Graphical Techniques for the Evaluation of Waterirock Equilibration Conditions by Use of Na, K, Mg and Ca-Contents of Discharge Waters

Abstract

Relative Na, K, Mg, Ca-contents of thermal waters, in full equilibrium with a thermodynamically stable mineral system, are, at a given temperature, uniquely fixed. They provide useful reference values for the assessment of the degree of attainment of fluid-rock equilibrium in natural systems. The solute pair Na-K equilibrates most slowly or only at elevated temperatures, while relative K-Mg-contents adjust much faster and at low temperatures. The system K-Ca is sensitive.to variations in Pco2. These subsystems are combined in graphical techniques for the evaluation of deep temperature and Pco2-conditions in geothermal systems on the basis of the Na. K, Mg and Ca contents of their discharges.