The ferric-ferrous ratio of natural silicate liquids equilibrated in air

Abstract

Results of chemical analyses of glasses produced in 46 melting experiments in air at 1,350° C and 1,450° C on rocks ranging in composition from nephelinite to rhyolite have been combined with other published data to obtain an empirical equation relating in $(X_{{\text{Fe}}_{\text{2}} {\text{O}}_{\text{3}} }^{{\text{liq}}} /X_{{\text{FeO}}}^{{\text{liq}}} )$ to T, $\ln f_{{\text{O}}_{\text{2}} }$ and bulk composition. The whole set of experimental data range over 1,200–1,450° C and oxygen fugacities of 10^−9.00 to 10^−0.69 bars, respectively. The standard errors of temperature and $\log _{10} f_{{\text{O}}_{\text{2}} }$ predictions from this equation are 52° C and 0.5 units, respectively, for 186 experiments.