ABSTRACT

Rb-Sr and K-Ar age determinations were made on the metasediments from Shidara and Takato regions in the Ryoke metamorphic belt, Central Japan. Both total rock isochron age and total rock-biotite isochron ages by Rb-Sr method and mineral age by K-Ar method fall in a range from 60 to 70 m.y. These are similar to the ages which have been obtained for the Ryoke granites, and are considered to indicate the time of the contact metamorphism due to the intrusion of the granites. The age of the regional metamorphism is not yet obtained, but would be obtained by further Rb-Sr total rock analyses of low grade metasediments.