雪隆囊地区堰塞湖溃坝沉积物的石英砂表面微观特征  

SEM Surface Microstructure of Quartz Grains Collected from Dam Break Sediments at Xuelongnang of Jinsha River

作　　者：刘超[1] 陈剑[1] 崔之久[2] 黎艳[1] 陈松[1] 

机构地区：[1]中国地质大学(北京)工程技术学院,北京100083 [2]北京大学城市与环境学院,北京100871

出　　处：《山地学报》2017年第3期357-368,共12页Mountain Research

基　　金：国家自然科学基金重点项目(41230743);国家自然科学基金面上项目(41571012)~~

摘　　要：石英砂表面微结构分析有助于理解沉积物的成因环境。四川省雪隆囊地区位于青藏高原东南缘金沙江上游,该处分布有堰塞湖溃坝沉积物。为了判断其溃坝沉积物的沉积成因和形成环境以及过程,采集石英砂样品并进行扫描电镜分析,初步获得堰塞湖溃坝沉积物石英砂的表面微观结构组合特征是次棱角状及次圆状颗粒为主,颗粒边缘形状为棱脊磨损及次棱脊,表面多为中、低起伏;少量出现贝壳状断口,小撞击坑出现较多,平行解理面少见甚至没有;擦痕、磨光面少量出现;化学溶蚀和沉淀形态包括蚀坑和蚀缝、硅质薄膜和硅质球。结果表明雪隆囊堰塞湖溃坝沉积物在沉积过程中不仅受到强烈的机械撞击作用,而且在后期也有比较强烈的水流作用参与其中,可以为分析溃坝沉积物的沉积过程和沉积环境提供参考。雪隆囊溃坝沉积物石英砂表面微观结构特征与残坡积、冰碛、冰水、冲积、洪积、泥石流、湖相沉积、海洋沉积、风成等沉积环境明显不同。In the study area,the dam break sediments of a landslide-dam were distributed in the Upper Jinsha River in southwest China. Systematical research was carried out regarding quartz grain microstructure characteristics by Scanning Electron Microscopy（ SEM）,using the Xuelongnang dam break sediment in Upper Jinsha River as the research object. The large amount of statistical data showed that the main microstructure assemblages of the quartz grains in the dam break sediment were common in the medium relief,small pits,sub angular,secondary ridges（ 50% to 75%）; sparse in the sub rounded,ridge wear,low relief,conchoidal fractures,parallel cleavage planes,striation（ 5%-50%）; and rare in the polished surface（ 5%）. Meanwhile,chemical dissolution/precipitation patterns were solution pits and crevasses,silica pellicle and globules. The results showed that the dam break sediment was modified not only by mechanical impact,but also by strong water flow afterwards. These findings could potentially be used as a microscopic discriminant mark to distinguish dam break sediment from those which are actually residual deposits,moraine,aqueoglacial deposits,alluvial deposits,diluvial deposits,debris flow deposits,lacustrine sediments,marine sediments,aeolian sediments,and so on.

关 键 词：雪隆囊 堰塞湖 溃坝沉积物 石英砂 扫描电镜 微观结构 

分 类 号：P642.2[天文地球—工程地质学]