Effect of carbon dioxide on the melting of granite and feldspars

Abstract

Unlike water vapor and F, carbon dioxide under pressure has little or no effect on the rates of melting or crystallization of granite or alkali feldspars, and the melting temperatures are apparently unaffected except insofar as pressure per se raises the temperature of melting. The melting temperature of granite in the presence of a mixture of carbon dioxide and water vapor at a fixed total pressure is raised if the proportion of carbon dioxide in the vapor is increased, indicating that carbon dioxide is less soluble in granitic liquids than is water. Although the solubility of carbon dioxide in granitic liquids is too small to be determined directly by the techniques used, any appreciable solubility would produce a measurable lowering of the melting temperature. It is suggested that the solution of carbon dioxide in silicate liquids depends upon the availability of cations which are not structurally bound to the silicate network of the liquid and are therefore available for carbonate formation in the liquid.