K-Ar ages of granitic rocks from the Outer Zone of Southwest Japan

Abstract

K-Ar age determinations were made on 13 samples (biotites and whole rocks) from granitic rocks in the Outer Zone of Southwest Japan. The ages range from 12 to 15 m.y. and are correlated to late Miocene, and generally agree with geological evidences. Supposedly these granitic rocks were emplaced during the period of uplift in the late Miocene.