Do the mineral assemblages of successive vein generations reflect the fluid compositions at different stages?
Determination of a fluid evolution history for the copper orebodies is, to a large extent, influenced by interpretation of overprinting criteria in the alteration system (Heinrich et al., 1989, Waring, 1990). Of most interest are the depositional conditions and fluids responsible for the economic sulphides. Perkins (1984) and Swager (1985) illustrated and described a sequencing of dolomite and quartz veins and breccias, all of which contained sulphides, principally chalcopyrite. Analysis of veins from epigenetic deposits generally assumes that the veins are essentially dilational, and consequently that all minerals were deposited within each vein generation prior to the subsequent generation. In these scenarios the evolving fluid composition must be capable of depositing the observed sulphides in the overprinting veins. Such an argument has been applied to Mount Isa copper genesis by J. M. Proffet (internal report to MIM Exploration-1992), that since chalcopyrite is observed in veins w
