CHIME zircon ages of granodiorite clasts from the Motodo Formation, Hida-Gaien Belt, central Japan

Abstract

CHIME (chemical Th-U-total Pb isochron method) dating of granodiorite clasts from the Motodo Formation of the Hida-Gaien Belt was carried out by precise microprobe analyses of zircon grains. The CHIME ages are 201±20 Ma and 202±30 Ma, indicating that the granodiorite intrusion in the provenance areas of the Motodo Formation occurred in the Early Jurassic time. The depositional age of the Motodo Formation was constrained by previous authors between the Late Permian and Early Cretaceous, but our data further restrict it between the Early Jurassic and Early Cretaceous. On the basis of age constraints and lithological similarities, the Motodo Formation correlates with the Kyongsang Supergroup in South Korea and the Kanmon Group in Southwest Japan. Early Jurassic granitoids are distributed in the Hida Belt in Japan and in the Korean Peninsula, which are considered as likely provenance areas for the sediments of the Motodo Formation.