SURFACE TEXTURES OF QUARTZ SAND IN THE SEDI-MENTS OFF THE SOUTHERN FUJIAN COAST TO THE CONTINENTAL SHELF OF TAIWAN PROVINCE

urface textures of quartz sand in 9 bottom samples from this region were studied. 150 quartz sand grains ( 0.25-0.5mm ) were observed with the scanning electron microscope. Our research shows that the surface of quartz sand have the traces of chemical solution, chemical precipitation and mechanical crushing in the study area. In these surface textures, quartz sand grains with chemical solution are the most abundant, while quartz sand grains with chemical precipitation or mechanical crushing is also present. The surface solution textures of quartz sand may be divided into four kinds on the basis of their forms: 1 ) solution pits 2 ) solution grooves 3 ) solution pictures as flower form 4 ) regular solution deltoid pits. In these solution, texturs the first and second kinds are of shallow Solution and the third and fourth ones are of deep solution. The analysis of the surface textures of quartz sand shows that the depositional environment, with the bottom water temperature of 20-24t! and salinity of 32.8-34.6% is favorable to the formation of chemical solution surface textures. The occurrence of the quartz sand with mechanical crushing surface in the study area indecate that this area was a near shore area in the wlirm glacial period. Our study shows that most of quartz sand grains have a better roundness in the investigated area. Their roundness coefficient is 40-50.As the chemical solution textures are much developed on the surface of these quartz sand grains, the subrounded and rounded quartz sand grains were resulted from the high-energy hydraulic action and high-energychemical action.