Abstract
Fission-track (FT) dating using both apatite and zircon was performed to better understand ancient fault activities of the Yanagase fault, central Japan. Samples were collected from two fine-grained diorites, and a granodiorite in the vicinity of the northern part of the fault. FT zircon ages on the granodiorite and a fine-grained diorite revealed acidic to intermediate igneous activities at 20-23 Ma. FT apatite age of ∼20 Ma on a fine-grained diorite which intruded into the Yanagase fault as a dyke revealed that the dyke intrusion occurred at ∼20 Ma, and also faulting initiated before ∼20 Ma.
