Sphalerite-pyrrhotite relationships at Quemont Mine

X-ray diffraction techniques were used to analyze 38 sphalerite samples for FeS and 27 pyrrhotite samples for Fe. The samples were selected from throughout the massive sulfides of the Quemont ore zones [Noranda, Quebec]. The data indicate the average temperature of formation of the sphalerite was 540 degrees C. with a standard deviation of + or -72 degrees C. The average temperature of formation of the pyrrhotite was 325 degrees C, with a standard deviation of + or -47 degrees C. This discrepancy is explained on the basis of the ore having formed from a sulfide melt with an original sphalerite-pyrrhotite equilibrium at around 540 degrees C., then subsequently the pyrrhotite phase has undergone readjustment in the solid state to form a more Fe-rich pyrrhotite plus pyrite. This readjustment was completed at around 325 degrees C.