内蒙古新安镇南浅藏卤水的形成及迁移机制

Migration and Origin of Brines in the South of Xin-an Township of Inner Mongolia

内蒙古新安镇南分布有浅藏卤水,主要存储于第四系上更新统含水层。以往研究表明,该地区卤水为深层承压卤水沿断裂上涌成因,但实验结果和野外调查表明,该地区卤水的成因表现出多样化的特征:首先,Na/Br和Cl/Br均远大于海水的Na/Br,在1200～12000之间,Na/Cl均小于1,并且多数小于海水的0.87,因此该地区卤水属于第四系石盐溶滤成因并具备有变质卤水的特征;缘于该地区位于乌拉山潜伏隆起构造带上,断裂较多,发生过变质作用的深层承压水沿断裂上涌溶解岩盐;地下水流场显示,地下淡水径流自西向东,同时卤水矿化度的分布也为西低东高,并且低矿化度卤水区有明显向高矿化度卤水区突出的舌状特征,说明该地区接受淡水补给并对卤水区有显著的稀释作用。

Brines in South of Xin′an township of Inner Mongolia stored in upper Pleistocene series of Quaternary system.In terms of chemical constituents,Na/Br=1 200～12 000,but Na/Cl0.87,it showed the dissolution of halite.The first process was halite formation,since quaternary,Hetao Basin was always submerged as a lake base,depositional environment was mostly oxygen-free,and salt was enriched.The deep confined water was enveloped by Tertiary red bed and mid-Pleistocene silt stratification which were abundant with salt,metamorphism happened when temperature and pressure changed,the buried depth of deep confined water became shallow when Wula Mountain concealed uplift,this uplift resulted in fractures of a full range of sizes,the fractures provided channels for deep confined salt water to dissolute upper Quaternary halite as the second process,two kinds of solute mixed completely,this course lead Na/Cl of modern brines to possess metamorphism characteristic.In the third process,Brines was desalting,because the distribution of brines appears lingulate,so did the flow field of ground fresh water which flows from west to east,this consistency showed that ground fresh water was recharging brines and desalting it,and the neoteric and modern irrigation history reality was that irrigation channels was drawing Yellow river water to spread all across in confusion in the whole Hetao Basin,the local peasants irrigated by flooding twice a year to provide the soil of farmland,consequently,this study extrapolated that brines in south of Xin′an township was desalting by leaching fresh water.