古尔班通古特沙漠蜂窝状沙丘沉积物理化特征及沉积环境

Physicochemical characteristics and sedimentary environment of honeycomb dunes in Gurbantunggut Desert

采样分析了古尔班通古特沙漠蜂窝状沙丘表层沉积物的粒度、元素和微形态特征,讨论了其沉积环境。结果表明:(1)古尔班通古特沙漠蜂窝状沙丘表层沉积物以细沙为主;与上部陆壳平均化学组成(UCC)比,常量元素产生亏损,微量元素Co富集明显;化学蚀变指数(CIA)与上部陆壳平均值接近;石英沙颗粒磨圆度适中,微形态特征以碟形坑与不规则撞击坑为主。(2)古尔班通古特沙漠东北部蜂窝状沙丘表层沉积物平均粒径最大,分选性最差,常量元素亏损严重,微形态特征最为复杂;西部CIA值最小。平均粒径从迎风坡坡脚到坡顶增大,在背风坡变小;元素与微形态特征无明显差异。(3)沉积物理化特征说明古尔班通古特沙漠处于大陆风化的早期阶段,干旱的气候条件使沙丘表层组成物质缺乏有效的化学风化,沉积环境复杂,以风成机械作用为主导。

In this paper,the characteristics of grain size,elements and Micromorphology of surface sediments of honeycomb dunes in Gurbantunggut Desert are sampled and analyzed,and its sedimentary environment is discussed.The results show that:(1)The surface sediments of honeycomb dunes in Gurbantunggut Desert are mainly fine sand;The major elements are depleted,and the trace element Co is enriched obviously;The chemical alteration index(CIA)is close to the average value of the upper continental crust;The roundness of quartz sand particles is moderate,and the micro morphological characteristics are mainly dished pits and irregular impact pits.(2)The northeast of the study area has the largest average particle size and the worst sorting performance;Serious loss of major elements;The micromorphological characteristics are the most complex;The CIA value in the west of the study area is the lowest.The average particle size increases from the toe of the windward slope to the top of the slope and decreases on the leeward slope;There was no significant difference between elements and micro morphological characteristics.(3)The sedimentary physicochemical characteristics show that the desert is in the early stage of continental weathering.The arid climate conditions make the surface components of sand dunes lack effective chemical weathering,and the sedimentary environment is complex,dominated by aeolian machinery.