西藏麻米错盐湖大型锂硼矿盆地水化学特征

Hydrochemical characteristics of large-scale lithium-boronmine basin in the Mami Co Saline Lake,Tibet

麻米错盐湖位于西藏阿里地区改则县麻米乡,氯化锂资源量250万t,固体硼矿石资源量3686万t,是西藏大型锂硼矿之一。本研究采集麻米错盆地河水、泉水及湖水等27件样品,分析其总溶解性固体(TDS)、pH值及主要化学成分,通过数理统计分析、Piper阴阳离子三角图和Gibbs等方法对比研究表明,河水径流水化学类型为Ca·Na·Mg-HCO_(3)·Cl型,河水支流水化学类型为Ca-HCO_(3)、Ca·Mg-SO_(4)·HCO_(3)型;泉水化学类型为Mg·Ca-HCO_(3)·SO_(4)、Na·Mg-HCO_(3)·Cl型;湖水水化学类型为Na-Cl。水化学离子组成主要受岩石风化和蒸发结晶作用控制,河水和泉水中主要离子来源于碳酸盐岩和硅酸盐岩风化。河水中主要离子含量介于雪山融水和泉水之间,且接近泉水含量,表明河水更多依靠泉水补给。盐湖中成矿物质来源于岩石风化和深部水岩反应。麻米错湖水正处于正均衡状态,水位持续上涨会对湖区生态和人民生活生产会产生一定影响,建议开展水位动态监测工作。

The Mami Co Saline Lake,located in Gertse County,Ali Prefecture,Tibet,has lithium chloride reserves of 2.5 million tons and solid boron ore reserves of 36.86 million tons.It is one of the large lithium boron deposits in Tibet.The river water,spring water and lake water in the Mami Co basin were collected,and their total dissolved solids(TDS),pH,major chemical composition were analyzed.A comparative study of mathematical statistical analysis,Piper anion-triangle map,and Gibbs diagram shows that water in the Mami Co basin has different hydrochemical types.The hydrochemical type of river runoff is Ca·Na·Mg-HCO_(3)·Cl,the hydrochemical types of river tributaries are Ca-HCO_(3)and Ca·Mg-SO_(4)·HCO_(3),hydrochemical types of spring water are Mg·Ca-HCO_(3)·SO_(4)and Na·Mg-HCO_(3)·Cl,the hydrochemical type of lake water is Na-Cl.The hydrochemical compositions are mainly affected by weathering of rocks and evaporation crystallization.The major ion concentration in the river water is between the snow melt water and spring water,and closer to the spring water concentration.It shows that the river water mainly depends on recharge by spring water.The ore-forming materials in saline lake are derived from rock weathering and deep water-rock reaction.The water of the Mami Co Saline Lake is in positive equilibrium,and the continuous rise of water level will have a certain impact on the ecology,local livelihood,and production in the lake area.It is suggested that a dynamic monitoring of water level should be carried out.