RARE EARTH ELEMENT CHARACTERISTICS OF SURFACE SEDIMENTS IN THE FUJIAN COASTAL AREA AND THEIR IMPLICATIONS FOR PROVENANCE

Rare-earth elements (REE) are analysis for 173 surface sediment samples collected from the Fujian coastal area in order to disclose the controlling factors onto the distribution pattern of REE and their provenance.The total content of rare-earth elements (ΣREE) for bulk samples ranges from 35.25 to 296.98 μg/g with a mean value of 171.05 μg/g.The average ΣREE content of the bulk sediments is quite close to the sediments from the Yangtze and Minjiang Rivers.On the other hand, the ratio of light REE/heavy REE (LREE/HREE) ranges between 7.56 and 16.35 with a mean of 11.27.The enrichment of LREE is quite pronounced in surficial sediments.Both the chondrite -normalized patterns and the ratios of (La/Sm)_CN, (Gd/Yb)_CN of REE of the sediments from the study area show an accordant steep right-dipping REE distribution pattern with significant fractionation of light REE and weak fractionation of heavy REE.In addition, observed are a moderate negative Eu anomaly ranging from 0.55 to 1.06 with a mean value of 0.80 and a less obvious Ce anomaly ranging from 0.71 to 1.19 with a mean value of 1.00.These features are rather similar to the upper continental crust.The upper continental crust-normalized patterns of REE of the sediments show no significant fractionation with respect to the upper continental crust.Therefore, the source of sediments is dominantly from the continental crust consisting of felsic rocks.The enrichment and distribution of REE is generally controlled by grain size of sediments.It seems that REE are more enriched in fine-grained fractions.In some areas, REE composition of the sediments is influenced by carbonate and heavy minerals.