Pressure Effects on the Solvi of some Sulphide Binary Systems

Abstract

Pressure effects on the solvi of some sulphide binary systems, NiS₂-FeS₂, Cu₅FeS₄-Cu₉S₅, Cu₅FeS₄-CuFeS₂, and ZnS-FeS, were investigated on the basis of thermodynamical considerations. It is assumed that activity coefficients and ΔV in phases are independent of pressure.
The result of the investigation has revealed that as confining pressure increases, the two phase region of the NiS₂-FeS₂ system is narrowed, while those of other systems are broadened. By finding equicomposition curves on the pressure-temperature coordinates, it is suggested that there is a possibility of determining the pressure-temperature condition under which these mineral assemblages were formed. This method requires, however, at least two suitable pairs of mineral aggregates which belong to mutually independent systems.