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静岡大学地球科学研究報告 (1975-) >
1999 26 >

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タイトル: 駿河トラフ収束境界域の第四紀地史についての新知見 : 収束境界火山群とその年代について
その他のタイトル: Quaternary volcanic activity chain active circa 0.7〜0.92Ma at a convergent plate boundary of Suruga Trough
著者: 大塚, 謙一
掲載誌名: 静岡大学地球科学研究報告
出版者: 静岡大学地球科学教室
巻: 26
開始ページ: 17
終了ページ: 27
出版日付: 1999-07
NDC: 452
抄録: Volcanic rocks were found at Eurasian side slope of Suruga Trough convergent plate boundary by dive 708 of the "Shinkai 2000". These volcanic rocks crop out at the eastern lower slope of the Senoumi North Bank at a water depth of 1,500 m. Two types of phyric andesite rocks, hypersthene-augite-andesite and hornblende-augite-andesite, were noticed, both containing distinctly large phenocrysts. These volcanic rocks overlie the conglomerate layers that date from 0.91 to 0.82 Ma within nanno fossil biostratigraphic horizon CN 14 a, so the age of igneous activity may be a little yonger than the nanno fossil age. The volcanic rocks have strong similarities with regard to the rock types, geological situation, and stratigraphic relations to the rocks of the "Iwabuchi pyroclastic rocks and Iwabuchi volcanoes group". These rocks cover Kambara Conglomerates at Kambara Hills 45 km to the north of this site. Nanno fossil age obtained from a muddy layer intercalated in "Iwabuchi pyroclastic rocks" is 0.92-0.46Ma, and the "Iwabuchi pyroclastic rocks" indicate paleomagnetic reversed polarity. So the volcanoes in the Suruga Trough area would be active in the later part of the Matuyama reversed magnetic polarity chronozone and also be younger than the Jaramillo sub chronozone of 0.92 Ma. The rock samples of hornblende-augite-andesite are conspicuously reddish-purple due to hematite micro crystals scattered through the groundmass and also replacing the phenocrysts, and hornblende phenocrysts are severely opacitized oxyhornblende. These facts suggest that the volcanic activity happened under an oxidizing environment, so the eruption might be aerial or in very shallow sea. The tectonic situation and geological environment would be very different from the persent, and more than one thousand and several hundred meters depression has occurred since then. Further research about convergent boundary volcanic activity is necessary not only for local geological interest but also for solving fundamentally important problems of tectonic history of the whole Suruga-Nankai Trough region and tectono-magmatic phenomena.
ISSN: 03886298 OPAC
NII論文ID: 110000413387 ciniia
NII書誌ID: AN00103190 OPAC ciniib
バージョン: publisher
出現コレクション:1999 26

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Others By: 大塚, 謙一 (オオツカ, ケンイチ) (Otsuka, Kenichi)



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