Basic Characteristics and Relationship to Tectonic Environment of the Late Cenozoic Basalts along the Coast of South China Sea
Feng Guorong Department of Geology
The eruption of the late Cenozoic basalts along the coast of South China mainly took place during the period from Pliocene to late Pleistocene. It was characterised by multiple stage eruptions, with pyroclastie materials increasing from early to late. The volcanic activities had a tendency to migration in space with the passage of time and the eruption type tended to evolve from fissure eruption to central—vent one. The basalts are mainly tholeiitic with some alkali and transitional series, and the latter two series contain xencliths and huge crystals of pyrolite. The materials of basalts were derived from the local melting of pyrolite and had undergone fractional crystallization and assimilation contamination. Petrochemical plots of the basalts show that the region of Leizhou Peninsula and North Hainan belonged to a continental rift environmunt in the Tertiary, and with the closing of the rift in the Quaternary, there occurred terrestrial eruptions of basaltic magma in the graben area; whereas the eruptions in the southeastern area of Fujian province took place along the extensional fractures paralleied to the continental margin.