论文部分内容阅读
对毛乌素沙地16个现代流动沙丘沙样品矿物分析结果进行归纳与研究。结果显示:(1)毛乌素沙地现代流动沙丘沙轻矿物占绝对优势,平均含量为94.8%,以石英、长石为主;重矿物所占比例很小,平均含量为1.6%,但种类较多,共含22种重矿物。(2)重矿物中2/3以上属硅酸盐类矿物,其含量前三的为角闪石、绿帘石、石榴子石;(3)重矿物以不稳定矿物和较稳定矿物占较高比例,绝大多数为硅酸盐类矿物,分别为100%和98.75%;(4)重矿物中硬矿物和极硬矿物含量高达80.17%,分别为61.57%和18.60%。结果还显示,轻矿物石英/长石含量比值(平均值为6.10)和重矿物矿物风化系数(平均值3.89)都较高,重矿物中造岩矿物(平均值26.7%)含量占近1/3。由此,并考虑到高含量的硬-极硬的重矿物的存在,表明其沉积时属于气候干冷、生物化学风化作用较弱的强风沙流环境。本文除证明了高含量的不稳定矿物和较稳定矿物与气候干旱具有本质上的联系外,还说明了干旱环境下沙丘沙中多种类、高含量的硬-极硬矿物的存在,极大地抑制了物理风化和生物化学两个方面的风化的难度,从而使其向土壤化根本逆转也很难。即使沙丘得以固定,由于其丘体的这种矿物组分,仍然难以消除潜在沙漠化的客观存在,故土地沙漠化引起生态环境的退化实际上也与沙丘沙碎屑矿物的物理性质具有本质上的联系。因此,干冷多风的气候条件及其导致的沙丘沙所具有的物质组成的特殊性应该是土地沙漠化的两个不可或缺的原因。
The results of mineral analysis of 16 modern mobile dune sand samples in Mu Us sandy land are summarized and studied. The results show that: (1) The sandy mobile sand dune in the Mu Us desert plays an absolutely dominant role with light minerals, with an average content of 94.8%, dominated by quartz and feldspar; heavy minerals account for a very small proportion with an average content of 1.6% More, a total of 22 kinds of heavy minerals. (2) More than two-thirds of heavy minerals belong to silicate minerals, and the first three are hornblende, epidote, garnet; (3) heavy minerals account for unstable minerals and relatively stable minerals The majority of them are silicate minerals, which are 100% and 98.75% respectively. (4) The content of hard and hard minerals in heavy minerals is as high as 80.17%, which is 61.57% and 18.60% respectively. The results also showed that the ratios of quartz / feldspar (average 6.10) and heavy mineral weathering (average 3.89) were higher for light minerals and rock-forming minerals (26.7% for heavy minerals) accounted for nearly 1 / 3. Thus, taking into account the presence of high levels of hard-ultra-hard heavy minerals suggests that it is a strong sand-flow environment with a dry climate and weak biochemical weathering when it is deposited. In addition to demonstrating that the high levels of unstable minerals are intrinsically linked to the more stable minerals and the climatic aridity, it also illustrates the presence of multiple, high levels of hard-to-hard minerals in sand dunes under arid conditions, greatly inhibiting It is also difficult to weather the two aspects of physical weathering and biochemistry, so that it can not be fundamentally reversed. Even if the sand dune can be fixed, due to the mineral composition of its mound, it is still difficult to eliminate the objective existence of potential desertification. Therefore, the degradation of the ecological environment caused by desertification of the soil is also essentially related to the physical properties of the sand and sand detrital minerals . Therefore, the dry and windy climatic conditions and the particularity of the material composition of the dune sand caused by it should be the two indispensable causes of land desertification.