Rare earth element composition of the surface sediments from the south Bay of Bengal and its implications for provenance

Rare earth element (REE) compositions and their spatial distribution pattern for 98 surface sediment samples collected from the southern part of the Bay of Bengal are carefully studied in this paper. The main sources of sediments are identified and the sediment transport modes discussed in combination with the hydrodynamic environment features. The results suggest that the total concentrations of rare earth elements in the surface sediments of the study area vary between 67.62 μg/g and 180.67 μg/g, with an average at 100.85 μg/g. The samples are rich in light REE and uniform in heavy REE with an obvious negative anomaly of Eu. Based on the major parameters of REE, the study area can be subdivided into two provinces, the province Ι located in the west part of the study area and the province Ⅱ located in the east. According to the chondrite-normalized La/Yb-Sm/Nd diagram for provenance identification, most of the surface sediments of the study area is provided by the erosion of the Himalayan Mountain and transported by the Ganges-Brahmaputra River. The subordinate source is the Indian Peninsula, of which the sediments were transported by the Godavari River-Krishna River in the province Ι located in the west part of the study area. The transportation of sediments in different source areas is mainly controlled by the seasonal surface circulation driven by the Indian monsoon system.