西风区末次冰期以来昭苏黄土剖面微量元素分布特征及其环境意义

The characteristics of distribution of trace elements and their paleoclimatic implications at the Zhaosu Loess Section in Westerly Area since the Last Glacial Period

通过对新疆伊犁昭苏黄土剖面微量元素和粒度的测定分析,并与黄土高原黄土进行对比,揭示了西风区末次冰期以来黄土微量元素地球化学变化特征,探讨了其古气候意义。分析结果表明,伊犁黄土除Sr和Cr元素出现富集外,其他微量元素含量与黄土高原总体具有较好的相似性,可能表明末次冰期以来伊犁黄土形成环境较黄土高原干旱;伊犁黄土除Sr、Zn、Co和Ni元素含量分布变化比黄土高原稍大外,其他微量元素变化均比黄土高原小的多,可能意味着末次冰期以来伊犁地区环境变化幅度总体较黄土高原小的多。此外,研究结果还表明,伊犁黄土Zr元素主要赋存在粒径>20μm的粗颗粒中,暗示着黄土中锆石组分主要赋存于这种粗颗粒组分中;该剖面微量元素在风化成壤过程中,其迁移性由强至弱依次为Zr>Y>Sr>Cr>V>Ga>Rb>Ni>Cu>Ba>Th>Zn>Co>U,均出现不同程度的富集,富集率均较低且变化幅度较小,可能指示末次冰期以来伊犁黄土沉积环境较为干旱且波动变化较小。

Based on trace elements and grain size analysis of Zhaosu loess from Yili basin inXinjiang, the authors reveal trace element variation characteristics in the westerly zone since thelast glacial period, and discuss its palaeoclimatic significance. The results show that the content ofother trace elements with the exception of the enrichment of Sr and Cr elements in the Ili loess havea better consistency with the Chinese Loess Plateau, which may indicate that the environment ofthe Ili loess formation was more arid than that of the Chinese Loess Plateau since the Last GlacialPeriod. The changes in distribution of contents of Sr, Zn, Co and Ni elements are slightly largerthan that of the Chinese Loess Plateau, and the rest much smaller than it, which suggest that therange of environmental change in the Ili region since the Last Glacial Period was much smallerthan the Chinese Loess Plateau. In addition, the results also imply that the Zr element of the Ililoess mainly contained in the coarse grain size 〉20 μm, which may indicate zircon components ofthe Ili loess dominatedly enrich in this kind of coarse particle size. In the process of weathering andpedogenesis, the trace elements migration intensity of Ili loess in the order from strong to weak wasZr 〉 Y 〉 Sr 〉 Cr 〉 V 〉 Ga 〉 Rb 〉 Ni 〉 Cu 〉 Ba 〉 Th 〉 Zn 〉 Co 〉 U, which there exist different degreesof enrichment, and small changes in the lower level of enrichment, suggesting that the environmentwas more arid and less fluctuating when the Ili loess deoposited .