Revised Quartz Solubility Temperature Dependence Equation along the Water-vapor Saturation Curve

From the application of chemical thermodynamics a quartz solubility regression expression along the water-vapor saturation curve for whole range of temperature from 0 to 374oC was developed. The equation is the following ( ) ( ) 08 . 0 88 . 4 ) ( 7 . 31 7 1175 ) ( log 2 ± + ± ⋅ − = K T ppm SiO The correction of total discharge silica composition from a well for the vapor fraction in the geothermal reservoir is a fundamental limitation to use this equation as a geothermometer. For knowing the vapor fraction there is indirectly need of knowing the reservoir temperature. It is possible to calculate the deep reservoir temperature with iteration process, but a basic assumption is that the reservoir fluid is in equilibrium with quartz. The concept is elucidated in case of the Cerro Prieto geothermal system.