对应分析在冀北蔡家营地区土壤形成过程研究中的应用

Application of Correspondence Analysis to Study of Soil Forming Process in Caijiaying Area,Northern Hebei

目的研究表生风化作用过程对土壤不同粒级的影响。方法运用多元统计中的对应分析对采自蔡家营地区不同粒级土壤样品的主量元素及稀土元素进行分析,结合显微镜观察及统计,探讨不同粒级土壤的物理化学风化以及该区风成沙主要渗入粒级的识别。结果在>4目、4~10目及10~20目粗粒级段主要以原地物理风化为主,岩石与矿物以棱角状为主,且轻稀土富集,具有正Eu和正Ce异常的稀土配分曲线为特征;在20~40、40~60、60~80、80~100目,石英以滚圆状及高含量为特征,Eu及Ce以正异常转为负异常为特征,在该粒级段物理化学均对土壤有重要影响,且有大量外来风积物的加入;在100~120目细粒级中,滚圆状石英含量减少,棱角状石英增加,黏土矿物含量升高,来源既有原地也有外来风积物的次生风化,稀土配分模式相似,但稀土总量升高,该粒级段以化学风化占支配地位。结论以上结果可以为该区地球化学方法技术的选择提供重要参考,减少该区风积物对化探找矿效果的影响。

Objective To study the influence of hypergenesis on the different soil fractions.MethodsThe correspondence analysis of the major elements and the REE of the soil from the Caijiaying area was applied to study the physical and chemical weathering of the different soil particles,and to identify the principle fractions of the eolian sand in this area,in combination with microscopic observation.ResultsFirstly,the coarse particles between>4and 4-20 mesh were mainly formed by physical weathering in situ and characterized by angular minerals and fragmental rocks,enrichment of light rare earth elements and positive anomaly of Eu and Ce in the REE patterns.Secondly,the middle particles of 20-40,40-60,60-80,80-100 mesh respectively had the features of mass rounded quartz and negative anomaly of Eu and Ce in the REE patterns.Physical and chemical weathering changed the mineral composition and the size of the soil,and the addition of eolian deposits changed the chemical composition.At last,the fine particles between100-120 mesh could be recognized that the content of the rounded quartz decreased,while the clay mineral increased,and chemical weathering dominated the process.The fine particle of soil was a mixture of weathering products around and eolian deposits.Conclusion The above conclusions can provide an important reference for the selection of geochemical exploration methods in this area and reduce the influence of the eolian sand.