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タイトル: 東伊豆沖海底火山群 : その1
その他のタイトル: The Higashi-Izu-oki Submarine Volcanoes, Part 1
著者: 葉室, 和親
荒牧, 重雄
加賀美, 英雄
藤岡, 換太郎
著者(別言語): Hamuro, Kazuchika
Aramaki, Shigeo
Kagami, Hideo
Fujioka, Kantaro
発行日: 1980年8月25日
出版者: 東京大学地震研究所
掲載誌情報: 東京大学地震研究所彙報. 第55冊第1号, 1980.8.25, pp. 259-297
抄録: More than 40 topographic highs resembling conical submarine volcanoes in the area between the eastern coast of the Izu Peninsula and the Izu-Oshima island, are identified by the detailed submarine topographic maps recently published. 17 dredge hauls were recovered from 26 dredge stations occupied during cruise KT78-10 of S.S. Tansei Maru of the Ocean Research Institute, University of Tokyo. Most of the rock samples are fresh basalts from the top part of the isolated peaks indicating that many of these topographic highs are young submarine volcanoes. They are very likely to be the submarine counterparts of the subaerial Higashi-Izu Monogenetic Volcano Group distributed on land just west of the dredge area. Most of them are high-alkali tholeiitic basalts with phenocrysts of olivine and plagiocalse. Augite phenocrysts may be present and some specimens contain abundant quartz and plagioclase xenocrysts derived from felsic plutonic rocks, a feature very similar to that found of the Higashi-Izu Monogenetic Volcano Group. Many are nearly aphyric and high in Al2O3 (19-17%) which is in strong contrast with the low alumina, low alkali tholeiites of Izu-Oshima island. In the Harker variation diagrasm, the highalumina, high-alkali tholeiites, both on land and under the sea, have distinctly high Na2O as compared with the basalts of Izu-Oshima. There seems no compositional gradation between the two although they are contemporaneous and occurring in adjacent areas.
URI: http://hdl.handle.net/2261/12756
ISSN: 00408972


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