|关键词: 艾比湖 碳酸盐沉积 化学演化
|CHEMICAL EVOLUTION OF AIBI LAKE WATER
Qinghai Institute of Salt Lakes, Academia Sinica, Xining 810008
|According to the field observation and the results of chemical analysis,this paper deals with the hydrochemical character of the Aibi Lake water from the following three aspects; (1) Salinity and pH value of the lake water, (2)Chemical composition of the lake water, and (3) The latteral distribution of chemical components in the lake water which reveal laws of hydrochemical changes and the migration and accumulation of main elements in the lake water. The carbonate minerals compositions in the lake sediments and their geochemical nature reflect the variation of the chemical composition in the lake water. This case is obvionsly influenced by the climate environment. Thereby, the carbonate sediments in the drilling hole CK4 and recorded information from the lake bottom may be as the indicators df chemical evolution of the lake water and the paleoclimate variation. According to the content of carbonate,the content of calcite,MgC03 in calcite crystal skeleton,the content of Sr, Sr X 1000/Ca ratio and so on, as combined with sedimental character, geochemical evolution of carbonate and evolution of palaeosandspit, the trend in chemical evolution of lake water has been illustrated further. On the basis of the above mentioned,the chemical evolution of lake water can be divided into three stages:J. The first stage(45000-23000 a B.P.):the lake water underwent two fluctuations and caused two lower levels with its carbonate mainly consisting of calcite. This stage belongs to fresh water deposition; 2. The second stage(23000-12000 a B.P.): the lake water level was higher than that of the first stage,the salinity of lake water is lower than that, the content of calcite appeared to decrease with MgC03 in calcite crystal skeleton equal to zero; 3. The third stage (12000 a B. P. to present): the lake water level was the lowest. Some aragonite was separated out from the lake water, gradually being at its dominant position,and exceeded calcite in content.
|Key words: Aibi Lake carbonate deposition chemical evolution