新疆伊犁黄土化学风化特征及其控制因素

Chemical Weathering Characteristics and Controlling Factors of the Ili Loess,Xinjiang

通过对伊犁盆地昭苏黄土剖面元素地球化学分析,结合与黄土高原典型第四纪风成堆积洛川剖面的对比,对伊犁黄土常量元素分布规律及化学风化特征进行初步研究发现,伊犁昭苏剖面黄土和古土壤主要元素含量具有较好的一致性,暗示着沉积后两者所经历的风化作用相似。与黄土高原相比,伊犁黄土和古土壤除CaO,MgO和Na2O,P2O5分别出现较大程度的富集和较小程度的亏损外,其它常量元素含量的变化趋势基本一致;CIA指数、Na/K比值及A-CN-K图解显示伊犁黄土和古土壤均经历了低等强度的化学风化作用,弱于黄土高原的洛川黄土及古土壤,黄土和古土壤风化分异作用不明显。气候条件尤其水热组合模式(降水、温度和蒸发量等)对伊犁黄土化学风化的起着重要的制约作用。

The element distribution characteristics and chemical weathering intensity of the loess and paleosol at the Zhaosu section in the Ili Basin are preliminarily studied through element geochemical analysis. Through comparing with the type Luochuan loess-palesol section of the Quaternary aeolian deposit in the Loess Plateau,we draw the following conclusions. The contents of major elements in the loess and paleosol at the Zhaosu section in the Ili region show similar variations,which indicate that both of them experienced the similar degree of chemical weathering after deposition. Major elements have the same changing trend as that of the Loess Plateau,with enriched CaO and MgO and depleted Na2O and P2O5 . CIA index,Na/K ratio and A-CN-K diagrams all indicate that the Ili loess and paleosol experienced weaker chemical weathering than that in the Loess Plateau. Furthermore,there is no obvious chemical weathering differentiation between loess and paleosol. The climate conditions such as hydro-thermal combination（precipitation,temperature and evaporation,etc.） may play an important role in chemical weathering of loess and paleosol in the Ili basin.