ABSTRACT
In gold, silver, copper, copper-nickel and other deposits, the deposition of sulphides, selenides and tellurides is proximated in time and, as a consequence, they form complex intergrowths with corrosion rims. Many minerals of selenium and tellurium, like sulphides, represent non-stoichiometrlc compounds in the form of solid solutions of varying composition. To determine phase relations between mineral parageneses covering oxides, sulphides, selenides and tellurides, oxide-sulphide-selenide, oxide-sulphide-telluride and selenide-telluride systems have to be thermodynamically analysed. One of the specific features of gold-telluride and silver-selenide ores is the presence of metastable phases of unusual composition which form intimate intergrowths with selenides, sulphides and tellurides. As a consequence, there are inconsistencies in phase relations as set out in the Gibbs phase rule in the ores of epithermal gold-telluride and silver-selenide deposits. This kinetic factor is clearly important for understanding the genesis of multiconstituent systems and calls for special investigations.
