Distribution pattern of rare earth elements in core sediments of the South Korea Plateau, East Sea

Abstract

Vertical distributions of rare earth elements (REEs) have been investigated in box- core sediments from two stations at water depth of 1400 (BO2) and 1700 m (BO 1) in the eastem South Korea Plateau of East Sea. The extractable (hydroxylalmine/acetic acid) REE concentrations show a different vertical profile from Fe and Mn which decrease rapidly at the uppermost few centimetres. At station BO2, the extracted REE concentrations increase remarkably with depth below Fe-redox boundary in sediment core. This similar vertical profile is also shown in the extractable P concentration. Plots of Post-Archean Australian Sedimentary rock (PAAS)-normalized extractable REE data show a distinctive middle REE enriched pattem ([Gd/Yb]PASS, average 2.81 at BOI and 2.63 at BO2), together with positive Ce anomalies ([Ce/Ce*]PASS, average 1.34 at BOI and 1.32 at BO2), whereas flat patterns are present in the residual REE data ([La/Yb]PASS, average 1.11 at BO1 and 1.23 at BO2). Middle REE enrichments of the extractable fractions are likely to be associated with authigenic precipitation of phosphatic minerals, which are an important pool of labile middle REEs in the sediments, based on multiple linear regression analysis using variables[Gd/Yb]PASS, and the extractable Ca and P concentrations.