The geology and geological development of the broken hill lode, in the new broken hill Consolidated mine Australia part II: Mineralogy

Abstract

Abstract Compositional relationships, textures, and patterns in the distribution of minerals which include garnet, rhodonite, bustamite, wollastonite, hedenbergite, knebelite, and sphalerite in metamorphosed sulphide ores have been interpreted in terms of variation in fco2 and some function of fs2 on the scale of the mine during prograde regional metamorphism. In general, rocks which were originally within carbonate and sulphur‐rich ore layers equilibrated at higher gas fugacities than the borders, or structurally disturbed parts of the lodes. The rather constant FeS content of sphalerite in all but the more Fe‐poor rocks indicates that it is in equilibrium with pyrrhotite, which is present in significant amounts only at the south end of the mine. At the other extreme, garnet is commonly out of equilibrium with closely associated minerals. These differences and others indicate significant variations in the size of equilibrium subsystems in the mine. Some mineral zoning patterns and associations of incompa...