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ID 58580
フルテキストURL
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著者
Uno, Koji Department of Earth Sciences, Okayama University
Furukawa, Kuniyuki Faculty of Business Administration, Aichi University
Nakai, Kotaro Department of Earth Sciences, Okayama University
Kamio, Takuma Department of Earth Sciences, Okayama University
Kanamaru, Tatsuo Department of Earth and Environmental Sciences, Nihon University
抄録
A palaeomagnetic study has been conducted to examine the deformation of thick crusts of rhyolite lava while its inner portions continue to flow. The Sanukayama rhyolite lava, which erupted in the Pleistocene in Kozushima Island, Japan, was chosen as the investigation site because of its well-exposed vertical lithofacies variations classified into three distinct zones (pumiceous, obsidian and crystalline). The targets of this study are the pumiceous and obsidian zones, which constitute the crust of the lava. Thermal demagnetization reveals three remanent magnetization components from the pumiceous and obsidian samples but only a single magnetization component from the inner crystalline rhyolite samples. Alternating field demagnetization is ineffective in isolating the magnetization components in the pumiceous and obsidian samples. The multiple components of remanent magnetization of the crust are interpreted to have been acquired during cooling as thermoremanent magnetizations. We suspect intermittent lava transport of the inner portions, the primary mode of rhyolite lava advancement, to be responsible for the presence of multiple components in pumice and obsidian of the lava crust. When the inner portions of the lava retain mobility to flow out of the crust, the solidified crust of the lava surface below the magnetite Curie temperature remains susceptible to deformation. Analysis of palaeomagnetic directions from the crust allows the deformation of the crust to be described in terms of rotation. Although the mode of rhyolite lava advancement is not well understood, because of its infrequent occurrence, our observations offer an important insight on how the mobile part of the lava is associated with the deformation of the crust during continued lava advance.
キーワード
Asia
Palaeomagnetism
Rock and mineral magnetism
Volcanic hazards and risks
備考
This article has been accepted for publication in Geophysical Journal International ©: 2019 Oxford University Press Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
発行日
2019-09-30
出版物タイトル
Geophysical Journal International
220巻
1号
出版者
Oxford University Press
開始ページ
190
終了ページ
200
ISSN
0956540X
NCID
AA10717798
資料タイプ
学術雑誌論文
言語
English
OAI-PMH Set
岡山大学
論文のバージョン
publisher
DOI
Web of Science KeyUT
関連URL
isVersionOf https://doi.org/10.1093/gji/ggz432
助成機関名
文部科学省
助成番号
JP15K05313
JP15K05342
JP19K04001