Rare earth element composition of the surface sediments from the Ninetyeast Ridge and its implications for provenance

Spatial distribution patterns of grain size and rare earth elements (REE) are studied in this paper for the 42 surface sediment samples collected from the Ninetyeast Ridge of the Indian Ocean. The main sources of sediments are identified and the sediment transport modes are discussed on the hydrodynamic environment features. The results suggest that the total concentrations of rare earth elements in the 42 surface sediments of the study area vary between 26.37 μg/g and 156.8 μg/g, with an average at 57.35 μg/g. The samples are rich in light REE and uniform in heavy REE with obvious negative anomalies of Eu and Ce. The composition and spatial distribution of REE are significantly controlled by the source of sediments. According to the chondrite-normalized Sm/Nd-δEu diagram for provenance identification and the discriminant function (F_D), the sediments in the northern study area are mainly coming from the Irrawaddy River, and the subordinate is sourced from the Indian Peninsula by the Godavari River-Krishna River. The sediments in the southern study area are significantly affected by the Sumatra. The transportation process of sediments from different sources in the study area is mainly controlled by seasonal surface circulation driven by the tropical monsoon system, turbidity currents and wind.