钾盐变质作用的矿物学和地球化学响应特征——以老挝沙湾拿吉钾盐盆地ZK004孔为例

Mineralogy and Geochemical Response Characteristics of Potash Metamorphism:A Case Study of Pore ZK004 in Savannakhet Potash Basin, Laos

中文关键词:  老挝沙湾那吉盆地  钾盐矿床  微量元素  盐类矿物  变质作用

英文关键词:Savannakhet Basin, Laos  Potash deposits  Trace elements  Salt minerals  Metamorphism

中文摘要:

      通过对老挝沙湾拿吉钾盐盆地ZK004钻孔岩芯中的钾盐层段矿物学、微量元素地球化学特征的分析,探讨了钾盐变质过程的矿物学和地球化学指标的响应特征。结果表明,ZK004孔变质作用大致可分为2个阶段:第一阶段为不均匀交代阶段,该阶段光卤石层受到非海相流体淋滤,在光卤石层顶部形成次生钾石盐；第二阶段为强烈淋滤重结晶阶段,早期交代成因次生钾石盐层受到多次非海相流体的交代淋滤作用,发生溶解—重结晶乃至淋失。元素地球化学分析表明,光卤石阶段石盐中Fe、Si和Sr具有较好的峰值对应且光卤石阶段的含量高于钾石盐阶段,指示了陆相地表水的补给作用主要发生在光卤石沉积阶段,钾石盐阶段石盐中Cu、Zn等具有较好的含量峰值对应关系,表明改造次生钾石盐的流体可能主要是地下水。

英文摘要:

      Based on the analysis of the mineralogy and trace element geochemical characteristics of the potash interval in the core of the ZK004 hole in the Savannakhet potash basin, Laos, the response characteristics of the mineralogy and geochemical indicators of the potash metamorphism process are discussed. The results show that the ZK004 pore metamorphism can be roughly divided into two stages. The first stage is the inhomogeneous metasomatism stage. In this stage, the carnallite layer is leached by non-marine fluids, and secondary potash halite is formed on the top of the carnallite layer. The second stage is the stage of intense leaching and recrystallization. The early metasomatogenic secondary potassium rock salt layer is subjected to repeated metasomatism and leaching by non-marine fluids, resulting in dissolution, recrystallization and even leaching. Elemental geochemical analysis shows that Fe, Si, and Sr in the carnallite stage halite have good peak correspondences, and the content of the carnallite stage is higher than that of the potash stage, indicating that the replenishment of terrestrial surface water mainly occurs in the light. During the halite depositional stage, the Cu, Zn, etc. in the rock salt in the sylvite stage have a good peak correspondence relationship, indicating that the fluid for transforming the secondary sylvite may be mainly groundwater.