抄録
The CHIME (chemical Th-U-total Pb isochron method) dating of tonalite clasts in the Middle Permian Usuginu-type conglomerate has been carried out by precise microprobe analyses of monazite and zircon. The CHIME ages are 257±19 Ma, 244±42 Ma and 248±11 Ma (zircon), and 247±24 Ma (monazite) for tonalites. The ages indicate the intrusion of tonalite around 250 Ma together with quartz diorite and diorite, and rapid uplift and denudation after the igneous activity occurred in the provenance area for the Usuginu-type conglomerate.
