Abstract

The Honeymoon Well Ni-Fe sulfide deposits occur in a thick assemblage of altered intrusive dunires and extrusive komatiites in an Archean greenstone belt near Wiluna in the eastern Yilgarn Block, Western Australia. The sulfides, host rocks, and surrounding intermediate to basic volcanics have undergone greenschist facies metamorphism in a low-strain environment; ultramafic rocks have been totally serpentinized and/or carbonated, but igneous textures are commonly well preserved. The coarse-grained dunitic rocks are interpreted as slowly cooled igneous cumulates on the basis of textural features and mineralogical and cryptic layering. Spinilex textures within the ultramafic assemblage, and rare interbedded black shale, suggest an extrusive origin for some of the rocks, and the dunite bodies are possibly consanguineous subvolcanic sills.Disseminated Ni-Fe sulfide mineralization occurs in two zones up to 100 m wide near the western and eastern contacts of the ultramarie assemblage. Pentlandite is the dominant sulfide in lizardite serpentinites and occurs in an intercumulus position, moulded around former olivine grains. In talc-carbonate rocks locally developed adjacent to the ultramarie contacts, pyrrhotite is also common. Exploration to date has outlined two major zones of Ni-Fe sulfide mineralization with mean grades ranging from 0.5 to 1 percent Ni.Honeymoon Well sulfide mineralogy is Ni rich in comparison with most other intrusive dunite-associated deposits in the region, and regular differences in S/Ni, Fe/Ni, and Ni/Cu ratios appear to correlate with the metamorphic setting and host rock mineralogy.

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