Geochemical characteristics of surface sediments from the middle deep-sea basin of South China Sea

This paper presents the major and trace elements compositions of the 224 surface sediments taking from the middle deep-sea basin of South China Sea (SCS). Data shows that the samples have low SiO₂ and relatively high Fe₂O₃, MgO, CaO, Na₂O, and MnO. The abundances of most trace elements are also higher compared to the upper continental crust. The sediments are composed of four fractions, i.e. the terrigenous silicate fraction, calcareous clastic fraction, pyroclastic fraction and authigenic mineral fraction. The terrigenous silicate and calcareous clastic fractions dominate, while the pyroclastic and authigenic mineral fractions are relatively low in general but significant in some regions. The geochemical characteristics of the surface sediments in the middle deep-sea basin of SCS are mainly controlled by water depth, depositional processes, and sediment sources. The distribution of calcareous clastic fraction is mainly controlled by water depth and deep bottom current transportation. The intensive dissolution of calcium carbonate results in the relatively low content of calcareous clastic fraction in the deep-sea basin deposits, while the terrigenous sediments are supplied to the middle deep-sea basin mainly from the source regions to the west and southwest. The pyroclastic fraction, which is characterized by relatively high content of Na₂O, is possibly derived from the Luzon arc, and mainly deposited in the eastern deep-sea basin and the region to the north of the spreading ridge.