Zircon U-Pb ages and whole-rock geochemistry from the Hida granites. Implications for the geotectonic history and the origin of Mesozoic granites in the Hida belt, Japan

The Hida granites, classified into the pre-Jurassic and Jurassic plutons in this study, are important components of the Hida belt, which is a Paleozoic-Mesozoic basement of the Japan arc and underwent Permian to Triassic metamorphism during the collision between the North and South China blocks. This study performed zircon U-Pb dating and whole-rock geochemical analyses for the Hida granites from the major plutonic bodies to reveal the geotectonic history and the origin of the Hida belt. Obtained ²³⁸U-²⁰⁶Pb weighted mean ages exhibit 239.1-238.3 Ma for the Katakaigawa body (augen granite) and 200.5-180.9 Ma for the other bodies (non-deformed granitoids), and these ages can be correlated to the pre-Jurassic and Jurassic plutons, respectively. Geochronological results suggest that the mylonitization forming augen granites of the pre-Jurassic plutons occurred during its intrusion and indicate that the Jurassic plutons are distributed widely in the Japan Sea side of the Hida belt. Meanwhile, geochemical characteristics of whole-rock major and trace element compositions indicate that the pre-Jurassic and Jurassic plutons seem difficult to distinguished geochemically and suggest that both of them are adakitic and non-adakitic granites generated in subduction zone. (author)