A Phase Equilibrium Study of Cu-Fe Sulfides Between 700°C and 800°C

2 The presence of small amounts of sulfide liquids in arc magmas has petrologic implications and applications for mineral exploration. Given that ore metals such as Ag or Au can partition into sulfide phases, small amounts of magmatic sulfides may “poison ” ore formation. With the progressive crystallization of sulfides, the silicate melt becomes depleted in ore metals, and the probability of the formation of a hydrothermal ore deposit decreases. Sulfide melts, including potential Cu-Fe-S melts, may, because of the relaxation of crystal-chemical constraints, extract a greater proportion of ore metals from a melt. There has been extensive research on the Cu-Fe-S system below 700°C. However, there are discrepancies regarding the presence of a liquid phase at 800°C in this system, and this problem was explored through sealed silica tube experimentation in this study. In the experiments, mixtures of sulfides, found not uncommonly in volcanic rocks, were heated to 750°C- 800°C. The run products were analyzed for the presence and composition of a melt, to determine the lowest temperature that sulfide liquid may exist in the Cu-Fe-S system. Methods of analysi