Analysis of Contents and Distribution Patterns of Rare Earth Elements in the Surface Sediments of the South Mid-Atlantic Ridge

A microwave digestion system was employed to digest sediment samples from 16 stations in the South Mid-Atlantic Ridge with HNO3-H2O2-HF as the digestion reagent. Rare earth elements (REEs) in the sediments were determined through inductively coupled plasma-mass spectrometry (ICP-MS), and the REE distribution characteristics were studied. The microwave digestion-ICP-MS method was used to determine the REEs with significant linear relationships (r = 0.9997–1.0000) for each element. The detection limit was at ng L−1 level, with relative standard deviation (RSD, n = 3) of less than 3% and the relative error within 6%. Moreover, the total amount of REEs (∑REEs) in the sediment samples from the 16 stations ranged from 37.25 to 134.8 μg g−1, the ratio range of the light/heavy REEs (LREEs/HREEs) was 0.61–1.70, the average value was 1.27, and the enrichment light rare earth elements in sediments was obvious. The REE distribution patterns in each station were similar, with obvious fractionation between the LREEs and HREEs. The REE distribution patterns in the sediments from different sources were also similar, but those between the terrestrial and marine sediments exhibited slight differences. The δEu and δCe in the sediments had negative anomalies, which showed that the REEs in the sediments originated from seawater. The content and distribution of the REEs in the South Atlantic were initially investigated in this study to provide data and technical support for the further study of REE distributions in the Atlantic region.

The chondrite-normalized REE pattern was established with the normalized ratio of the REE contents in the sediments and in chondrite, which could eliminate the abundance changes between odd and even atomic numbers, and the curve mapped the geochemical differentiation of the sediments to the original rare earth composition. In this study, Gd appeared with negative anomaly in all stations.Figure optionsDownload as PowerPoint slide