柴达木盆地西南缘山前沙丘区沉积物地球化学特征及其指示意义

Geochemical characteristics and implications of sediments in the piedmont of southwestern Qaidam Basin,China

以柴达木盆地西南缘山前沙丘区为研究区,采用地球化学元素分析方法,阐明了研究区不同类型地表沉积物的地球化学元素特征,并探讨其风化特征、物质来源及输移过程。结果表明:(1)研究区沉积物常量元素组成以SiO2、Al2O3和CaO为主,三者的平均含量总和超过83%。微量元素以Cl、Ba、Sr和Zr含量较高。与上陆壳(UCC)平均化学元素组成相比,常量元素CaO轻微富集,微量元素As高度富集,Co轻微富集。(2)研究区化学蚀变指数(CIA)变化较小,为40.90~53.05,平均47.51,化学风化程度较弱,均处于风化的初期阶段。(3)特征元素比值表明,研究区沉积物具有相同的物质来源。柴达木盆地西南缘东昆仑山中的岩石经过风化剥蚀产生的碎屑物质在季节性流水作用下被搬运至山前堆积,形成广布的山前冲-洪积平原,后经风力吹蚀改造形成现在的地表景观。本研究不仅可以丰富区域风沙地貌研究内容,而且也可为区域风沙灾害的防治提供理论基础。

This paper selected the piedmont dune area in southwest margin of Qaidam Basin as the study area,used geochemical element analysis,elucidated the characteristics of geochemical elements of different types of surface sediments in the study area,discussed the weathering characteristics,material sources and transport process.The results indicated that major elements of the sediments are predominated by SiO2,Al2O3,and CaO,and the average total content was more than 83%,while the higher content of trace elements were Cl,Ba,Sr and Zr.Compared to the average content of chemical elements for the upper continental crust,the main element CaO was slightly enriched,and the trace element As was highly enriched,and Co was slightly enriched.The variation range of CIA in the study area was small,between 40.90 and 53.05,with an average of 47.51.The degree of chemical weathering was weak,and all of them were in the early stage of weathering.The ratio of characteristic elements indicated that the sediments in the study area had the same material source.The clastic materials generated from the weathering and denudation of the rocks in the East Kunlun Mountains at the southwest margin of the Qaidam Basin were transported to the piedmont and accumulated under the action of seasonal water flow,forming a widespread piedmont alluvial proluvial plain,and then formed the current surface landscape through wind erosion.This study can not only enrich the research content of regional aeolian geomorphology,but also provide theoretical basis for the prevention and control of regional aeolian sand disasters.