著者

近重 史朗 小坂 和夫

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.106, no.8, pp.574-577, 2000-08-15 (Released:2008-04-11)

参考文献数

17

被引用文献数

1 2

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Yorii welded tuffs in the northeastern Kanto Mountains are penetratively crushed and strongly hydrothermally altered. They are younger constituents of the Atokura Nappe and their ages indicate the lower limit of the time when the Atokura Nappe thrusted up on the Sanbagawa belt.The whole rock K-Ar ages of the altered Yorii welded tuffs give 58.0±2.9 Ma which is consistent with zircon FT age (59.6 Ma). This suggests that the hydrothermal alteration followed the formation of welded tuffs at the last stage of cooling process. After this hydrothermal alteration, the Yorii welded tuffs thrusted up on the Sanbagawa belt.