PHASE RELATIONS AMONG TELLURIDES, SULFIDES, AND OXIDES: I. THERMOCHEMICAL DATA AND CALCULATED EQUILIBRIA.

Thermodynamic data for binary tellurides are compiled and combined with available data for sulfides and oxides to calculate phase relations among tellurides, sulfides, and oxides at low temperatures (100 degree -300 degree C). Calculated equilibria show that tellurides of Mo, Sn, Mn, and Zn are unstable with respect to corresponding sulfides and/or oxides in natural systems and that some tellurides, such as As//2Te//3, are likely to occur in nature, although they have not yet been found as minerals. The composition of electrum in equilibrium with hessite is useful as a sliding-scale indicator of the fugacity of Te//2 at relatively low The calculated phase relations explain particular associations or antipathies among ore minerals and may be used to predict other minerals which should be present at equilibrium.