Comment
Figure shows first heating and cooling cycle.　
Sulfidation reaction ranges from 115 to 185℃（90%）. First peak, at 129℃（overlapping with melting of S）. Second peak, at 162℃.
The enthalpy of formation
　Product is an orthorhombic Cu2S.
Calculated ΔHf= 15.3Kcal/mol. Ref（19.6Kcal）.