Post-spreading volcanism in the central South China Sea: insights from zircon U–Pb dating on volcaniclastic breccia and seismic features

Abstract

Post-spreading volcanism in the central South China Sea (SCS) is of broad interest and has been well-studied using mainly geophysical data. The zircon U–Pb dating of volcaniclastic breccia cores recovered by the International Ocean Discovery Program (IODP) Expedition 349 provides important insights into the characteristics and origin of the volcanism in conjuction with the evolution of the SCS and related regional tectonic events. The results show that two volcanic eruptions were dated as 11.29 ± 0.53 Ma at Site U1431 in the East sub-basin and 7.56 ± 0.28 Ma at Site U1434 in the Southwest sub-basin; both ages are in good agreement with the shipboard ages derived from biostratigraphic and paleomagnetic datums and are a little older than the published K–Ar ages of dredged samples from nearby seamounts. Furthermore, by integrating the IODP borehole data and regional multichannel seismic data, the distribution of the post-spreading volcanism in the central SCS is mapped through geological time. The volcanism was mainly concentrated in the Late Miocene and did not occur immediately after the cessation of seafloor spreading at ~ 15.5 Ma. The origin of the post-spreading volcanism in the central SCS is discussed and we propose that it resulted from the post-spreading cooling and subsidence of the SCS, the changed subduction direction of the Philippine Sea plate, the rapid uplift of the southeastern Tibetan Plateau in the Late Miocene and potential Hainan mantle plume activities.