中国北方三流域河流—沙漠过渡带地表沉积物化学元素空间差异分析

The Spatial Distribution Difference of Surface Elements in the River-desert Transition Zone of Three Drainages in Northern China

通过对克里雅河、毛布拉格孔兑以及西拉木伦河三流域的河流—沙漠过渡带地表沉积物的7种常量氧化物以及15种微量元素进行因子分析,结果显示:三个流域之间或不同河段因子分析提取的公因子均可以概括为较稳定的铁锰矿物、较不稳定的长石类和方解石(白云石)类等硅酸盐矿物以及稳定的稀土元素和重矿物等类别;河流间因子分析结果表明,自西向东三个流域沿河地表沉积物的化学元素富集与迁移程度呈递增趋势,化学风化程度增强;流域内因子分析结果表明,自上游至下游,样点化学组成均愈变复杂,不同河段或不同河岸沉积物化学元素空间分布规律与其物源、地貌格局以及水分条件等因素有关;自河床至阶地,不同地貌单元地表沉积物化学元素呈相异的递变规律,这与在距离河道远近不同,物源、动力因素的分配不同有关。

As the geochemical characteristics of surface sediments usually recorded the information of the sediments,such as the transport medium and sedimentation process,analyses of their mineral composition and provenance can provide valuable indications for paleoenvironmental reconstruction. This study provides factor analyses of 7 major dioxides and 15 micro elements in the surface sediments taken from the river-desert transition zones in the Keriya River,Mu Bulag River,and Xi Xar Moron River basins. It was found that the common factors derived from the factor analyses among the three river basins or their upper,middle,and lower reaches mainly included stable Fe and Mn minerals,less stable feldspars,calcite（ dolomite） and other silicate minerals,and stable rare earth elements and heavy minerals. The factor analysis of the relationships between the rivers indicated that the surface sediments along the rivers from west to east showed progressively increasing abundance and movement of chemical elements and degrees of chemical weathering. The factor analyses at a river basin scale indicated that from the upper reaches to the lower reaches,samples exhibiting increasingly complex chemical compositions. The spatial distribution patterns of the chemical elements in the surface sediments from different river sections or different river banks showed correlations with their provenance,geomorphic pattern,water conditions,and other factors. From the riverbed to the river terrace,the surface sediments on the three geomorphic units,from riverbed-flood plain,low river terrace composed of sand dunes to the high terrace,exhibited heterogeneous,progressive variations in their chemical compositions. This may result from their varying distances from the river courses,provenances and dynamic factors. The preliminary results of the study are expected to provide references for research into the chemical composition characteristics of surface sediments in river-desert transition zones and their variation mechanisms in response to changes of aeolian-fluvial interactions.