[S-GL18] Geologic structure and tectonic history of East Asia and Japanese Islands

[SGL18-04] Geotectonic link of the Hida belt to the mainland Far East Asia: Cretaceous world on the continent-side of the Yamato tectonic line

*Yukio Isozaki¹, Yusuke Sawaki¹, Hideki Iwano^2,3, Takafumi Hirata² (1.Department of Earth Science and Astronomy, Multi-disciplinary Sciences - General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo, 2.University of Tokyo, 3.Kyoto Fission Track Co. Ltd)

Keywords:Hida belt , Laoelin-Grodekov belt, Nipponides, Yamato tectoic line, Greater South China, Cretaceous

The Hida belt in central Japan, characterized by the unique granitoid age pair of ca. 250 Ma and 180 Ma, represents an exceptional geotectonic unit, in sharp contrast with the rest of Japan (Nipponides) formed by Phanerozoic oceanic subduction-related processes. Although the pre-Japan Sea paleogeography has long been debated, any clear geotectonic link to the opposite side of the Japan Sea was not confirmed for years. Recent progress in high-resolution grain-by-grain U-Pb dating of zircons, nonetheless, provided a new insight on this long-term conundrum. In particular, the latest identification of the Late Triassic A-type deep-red granitoids in the clasts of Lower Cretaceous conglomerate in the Hida belt added a new clue for the geotectonic correlation with the geology of the opposite coast of the Japan Sea. As this rock type of this age is extremely rare in Far East Asia, the Laoelin-Grodekov belt in the border domain among Primorye (Russia), NE China, and North Korea appears like the most promising candidate for the pre-Miocene counterpart of in the Hida belt via the Yamato Ridge in the mid-Japan Sea. In order to confirm the source of the Late Triassic A-type granitoid, U-Pb dating and trace element analysis of detrital zircons were conducted for sandstones of the Cretaceous Tetori Group deposited in the Hida belt. The analyzed results clarified the ubiquitous occurrence of Late Triassic "A-type zircons" from the Tetori Group throughout the Hida belt, which supports the claimed link between the Hida and L-G belts via the mid-Japan Sea Yamato ridge. On the basis of the analysis of coeval sands from Primorye, the reconstruction of the Cretaceous provenance and sedimentary setting of the Far East Asian continental margin is discussed. These strata deposited on the continent side of the Yamato tectonic line have common characteristics in lithofacies and fossil flora.

Isozaki et al. (2023a) Island Arc 32, e12475; Isozaki et al. (2023b) Bull. Nat. Mus. Nature+ Science C49, 1-13.