Abstract
Evidence of mineral associations in natural ores is reviewed and used as a basis of phase diagrams for the quaternary system Cu-Fe-As-S. Published experimental work is used to supplement this evidence. Diagrams proposed in earlier papers are revised and made more complete. A number of assemblages are denoted which should be observed as indicative of their conditions of formation. If studied experimentally they might be useful indicators of temperature and S activity. Several paragenetic paths of increasing S content and constant Cu/Fe ratio are described, which define certain sequences of assemblages apparently characteristic of some Cu mining districts. Zonal progressions of assemblages in some districts appear also to manifest these sequences.