湖南澧水下游表层沉积物稀土元素特征

REE Characteristics of the Surface Sediments in the Lower Reaches of Lishui River, Hunan, China

采样测定了湖南澧水下游表层沉积物21个样品的稀土元素地球化学含量,分析了稀土元素组成特征,据此探讨其物质来源。结果表明:澧水下游表层沉积物中稀土元素总含量为(109.12～192.27)×10^(-6),平均为148.37×10^(-6);与湖南土壤背景值相比较,澧水下游表层沉积物含量处于略偏低水平;21个样品的稀土元素含量变化规律高度一致,组成特征变化较小;稀土元素组成表现为轻稀土元素相对富集而重稀土元素相对亏损,Eu呈中等程度亏损,Ce呈弱的负异常;澧水下游表层沉积物的稀土元素总含量、特征参数,与湖南土壤、长江沉积物背景值比较接近,其大陆上地壳标准化和球粒陨石标准化稀土元素配分模式与长江沉积物很接近,这可能暗示了澧水下游表层沉积物除了主要来源于澧水河流侵蚀搬运物外,部分可能来源于松滋口、太平口和藕池口等荆江3口泄洪带入的长江沉积物。

The geochemical contents and compositions of rare earth element (REE) from 21 samples of the surface sediments in the lower reaches of Lishui river, Hunan, were analyzed for source tracing. The results show that the total contents of REE vary in the range of (109.12-192.27)× 10^-6 with an average of 148.37×10^-6;compared with the background value of soil in Hunan, the contents of the surface sediments in the lower reaches of Lishui river are at a slightly low level;the variation trend of REE contents from 21 samples is highly consistent, and there is little change in compositions of REE;the characteristics of REE show that LREEs are relatively abundant, and HREEs are relatively depleted with moderate negative Eu anomalies and weak negative Ce anomalies;the total contents of REE and their characteristic parameters are close to the background values of sediments in Yangtze River and soil in Hunan, and upper continental crust-normalized and chondrite-normalized REE patterns are similar to that of sediments in Yangtze River, indicating that the source of the surface sediments in the lower reaches of Lishui river mainly comes from weathered materials of Lishui river catchment, followed by sediments in Yangtze River brought by three Jingjiang flood discharges including Songzikou, Taipingkou and Ouchikou.