柴达木盆地盐湖物质来源识别

Identification of material source for the salt lakes in the Qaidam Basin

柴达木盆地是我国重要的盐矿资源战略基地,深入认识其物质来源具有重要的科学及社会意义。本研究根据柴达木盆地盐湖水、晶间卤水,以及格尔木河流域地表水、地下水化学组成,利用多元统计方法,探讨盆地区盐湖物质来源。结果显示:从山前到湖区,水体溶解性总固体逐渐增大,微量组分含量也逐渐升高,二者均表现为晶间卤水>盐湖水>格尔木河流域水体;阳离子变化趋势为:补给源头由昆仑山雪融水以Ca2+为主过渡到格尔木河流域以Na+为主;再到盐湖区以Mg2+为主;阴离子则从以HCO-3为主逐步过渡到以Cl-为主;盐湖水和晶间卤水的化学组成差异显著。因子分析表明,对于格尔木河流域河水和地下水,岩石风化淋滤是其化学组分的主要来源。而岩石风化淋滤来源和深部水来源对柴达木盆地不同盐湖区化学组成的贡献率差异很大,该差异取决于周围岩石的化学组成和深部水的存在及其化学组成,以及断层是否导通为深部水补给盐湖提供了通道。

The Qaidam Basin is the important strategic base for salt resources in China. Understanding the material source for the salt lakes is of important scientific and social significance. In this study,the material source for the Qaidam Basin was studied by the multivariate statistical analysis based on chemical constitution of the salt lake water,intergranular brines,surface water and groundwater in the Golmud River. The results showed that both TDS and content of minor elements increase from the Piedmont to the salt lakes. The cation is dominated by Ca2 ＋for the meltwater,Na＋for the water in the Golmud River and Mg2 ＋for the water in salt lake area. The anion is gradually from HCO-3based to Cl-based. TDS and minor elements contents show a trend that the intergranular brine is greater than the salt lake water,and the salt lake water is greater than the water from the Golmud River.Composition differences between the salt lake water and the intergranular brine are significant. Factor analysis shows that rock leaching is the main material source for the river water in the Golmud River and the groundwater.Contributions of rock leaching and deep water on chemical compositions of different regions varies greatly in the Qaidam Basin. This difference is controlled by chemical composition of the source rocks,existence of deep water and its compositions,and whether the fault may provide access to deep water recharge.