Abstract
Laser ablation inductively coupled plasma mass spectrometry was used to perform U-Pb dating on zircons from granitic rocks in the Hida Mountain Range, central Japan. Samples were targeted for dating that showed a marked difference in cooling age across the Takasegawa Fault (Ito and Tanaka, 1999). The Okukurobe granite to the west of the fault, and the Oshirasawa granite to the east of the fault, yielded ages of 65.1 ± 1.6 Ma and 64.7 ± 2.3 Ma, respectively. These ages imply that both granites were intruded at the same time (ca. 65 Ma). The Oshirasawa granite has a mylonitic texture, which probably reflects rapid uplift and erosion by faulting in the past 2 Myr. The Kanazawa granodiorite to the east of the Takasegawa Fault was dated as 2.15 ± 0.15 Ma, indicating that this pluton was intruded in the Quaternary. In addition to the Takidani granodiorite, this is the second confirmed occurrence of an outcropping Quaternary pluton in the Hida Mountain Range.
