Abstract
K-Ar and zircon fission-track dating was carried out on some granitic rocks in the Hida Range, central Japan. The samples analyzed were collected on both sides of one of the major faults in the Hida Range : the Kurobe-Takase fracture zone. Ages obtained west of the fault are ∼60 Ma, while those obtained to the east of the fault are less than ∼5 Ma.These results indicate a remarkable age difference across the fault. The Okukurobe granite, located west of the fault, cooled rapidly from ∼600°C to ∼240°C between 60-55 Ma, and the Kanazawa granodiorite, located east of the fault, cooled rapidly from ∼600°C to ∼240°C between 5-1 Ma. The Okukurobe granite has remained cooler than ∼240°C since ∼55 Ma. Thus, it was found that the granitic rocks across the fault have experienced a remarkable different cooling history.
