Prompt K-Ar analysis using a small amount of samples and its application to geochronology in Japanese Islands

This is a review paper regarding the development of a mass spectrometric system for K-Ar dating using a small amount of samples and the prompt analyses of argon isotopes, and its application to geochronology of the Japanese Islands. The results, in particular, contributed to the volcanostratigraphy of late Cenozoic volcanoes, reconstructed unknown geologic units in accretinary complexes and analysed age distribution pattern of both high and low P/T metamorphic sequences. The application is based on the systematic sampling of lithologies from the geologic units to be examined and the K-Ar dating of mineral separates, making it possible to map geologic sequences by absolute ages. The geochronological mapping was also applied to major orogenic belts in the world and provided remarkable results to geologists. (author)