| Project/Area Number |
22540469
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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 | Shimane University |
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Principal Investigator |
KOMURO Hiroaki 島根大学, 総合理工学研究科, 教授 (80135897)
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| Co-Investigator(Kenkyū-buntansha) |
KAMEI Atsushi 島根大学, 総合理工学研究科, 准教授 (60379691)
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| Project Period (FY) |
2010 – 2012
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| Project Status |
Completed (Fiscal Year 2012)
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| Budget Amount *help |
¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2012: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2011: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2010: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
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| Keywords | 火山 / 巨大噴火 / 地質年代 / 島弧 / 白亜紀 |
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| Research Abstract |
The igneous activity along the Eurasian continental margin in Cretaceous to Paleogene is characterized by catastrophic eruptions associated with cauldron formations. This study focuses on the dating of the cauldrons in the central Chugoku district, where insufficient data are only known.
(1) Futakamiyama cauldron. Andesitic agglutinate of the cauldron infill: 83±13Ma (Rb-Sr isochlon); granodiorite porphyry: 72.8±1.8 Ma (hornblende K-Ar); quartz diorite: 66.6±2.4 Ma (hornblende K-Ar); hornblende-biotite granite (the basement rock): 85.2±1.9Ma (hornblende K-Ar). These ages suggest that the volcanic activity of the Futakamiyama cauldron occurred during 85 - 73Ma.
(2) Hikihara cauldron. Rhyolitic welded tuff of the cauldron infill: 73.2±2.5Ma (FT); quartz porphyry: 69.0±2.2Ma (FT); biotite granite: 63.1±2.3Ma (Rb-Sr isochlon). These ages suggest that the volcanic activity of the Hikihara cauldron occurred during 75 - 60Ma.
(3) Sakuto cauldron. Rhyolite lava of the cauldron infill: 77.3±4.3Ma (Rb-Sr isochlon); quartz diorite: 71.3±3.7Ma (hornblend K-Ar). These ages suggest that the volcanic activity of the Sakuto cauldron occurred during 80 - 70Ma.
(4) Yanahara cauldron. Quartz diorite: 79.8±1.8Ma (hornblend K-Ar). This suggests that the volcanic activity of a cauldron occurred in ca. 80Ma.Accordingly, these data show that the catastrophic eruptions associated with cauldrons concentrated in the central Chugoku district during 80 - 70Ma. This hotspot-like volcanism was replaced by the Paleogene (44 - 30Ma) arc volcanism with a clear volcanic front.
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