Late Paleozoic magmatism in South China: Oceanic subduction or intracontinental orogeny?

A gneissic granite with an U-Pb age of 313±4 Ma was found in northeastern Fujian Province, South China. It is an S-type granite characterized by high K₂O, Al₂O₃ and low SiO₂, Na₂O contents with high A/CNK ratio of 1. 22 for the whole rock. Zircons with stubby morphology from the gneissic granite yield ²⁰⁶Pb/²³⁸U ages ranging from 326 to 301 Ma with a weighted average age of 313±4 Ma, and negative e{open}_Hf(t) values from -8. 35 to -1. 74 with Hf model ages (T^C _DM) of 1. 43 to 1. 84 Ga. This S-type granite probably originated from late Paleoproterozoic crust in intracontinental orogeny. Integrated with previous results on paleogeographic reconstruction of South China, the nature of Paleozoic basins, Early Permian volcanism and U-Pb-Hf isotope of detrital zircons from the late Paleozoic to early Mesozoic sedimentary rocks, we suggest the occurrence of a late Paleozoic orogeny in the eastern Cathaysia Block, South China. This orogenic cycle includes Late Carboniferous (340-310 Ma) orogeny (compression) episode and Early Permian (287-270 Ma) post-orogenic or intraplate extension episode. Therefore, the late Paleozoic magmatism in the southeastern South China probably occurred during the intraplate orogeny rather than the arc-related process.