察尔汗盐湖矿物组合特征及其成因指示

The Characteristics of the Mineral Assemblage and the Forming Cluein Qarhan Salt Lake

中文关键词:  察尔汗盐湖  矿物组合  卤水特征  混合成因

英文关键词:Qarhan Salt Lake  Mineral assemblage  Characteristics of the Brines  Mixing theory

中文摘要:

      察尔汗盐湖赋存有硫酸镁亚型和氯化物型两种水化学类型,沉积了中国最大的液体钾镁盐矿床。为了解释察尔汗盐湖卤水矿床成因,本文拟在盐湖别勒滩、达布逊、察尔汗和霍布逊区段选择四个剖面,剖面深度在0~7m之间,属于全新统上含盐组的上部盐层,每隔10cm进行采样,运用XRD半定量方法分析矿物组合特征。结果表明,整个湖区石盐、石膏、水氯镁石和碳酸盐总平均含量分别达70%以上、4.7%、3.4%和1%；显示其矿物组合特征简单,盐层主要沉积石盐而贫石膏和碳酸盐矿物。同时,研究发现各区段石膏(硫酸盐矿物)平均含量自西向东明显下降,含镁矿物平均含量自西南向东北明显下降。结合察尔汗盐湖区卤水化学组成和水化学类型的分带,基本符合盐湖北部和东北部卤水富Ca₂₊而贫Mg₂₊和SO_42-的沉积事实,进一步说明盐湖北部和东北部卤水和盐类沉积受具有深源特征盐泉水的补给影响,为察尔汗盐湖混合掺杂成因提供了一定的矿物学证据。

英文摘要:

      Qarhan Salt Lake contains two water types, namely the chloride type and Mg-sulfate type, and deposits the largest liquid potassium-magnesium salt deposits in China. In order to interpretate the origin of brine deposits in this playa, four profiles were selected in the four sections of Qarhan Salt Lake, respectively. The depth is in the range from 0 to 7.0 m and these sediments belong to Holocene salt group. We collected 180 samples with 10 cm interval in four porfilesand analyzed mineral assemblages by XRD method. The results show that total average concentration of halite, gypsum, bischofite and carbonate was more than 70%, 4.7% , 3.4% and less than 1%, respectively, which implies that the mineral assemblage was simple and mainly deposited halite and poor gypsum and carbonate minerals. At the same time, the study found that the average content of gypsum in each section from west to east obviously decreased, the average content of Mg-bearing minerals decreased from the southwest to the northeast part of Qarhan playa. Based on the characteristics of the brines in Qarhan Salt Lake, the fact that brines in the north and northeast part of Qarhan enrich Ca₂₊ and poor Mg₂₊ and SO_42-, it further indicates that the brine and salt deposit in the north and northeast of Qarhan Salt Lake have received the supply from deep spring in order to offer the mineral evidence for the mixing theory.