巢湖东部第四纪红土微量元素地球化学特征及物源初探

Geochemical Characteristics of Trace Elements and Provenance at the Quaternary Red Earth Section in the East Chaohu Area,China

在野外地质地貌考察与采样的基础上,利用X射线荧光光谱分析对巢湖东部第四纪红土的微量元素含量进行测定,结合微量元素富集指数和因子分析方法,并将巢湖东部第四纪红土与长江河漫滩沉积物、西北黄土沉积物和上陆壳的相应微量元素通过判别函数和物源指数相比较,初步探讨了巢湖东部第四纪红土的微量元素地球化学特征及其物源。结果表明:(1)微量元素变化率△值显示,微量元素Sr的△<0且|△|<10%,表明其相对Ti发生了少量的迁移,微量元素Ni、Mo、Ga、Zn、V、Cu、Ba、Co、Cr、Pb、Th和Nb的△值> 0,表明这些元素相对Ti在化学风化过程中发生了富集;(2)巢湖东部第四纪红土、长江河漫滩沉积物和西北黄土沉积物的各微量元素与上陆壳(UCC)微量元素平均值的对比发现,巢湖东部第四纪红土与西北黄土沉积物的微量元素相似度较高,而长江河漫滩沉积物显示了Pb、Zn、Cu和V的富集,与上述两者不同;(3)将三地的判别函数FD值和物源指数IP进行分析,巢湖东部红土IP黄土为0. 395(<0. 5),而IP长江河漫滩为0. 605(> 0. 5),表明巢湖东部第四纪红土的元素组成更接近于西北黄土沉积物,而不同于长江河漫滩沉积物,主要物源十分类似于西北黄土,而异于长江河漫滩沉积物。

On the basis of the field investigation and sampling,the trace elements of Quaternary red earth in the East Chaohu Area were determined with X-ray fluorescence spectrometer.Combining the trace element enrichment index with the factor analysis,as well as the F D and I P indexes comparisons of the trace elements of Quaternary red earth in the study area,the floodplain sediments of Yangtze River,the northwest loess sediments,and the upper continental crust,we discussed the geochemical characteristics of trace elements and provenance at the Quaternary red earth section in the East Chaohu Area.The results showed that：1）The change rate of these trace elements showed the rate of Sr is less than 0,but its absolute value is below 10%,which is said Sr removed a small amount comparing with Ti.But the change rate of other trace elements are more than 0,that showed these trace elements had much enriched in this area,such as Ni,Mo,Ga,Zn,V,Cu,Ba,Co,Cr,Pb,Th and Nb.2）Comparing the average value of the red earth in the East Chaohu Area with the floodplain sediments of Yangtze River,the northwest loess sediments and the upper continental crust,trace elements in the red earth in the East Chaohu Area had more similar with northwest loess sediments.The floodplain sediments of Yangtze River showed the enrichment of Pb,Zn,Cu and V.This is different with above two.3）From the analysis of F D and I p among these three areas,the I p of the red earth in the East Chaohu Area comparing with the northwest loess sediments equaled to 0.395,which is below 0.5.The I p of the red earth in the East Chaohu Area comparing with the floodplain sediments of Yangtze River equaled to 0.605 ,which is above 0.5.This suggested that elements of Chaohu area are more similar with the northwest loess sediments,but different from floodplain sediments of Yangtze River.