Provenancial correlation between Kanmon Group and Tetori Group, SW Japan and Gyeongsan Supergroup, Korea by age distributions of detrital zircon

The Japanese Island Arc System was located along the eastern margin of Asian Continent before opening of the Sea of Japan at around 15 Ma, and abundant clasts from Asian Continent. Now a question arises as to how the Japanese Archipelago was connected to the continent of Asia? Marine to non-marine sediments of Lower Cretaceous Gyeongsang Basin are widely spread over southeastern Korean Peninsula facing the Japan Sea. On the other side of the sea, in the Southwest Japan, the Lower Cretaceous Kanmon Group distributed from Northeastern Kyushu to the western edge of Honshu, and the Tetori Group distributed in the Hida Mountains, also exist. Gyeongsang Supergroup in the Gyeongsang Basin and the Kanmono Group demonstrate good correlation based on their sedimentary phases and whole rock REE composition. Paleomagnetic studies moreover, have shown that the Kanmon Group distributed in close to the Gyeongsang Basin before opening of the Japan Sea. Some geologists, however, suggest that the Gyeongsang Supergroup and the Tetori group are correlated. This idea rests on a paleogeographic model, which in turn is based on Pre-Cretaceous basement of Japan, being correlated with southern Primorye of Russia (Yamakita and Otoh, 2000). In this study, we compare the provenance of their sediments using detrital zircon or monazite age, and discuss the immediacy of their depositional site. We separated zircon and monazite from sandstone, and dated single grain U-Th total Pb age using EPMA. Sandstone was sampled from the early Cretaceous Gyeongsang Supergroup in South Korea, and the early Cretaceous Kanmon Group, the late Jurassic to early Cretaceous Toyonishi Group, the middle Jurassic Toyora Group in Shimonoseki area of Yamaguchi Prefecture, and the late Jurassic to early Cretaceous Tetori Group. As a result of EPMA analysis and statistical processing, zircons and monazites from sandstones in the Lower Cretaceous Gyeongsang Supergroup yield a wide range of ages and, according to their single grain ages, show peak ages at 2400Ma, 1870Ma, 1100Ma, 730-900Ma, 440Ma, 360Ma, 240Ma, 190Ma. The peak position and shape of the zircon and monazite age population of the Gyeongsang Supergroup has huge similarity to that of the Lower Cretaceous Kanmon Group. Therefore, the Gyeongsang Supergroup and the Kanmon Group might have a shared provenance and could have been deposited in the same basin or in adjacent basins. U-Pb age of 1.5Ga-2.5Ga is reported mainly in Yeongsnam Massif, which constitutes the basement of the Gyeongsang Basin, but 700-900 Ma might origin from Gyeonggi Massif or Ocheon Belt, of central Korean Peninsula. However, no zircon grains show 700-900 Ma from the same year-old strata in the Tetori Group. The Tetori Group might have been deposited in a different basin from the Kanmon Group and the Gyeongsang Supergroup.