Late Triassic-Late Cretaceous accretion/subduction in the Taiwan region along the eastern margin of South China - evidence from zircon SHRIMP dating

To examine the tectonic history of the Taiwan segment of the eastern margin of South China, six rock samples from the Tailuko belt, the metamorphic basement of Taiwan, were selected for zircon SHRIMP dating. The aim was to identify evidence shedding light on the timing of the change from passive to active tectonics for this part of the continental margin since South China separated from the supercontinent of Rodinia. The results lead to two age groups, 190-200 and 88-90Ma. These age groups, augmented by the previously published age data, suggest that they could have resulted from two Mesozoic accretion/subduction events. In addition, this mid-late Mesozoic Tailuko belt might have also been reactivated and structurally complicated by the late Cenozoic collision/accretion of the Luzon arc with the Eurasian continent. Records of older tectonic events, such as those derived from the Japanese Islands, are absent in this metamorphic basement. An important finding of this study is the existence of the 19110Ma Talun metagranite, the oldest granitic intrusion ever reported in the Taiwan region and along the eastern coast area of South China. In spite of a large age uncertainty, the occurrence of this metagranite is not consistent with the apparent younging trend of Jurassic-Cretaceous igneous activity toward the coastline in South China, and should be taken into consideration by future studies.