中国大陆架海底沉积物中的稀土元素

RARE- EARTH ELEMENTS IN CONTINENTAL SHELF SEDIMENTS OF THE CHINA SEAS

选择渤海、黄海、东海和南海有代表性的大陆架沉积物样品,利用X射张荧光光谱法测定了15个稀土元素。中国大陆架沉积物稀土元素的丰度为156ppm,相对接近于中国黄土和花岗岩的丰度,而与太平洋沉积物的丰度相差较远,具有明显的“亲陆性”。稀土的配分模式旦显著的负斜率,属陆壳稀土的典型特征。稀土含量受沉积物粒度控制。实验表明稀土主要以类质同像存在于粘土矿物之晶体构造中。根据数理统计,稀土与亲陆源粘土矿物的元素为一类,彼此呈正相关;与亲海洋生物的元素为负相关。事实说明中国大陆岩石的风化和搬运,是中国海大陆架沉积物中稀土的主要物质来源。

The representative samples of continental shelf sediments from the Bohai Sea, Yellow Sea, East China Sea and South China Sea have been selected and the concentrations of 15 rare earth elements (REE) in these sediments have been mcasurde by X-ray fluorescent spectral analysis.Relative eucrs of the measurement are less than 10% .The results of stults show that the abundance of REE in continental shelf sediments of the China Seas is 156ppm, which is relatively close to that in Loess of China and Fujian granite, but different from that in Pacific sediments.It is evident that the REE have an' inherited' or 'philo- continental' property.The average content of REE is controlled by sediment grain-size, that is, REE contents increase gradually with the decrease in grain size. REE distribution patterns demonstrate a distinctly negative slope, which means that the light rare earth element (LREE) concentrations are obviously larger than those of the heavy rare earth elements (HREE), indicating a typical characteristic of rare earth elements of the continental crust. Experiments show that REE mainly concentrate in the clay minerals (<2u), and thye are not largely absorbed as cations by clay minerals, but mainly esist in crystal lattices of clay minerals as isomorph.Secondly, some of REE lie in heavy minerals.In regard to the correlation analysis and cluster analysis, the REE have a close relationship with most elements related with clay minerals, such as Al, Ti, K, Rb, Fe, etc.In contrast, the Ca and Sr.All mentioned above suggests that the rocks widely distributed in continent of China, which were weathered and transported, are the main soured of REE in continental shelf sediments of the China Seas.