Geochemical process model for the Mt Isa Cu-Co-Ag deposits

Significance of strain localization and fracturing in relation to hydrothermal mineralization at Mount Isa, Australia

“…Finer-grained beds in this proximal zone are altered to graphitic shale, which is rarely fractured but shows evidence for layerparallel shear. Geochemical studies (Wilde et al, 2005) suggest that the chemical composition of the Urquhart shale does not vary significantly from other Mount Isa Group members. Hence the question is, if and how the layering of the Urquhart shale relates to the creation of deformation-related permeability during multiple hydrothermal fluid flow events.…”

Mineral Systems in the Mount Isa Inlier

“…It is postulated (Heinrich et al, 1993;Matthai et al, 2004;Wilde et al, 2006) that ore deposition was due to mixing of an oxidised brine that circulated within metabasalts with a sulfur-rich fluid from overlying Mount Isa Group metasedimentary rocks or a younger Mesoproterozoic basin at the site of deposition.…”

“…cooling; a number of wall-rock reactions (reduction by carbonaceous matter, replacement of quartz and dolomite). Dissolution of carbonate minerals, feldspar, and micas buffered pH at somewhat neutral values, optimising Cu extraction (Wilde et al, 2006); fluid mixing between magmatic and one or more fluids of a different origin (mantle/metamorphic/basinal evaporate/meteoric) (Kendrick et al, 2006).…”