兰州黄土地球化学特征及其意义

The Geochemical Characteristics and Its Significance of Lanzhou Loess

本文用对应分析方法讨论了兰州黄土地球化学特征,发现化学元素存在四个最基本关联,代表了黄土化过程中 P_2O_5与 CaO 等的相对增加及土壤化过程中 Al_2O_3、K_2O、MnO_2和 Fe_2O_3等的富集.常量元素氧化物中 Fe_2O_3、K_2O 和 MnO_2在古土壤中富集最明显,而 CaO 与 Na_2O 产生明显淋失;微量元素中 Cu、Zn、Ni、As 等在古土壤中含量比黄上层高10%以上,而 Zr、Ba 和 sr含量偏低.REE 分布模式说明,兰州黄土主要是风成的,物质来源于中国西部沙漠.碳氧同位素中碳同位素更敏感反映气候变化.

In this paper,the geochemical Characteristics of Lanzhou loess are discussed with corresponding analysis method.It is found that there are fourbasic geochemical interrelations in Lanzhou loess.They represent the relativeincrease of P_2O_5 and CaO(CaCO_3)in loess format on and the accumulationof Al_2O_3,K_2O,MnO_2,Fe_2O_3 and other compositions ill polaeosol formation.In common elements,Fe_2O_3, K_2O and MnO_2 accumulate apparently inpalaeosol layers,but CaCO_3 and Na_2O are leached in palaeosol layers.In trace elements,the content of Cu,Zn,Ni,As and others is 100% more inpalaeosoi layers than in loess layers,while the content of Zr,Ba and Srelements is low in palaeosol layers.It is shoun by REE distribution modelthat lanzhou loess was formed by dust deposition and the material mainlycame from desert area of west China.In carbon and orygen isotope, δ^(13)Cis low in palaeosol layers,but δ^(18)O is high in palaeosol layers.