Variation in rare earth elements and provenances of the sediments along the Kuroshio mainstream to the east of Taiwan over the past millennium

Rare earth elements (REE) and their fractions in the sediments of Kuroshio mainstream off eastern Taiwan were determined to reveal the REE geochemical characteristics and provenances of the sediments for the past millennium. AMS¹⁴C is used for dating. The average ratio of light REE to heavy REE (LREE/HREE) is 11.30 in the sediments of research core, obviously enriched in light REE. The average total REE content is 119.82 ppm, which was under the REE abundance of upper continental crust (UCC) and China loess, and close to the figure of Okinawa Trough. The chondrite-normalized REE patterns and the UCC-normalized REE patterns show a similar trend: light REE enriched with slightly positive Ce anomalies. The research core may be subdivided into three layers according to the chronohorizon and variation trend of REE: 0~8.5cm, 8.5~21.5cm, 21.5~30cm respectively. The average REE contents increase with depth, while the LREE/HREE ratio decrease and the extent of positive Ce anomalies weaken with depth. The results of REE fractionation show that La, Ce, Pr and Nd come from terrigenous sources, as the other REEs are susceptible to the oxidation-deoxidation conditions. The residual fractions of the sediments of the research area are mainly the uppermost fractions of REE, and followed by the Fe/Mn-oxides fractions as the second. Facts show that the residual fraction of REE play a decisive role in the total REE patterns of the Kuroshio mainstream sediments, as well as the key factor of positive Ce anomalies in the total REE. The REE features show no obvious relations with grain size, and the provenance of REE was relatively stable over the past millennium. It is inferred that the rivers input from eastern Taiwan was the most important source of REE in the sediments of the research area, and input from East Asian monsoon subordinates.