A mineralogical and geochemical investigation of sulfide mineralization in the McConnell Ni-Cu-PGE occurrence, McConnell Offset Dyke, Garson Mine area, Sudbury, Ontario, Canada

Abstract

The Sudbury mining camp hosts the largest and only known impact-related metallogenic system in the world, containing significant resources of Cu-Ni-platinum group element-rich sulfide mineralization. The undeveloped, Vale-owned McConnell concentric offset dyke hosts low Ni grade magmatic Ni-Cu sulfide mineralization with unusually high PGE tenor, showing marked differences in mineralogy and geochemistry compared to other South Range offset-type deposits. This study shows that: (i) the low As, Ni, and high PGE in bulk assays and Co and Pd-rich pentlandite in the ores reflects an unusual evolution of the McConnell sulfide melt explained by three possible models, or a combination of models (“uncontaminated”, “locally enriched”, and “late-stage” sulfide melts); (ii) a post-crystallization hydrothermal fluid passed through the system, remobilizing Ni and Pb within the deposit and altering primary ore mineralogy forming pyrite and marcasite; and (iii) the McConnell ores crystallized from an O-rich Ni-poor sulfide melt, as reflected by magnetite geochemistry.