EXPERIMENTAL DATA BEARING ON MOVEMENT OF IRON IN AN AQUEOUS VAPOR

Hypersolidus and subsolidus hydrothermal quenching experiments on calc-alkaline plutonic rocks between 1 1/4 and 10 kb water pressure indicate that iron fractionates into the vapor phase. Isothermal melting experiments on granitic rocks show that quench hematite crystals develop only at the noble metal-silicate charge interface. Subsolidus polythermal experiments on andesite and diabase corroborate the movement of iron in the vapor phase and the nucleation of hematite at approximately 500° C. The presence of a melt, of a specific rock type, or of chloride, fluoride, sulfide, or carbonate anions does not seem mandatory for the leaching and transport of iron in the vapor. Experimental data confirm the efficiency of the process at geologically reasonable pressures and temperatures and emphasize the necessity of a free vapor phase. These experimental data are applied to the origin of specular hematite incrustations near volcanic vents and fumaroles and to the generation of iron-bearing ore fluids that give rise to contact metasomatic iron ore deposits. © 1969 Society of Economic Geologists, Inc.