MESOZOIC CRUSTAL REARRANGEMENT BY LARGE-SCALE LATERAL FAULT SYSTEM EAST ASIA DETECTED BY DETRITAL ZIRCON CHRONOLOGY

Crustal rearrangement in Mesozoic East Asia have been attributed to strike-slip movements by many authors. Contemporary fault systems do exist in South-Eastern China, Korean peninsula, Japanese islands and Far East Russia. Scale of each displacement is of the order of several hundreds of kilometers, as exemplified by Tan-Lu fault system in SE China. These fault systems, however, are covered to a large extent by younger sediments and seawater, which make determination of their continuities and exact scale of displacements difficult. We examined these aspects by means of detrital zircon chronology, in order to clarify the whole kinematics of large-scale continental margin tectonics in East Asia.

Detrital zircon chronology, in this study, was conducted with LA-ICP-MS on a large number of grains separated from Mesozoic formations in the Circum Japan Sea area, South Korea, and Far East Russia. Age population of zircon grains from each sample suggests provenances of North China Block, South China Block, Central Asian Orogenic Belt (CAOB) and Khanka-Jiamusi-Bureya (KJBM), and show temporal and spatial changes.

The results moreover, demonstrate that substantial changes in provenance occurred at late Triassic to early Jurassic and late Jurassic times. Provenance of central and northeastern part of the Inner Zone of SW Japan, changed from KJBM to CAOB during late Triassic to middle Jurassic time. Subsequently, the provenance slowly changed to the North China Block during early Cretaceous time. Provenance of southeast Korea and western part of the Inner zone of SW Japan, changed from the North China Block to the mixed area of the North and South China Blocks during late Middle Jurassic to late Jurassic time. The earlier change in provenance is considered to have been caused by a dextral lateral movement coeval with well known Jurassic dextral shearing along the Honam shear zone of Korea and Funatsu shear zone of central Japan, and the later may have been caused by north-westward compression and uplifting in the central part of the Korean Peninsula.