The partitioning of copper and molybdenum between silicate melts and aqueous fluids

The partitioning of copper and molybdenum between silicate melts and aqueous fluids has been determined at 750°C, and 1.4 Kb. The experiments were conducted in a $\text{1}\text{2}$ inch ID, rapid quench, cold seal pressure vessel. The aqueous and glass phase run products were analyzed by atomic absorption spectrophotometry and ion microprobe, respectively. The vapor/melt partition coefficient for copper, $\text{D}{}^{\mathrm{<mtext>v</mtext><mtext>l</mtext>}}{}_{\mathrm{Cu}}$, defined as the ratio of the concentrations of copper in the vapor to copper in the melt was found to be $\text{D}{}^{\mathrm{<mtext>v</mtext><mtext>l</mtext>}}{}_{\mathrm{Cu}}\text{= (9.1 ± 2.5)m}{}^{\mathrm{v}}{}_{\mathrm{Cl}}$ at NNO up to at least 4.5 moles of chlorine per kg of solution. The partition coefficient for molybdenum is equal to 2.5 ± 1.6 at NNO and QFM; its value is independent of the fluorine concentration of the melt up to at least 1.7 wt. percent fluorine, and of the chlorine concentration up to at least 4.5 moles of chlorine per kg of solution. Copper is probably present in the univalent state in both the silicate melt and in the associated aqueous phase at NNO; the most important aqueous complex of copper is probably CuCl⁰. Molybdenum is probably present in the aqueous phase as one or more molybdate species.