The Solubility of Quartz in H2O in the Range 1000-4000 Bars and 400-550c

摘要

The solubility of quartz in H2O has been measured between 1-4 kilobars at 400, 450, 500, and 550 C. Two rate studies at 400 and 625 C are consistent with an equation of the form dx/dt = a-bx for the rate of solution of quartz in H2O, where x is the concentration of SiO2 in solution at time t. The temperature dependence of the two specific rate constants, a and b, give values of approximately 16.5 and 14.5 kcal/mole for the activation energies of the dissolution and crystallization processes respectively. The temperature and pressure dependence of solubility used in conjunction with the most widely accepted reaction for the solution of quartz, SiO2 (qtz) + 2H2O reversibly yields Si (OH)4, lead to thermodynamic calculations indicating unreasonable behavior of the assumed solute species. It is suggested that these anomalies may reflect the inability of the accepted solution reaction to represent the heterogeneous equilibrium between quartz and solution over a large range of temperature and pressure. (Author)