湖北潜江凹陷古近系深层富钾卤水成因及演化

地下深层富钾卤水是非常重要的钾盐资源，目前很少从区域尺度系统研究沉积盆地中富钾卤水水化学特征及成因. 对潜江凹陷深层富钾卤水进行了主、微量元素分析. 研究区卤水矿化度为125.70~347.00 g/L，K含量为0.32~6.83 g/L；富集Li、B、I、Na、Cl，亏损Mg、Br，Ca、SO₄有富集也有亏损. 储层岩石矿物学特征、Na_deficit与Ca_excess值以及Na/Cl摩尔比（0.83~1.32）和Cl/Br质量比（212~2 017），表明了多种水岩反应过程. 盆地卤水主要经历两个阶段的演化:盐湖含盐系地层沉积期，石膏、钙芒硝、含钾或镁硫酸盐等盐类矿物沉淀后，卤水中K初步富集，储层中硬石膏、方解石胶结作用和白云石化等成岩作用改变了卤水的成分；构造变形和剥蚀期，石盐及含钾盐类矿物被溶滤，导致卤水中K进一步富集. 

Origin and Evolution of Deep-Seated K-Rich Brine in Paleogene of Qianjiang Depression,Hubei Province

Deep-seated K-rich brine is a very important potash resource.However,there are few systematic studies on the chemical characteristics and genesis of K-rich brine in sedimentary basins on a regional scale.The major and trace element analyses of the deep-seated K-rich brine in Qianjiang Depression were carried out.The brine salinity in the study area is 125.70-347.00 g/L,and the K content is 0.32-6.83 g/L;Li,B,I,Na,Cl are enriched,Mg and Br are depleted,and Ca and SO₄ are either enriched or depleted.Mineralogical features of reservoir rocks,the Na_deficit and Ca_excess values as well as the molar ratio of Na/Cl(0.83-1.32)and the mass ratio of Cl/Br(212-2017)indicate multiple water-rock reaction processes.The brine in the basin has undergone two main stages of evolution:during the depositional period of the salt-bearing strata in the salt lake,the precipitation of salt minerals such as gypsum,glauberite,potassium-and magnesium-bearing sulfate led to the initial enrichment of K,and the diagenesis processes such as anhydrite and calcite cementation and dolomitization in the reservoir caused a change in the composition of the brine;during the tectonic deformation and erosion period, the halite and potassium-containing salt minerals weredissolved by shallow or surface waters, leading to the further enrichment of K.