[S-MP25] Oceanic and Continental Subduction Processes

[SMP25-P03] Cenozoic terrane accretion from East China Sea to South China Sea margins: a perspective of detrital zircon U-Pb geochronology

★Invited Papers

*Jian-wei Lin¹、Tung-Yi Lee¹、Yu-Ling Lin²、Hao-Yang Lee³ (1.Department of Earth Sciences, National Taiwan Normal University, Taiwan、2.Department of Geology, National Museum of Natural Science, Taiwan、3.Institute of Earth Sciences, Academic Sinica, Taiwan)

キーワード：zircon U-Pb geochronology , Cenozoic terrane accretion, East-South China Sea margin

The terrane accretion model, involving microcontinents that drifted due to South China Sea (SCS) rifting and Philippine Sea Plate (PSP) northward movement, contradicts conventional tectonics of the Southeast Asian margin. To examine this evolving viewpoint, detrital zircon (DZ) U-Pb ages from Eocene-Miocene onshore and offshore strata in Taiwan Island, the East China Sea Shelf Basin (ECSSB), and the Mindoro-Palawan terrane (MPT) were analyzed to understand sediment provenance and reconstruct regional paleogeography. On the basis of multidimensional scaling (MDS) analysis of DZ age data, a strong correlation between ECSSB, the Coastal Range of Taiwan, and Mindoro is evident, while confirming the similarity between onshore Taiwan and Palawan. Conversely, a distinct group on the MDS plot highlights the crustal dissimilarity between the South China Block (SCB) and the eastern continental margins. Furthermore, a prominent ~1.8 Ga age population, observed in Taiwan, ECSSB, and MPT, suggests the influence of detritus from exotic terranes, independent of the SCB. These new findings strongly support the existence of microcontinents that have drifted along plate boundaries and subsequently accreted to each other.