毛乌素沙地中部风成沙的组成与微形态特征

分析了毛乌素沙地中部流动沙丘与固定-半固定沙丘沉积物粒度、元素和微形态特征。结果表明：流动沙丘沙和固定-半固定沙丘沙均以细沙和中沙为主，流动沙丘沙的分选性较好，而固定-半固定沙丘沙的分选性较差，沙丘在频繁强烈的风沙活动环境下跃移搬运，且搬运方式一定，搬运动力稳定。与上部陆壳平均化学组成（UCC）相比，常量元素SiO₂和Na₂O富集，其余均亏损，而微量元素中，Co富集明显。沙丘沙物质CIA值与上部陆壳平均值接近，表明沙丘经历了低等的化学风化。流动沙丘和固定-半固定沙丘颗粒磨圆度普遍较差，大多呈现棱角状或次棱角状外形，真正圆状外形较少。风成环境的典型标志碟形撞击坑占比很大，推断毛乌素沙地中部气候相对干燥，机械作用占主导地位，化学风化作用甚微。

Composition and Micro-morphological Characteristics of Aeolian Sand in the Middle of the Mu Us Sandy Land

In this paper, the grain size, element and micro-morphological characteristics of mobile dune and fixed/semi-fixed dune in the middle of the Mu Us Sandy Land are analyzed. The results show that both the mobile dune and the fixed/semi-fixed dune are composed of fine sand and medium sand, while the sorting of mobile dune is better, and the sorting of fixed/semi-fixed dune is poor. The transport style of dunes is saltation in a frequent and strong wind activity environment, and the way of transportation is fixed and the power of transportation is stable. Compared with UCC, SiO₂ and Na₂O are rich in major elements, others are loss, and Co is enriched obviously for trace element. Values of CIA of dunes are close to the average of the upper continental crust, indicating that the dune has experienced a low degree of chemical weathering. The roundness of mobile dune and fixed/semi-fixed dune is poor, and most of them are angular shape or sub-angular shape, and the real round shape is less; The typical mark of the windy environment is dish-shaped pits accounted for a large proportion, and it is inferred that the climate of the Mu Us Sandy Land is relatively dry, the mechanical action occupies a dominant position while the chemical weathering plays a small role.