Role of Melting in the Evolution of the Broken Hill Orebody

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Frost and SwappEAR-0125113This project aims to determine the effect that melting had on the world-class lead-zinc ore deposit at Broken Hill, Australia, which was metamorphosed at granulite facies, well within the range of melting for the pure Pb-Zn-Fe-Ag-S system. We plan to study the textures, assemblages and mineral compositions within the ore body and its alteration halo to see if the relations observed can be explained by reactions between the country rock and a crystallizing and differentiating polymetallic melt. We plan to use trace element geochemistry to determine if the pyroxenoid horizon around the ore crystallized from the polymetallic melt. It will also determine if the high-variance assemblages around the ore body that involve garnet could have been produced by fluids that were released from the melt during crystallization of the pyroxenoids. It also intends to study assemblages within the ore body to see if they record a liquid line of descent, with the melt becoming enriched in incompatible elements, Ag, Au, As, Bi, Sb, and Tl, during differentiation.