格尔木河上游水成沉积物元素时空变化、流域风化及其驱动机制

Spatiotemporal Variations of Elements in Hydrogenic Sediments,Watershed Weathering and its Driving Mechanism in the upper Golmud River

格尔木河流域上游山区沉积物元素的风化迁移规律对察尔汗盐湖中盐类资源的补给具有重要意义。文章结合已有的光释光(OSL)年代学数据,对该流域的上游纳赤台(NCT)和中游小干沟(XGG)剖面进行了主要常微量元素变化规律研究,并对流域内上下游不同类型沉积物的元素特征进行对比分析,得出如下结论:1.末次间冰期以来,格尔木河中游河谷沉积物中主要元素含量较上游西大滩、昆仑河小流域次级盆地中高,表现出较为明显的富集状态。2.流域上游湿冷山前地带河谷沉积物的风化程度明显高于中游干热河谷,表明上游冰川融水和较充沛的降水条件导致充分的水岩反应过程是主导流域风化的主要因素,且物质在流域各个次级盆地间物质输送具有跳跃性、传递性和继承性。3.流域内的风化过程与晚更新世以来的冰期-间冰期气候旋回和季风-西风相互转换密切相关,即暖湿阶段主要受季风控制,以化学风化为主;干冷阶段受西风控制,以物理风化为主。综上,格尔木河流域上游山前地带元素的风化迁移和中游河谷沉积物对元素的继承转移是流域内物质流动的主要形式。

The weathering and migration of elements in the sediments in the middle and upper reaches of Golmud River catchment is of great significance to the replenishment of salt resources in Qarhan Salt Lake.In this paper,the formation ages of Nachitai(NCT)and Xiaogangou(XGG)profiles in the Golmud River catchment and the variation of some major and trace elements were studied,and the element characteristics of different sediment types in the upper and lower reaches of the catchment were compared and analyzed,and the conclusions are as follows:(1)Since the last lnterglacial period,the major elements in the sediments of the middle Golmud River valley are higher than those in the upper Xidatan and Kunlun River sub-basins,showing an obvious enrichment state.(2)The degree of weathering of the sediments in the wet and cold foothills in the upper reaches of the catchment is significantly higher than that in the hot and dry valleys of the middle reaches,indicating that the meltwater of glaciers,abundant precipitation and strong water-rock reaction process in the upper reaches are the main factors influencing the weathering of the catchment,and the material transport among the sub-basins of the basin has the characteristics of jumping,transferring and inheriting.(3)The weathering process in the catchment is closely related to the glacial-interglacial climatic cycles and monsoon-westerly interactions since the late Pleistocene,that is,the warm and wet stages is mainly controlled by monsoon,and chemical weathering.The dry and cold stage is subject to westerly control,and physical weathering dominates.In conclusion,the weathering and migration of elements in the foothills of the upper reaches of Golmud River catchment,and the inheritance and transfer of elements in the sediments of the middle reaches of Golmud River catchment are the main forms of material flow in the drainage basin.