Geochemical constraints on the provenance of surface sediments of radial sand ridges off the Jiangsu coastal zone, East China

The Jiang harbor-centered radial sand ranges (RSRs) off the Jiangsu coast are the largest in the Yellow Sea. However, the provenance of the RSRs remains controversial. In this study, we compare major and trace element geochemistry together with grain size and main mineral composition in carbonate-free sediments from RSRs and potential sources. Onshore and offshore RSR sediments have different grain size characteristics: onshore RSR sediments have mean grain-sizes of < 50 μm whereas offshore RSR sediments are between 50 and 160 μm in mean grain size. Despite these differences in grain size onshore and offshore RSRs have similar mineral compositions. Relative to upper continental crust (UCC), onshore RSR sediments are enriched in SiO2, TiO2, Li and partly in Cs, Zn and some high field strength elements (Y, Zr, Nb, Pb and Th) while depleted in other elements. Offshore RSR sediments are complicated in geochemical compositions. Some of them have very high contents of high field strength elements, and others are similar to onshore RSR sediments. Onshore and offshore RSR sediments have different controlling factors of geochemical compositions: onshore RSR sediments are influenced by clay-size minerals whereas offshore sediments are controlled by heavy minerals. The identification of Zr/Nb and Ti/Zr vs. K/Rb shows that onshore and offshore RSRs seem to have similar sources. Their differences in grain size are a result of hydrodynamic sorting. The identification of elemental ratios reveals that sources of RSR sediments are variable in space and time and the inputs of the Chinese Rivers, especially the old Yellow River and the Yangtze River are still dominant but the effect of the Korean field cannot be neglected. Our findings also demonstrate the potential of elemental ratios such as Zr/Nb and K/Rb as tracer pairs for provenance of sediments in the Yellow Sea.