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

Abstract

The Hida granites, classi fi ed 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 238 U – 206 Pb 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 di ffi cult to distinguished geochemically and suggest that both of them are adakitic and non – adakitic granites generated in subduction zone.