羌塘盆地多格错仁地区盐泉地球化学特征及成钾预测

Geochemial Characteristics on Salt Springs and Potash Perspective in Dogai Coring Area of Qiangtang Basin

多层次、大面积发育的石膏和前人的古地理资料表明,羌塘盆地侏罗纪海相地层具有较好的成盐地质条件。在多格错仁周缘地区侏罗系发育有一系列氯化钙型的盐泉。通过野外地质工作,采集了30个盐泉的水样,并在室内对其地球化学组成和氢氧同位素组成进行了测定。地球化学分析表明,盐泉中富集Na+、Cl-、Ca2+、K+、Li和Rb,Br和B含量相对贫乏,而地球化学特征系数显示了明显的找钾异常。盐泉水的氢氧同位素特征表明盐泉的供给水源为大气降水,大气降水进入研究区岩层后成为地下水,溶滤了地层中的盐类矿物,从而形成了溶滤卤水,这与地球化学特征系数的判别结果是一致的。综合看来,多格错仁南岸找钾远景显示最好,该点盐泉具有盐度高、K+含量高的特征,而且很可能溶滤了钾盐-石盐岩、钾盐层,万安湖西北、源泉河、东温泉盐泉找钾远景次之,主要表现为盐度相对较低,但是含钾显示也异常明显。

Multi-layers and a large amount of gypsum and lithofacies paleogeographic data from predecessors indicate that Jurassic marine layers of Qiangtang basin have good saline condition.There is a series of Ca-chloride springs in Jurassic layers of Dogai Coring area.For this study 30 salt springs water samples were collected from field.Then,chemical composition,δ18O and δD of water samples were determined in laboratory.Geochemical analysis demonstates that salt springs have high concentration of Na＋,Cl-,Ca2＋,K＋,Li,Rb and poor concentration of Br,B.In addition,geochemical coefficients of water samples have obvious anomaly of potash mineral.δ18O and δD of salt springs reveal that springs water came from atmospheric precitation.When meteoric water entered into stratum and became groundwater,saline minerals of stratum were dissolved and lixiviation brine have been generated as groundwater.This is consistent with the result of coefficients of geochemistry analysis.In sum,potash perspective of south bank of Dogai Coring Lake is the best one of four sampling locations,whose salt springs have high salinity and concentration of K＋ and might lixiviate potash-halite and potash stratum.Northwest side of Wananhu,Yuanquanhe and Dongwenquan take a second place of potash perspective.They have relatively lower salinity and anomaly of potash mineral.