柴达木盆地西部构造裂隙孔隙卤水地球化学组成及来源示踪

Geochemical Composition and Origin Tracing of Structural Fissure and Pore Brine in Western Qaidam Basin

柴达木盆地西部构造裂隙孔隙卤水是我国重要的深层卤水资源之一,关于其成因争论较大.对柴达木盆地西部碱石山、红三旱四号、鸭湖和俄博梁II号四个地区构造裂隙孔隙卤水样品的常量、微量元素以及He、Ne、Ar同位素进行了研究.结果表明,柴达木盆地西部构造裂隙孔隙卤水钠氯系数介于0.84~0.91,钾系数介于3.19~12.35,钾氯系数介于5.26~20.61,脱硫系数介于0.33~2.00;水化学类型在Piper图上显示为Cl-Na型;同位素中^(3)He/^(4)He介于0.01~0.16 Ra,^(40)Ar/^(36)Ar介于318~352,^(38)Ar/^(36)Ar介于0.182~0.193,^(20)Ne/^(22)Ne介于9.8~10.6,21Ne/^(22)Ne介于0.025~0.032.由此认为基岩山区岩石风化破碎,其盐分被地下水迁移至盆地内,经蒸发成盐、埋藏,与深部地下水发生水‒岩作用,富集形成高矿化度构造裂隙孔隙卤水.

The structural fissure and pore brine in western Qaidam Basin is the most important deep brine resources in China,and its causes have been debated over many years.In this paper,it discusses its geochemical causes by studying its major,trace element characteristics and He,Ne,Ar isotopes of the brine samples from the Jianshishan,HongsanhanⅣ,EboliangⅡand Yahu areas in western Qaidam basin.It is shown that the sodium-chloride coefficients of structural fissure and pore brine in western Qaidam Basin range from 0.84 to 0.91,the potassium coefficients range from 3.19 to 12.35,the potassium-chlorine coefficients range from 5.26 to 20.61 and the desulfurization coefficients range from 0.33 to 2.00.The brine type is shown as the Cl-Na type on the Piper plot.The^(3)He/^(4)He ratios range in 0.01-0.16 Ra,the^(40)Ar/^(36)Ar ratios range from 318 to 352,the^(38)Ar/^(36)Ar ratios range from 0.182 to 0.193,the^(20)Ne/^(22)Ne ratios range from 9.8 to 10.6 and the 21Ne/^(22)Ne ratios range from 0.025 to 0.032.Therefore,it is believed that the salt components formed by rock weathering were migrated to the basin by groundwater at first,and then evaporated into salt deposits,after being buried,the water-rock interaction occurred between these salt deposits and deep groundwater and then were enriched to form the structural fissure and pore brine with a high mineralization.