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    中国东部海域表层沉积物稀土元素赋存特征及物源探讨

    The rare earth element content in surface sediments of coastal areas in eastern China's sea areas and an analysis of material sources

    • 摘要: 通过中国地质调查局近20年对中国东部海域的高精度调查取样,对渤海、黄海和东海表层沉积物中的稀土元素数据进行了系统总结,旨在揭示其赋存特征、分布规律及其控制因素。结果表明,整个中国东部海域大致可以划分为4个稀土含量富集区,分别位于渤海西部泥质区、南黄海中部泥质区、济州岛西南泥质区以及东海内陆架泥质区,富集区内的表层沉积物稀土含量普遍高于180 mg/g;稀土元素的球粒陨石配分模式和UCC配分模式显示出各海域较为一致的总体特征,与中国大陆的稀土元素分配曲线类似,指示了较强的陆源特征。通过对稀土元素各特征参数的相关性分析,发现与中国东部海域稀土元素含量相关性最强的是δEu,呈明显负相关,其次是沉积物的平均粒径,呈明显正相关。利用δEu-(La/Yb)n物源判别图对这4个稀土含量富集区的样品进行判别,结果表明渤海西部泥质区和南黄海中部泥质区的沉积物具有同源性;南黄海东南部的济州岛西南部泥质区除了有来自长江和黄河物质以外,朝鲜半岛东南部的河流输入作用也不可忽视;东海内陆架泥质区北端的沉积物基本来源自长江,而南端则表现出不同的稀土分馏特征,很可能与闽浙沿岸和台湾岛中小河流的输入有关。大型河流和中小河流带来的物源、沉积物粒度以及海域流系格局控制了中国东部海域表层沉积物稀土元素的地球化学特征。

       

      Abstract: The geochemical characteristics of rare earth elements in the surface sediments of the Bohai Sea, the Yellow Sea and the East China Sea have been studied systematically and macroscopically through the investigation, sampling, testing and analysis of eastern China's sea areas by China Geological Survey in the past 20 years. The results show that there are four REE enriched areas in the surface sediments of the eastern coast of China with the REE content generally higher than 180 μg/g. The distribution of highvalue areas is consistent with mud areas in eastern coast of China, such as mud area of western Bohai Sea, middle of south Yellow Sea, southeast of Jeju Island and inner shelf of the East China Sea. Chondrite- normalized REE patterns and UCC- normalized patterns in the surface sediments of the three seas are relatively homogeneous, with the distribution characteristics similar to features of China's mainland. It is found that δEu is most strongly negatively correlated with the content of rare earth elements in eastern China's sea areas, followed by the average grain size of sediments with significant positive correlation, as shown by the correlation analysis of the characteristic parameters of rare earth elements. The δEu- (La/Yb)n map was used to identify the material sources for the REE high-value areas, and the result indicates that the sediments in the mud area of west Bohai Sea and the middle of south Yellow Sea are mainly from the same source. It is generally considered that sediments from the mud area of the southwest of Jeju Island are mainly from Yangtze River and Yellow River, but the river input from the southeast of the Korean Peninsula can't be ignored, that the sediments from the north end of the mud area of the inner shelf of the East China Sea are basically from the Yangtze River, while the south end shows different REE fractionation characteristics which are related to the input of small and mediumsized rivers along the coast of Fujian, Zhejiang and Taiwan Island. The material source, sediment grain size brought by large and middle-small rivers and the flow system patterns of the sea areas jointly determine the geochemical characteristics of REE in the surface sediments of eastern China's sea areas.

       

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