Abstract:

Interflow and interpillow volcanic sedimentary rocks (VSR) in the hanging wall to the Paleoproterozoic Callinan and 777 volcanogenic massive sulfide deposits are altered for 910 m above the deposits. Elevated concentrations o f Hg, Ni, Tl, Cr, Sb, U, Mo and Zn extend up to 15 m into the hanging wall (Zone A), immediately above the massive sulfide deposits, and are the best indicators o f hydrothermal alteration related to the formation of Callinan and 777 mineralization. Less-elevated and zoned Ni, Cr, Zn, Cl, Hg, K20/K20+Na20 and Al2 0 3 /Na2 0 (Zones B, C, D and E) anomalies occur up to 910 m above the massive sulfide deposits. Similarities in anomalous elements observed in Zone A suggest that anomalies produced in Zones B, C, D and E may reflect a weaker part of the same through-going, waning hydrothermal system responsible for the anomalies in Zone A. Localized and intense epidote-quartz alteration and silicification overprint the VSR throughout the study area and are interpreted to be a product o f younger superimposed, stacked hydrothermal systems that diluted the geochemical signature produced by the earlier through-going, waning hydrothermal event.<br/>Variations in the immobile trace elements: Zr, Sc, Co, V, rare-earth elements, and the trace element ratios: La/Sc, Zr/Sc, Co/Zr, Sc/La, Sc/Zr, indicate that the VSR are heterogeneous in composition and are derived from both felsic and mafic volcanic components. A decrease in the felsic component within the VSR up section (indicated by increasing La, Zr, Zr/Co, La/Sc and Zr/Sc) shows proximity to the rhyolite-hosted Callinan and 777 VMS deposits.