著者

金井 豊 坂巻 幸雄 笹田 政克

出版者

公益社団法人 日本アイソトープ協会

雑誌

RADIOISOTOPES (ISSN:00338303)

巻号頁・発行日

vol.42, no.3, pp.143-150, 1993-03-15 (Released:2010-09-07)

参考文献数

11

被引用文献数

2 2

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筑波トンネルの掘削工事に伴う湧水中の, ウラン濃度, 234U/238U放射能比および水質について調査した。トンネル内では, 坑口からの距離や壁岩の岩質の変化に伴いウラン濃度や水質が変化した。234U/238U放射能比は, 壊変に伴う反跳効果でいずれも1よりも大きな値を示したが, 最大3.9という試料が見いだされた。これは比較的還元的環境下の試料であったがウラン濃度も高く, 岩石と長時間接触・滞留していたHCO3-濃度の高い深層地下水と判断された。

著者

松本 哲一 水垣 桂子 玉生 志郎 小野 晃司 北原 哲郎 品田 正一 笹田 政克

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.38, no.1, pp.1-13, 1993-04-01 (Released:2017-03-20)

参考文献数

21

被引用文献数

1

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Taga Volcano, in northern part of the Izu Peninsula, central Japan, is a large Quaternary strato volcano made of andesite and basalt. The Hata Basalts underlying the Taga volcanic rocks is a pile of pyroclastics with some lava flows mainly of basalts which include the most mafic basalt in the late Tertiary to Quaternary volcanic rocks of north Izu and Hakone region. This Basalts has been treated as the late Tertiary product by previous workers. In order to clarify the volcano-stratigraphic relationship between the Hata Basalts and the Taga volcanic rocks, geologic investigations were carried out in and around the Tanna Basin, and the core and cuttings samples from three 500-600 m drill holes in the Tanna Basin were examined. The Hata Basalts is lithologically characterized by dominant pyroclastics, especially high-temperature oxidized, reddish-brown agglutinate, whereas the products of Taga Volcano are characterized by dominant lava flows. The Hata Basalts is overlain by the Taga volcanic rocks (TV4 and TV5) unconformably at the eastward of the Tanna Basin, and overlain by the Shimo-Tanna Shales and the Taga volcanic rocks unconformably at the westward. Petrography and major elements chemistry suggest that both the Hata Basalts and the Taga volcanic rocks are petrologically very similar to each other. K-Ar dating of two rock samples of the Hata Basalts and one sample of Taga Volcano revealed that they were products of almost the same age, around 600-700 ka. All the samples dated can be correlated to the Brunhes normal polarity epoch. We conclude that the Hata Basalts is the early stage products of Taga Volcano.