Magnesium correction to the NaKCa chemical geothermometer

Equations and graphs have been devised to correct for the adverse effects of magnesium upon the Na-K-Ca chemical geothermometer. Either the equations or graphs can be used to determine appropriate temperature corrections for given waters with calculated NaKCa temperatures > 70°C and R < 50, where $\text{R = {}\text{Mg}\text{(Mg + Ca + K)}\text{} × 100}$ with cation concentrations expressed in equivalents. Waters with R > 50 are probably derived from relatively cool aquifers with temperatures approximately equal to the measured spring temperature, irrespective of much higher calculated Na-K-Ca temperatures.