A Revised Equation for the NA/K Geothermometer

Abstract

The Na/K geothermometer has been reevaluated using data from wells drilled in geothermal systems in a wide variety of geological environments and spanning a large temperature range. A new equation recommended for geothermometry is t°C= 1217/log (Na/K) + 1.483 - 273.15, where Na and K concentrations are in parts per millions. Most waters from reservoirs with temperatures above 100°C have Na/K ratios between those expected for solution equilibrium with low albite plus microcline and those with high albite plus sanidine. The Na/K geothermometer generally works well for waters from reservoirs with temperatures greater than 150°C to 200°C, but is likely to given anomalously high estimated temperatures when applied to waters from environments where temperatures are less than about 100°C.