黄河沉积物稀土元素地球化学特征

Composition Characteristics of Rare Earth Elements in Yellow River Sediments

本文以黄河口和小浪底水库表层沉积物、利津水文站悬浮沉积物为研究对象,在分析其物质组成特征的基础上,研究了稀土元素(REE)的含量、配分模式、分异特征及其制约因素,探讨了黄河沉积物REE的物源示踪意义。结果表明,黄河口和小浪底水库表层沉积物、利津水文站悬浮沉积物稀土元素总量(∑REE)平均值分别为178.16×10^(-6)、181.38×10^(-6)、158.26×10^(-6);三种沉积物REE的上地壳标准化配分模式均为轻稀土富集的略右倾模式,轻稀土的分异程度与黄土相比较高,而重稀土未出现明显分异;Eu和Ce相对于上陆壳物质REE没有发生明显分异;黄河口表层沉积物REE配分模式和分异程度与利津站悬浮沉积物相似度较高,而与小浪底水库沉积物略有差异。黄河口沉积物中的∑REE除受到源岩和沉积物粒度的显著影响外,主要与碳酸盐、磷酸盐及Fe-Mn氧化物等矿物和物质相结合。黄河沉积物REE分异显著弱于长江沉积物,造成两者差异的因素主要为源岩不同导致的沉积物组成的差异,这可作为两类沉积物识别的重要标志。本研究结果可为进一步认识现代黄河沉积物REE组成特征及其示踪意义提供依据。

Based on the analysis of grain size,major elements,mineral compositions and rare-earth elements(REE)in the surface sediments of the Yellow River estuary and Xiaolangdi Reservoir,as well as the suspended sediments of Lijin Hydrological station,we studied the contents,distribution patterns,differentiation characteristics,the restriction factors and its significance of provenance tracing of REE.The results showed that the average∑REE of surface sediments in the Yellow River estuary and Xiaolangdi Reservoir,suspended sediments in Lijin Hydrological station are 204.70×10^(-6),209.73×10^(-6)and 183.11×10^(-6),respectively.The upper continental crust(UCC)normalized distribution patterns of REE in the three types of sediments are all slightly right-leaning patterns with LREE enrichment,and LREE differentiation is higher than loess,while HREE differentiation is not obvious.The anomalies of Eu and Ce indicate that there is no significant differentiation with respect to the UCC.The REE distribution pattern and differentiation degree of surface sediments in the Yellow River estuary are consistent with the suspended sediments in Lijin Station,but slightly different from the sediments in Xiaolangdi Reservoir.The REE content in the sediments of the Yellow River estuary is significantly affected by the grain size of the sediments and is mainly concentrated in the fine-grained materials,which is mainly associated with carbonate,phosphate and Fe-Mn oxides.The differences of REE differentiation,LREE and HREE differentiation in the Yellow River sediments are significantly smaller than those in the Yangtze River sediments,caused by the differences of source rocks and the composition of sediments,which can be used as an important indicator for the identification of the two types of sediments.This study provides a basis for further understanding the REE composition characteristics of the Yellow River sediments and using it as a tracer index for the diffusion of the Yellow River material.