柴达本盆地沙下盐湖的卤水化学及矿物沉积特征——以察尔汗盐湖区北部外围地带为例

BRINE CHEMISTRY AND MINERAL SEDIMENTARY CHARACTERISTICS OF UNDERSAND SALT LAKES IN QAIDAM BASIN: AN EXAMPLE FROM THE PERIPHERAL ZONE OF QARHAN SALT LAKE

对柴达木盆地察尔汗盐湖区外围沙下盐湖的卤水及沉积进行了综合研究。沙下盐湖卤水化学组成与地表径流和开放性盐湖卤水之间存在明显的差异性,具有高Na^++Cl^-、低Mg^(2+)+Ca(2+)+SO_4^(2-)、贫K^++CO_3^(2-)+HCO_3^-等特征。沙下盐湖析盐层位含有新生矿物并夹带碎屑矿物,其盐类矿物组合为:石盐+羟氯镁铝石+光卤石。25℃等温蒸发相图表明,其卤水演化方向往光卤石析出区迁移,在穿越上覆盖层通道中卤水发生的物理化学反应与独特的沉积特征,可以作为继续寻找沙下盐湖的指导。

There are undersand salt lakes around Qarhan Salt Lake of Qaidam Basin. Their brine chemical compositions are obviously different from those of surface flows and open salt lakes, with higher Na^(+)+Cr, lower Mg^(2+)+Ca^(2+)+SO_(4)~2-, poor K^(+) +CO_(3)^(2-)+HCO_(3)^(-)etc.. Salt-forming beds of undersand salt lakes contain neogenic minerals with detrital minerals carried, of which salt mineral assemblage is: halite + koenenite + carnallite. The facial map of isothermal evaporation at 25℃ indicates that the evolution direction of their brine tends to immigrate to carnallite area. When their brine passes through the channel of covering strata, physical and chemical affection may occur, and special sedimentary characteristics be observed. All these indicative characteristics may provide evidences for further exploitation of undersand salt lakes.