Spatial Distribution Of Particle Size And Geochemical Characteristics Of Surface Sediments In The Hobq Desert

The Kubuqi Desert is a key area for sand prevention and control.Due to the spatial instability of wind-sand activities,the transport distance,material composition and regional environment of sediments are different.Under the action of wind,the grain size composition and geochemical characteristics of surface sediments are also affected to varying degrees.In order to expound the spatial distribution characteristics of grain size and geochemistry in the Kubuqi Desert,and analyze the sedimentary environment and provenance information,this thesis studies the sedimentary characteristics and sedimentary environment of surface sediments in the Kubuqi Desert from the aspects of grain size characteristics,geochemical characteristics and spatial distribution of sediments by means of field investigation and data access,and by using the principle of aeolian sand physics.The results are as follows:（1）The dominant grain size of the surface sediments in the Kubuqi Desert is fine sand（44.28%）and medium sand（40.21%）.The average particle size is 2.410φ,which is fine as a whole.The sorting coefficient is 0.730,which is in the middle of sorting.The skewness is-0.030,which belongs to near symmetry,and the kurtosis is0.780,which belongs to wide kurtosis.The sediment particles in the desert gradually increased from east to west,the content of fine sand components gradually decreased,and the content of medium sand components gradually increased.The average particle size and skewness decreased gradually,and the sorting coefficient and kurtosis increased first and then decreased.The grain size of sediments becomes finer along the main wind direction;the sediment particles in the western desert continued to develop to the coarse particle stage.（2）Quartz,feldspar,muscovite,chlorite,calcite,dolomite and tremolite are the main minerals of surface sediments in Kubuqi Desert.From east to west,quartz shows an increasing trend distribution,feldspar shows a decreasing trend distribution,calcite shows an inverted V-shaped distribution,chlorite shows a V-shaped distribution,dolomite shows an M-shaped distribution,muscovite and tremolite show a trend distribution of decreasing first,then increasing and then decreasing.The major elements are Si O₂（76.28%）and Al₂O₃（8.85%）.The trace elements are mainly Cr（48.17%）,Zr（40.38%）and Zn（35.03%）.（3）Compared with the UCC of the upper continental crust,the major elements in the Kubuqi Desert are rich in Si O₂,Ca O,Fe₂O₃,K₂O,Ti O₂and poor in Al₂O₃and Na₂O.The Zr element in the trace elements is strongly depleted,and the other elements are moderately depleted.The CIA value is between 35 and 50,which is in an unweathered or weakly weathered state.Major elements and light minerals have obvious particle size effect,and trace elements have no obvious particle size effect.（4）The sedimentary environment of Kubuqi Desert can be divided into three types:aeolian sedimentary environment,lake sedimentary environment and river sedimentary environment.Kubuqi desert samples are mostly lithic sandstone;the sediments in the eastern desert are’near source’,and the sediments in the western desert are’far source’.