Elemental and Sr-Nd Isotope Geochemistry of Sinking Particles in the Northern South China Sea: Implications for Provenance and Transportation

Major and trace elements, Sr and Nd isotopes of bulk particles from the SCS-NW and SCS-N-03 traps were studied to trace the provenance of sinking particles in the northern South China Sea (SCS). About 63% of biogenic materials and most of lithogenic materials from the SCS-NW trap may be contributed from resuspended sediments, and more biogenic materials are collected in winter than in summer. The immobile-element discrimination diagrams also indicate that the lithogenic materials of particles are, to a large degree, from local seafloor sediments, and that the lithogenic materials of particles from SCS-N and SCS-W traps have seasonal variations. Sr isotopes (Sr-87/Sr-86 and Sr-88) of bulk particles are significantly influenced by biogenic materials and cannot be used in provenance tracing. In contrast, Nd isotopes are ideal tools to trace particle provenance. However, the traditional Nd isotope (Nd-143/Nd-144) shows no statistical difference on the particles of the SCS-NW and SCS-N-03 traps, making it unable to identify their provenance. Fortunately, the stable Nd isotope, epsilon Nd-146, shows different correlation trends to epsilon Nd-143 in these two traps, suggesting that stable Nd isotope can potentially identify the sources of lithogenic materials in the northern SCS. Our results indicate that distribution and transportation of sinking particles are controlled by currents of the SCS mainly driven by the East Asian Monsoon. Plain Language Summary As the largest semi-enclosed marginal sea in the west Pacific, the South China Sea (SCS) is supplied with a large amount of suspended sediments from its surrounding continents and islands. Studies on sedimentary process and source of sediments in the SCS have long been carried out, but no consensus has been reached yet. This study presents elemental and Sr-Nd isotope geochemistry of sinking particles from the northern SCS. According to fluxes and element concentrations of sinking particles, we find that resuspended sediments are an important contributor to sinking particles in the SCS. The relationship between trace elements of sinking particles and offshore surface sediments indicates that these resuspended sediments may be derived from continental shelves. The distribution and transportation of sinking particles are influenced by hydrological conditions of the SCS mainly driven by the East Asian monsoon. This study also reveals that stable Nd isotope could be a powerful tool in tracing sediment provenances in the northern SCS. Therefore, our results will improve the understanding of sediment transportation and sedimentary processes in the northern SCS.