A review on thermodynamics and kinetics of quartz dissolution under supercritical geothermal conditions

The knowledge of the dissolution behavior of quartz is crucial to understanding geochemical processes in supercritical geothermal systems, as well as hot dry rock, offshore geothermal, and mid-ocean ridge systems. This review presents the experimental and model studies of quartz-water reactions under supercritical geothermal conditions. The quartz database under supercritical geothermal conditions is developed by compiling (1) the equilibrium constants at 21–800 ℃ and 0.1–100 MPa obtained from 14 thermodynamic experiments, and (2) the rate constants at 22–625 ℃ obtained from 23 kinetics experiments. The comparison of experimental systems indicates that an assistance device for equilibrium identification and the in situ sampling methods should be considered in the instrumental design, which would help improve the test accuracy and efficiency of the water-rock experiments. The retrograde behavior of quartz dissolution near supercritical and at low-density regions is interpreted by the experimental results and theoretical analysis. We renewed the Arrhenius fit and proposed a pressure-term framing to characterize the potential effect of pressure on quartz dissolution rate. The kinetic phenomena and the pressure-term kinetic model need further study in the future. The compiled quartz database lays the foundation for density-based model development and numerical prediction of quartz dissolution behavior in supercritical geothermal systems.