纳米比亚红沙漠沙粒特征及其成因

Characteristics of Namibia red desert sand and its genesis

针对纳米比亚红色沙漠呈现红色的原因及其形成环境,借助双目镜、电子显微镜及扫描电镜等手段,统计测定了沙粒形态和矿物成分,研究了红色沙漠沙粒及其红色包裹物成分。研究表明,沙粒主要由石英(91%)、长石(4%)和岩屑(5%)颗粒组成,原岩以花岗岩为主,还有火山碎屑岩、泥岩和粉砂岩,不同类型沙粒磨圆度存在差异。由于不同含量的黏土矿物和铁氧化物附着于沙粒表面,使沙粒呈现不同程度的红色,进而导致沙漠呈现红色。黏土矿物和铁氧化物中主要元素为O、Si、Fe、Al、Mg,含少量K、Ca、Ti、Cl、P,矿物成分相当于伊利石、蒙脱石、高岭石、绿泥石、赤铁矿、针铁矿和钛铁矿等,矿物组合特征揭示了红色包裹物的形成环境以偏冷、湿润气候为主。

In order to explore the red color of the Namibia desert and its formation environment,the morphology and mineral composition of the red sand and its coating have been studied using binocular,electron microscope and scanning electron microscope measurement.The results show that the sand is mainly composed of quartz( 91%),feldspar( 4%) and rock grains( 5%).The provenance is mainly granite,and also volcanic clastic rocks,mudstones and siltstones.The sand of the red desert varies in roundness.The red color of the desert is a result of the clay minerals and iron oxides coating and attaching to the sand surface.The coating is rich in O,Si,Fe,Al,Mg with some K,Ca,Ti,Cl and P.The compositions are equivalent to illite,montmorillonite,kaolinite,chlorite,hematite,goethite and ilmenite,indicating cold and humid environment for the desert formation.