K–Ar geochronology of the temporal change of eruptive style in the eastern Izu peninsula, central Japan |
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| Authors: | Ayako Ozawa Takahiro Tagami and Masafumi Sudo |
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| Institution: | Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan (email: ) and; Universitaet Potsdam, Institute fuer Geowissenschaften, Karl Liebkanecht Straße 24/H25, 14476, Golm, Germany |
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| Abstract: | Abstract A recent K–Ar study elucidated that eruptive style in the eastern Izu peninsula changed from polygenetic to monogenetic volcano at 0.3–0.2 Ma. To narrow down the time of change, we determined 10 K–Ar ages on Togasayama Andesite of Amagi volcano, the youngest polygenetic volcano in the area, and Togasayama Monogenetic Volcano, one of the oldest monogenetic volcanoes in the area, which overlies a part of the Togasayama Andesite. Dating results showed that the Togasayama Andesite effused at least from 0.34 to 0.20 Ma, whereas the Togasayama Monogenetic Volcano erupted at 0.26–0.29 Ma, suggesting that the northern part of the Togasayama Andesite effused after the eruption of the Togasayama Monogenetic Volcano. Considering previous data, it is therefore inferred that change of eruptive style in the eastern Izu area occurred during the period 0.29–0.20 Ma, with considerable overlap of both polygenetic and monogenetic volcanism. |
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| Keywords: | eastern Izu area K–Ar dating mass fractionation monogenetic volcano polygenetic volcano Quaternary |
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