CHEMICAL EVOLUTION OF AIBI LAKE WATER

Abstract

本文通过野外地质调查和大量样品的分析测试结果,从以下三个方面对艾比湖湖水的水化学特征进行论述:（1）湖水的矿化度和pH;（2）湖水的化学组成;（3）湖水化学组分的侧向分布。初步揭示了湖水水化学变化和主要化学元素迁移和富集的规律。艾比湖沉积物中碳酸盐矿物组成及其地球化学性质反映湖水化学组成的变动。这种变动明显受气候环境变化的影响。因此,CK4孔和湖底沉积物中的碳酸盐沉积,提供了许多信息作为湖水化学演化和古气候波动的标志,根据其碳酸盐含量、方解石含量、方解石格架中MgCO₃mol.%、Sr含量和Sr×1000/Ca比值,最后结合碳酸盐的沉积特征、地球化学演化和古沙嘴的演变,进一步阐明了湖水化学演化的趋势。;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.