Signatures of rare-earth elements in banded corals of Kalpeni atoll-Lakshadweep archipelago in response to monsoonal variations

Abstract

Concentrations of rare-earth elements (REE) have been determined in seasonal bands of Porites species collected from the Lakshadweep lagoon. Total REE (Sigma REE) are very low (<3 ppm) in these corals. Seasonal variations in REE appear to have occurred with Sigma REE and the light rare-earths (LREE) enriched in the high density (representing monsoon season) bands. In contrast, the heavy rare-earths (HREE) are enriched in the low density bands. LREE enrichment in the high density bands is attributed to their higher availability during the rainy season due to the increased weathering of the continental sources. Elemental ratios and SEM photographs reveal the increased incorporation of terrigenous material into the growth bands during the monsoon season.