The Archaean massive sulphide Cu|Zn deposit at Hongtoushan has been metamorphosed to upper amphibolite facies. An investigation on ore textures shows that pyrrhotite in the deposit was originally produced by submarine exhalation, and subsequently metamorphosed, annealed and recrystallised. Deformation textures formed by progressive metamorphism of pyrrhotite were erased almost completely under peak conditions, and the presently|existing deformation textures and ore mylonites are largely resultant from diaphthoresis. Deformation and annealing of pyrrhotite could have been enhanced by fluids. Retrogressive fluids are characterized by high oxygen fugacity. The Archaean massive sulphide Cu | Zn deposit at Hongtoushan has been metamorphosed to upper amphibolite facies. An investigation on ore textures that that pyrrhotite in the deposit was originally produced by submarine exhalation, and subsequently metamorphosed, annealed and recrystallized. Deformation textures formed by progressive metamorphism of pyrrhotite were erased almost completely under peak conditions, and the presently | existing deformation textures and ore mylonites are blocked from diaphthoresis. Deformation and annealing of pyrrhotite could have been enhanced by fluids. Retrogressive fluids are characterized by high oxygen fugacity .