罗布泊风积物与冲洪积物磁性变化特征的对比研究

Comparative study on magnetic variations of eolian and alluvial-proluvial sediments from Lop Nur area

文中对新疆罗布泊北部21个风积物样品和56个冲洪积物样品进行了磁性特征和粒度的分析,初步探讨了罗布泊风积物与冲洪积物磁性变化的差异性。结果表明:1)风积物与冲洪积样品中对磁化率起主要贡献的是磁铁矿和磁赤铁矿;2)风积物的磁化率与百分比频率磁化率呈负相关,与粗粒(>63μm)组分呈正相关,与细粒(<5μm)组分呈负相关关系,说明风积物磁化率与非成土风积粗粒组分密切相关;3)冲洪积物1.25m～1.90m之间的磁化率和百分比频率磁化率呈正相关关系,和SIRM/χ呈反相关关系,和粒度呈反相关关系,揭示了后期的化学风化可能主导着磁化率的变化。

The grain size and magnetic properties of 21 eolian samples and 56 alluvial-proluvial deposit samples from Lop Nur area,Xinjiang were investigated,the difference in magnetic variations between topsoil and alluvial-proluvial sediments were discussed preliminary.The results show that magnetite and maghemite contribute dominantly to susceptibility in eolian deposits samples and alluvial-proluvial sediment samples;susceptibility are negatively correlated to percentage frequency dependant and fine fractions（5μm）of eolian deposits samples,but positively correlated to coarse fractions（63μm）,declaring that susceptibility and non into folk product coarse fractions are closely related.In 1.25m～1.90m of the alluvial-proluvial deposits,there is the positive correlation between susceptibility and percentage frequency dependant susceptibility,but negatively correlation between susceptibility and SIRM/χ and grain size which implies that the chemical weathering after deposit probably did the mainly contribution to the variation of susceptibility.