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 Clue in 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 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。为解释察尔汗盐湖卤水矿床成因,拟在别勒滩、达布逊、察尔汗和霍布逊区段选择4个剖面,剖面深度在0~7 m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,整个湖区矿物组合由石盐、石膏、水氯镁石和碳酸盐组成,其平均含量分别为>70%、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⁺,贫Mg²⁺和SO₄2-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氯化物型盐泉水的补给影响,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 deposited in two hydrochemcial water types:chloride type and magnesium sulphate subtype, which is the largest liquid potassium magnesium salt deposits in China. In order to interpret the origin of brine deposits in this playa, four profiles from Bieletan, Dabuxun, Qarhan and Huobuxun sections in Qarhan Salt Lake were selected in this study. The depth is in the range from 0 to 7.0 m and the stratigraphy of these salt sediments belongs to Holocene salt group. We collected 180 samples in 10 cm interval from four porfiles and analyzed mineral assemblages of sediments by XRD method in the laboratory. The results show that total average concentrations of halite, gypsum, bischofite and carbonate were more than 70%, 4.7% , 3.4% and less than 1%, respectively, which implies that the mineral assemblage was relatively simple and mainly deposited halite, poor gypsum and carbonate minerals. Meanwhile, 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 from the southwest to the northeast part of Qarhan playa also decreased. Based on the sedimentary features of four profiles and the elemental characteristics of brines with enriching in Ca²⁺ and depleted Mg²⁺, SO₄2- in the north and northeast part of Qarhan playa, we concluded that the north and northeast of Qarhan Salt Lake should be received the supply from chloride type spring, which offers the mineral evidence for the mixing theory between river waters and deep spring.