K-Ar age determinations of age-unknown rocks in the Japanese Islands

-volcanic and plutonic rocks in the areas associated with Geological Map Project (fiscal 2011 version)-

Abstract

In order to construct accurate geological maps of Japan, K-Ar ages of ten igneous rocks have been determined during fiscal 2008-2011 by the geochronological laboratory of Geological Survey of Japan, AIST. The five volcanic rock samples were prepared as the groundmass fraction, in which large phenocrysts were removed as much as possible using an isodynamic separator. The phenocrysts of biotite and hornblende in five plutonic rock samples were isolated by using an isodynamic separator and heavy liquids. Each data of rock samples determined is associated with rock name, locality, collector, geological setting, K-Ar age, analytical data and geological interpretation.