Characteristics of clay mineral assemblage in northern South China Sea continental margin and its geological implications

The clay minerals of sediments from 9 wells in the northern South China Sea during the period from Oligocene to Miocene. were systemically analyzed based on sedimentary mineral analytical methods, Results show these clay minerals assemblage changes regulary with time and space. Illite-smectite transition depth decreases from north to south, which is similar to the increasing trend of geothermal gradients. This illite-smectite transition pattern reflects the thinning of the oceanic-continental transitional crust in the northern South China Sea, and the uplifting of Moho surface, and the increasing of thermal flow index. The study of the relationship between clay mineral assemblage evolution and the trend of thermal flow change can help to forecast regional temperature field change law and understand thickness change of the oceanic-continental transitional crust in the northern South China Sea.