|其他摘要||The characteristics of surface textures of quartz grains are widely used in identification of material source of sediments, transportation process and early diagenesis history. There is still not a unified standard about the characteristics of surface textures of eolian quartz grains now. But as we know grain size has a great influence on surface textures of quartz grains, therefore, we choose some typical eolian sediments, including eolian coarse sand, desert sand, loess, dust full and so on, to analyze the surface textures of quartz grains in them from fine to coarse, which aims to establish a sequence of surface textures of eolian quartz grains cover different sized grains. Finally, 817 eolian quartz grains ranged from 5m to 1000m have been tested, including the type, quantity, size and area of surface textures, and then grade these 817 quartz grains into five groups by transportation forms: 5-20μm, which mainly transported by long-distance suspension, 20-70μm, which mainly transported by close-distance suspension, 70-100μm, which mainly transported by long-distance saltation, 100-500μm, which mainly transported by close-distance saltation, 500-1000μm, which mainly transported by rolling, analyzing each grade one by one. The findings imply that different sized eolian quartz grains have different surface textures feature:
(1) There are typical surface textures on eolian quartz grains including conchoidal fractures, rounded pits, crescent pits, V-shaped pits, irregular pits, V-shaped ditches. Beyond that, the type of surface textures on 70-500μm grains is the most diversified, and these textures are always large and deep. The quantity of surface textures on 500-1000μm grains is the most, and the irregular pits are the main type. Grains of 5-70μm with some inherited textures have the least amount of surface textures and the types is lack too.
(2) As the size of quartz grains increased, the shape of quartz grains changes from sharp-angled lance shape to spindle and ellipse shape, to standard ground shape finally. At the same time, roundness of grains is getting better, pitted surface and eolian erosion trace are getting clearer. Meanwhile, the integrity of surface textures is getting higher too. Grains of 5-70μm only form the combination of irregular pits-V shaped pits. There are different kinds of textures on the surface of grains of 70-500μm, which makes grains feature with irregular pits-rounded pits-V shaped pits-crescent pits. The types of surface textures on 500-1000μm grains are consisted of irregular pits-crescent pits-conchoidal fractures. The distribution area of surface textures is changed among grades, such as 70-500μm grains own the maximum distribution area of surface textures, 500-1000μm grains have the moderate distribution area of surface textures, and 5-70μm grains have the minimum distribution area of surface textures.
(3) The sizes of surface textures of different types have a settled pattern that the conchoidal fracture is always larger than crescent pit, V-shaped pit is the smallest impact crater and rounded pit, irregular pit are relatively larger impact craters, exfoliation and V-shaped ditch are always large textures.
(4) Different sized eolian quartz grains transported by different forms develop absolutely unlike characteristics of surface textures. Three main factors composed of impacting frequency, grain size and velocity of movement effect the growing condition of surface textures on eolian grains. A large quantity of surface textures could be formed by high impacting frequency and supported by coarse grains. Meanwhile, high velocity collision would lead to grow out diversified and large sized textures. In the detection of sedimental environment by surface textures of quartz grains, choosing relevant fraction of surface textures characteristic by grain size is crucial and efficient in identifying.|