The distribution of the halogens in Sudbury Breccia matrix as pathfinder elements for footwall copper-PGE mineralization at the Fraser copper zone, Barnet main copper zone, and surrounding margin of the Sudbury igneous complex, Onaping-Levack area, Ontari

A very hydrous, halogenated alteration halo exhibiting retrograde albite-epidote hornfels facies metamorphism has been identified in the pseudotachylite matrix of Sudbury Breccia which is detectable up to 150m from footwall Cu-Ni-PGE mineralization, within the ore-hosting Sudbury Breccia zones. Matrix within this alteration halo demonstrates elevated bulk [Cl] and [Br], bulk Cl/Br ratios, soluble [Cl−] and [Br−], bulk [Cu], and bulk [Pt+Pd+Au]. The insoluble alteration signature is carried by amphibole, chlorite, and biotite which increase in abundance, Cl-content, and Cl/(Cl+F) ratio as the ore-hosting breccia zone is entered and mineralization is approached. The soluble signature is carried by increasing amounts of fluids and salts trapped in primary fluid inclusions. The maximum temperature of this alteration event is estimated at ∼550°C and may have involved a fluid with elevated and widely variable f(HCL)/ f(HF) which changed the composition of hydroxysilicates and feldspar within the matrix. Evidence for mixing of magmatic fluid exsolved from the SIC with local groundwaters is presented.