Zircon U‐Pb Dating on Granitoids from the Northern South China Sea and its Geotectonic Relevance

Abstract:Zircon U‐Pb ages of 163.8–100.4 Ma and 146.6–134.5 Ma are obtained for the granitoids from the Pearl River mouth basin, and from southern Guangdong Province, respectively. These new dating data accord well with the crystallization ages of Yanshanian granitoids broadly in the Nanling. The active continental margin of South China, as revealed by a combination of zircon U‐Pb data, underwent a key granitoid‐dominated magmatism in 165–100 Ma. Its evolution varied temporally, and spatially, registering under control of the paleo‐Pacific slab subduction. The granitoids that occurred in 165–150 Ma broadly from the South China Sea to the Nanling are preferably related to two settings from volcanic‐arc to back‐arc extension, respectively. The activities of Cretaceous granitoids migrated from the southeastern Guangdong (148–130 Ma) to the Pearl River Mouth basin (127–112 Ma), corresponding to the model of a retreating subduction. The subduction‐related granitoid magmatism in South China continued until 108–97 Ma. A tectonic transformation from slab‐subduction to extension should occur at ∼100 Ma.