| Project/Area Number |
16403009
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
Geology
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| Research Institution | Kyoto University |
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Principal Investigator |
TAGAMI Takahiro Kyoto University, Graduate School of Science, Associate Professor, 大学院理学研究科, 助教授 (80202159)
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| Co-Investigator(Kenkyū-buntansha) |
OBATA Masaaki Kyoto University, Graduate School of Science, Professor, 大学院理学研究科, 教授 (20126486)
KAMATA Hiroki Kyoto University, Graduate School of Human and Environmental Sciences, Professor, 人間環境学研究科, 教授 (80303791)
ISHIKAWA Naoto Kyoto University, Graduate School of Human and Environmental Sciences, Associate Professor, 人間環境学研究科, 助教授 (30202964)
TATSUMI Yoshiyuki Japan Marine Science and Technology Center, IFREE, Division Director, 固体地球統合フロンティア研究センター, 領域長 (40171722)
KANI Tomomi Kumamoto University, Graduate School of Natural Sciences, Assistant Professor, 自然科学研究科, 助手 (60332863)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥13,300,000 (Direct Cost: ¥13,300,000)
Fiscal Year 2006: ¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2005: ¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2004: ¥5,100,000 (Direct Cost: ¥5,100,000)
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| Keywords | Hotspot / Hawaiian plume / unspiked K-Ar method / Geochemistry / Maui / Oahu / kauai / Hawai / 同位体分析 / XRF化学分析 |
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| Research Abstract |
Here we summarize below our recent results of unspiked K-Ar dating on rejuvenated lavas from five Hawaiian volcanoes.
(1) West Maui (Sherrod et al., in press) : Nine ages for the underlying postshield and 28 for shield stage units range from 1.8-1.3 Ma and 1.3-1.2 Ma, respectively. Therefore, the duration of volcanic quiescence prior to rejuvenation is about 0.6 m.y. at West Maui, much longer than estimated previously.
(2) Koolau, Oahu (Ozawa et al., 2005) : New ages, on 41 samples from 32 vents of rejuvenated-stage Honolulu Volcanics and on eight samples of underlying shield-stage Koolau Volcanics show that shield volcanism ended at 2.1 Ma and that rejuvenated volcanism started at 0.8 Ma, resulting in a 1.3 m.y. hiatus in volcanic activity. Two distinct pulses were found for Honolulu volcanism at 0.8-0.35 and 〜0.1 Ma.
(3) Kahoolawe (Sano et al., this meeting and submitted) : youngest eruptions left five small deposits of dike-fed cinders and sparse lava flows, which were previously undated but thought part of a rejuvenated stage on the basis of a substantial erosional unconformity. Two samples from the southernmost site and one sample from the next site northward show ages of 1.0 to 1.4 Ma, suggesting a short gap between the postshield and youngest eruptions.
(4) Kauai (Sano et al., in prep.) : New ages of 23 samples from rejuvenated Koloa Volcanics range from 0.15 to 3.9 Ma, whereas ages of five samples from late shield-stage Waimea Canyon Basalt are 4.1-4.5 Ma. Hence, the volcanic quiescence before rejuvenation is at most about 0.3 m.y. The Kauai rejuvenated-stage can be divided into at least five eruptive pulses.
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