Na-K-Mg三角图修正与Na-K温标选取

Na-K-Mg三角图作为水-岩平衡状态初步判定的方法，未考虑具体温标公式和矿物成分对平衡状态的影响，因此通过基于不同Na-K温标公式修正后的Na-K-Mg三角图判断水岩平衡状态，并利用适合的Na-K温标公式计算地下热储温度，对划分地热系统成因类型和开发利用地热资源具有重要意义。研究发现，修正后的Na-K-Mg三角图中任意一点，对某种温标公式确定的曲线处于平衡状态，对另一温标公式确定的曲线则有可能处于部分平衡状态；且温度越低，这种现象越显著。最贫Mg上边界和最富Mg下边界是由不同的温标公式确定的，随温度具有明显的分段性。利用各Na-K温标公式作出T-lg（Na/K）曲线图，绘制曲线交点对应的基于各

Modification of Na-K-Mg triangular diagram and selection of Na-K geothermometer

Na-K-Mg triangular diagram is a preliminary method of determining the water-rock equilibrium state. It does not specifically consider the effect of geothermometer equations and mineral compositions on the equilibrium state. Therefore, using the Na-K-Mg triangular diagram modified by different Na-K geothermometer equations to judge water-rock equilibrium state, and using the suitable Na-K geothermometer equation to calculate the temperature of geothermal reservoirs, is of great significance to divide the genetic types of geothermal systems and develop or utilize geothermal resources. It is found that any point in the modified Na-K-Mg triangular diagram is fully equilibrated with the curve determined by one Na-K geothermometer equation and it is possibly partially equilibrated with the curve determined by the other Na-K geothermometer equation, and this phenomenon becomes obvious with the decrease of temperature. The most Mg-poor upper boundary and the most Mg-rich lower boundary are determined by different geothermometer equations. Using different Na-K geothermometer equations to draw the curve of logarithmic function of the ratio of Na to K with temperature, and drawing the Na-K-Mg triangular diagram based on all "fully equilibrated curves" corresponding to the intersection points of the curve arrives at the selection methods and Tibet Yanjing area was taken as an example to calculate the temperature of geothermal reservoirs.