The application of gas chromatography in characterizing bulk fluid inclusion hydrocarbons in the footwall of the Sudbury ingeous complex and other magmatic, hydrothermal and surficial ore-forming environments

Abstract

The North Range of the Sudbury Igneous Complex hosts footwall-style Cu-Ni-platinum group element-rich sulfide deposits of predominantly magmatic origin but that have been influenced by multiple hydrothermal events. The composition of hydrocarbon phases (unsaturated and saturated, C1 to C6) in fluid inclusions within the matrix of Sudbury breccia, a rock unit permeable to circulating volatiles and that commonly hosts footwall-style Cu-Ni-PGE deposits, has been investigated by in-line rock-crushing gas chromatography (GC). Zones of breccia that are known to contain economic footwall sulfide deposits and zones barren of such deposits were investigated. Subtle but strategically significant differences have been found in the composition and abundance of bulk hydrocarbons that are released from mineralized and barren breccias when fluid inclusions are opened. These findings strongly suggest that fluid hydrocarbon signatures should be taken into consideration when exploring for Cu-Ni-PGE-rich footwall-style ore bodies as a supplemental criterion to traditional visual and geochemical approaches.