The large Cerro de Pasco Cordilleran base metal deposit in central Peru is located on the eastern margin of a Middle Miocene diatreme-dome complex. A striking characteristic is the presence of a N-S trending massive funnel-shape pyrite-quartz replacement ore body that contains pyrrhotite pipes grading outwards to lead-zinc replacement bodies, along the eastern contact of the diatreme-dome complex. Earlier workers interpreted the pyrrhotite pipes as postdating the pyritequartz body. This study, that has been possible through access to new mining areas and drill cores, allows an alternative interpretation. The new data strongly suggest that the pyrrhotite pipes and their associated lead-zinc replacement bodies predated the formation of the pyritequartz body