Zircon U–Pb ages and Lu–Hf isotopes of the Jurassic Granites on the east coast of the Korean Peninsula and Southwest Japan: Petrogenesis and tectonic correlation between the Korean Peninsula and Japanese Islands

Abstract

Jurassic granitoids in the Korean Peninsula and Japanese Islands are key for deciphering the tectonic evolution of East Asia and the tectonic correlation between them. Zircon U–Pb age dating of seven granitoids in Southwest Japan gives 247.3 ± 1.8 and 192–191 Ma for the Ebi Granites and 200.8 ± 2.1 and 184–183 Ma for the Hida Granites. On the east coast of the Korean Peninsula, 188–186 Ma, 183–177 Ma, 167.7 ± 1.5 Ma, and 173–166 Ma are obtained for the granitoids in the Gyeongsang Basin, Yeongnam Massif, Taebaeksan Basin, and Gyeonggi Massif, respectively. All granitoids show depletions in Nb, Ta, P, and Ti in whole-rock compositions, suggesting an arc environment. The studied granitoids can be divided into two types. The early-stage (∼201–183 Ma) granitoids from Southwest Japan and the Gyeongsang Basin are characterized by the absence of Precambrian inherited zircons, high εHf(t) values of +13.0 to −0.8, and higher crystallization temperatures of ∼750–830 °C. The later-stage (∼183–166 Ma) granitoids from the remaining areas have abundant Paleoproterozoic inherited zircons, low εHf(t) values of −13.9 to −25.0, and lower crystallization temperatures of ∼680–750 °C. The early-stage granitoids formed during a steep subduction regime under higher temperatures due to the heat supply from the asthenospheric mantle. In contrast, later-stage granitoids mostly have an adakitic nature and formed by the partial melting of garnet- and hornblende-bearing thickened Precambrian lower crust under lower temperature conditions during flat subduction. The Ebi and Hida Granites in Southwest Japan formed along the continental arc passing through the Gyeongsang Basin to the Dumangang Belt of the Korean Peninsula, indicating their paleopositions. A change in the subduction angle from steep to flat caused the migration of magmatism to the northwest or west throughout Northeast Asia, including Japan, Korea, and China.