Partial melting of the Broken Hill galena-sphalerite ore: Experimental studies in the system PbS-FeS-ZnS-(Ag2S)

For many years the genesis of the Broken Hill Pb-Zn-Ag deposit has been, an d continues to be, hotly debated, mostly because many of die original chara cteristics of the deposit have been obscured by high-grade metamorphism and deformation. Metamorphism not only overprinted the deposit but fundamental ly modified the sulfides through metamorphic remobilization. Based on exper imental studies it had also been speculated that partial melting of the sul fides may have occurred. The lack of experimental data at elevated pressure s in die PbS-FeS-ZnS system has limited this suggestion to mere speculation . We present the results of an experimental study of the melting behavior o f sulfides, which Show that Broken Hill ores must have been partially molte n under peak metamorphic conditions.