A thermodynamic model of quartz solubility in H2O-CO2-NaCl systems up to 1000℃ and 1.5GPa
H2O-CO2-NaCl体系石英溶解度模型(适用于高达1000℃、1.5GPa的高温高压环境)

There are numerous experimental measurements of quartz solubility has been studied over a broad spectrum of aqueous fluid compositions and temperature-pressure range. Here,we proposed an equation,which can calculate the solubility of aqueous silica in H 2 O-CO 2 -NaCl fluid mixture at high temperatures and high pressures from 0 ～ 1000℃ and 0 ～ 1. 5GPa,as follows: logm SiO2 = A( T) + B( T) ·log M H2 O V * H2 O + C( t) ·logx H2 O Here A( T) 、B( T) and C( t) are polynomials of temperatures T( K) and t( ℃ ) ,x H2 O and V * H2 O stand for the mole fraction and effective partial molar volume of H 2 O in fluid,respectively. The value of V * H2 O is calculated from the relation V mix = x HO V * H2 O + Σ x s V s , where V mix represent the molar volume of the fluid mixture,which is calculated from the recent model of Mao et al. ( 2010) ,x s and V s denote the mole fraction and the intrinsic volume of the solute,respectively. Values V CO2 = 29. 9cm 3 / mol and V NaCl = 30. 8cm 3 / mol were adopted by this thermodynamic model. The accuracy of our model is better than previous models,and our model is able to predict the solubility of quartz over a much wider T-P-x s conditions relevant to the deep crust,so that it could be used to evaluate aqueous silica transport in Barrovian metamorphic belts and subduction zones and so on. In addition,our model is helpful to establish quartz geothermometer,discover the formation mechanics of deposits relevant to the quartz veins. Online calculation of the solubility of quartz is available on: www. geochem-model. org.