新疆库车盆地盐泉水水化学特征、来源及找钾指示意义

Chemical Characteristics and Origin of Saline Springs and Their Significance to Potash Prospecting in the Kuqa Basin,Xinjiang

库车盆地是塔里木盆地的一个次级凹陷,位于新疆塔里木陆块北缘与西南天山之间。文章介绍了库车盆地盐泉水的化学特征、来源及其找钾指示意义。对库车盆地几个代表性盐泉出露区进行盐泉水样品(21件)采集和分析,研究了其化学组成特征、水化学类型和氢氧同位素组成,同时根据收集的129件盐泉水化学数据资料,生成了盐泉水水化学分布图。新采自库车盆地的21件盐泉水样品矿化度范围为120.216~305.322g/L,水型以氯化物型(瓦里亚什科分类法)为主,具有明显的深部地层氯化钙型卤水的特征。氢氧同位素组成分析发现,盐泉水δ18 O范围为-9.1‰~4.7‰,δ2 H值范围为-75‰^-28‰,投点偏离大气降水线且δ18 O和δ2 H具有一定的正相关关系(r=0.81),表明该区盐泉水曾受到强烈蒸发作用影响,同时也受水—岩作用影响,存在一定的δ18 O漂移现象。库车盆地盐泉水组成特征与深部岩层岩性有密切关系,而断裂控制盐泉水出露与分布,盐泉水形成的地表地球化学异常对于该区找钾有一定的指示意义。

The Kuqa Basin is located between the northern margin of the Tarim Basin and southwestern part of the Tianshan Mountains in Xinjiang,which is a sub-depression of the Tarim Basin.This paper covers mainly chemical characteristics and origin of saline springs in the Kuqa Basin,as well as their significance to potash prospecting.Totally 21 representative saline spring samples were collected from the Kuqa Basin and their chemical compositions,water types,and hydrogen and oxygen isotopic compositions were analyzed.Besides,contour maps for chemical components of saline springs were drawn on the basis of collected data of 129 saline spring samples from old references.21 new saline spring samples are characterized by total dissolved solids（TDS）ranging from 120.216 to 305.322g/L and the chloride type（Valyashko＇s classification）as the dominant water type;these waters show obvious features of CaCl2-type brine recharged from deep strata.δ^18 O andδ^2 H are in range-9.1‰ -4.7‰ and-75‰ --28‰,respectively,with data points deviating from the Global Meteoric Water Line（GMWL）andδ^18 O andδ^2 H showing a certain positive correlation（r=0.81）.This indicates that saline spring waters in the Kuqa basin have experienced strong evaporation and positive shifts in δ^18 O values reveal certain water-rock interactions.Chemical characteristics of saline springs in the Kuqa Basin are closely related to underground lithology;outcropping and distribution of saline springs are mainly controlled by faults;surface geochemical anomalies caused by saline springs are of great significance to potash prospecting in this area.