Terrigenous and volcanogenic contribution to the deep basin of the South China Sea: Evidence from trace elements and Sr-Nd isotopes

The deep basin of the South China Sea (SCS) receives terrigenous materials from the surrounding continents and islands, making it an ideal region for studies on source-to-sink transport. The analysis of grain size, major and trace elements, and Sr-Nd isotopes of 130 surface sediment samples throughout the SCS deep basin has been performed for identifying the contribution of terrigenous and volcanic materials. Based on the analysis results, the SCS deep basin can be divided into three geographic areas with different provenances: the northern area of the East Subbasin (NES), the southern region of the East Subbasin (SES), and the Southwest Subbasin (SWS). The predominant provenances of sediments in the NES and SWS are Taiwan rivers and Mekong River, respectively. Sediments from the SES exhibit higher mean grain size, less radiogenic Sr-87/Sr-86, and more radiogenic Nd-143/Nd-144 than those from the NES and SWS. Pinatubo ash input from the Luzon Island may be a predominant source in the SES. The contribution of Pinatubo ash decreased westward from 80% to 20% in the SES. The supply of Pinatubo ash could be considered insignificant to the NES and SWS. Sediments from Taiwan rivers or Mekong River were the subordinate source in the SES. The deep-water current and mesoscale eddies may play a role in transporting terrigenous materials into the SCS deep basin as well as the turbidity current.