1999 Fiscal Year Final Research Report Summary
Diversity and dynamics of pyroclastic eruptions at Aso caldera indicated by thermoremanent magnetization
| Project/Area Number |
10640437
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | Kobe University |
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Principal Investigator |
KAMATA Keiko Faculty of Science, Kobe University, Associate Professor, 理学部, 助教授 (20192544)
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| Co-Investigator(Kenkyū-buntansha) |
INOKUCHI Hiroo School of Humanities for Environmental Policy and Technology, Himeji Institute of Technology, Professor, 環境人間学部, 教授 (40112073)
KAMATA Hiroki Faculty of Integrated Human Studies, Kyoto Univ., Professor, 総合人間学部, 教授 (80303791)
SATO Hiroaki Faculty of Science, Kobe University, Professor, 理学部, 教授 (60019495)
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| Project Period (FY) |
1998 – 1999
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| Keywords | large-scale pyroclastic flow deposit / remanent magnetization / Aso pyroclastic flow deposit / Aso caldera / emplacement temperature / welding / 堆積温度 / 溶結度 |
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| Research Abstract |
Paleomagnetic investigations were performed to evaluate emplacement temperatures of the several units from the Aso pyroclastic-flow deposits which are distributed north and east of Aso Caldera, central Kyushu, Japan. Blocking temperatures of natural remanent magnetizations of the rock specimens are assumed as temperatures at which they were settled in the ambient field. It is concluded that most of the essential fragments in welded parts carried one-component magnetizations which are almost unblocked in thermal demagnetization up to 560℃. Welded tuffs of the Aso-2A, 2R, 3B, 4A and 4B carried stable one-component magnetizations during cooling from above the Curie temperature. Palaeomagnetic measurements of the Aso-4B showed one order of magnitude stronger magnetization than those of the other tuffs. The Aso-1 tuff with squeeze-out structure in north of the caldera showed two components suggesting a possibility of secondary flowage. On the contrary, The Aso-4 with the similar squeeze-out structure in east of the caldera showed only one component suggesting that the squeeze-out part of the welded tuff was emplaced above blocking temperature. The Aso-2R with a typical secondary flowage texture indicated one component suggesting that the tuff was emplaced above at least 500℃.
The other notable characteristics are that the Aso-2A and 2B showed larger angle on inclination and the Aso-3B indicates eastward declination as are consistent with the previously reported results.
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