CHARACTERISTICS OF LATE CENOZOIC MAGMATIC ACTIVITIES ON THE NORTHERN MARGIN OF SOUTH CHINA SEA AND THEIR TECTONIC IMPLICATIONS

The northern margin of South China Sea is characterized by unique magmatic activities. They were weak during the period of continental rifting and breakup but intense in the late Cenozoic of post-rifting stage, particularly after the cessation of seafloor spreading. In this paper, studied are the characteristics of magmatic activities in the late Cenozoic including the scale, material properties, tectonic pattern and conduit features by summarizing the previous research results of petrology, chronology and geophysics. Our results show that: (1) The Late Cenozoic basalts on the northern margin of South China Sea is a kind of oceanic island basalts (OIB), having similar isotopic distribution pattern with the typical hotspot OIB of the world; (2) The volume and scale of the submarine volcanism on the northern margin of South China Sea are comparable to the typical igneous rocks of the world; (3) The tensile faults formed during the extension and rifting of the lithosphere may provide a good conduit for the basaltic magma to move upward; (4) The dyke and dike complexes found in the sedimentary strata have the same magmatic source as the submarine volcanism; (5) Global and regional seismic tomography results show a clear deep low-speed channel, suggesting that the Late Cenozoic basaltic magmatism on the northern margin of South China Sea may be closely related to a deep mantle plume.