The combined solubilities of Fe, Zn and Pb sulphides were determined at elevated P and T in chloride solutions buffered in pH by a silicate assemblage of quartz monzonite composition plus added muscovite, and buffered in fS2 and fO2 by the assemblage pyrite-pyrrhotite-magnetite. Higher T and higher chloride concentration favour higher metal solubilities, but the P effect is opposite. At 500oC, 0.5 kbar and 1 M total chloride, Fe, Zn, Pb solubilities were 8500, 4300 and 8700 ppm, respectively, whereas at 1 kbar they were 4200, 2400 and 2600 ppm, and at 2 kbar, 1700, 800 and 1200 ppm. The P effect is of considerable importance to problems of ore-mineral transport; the metal could be carried over long distances on a decreasing P gradient so long as the T decreases were sufficient; this condition could be approximated by a near-adiabatic transport cooling path. Such a condition is probably common for hydrothermal processes involving fairly deep-seated sources of heat and mineral components.-L.C.H.
Additional publication details
Effect of pressure on ore mineral solubilities under hydrothermal conditions.