Igneous rocks in Jinghai Sag, Pearl River Mouth Basin and their geological significance

Igneous rocks in the Jinghai sag are identified through 3D seismic interpretation by the contact relationship between the rocks and the overlying deposits. Four magmatic stages are recognized in the study area, separated by three unconformity reflections, i.e the late Cretaceous Tm18, the late Miocene T35 (10.5Ma), the late Pliocene T20 (2.6Ma) and the overlying Quaternary. Among them the Quaternary eruption is the strongest. Volcanic and intrusive bodies are mainly distributed along the NE trending Chaoshannan fault, in a form of scatter small scale central volcanoes. The distribution trend of the volcanoes seems irrelevant to the increase in paleogeothermal gradient toward the oceanic crust in the south. Limited impact is expected to the oil gas accumulations in the sag.