柴达木盆地别勒滩杂卤石矿床特征及其沉积环境研究

Study on characteristics and depositional environment of polyhalite deposits in Bieletan area of Qaidam Basin

别勒滩是青海察尔汗盐湖固体钾矿的主要分布区段,也是企业固转液开采和生产钾盐的主要矿区,该区段分布着大面积的杂卤石矿(K_(2)Ca_(2)Mg[SO_(4)]_(4)2H_(2)O)。文章利用2022年察尔汗盐湖储量核查项目获得的岩芯样品和钻孔资料,通过系统的分析测试,开展别勒滩杂卤石成矿特征及沉积环境研究。文章首次查明别勒滩区段杂卤石矿床分布面积超过150 km^(2),平均厚度0.8 m,w(K_(2)SO_(4))平均大于5%,计算获得K_(2)SO_(4)资源量2089.79×10^(4) t。研究认为,别勒滩杂卤石形成于钾石盐、光卤石析出阶段的高浓缩盐湖相沉积环境,周期性淡化带入的大量Ca^(2+)和SO^(2-)_(4)与卤水中含量较高的K^(+)、Mg^(2+)离子反应形成了杂卤石矿层。别勒滩杂卤石矿层具有较好渗透性和给水能力,适合选用固液转化的方式进行开采。但考虑到杂卤石溶解效率远低于钾石盐和光卤石,因此短期内杂卤石开发价值有限。

Bieletan is the main area of solid potassium deposit in Qarhan Salt Lake,where a large area of polyhalite(K_(2)Ca_(2)Mg[SO_(4)]_(4)2H_(2)O)is deposited.Bieletan is the main mining area for brine exploitation and potash production by mining companies.This study takes the borehole data obtained from the Qarhan Salt Lake Resource Verification Project 2022 as study object.Through systematic analysis and test,the mineralization characteristics,sedimentary environment and development conditions of the polyhalite in the Bieletan area were studied.This study identified for the first time that the distribution area of polyhalite deposits in Bieletan area is over 150 km^(2),the average thickness is 0.8 m,and the average content of K_(2)SO_(4) is over 5%.The identified resource(calculated in K_(2)SO_(4))was calculated to be 2089.79×10^(4) t.This study believes that polyhalite in the Bieletan area deposited in a highly concentrated salt lake facies environment during the sylvite and carnallite depositional stage,when a large amount of Ca^(2+)and SO^(2-)_(4) brought in by periodic desalination reacts with K^(+) and Mg^(2+) previously existed in high concentrated brine.The polyhalite-bearing deposit has good permeability and water supply capacity,and is suitable for solid potassium liquefy exploitation.However,considering that the dissolution efficiency of the polyhalite is far lower than that of sylvite and carnallite,the development value of polyhalite is limited in the short term.