RARE EARTH ELEMENT GEOCHEMISTRY OF SURFACE SEDIMENTS IN SOUTHEASTERN ANDAMAN SEA AND IMPLICATIONS FOR PROVENANCE

In this paper, grain size and rare earth elements (REEs) of 95 surface samples taken from the southeastern Andaman Sea have been analyzed for investigation of provenance. The total REEs vary in a range from 31 to 228 μg/g, with an average of 117 μg/g. The samples are relatively enriched in light REEs, with flat HREEs patterns and moderate negative Eu anomalies, but no Ce anomalies have been found. The REE shows obvious terrigenous affinity. According to REEs characteristics, the study area could be divided into four zones, the UCC-normalized patterns of each zone are obviously different. Provenance discrimination shows that the sediments in northwestern study area (ZoneⅠ) are mainly contributed by the Irrawaddy River. The sediments of the inner continental shelf of Malay Peninsula (ZoneⅡ) are mainly from the rivers on Malay Peninsula and modern coastal erosion. The northern study area (Zone Ⅲ) is covered by relict sands, formed during the Holocene transgression. The central and southern area (Zone Ⅳ) is a mixing zone where the sediments are transported by the southwest monsoon currents from the Irrawaddy River and Malay Peninsula, dominated by the later one.