Multielement geochemistry of offshore sediments in the southeastern Yellow Sea and implications for sediment origin and dispersal

Abstract

In total, 116 surface sediments were collected from an offshore area of the southeastern Yellow Sea including a large mud belt (southeastern Yellow Sea mud: SEYSM) and analyzed for grain size and geochemical composition (organic carbon and 42 elements). Principal component analysis revealed that elemental compositions of the offshore sediments were mostly controlled by common aluminosilicate clay minerals and quartz (most elements), heavy minerals [Hf, Zr, U, Th, rare earth elements (REEs)], biogenic calcium carbonates (Ca, Sr), feldspar and mica (K, Ba, Pb), and Mn-oxides (Mn-oxide coatings on sand grains). Notably, total REE concentrations may be associated with heavy minerals (possibly zircon and monazite), especially in silty grains, even though heavy REE (HREEs) concentrations are more strongly controlled by clay minerals in muddy sediments. The diagnostic discrimination plots of geochemical compositions [e.g., Fe vs. Al, Mg vs. Al, light REE vs. HREE, and (La/Lu)ucc vs. (La/Y)ucc] suggested that the offshore sediments (especially in SEYSM deposits) were composed of a mixture of Korean river-derived silts and Chinese river-derived clays. This demonstrated that Chinese river sediments (especially clay particles) largely contributed to the formation of the giant mud belt in the Korean coastal area. Furthermore, the observed geochemical end-members provide new markers of sediment provenance, which can be used to track dispersal patterns and sediment limits from Chinese and/or Korean rivers.