Rare earth elements of sediments in rivers and estuaries of the east coast of India

Abstract

The rare earth elements (REE) in the clay fraction of sediments in 15 rivers and their estuaries along the east coast of India were analysed in this study. The total REE content (ΣREE) varied from 130.98 to 289.85 μg/g and from 70.89 to 352.61 μg/g in rivers and estuaries respectively. The ΣREEs of estuarine clays (except the Brahmani and Baitarani) was lower than in rivers. The Post-Archean average Australian Shale-normalized REE patterns in rivers and estuaries were similar and categorized into three types. The REE patterns reflect the composition of dominant geological formations in river basins and extent of sediment mixing from different sources during transport. Hydrodynamic conditions controlled the abundance and fractionation of REE in the estuaries. The Sm/Nd ratios of clays were largely controlled by mineral composition and Y/Ho ratios were affected by sedimentary processes in the estuaries.