Zircon U–Pb ages of the Higo plutonic complex: Implication for migration of Cretaceous igneous activity in Kyushu, southwest Japan

Abstract

Zircon U–Pb weighted mean ages of seven samples from the Higo plutonic complex (HPC) in Kyushu were determined as follows; Shiraishino granodiorite: 109.3 ± 0.9 Ma and 109.0 ± 1.1 Ma; Kugushima granodiorite: 109.1 ± 1.1 Ma; Miyanohara tonalite: 107.7 ± 1.3 Ma and 108.3 ± 0.9 Ma; Manzaka tonalite: 108.0 ± 0.9 Ma; Joyama tonalite: 112.7 ± 1.2 Ma. The plutonism of batholithic granitoids in the HPC occurred in 109–108 Ma, and granitic intrusions occurred in 113 Ma. The previously reported zircon U–Pb ages range from 107 to 98 Ma in northern Kyushu and concentrate around about 106 Ma in the Chikuhi area in the northern part of central Kyushu. The previously published age data and newly obtained data in this study demonstrate that Cretaceous igneous activity in Kyushu migrated northward from 114 to 98 Ma, accompanied by widespread igneous activity throughout central and northern Kyushu at 106–105 Ma. The HPC situated in the southernmost part of central Kyushu was the origin of this northward migration.