STABILITY PROPERTIES OF THE CUS2-FES2 SOLID-SOLUTION SERIES OF PYRITETYPE

Experimental investigations on the Cu-Fe-substitution and the formatio n of a solid solution series in the system CuS2-FeS2 were carried out under hydrothermal conditions up to 350 degrees C and 3 kb and by mean s of a piston cylinder apparatus at higher temperatures and pressures up to 900 degrees C and 45 kb. Under dry conditions at 440 degrees C a nd above 17 kb the system was found to be binary with a miscibility ga p between an iron-rich phase near the FeS2 end-member and a coexisting copper-rich phase being the solvus composition of a homogeneity regio n from 75 to 100 mole% CuS2. This solvus of the copper rich phase was found to be almost independent of temperature and pressure up to 45 kb and 700 degrees C. The solubility of CuS2 in FeS2 at 45 kb increases from 0.6 mole% at 700 degrees C to 4.5 mole% at 900 degrees C. Under h ydrothermal conditions up to 3 kbars the solvus of metastable (Cu, Fe) S-2 is strongly dependent on pressure only in the Cu-rich part of the system.