Rare earth element geochemistry of Lake Perumal sediments: its implications for geochemical response to sources and depositional environment

The rare earth element (REE) concentration and distribution patterns were investigated for core sediment from Lake Perumal, Tamilnadu. The study of sediments deposited in the bottom of the lake Perumal have contributed to understanding of depositional environmental history. The PAAS normalised REE patterns of lake Perumal sediments show a similar variation to those for typical upper continental crustal materials. Total REE (ΣREE, the sum from La to Lu not including Y) concentration ranges between 246.8 and 497.6 μg g-1 with relatively small variation. The concentration of most individual REE in sample showed good correlation with each other and also with ΣREE. The presence of positive Eu anomaly clearly indicates that the lake sediments of Perumal were mainly derived from homogenous felsic rich source rocks. Depth profile of (La/Sc, La/Co, Th/Sc and Cr/Th) ratios show similar distributional pattern and indicates that grain size is not a dominant controlling factor of the ratios. The Ce anomaly values falls between the two limits of 23.97 and 40.92 μg g-1. The Ce anomaly Vs Nd values indicate slow sedimentation pattern under anoxic condition. The analytical results of this study directs to the conclusion that REE is a constructive surrogate in inferring the source and depositional environment. (author)