2007 Fiscal Year Final Research Report Summary
Study on magma plumbing system of Aso volcano by methods of mare drilling isotope analysis
| Project/Area Number |
17540454
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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 |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | Kyoto University |
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Principal Investigator |
KANEKO Katsuya Kyoto University, Graduate school of Human and Environmental studies, Assistant professor (40335229)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIKAWA Masako Kyoto University, Graduate school of Science, Assistant of chemical analysis (00378605)
TAKAHASHI Toshiro Japan agency for Marine-Earth Science and Technology, Institute for Research on Earth Evolution (IFREEP), Research associate (20392946)
SHIBATA Tomoyuki Kyoto University, Graduate school of Science, Assistant professor (40332720)
KOYAGUCHI Takehiro University of Tokyo, Earthquake Research Institute, professor (80178384)
KAMATA Hiroki Kyoto University, Graduate school of Human and Environmental studies, Professor (80303791)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Aso volcano / caldera / Isotope ratio of Strontium / zoned magma chamber / micro drilling analysis / Compatible element / lower crust / magma plumbing system |
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| Research Abstract |
Activities of Aso volcano are characterized by four large pyroclastic eruption cycles (LPEC) and many minor eruptions between them after 300 ka. In order to understand magma genesis of Aso volcano, we investigated petrological and geochemical features of magmas of three large eruption cycles between 150 ka and 90 ka. It is emphasized that systematic data of Sr isotope ratio of whole-rock, glass, and plagioclase phenocryst (micro-drilling method) have been obtained.
In each LPEC, the magmas erupted from a layered magma chamber with silicic magmas overlying denser mafic magmas. Important geochemical features of silicic and mafic magmas are summarized as follows. 1. Whole-rock Ni content of a silicic magma is equal to or larger than that of a mafic magma in each large eruption cycle. 2. Silicic and mafic magmas in each LPEC have identical Sr isotope ratios in whole-rock, glass, and plagioclase phenocryst. 3. Magmas of the three LPECs have different Sr isotope ratios. 4. Water content of ma
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fic magma is larger than that of silicic magma at least in Aso-2 and Aso-3. 5. petrological features of magmas of Aso volcano systematically change with time : magmatic temperature decreases, K2O content to SiO2 content decreases, oxygen fugacity increases.
The feature 3 indicates that the magmas of each LPEC were produced by distinct processes from those of magma generation of the other LPECs. The feature 2 strongly suggests that the silicic and mafic magmas of each LPEC are from a same source material. On the other hand, the feature 1 indicates the silicic magma was not generated by fractionation of the mafic magma. These geochemical data request that the silicic and mafic magmas of each LPEC were generated from a same source material whereas they have no parent-daughter relationship on fractionation. The magma genesis of these silicic and mafic magmas can be explained qualitatively as follows. The source material is a gabbro. The mafic magma was produced by fractional crystallization of segregated partially-molten magma from the gabbro with high degree of partial melting and then fractional crystallization. The silicic magma was generated as segregated partially-molten magma from the gabbro with low degree of partial melting that was not fractionated after segregation. Magma generation of partial melting of a gabbro probably occurs in a lower crust : hot magmas from mantle rise and heat up the lower crust. The mafic magma is produced near the hot mantle magma. The silicic magma is generated by low degree of partial melting of the lower crust relatively far from the mantle magma. The feature 5 is explained by increase of water content in lower crust (i.e., source material of magma). Less
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Research Products
(20 results)
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[Journal Article] Repeated large-scale eruptions from a single compositionally stratified magma chamber: An example from Aso volcano, Southwest Japan.2007
Author(s)
Kaneko, K., Kamata, H., Koyaguchi, T., Yoshikawa, M., and Furukawa, K.
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Journal Title
Journal of Volcanology and Geothermal Research 167
Pages: 160-180
Description
「研究成果報告書概要(和文)」より
Peer Reviewed
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[Journal Article] Repeated large-scale eruptions from a single compositionally stratified magma chamber : An example from Aso volcano, Southwest Japan2007
Author(s)
Kaneko, K., Kamata, H., Koyaguchi, T., Yoshikawa, M., Furukawa, K
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Journal Title
Journal of Volcanology and Geothermal Research 167
Pages: 160-180
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] Formation processes of magma chamber of Aso-3 large pyroclastic eruption cycles at Aso volcano2006
Author(s)
Inoue, K., Kaneko, K., Koyaguchi, T., Yoshikawa, M., Shibata, T., Furukawa, K., Kamata, H
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Journal Title
Earth monthly 28
Pages: 392-399
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] A new technique of radiation thermometry using a consumer digital camcorder : Observations of red glow at Aso volcano, Japan2005
Author(s)
Saito, T., Sakai, S., Iizawa, I., Suda, E., Umetani, K., Kaneko, K., Furukawa, Y., Ohkura, T
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Journal Title
Earth Planets Space 57
Pages: 5-8
Description
「研究成果報告書概要(欧文)」より
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