RARE EARTH ELEMENTS GEOCHEMISTRY AND PROVENANCE OF THE SEDIMENTS FROM CORE XH-CL16 IN THE XISHA TROUGH, SOUTH CHINA SEA

The Xisha Trough is an important gas hydrate exploration prospect in the northern South China Sea. The provenance of Xisha Trough sediments remains controversial. The sediment from Core XH-CL16 in the Xisha Trough are characterized by relatively high total rare earth element contents (ΣREE=131~171 ppm), slightly enriched light REE (La/Yb_N=9.5) and clearly negative Eu anomalies (δEu=0.66~0.79). Their chondrite-normalized REE patterns are similar to the upper continental crust and the sediments from Chinese loess, the Pearl River and Mekong River, but different from the normal middle oceanic ridge basalt (N-MORB) and deep-sea clay. Thus, the sediments of the Xisha Trough show terrestrial affinity, which probably result from multi-provenance and multi-transmission. Contrasting with the standard carbonate formation in the Xisha Trough, the variations in CaCO₃ contents for the sediments from Core XH-CL16 suggests that they were deposited since approximately MIS3. In addition, sediments in MIS2 have higher ΣREE, CaCO₃ and Ti contents than those of sediments in MIS1 and MIS3, which may indicate more continental contribution during the MIS2.