorite, calcite, prehnite, pumpellyite, etc. The colour index is 40~50. The intrusive rock with such a mineral composition may be called vogesitic kersantite (somewhat leucocratic variety) belonging to the lamprophyres. It is to be noted that the K-Ar age of this dyke rock is 16±2 m.y., and the magnetic polarity is Re.
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Keizo YOSHIKAWA, Kiyoshi NISHI
Article type: Letter
1972 Volume 17 Issue 2 Pages
98
Published: October 01, 1972
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Naoki ISSHIKI
Article type: Letter
1972 Volume 17 Issue 2 Pages
99
Published: October 01, 1972
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D. Shimozuru
Article type: Abstract
1972 Volume 17 Issue 2 Pages
100-
Published: October 01, 1972
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T. Ui
Article type: Abstract
1972 Volume 17 Issue 2 Pages
100-101
Published: October 01, 1972
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Article type: Abstract
1972 Volume 17 Issue 2 Pages
101-
Published: October 01, 1972
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S. Taneda
Article type: Abstract
1972 Volume 17 Issue 2 Pages
101-
Published: October 01, 1972
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H. Fukuyama
Article type: Abstract
1972 Volume 17 Issue 2 Pages
101-
Published: October 01, 1972
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K. Nishi
Article type: Abstract
1972 Volume 17 Issue 2 Pages
101-102
Published: October 01, 1972
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K. Nishi
Article type: Abstract
1972 Volume 17 Issue 2 Pages
102-
Published: October 01, 1972
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T. Eto, F. Ohya
Article type: Abstract
1972 Volume 17 Issue 2 Pages
102-
Published: October 01, 1972
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M. Kamada, H. Matsumoto
Article type: Abstract
1972 Volume 17 Issue 2 Pages
102-103
Published: October 01, 1972
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K. Kaminuma, M. Yamaguchi, F. Masutani
Article type: Abstract
1972 Volume 17 Issue 2 Pages
103-
Published: October 01, 1972
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T. Wada, Y. Sudo, K. Kamo
Article type: Abstract
1972 Volume 17 Issue 2 Pages
103-104
Published: October 01, 1972
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H. Kurasawa, K. Ono, T. Kobayashi
Article type: Abstract
1972 Volume 17 Issue 2 Pages
104-
Published: October 01, 1972
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H. Matsumoto
Article type: Abstract
1972 Volume 17 Issue 2 Pages
104-
Published: October 01, 1972
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H. Matsumoto, T. Matumoto, T. Tsunetomi
Article type: Abstract
1972 Volume 17 Issue 2 Pages
104-
Published: October 01, 1972
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A. Kubotera, S. Kikuchi, M. Otsuka, T. Higaki
Article type: Abstract
1972 Volume 17 Issue 2 Pages
104-105
Published: October 01, 1972
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T. Yamazaki, I. Kato, M. Muroi, M. Abe
Article type: Abstract
1972 Volume 17 Issue 2 Pages
105-
Published: October 01, 1972
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N. Murakami, K. Miura, T. Inoue, H. Nishino
Article type: Abstract
1972 Volume 17 Issue 2 Pages
105-106
Published: October 01, 1972
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S. Aramaki, H. Kagami, M. Ozima, H. Haramura
Article type: Abstract
1972 Volume 17 Issue 2 Pages
106-
Published: October 01, 1972
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M. Ozima, I. Kaneoka, S. Aramaki, N. Ueno
Article type: Abstract
1972 Volume 17 Issue 2 Pages
106-
Published: October 01, 1972
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K. Yagi, J. G. Souther
Article type: Abstract
1972 Volume 17 Issue 2 Pages
106-107
Published: October 01, 1972
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J.G. SOUTHER
Article type: Abstract
1972 Volume 17 Issue 2 Pages
107-108
Published: October 01, 1972
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S. Taneda, K. Kinoshita
Article type: Abstract
1972 Volume 17 Issue 2 Pages
108-
Published: October 01, 1972
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N. Isshiki, K. Nakamura
Article type: Abstract
1972 Volume 17 Issue 2 Pages
108-109
Published: October 01, 1972
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T. Kizawa, Y. Tanaka
Article type: Abstract
1972 Volume 17 Issue 2 Pages
109-
Published: October 01, 1972
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Y. Mizutani, T. Hamasuna
Article type: Abstract
1972 Volume 17 Issue 2 Pages
109-110
Published: October 01, 1972
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T. Hirano, S. Odaka, Y. Oki
Article type: Abstract
1972 Volume 17 Issue 2 Pages
110-
Published: October 01, 1972
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K. Noguchi, K. Aikawa
Article type: Abstract
1972 Volume 17 Issue 2 Pages
110-111
Published: October 01, 1972
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S. Hiraga, H. Ito
Article type: Abstract
1972 Volume 17 Issue 2 Pages
111-
Published: October 01, 1972
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Y. Oki, S. Odaka
Article type: Abstract
1972 Volume 17 Issue 2 Pages
111-
Published: October 01, 1972
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O. Oshima
Article type: Abstract
1972 Volume 17 Issue 2 Pages
111-112
Published: October 01, 1972
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J. Ossaka, T. Ozawa, J. Hirabayashi
Article type: Abstract
1972 Volume 17 Issue 2 Pages
112-
Published: October 01, 1972
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I. Moriya
Article type: Abstract
1972 Volume 17 Issue 2 Pages
112-
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K. Tanaka
Article type: Abstract
1972 Volume 17 Issue 2 Pages
112-113
Published: October 01, 1972
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M. Watabe
Article type: Abstract
1972 Volume 17 Issue 2 Pages
113-
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Article type: Abstract
1972 Volume 17 Issue 2 Pages
113-
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K. Tsuchiya
Article type: Abstract
1972 Volume 17 Issue 2 Pages
113-114
Published: October 01, 1972
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Article type: Abstract
1972 Volume 17 Issue 2 Pages
114-
Published: October 01, 1972
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H. Kinoshita, M. Kono, Y. Aoki, K. Ishibashi, I. Kaneoka
Article type: Abstract
1972 Volume 17 Issue 2 Pages
114-
Published: October 01, 1972
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I. Yokoyama
Article type: Abstract
1972 Volume 17 Issue 2 Pages
114-115
Published: October 01, 1972
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K. Nakamura
Article type: Abstract
1972 Volume 17 Issue 2 Pages
115-
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H. Yamagishi
Article type: Abstract
1972 Volume 17 Issue 2 Pages
115-
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T. Suzuki
Article type: Abstract
1972 Volume 17 Issue 2 Pages
116-
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H. Tsukie
Article type: Abstract
1972 Volume 17 Issue 2 Pages
116-
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H. Sato
Article type: Abstract
1972 Volume 17 Issue 2 Pages
116-117
Published: October 01, 1972
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M. Yamasaki, S. Banno
Article type: Abstract
1972 Volume 17 Issue 2 Pages
117-
Published: October 01, 1972
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