Orogenic gold in the Trans-Hudson orogen, Saskatchewan, Canada: Petrographic and geochemical insights from the Porky Lake system

Gold mineralization occurs within the Pine Lake greenstone belt in several known and prospective deposits in northern Saskatchewan, Canada. Systematics of gold mineralization at some locations within the Seabee Gold Operation, including the Porky Main and Porky West deposits, are poorly constrained but lie adjacent to the recently decommissioned Seabee mine, existing mill infrastructure, and active mining at the Santoy Mine Complex, enhancing their prospectivity. The Porky deposits are spatially associated with a shear zone separating mafic volcanic rocks (Assemblage A) from arenaceous metasedimentary rocks (Porky Lake Group) and are hosted in diverse rock types previously lacking petrographic and geochemical characterization. Gold mineralization is linked to calc-silicate alteration and occurs both in mafic volcanic rocks of Assemblage A and smoky quartz veins within the Porky Lake Group. To further assess the Porky deposits, mineralized drillcore samples were analyzed to determine the mineralogical and trace-element characteristics of sulfide-gold mineralization. Multiple sulfide generations are defined in a mineral paragenesis chart that outlines five sulfide phases (including pyrite), three of which are gold-bearing. These include sieve-textured Py3-Po2-Ccp2 ± Sp-Gn in pervasive calc-silicate alteration, oscillatory zoned Apy-Py4a/b-Po3-Ccp3 ± Ilm1 in smoky quartz veins, and remobilized Py6a/b with Au in fractures of earlier sulfide phases. Similar paragenetic features at the Santoy Mine and Fisher property support a belt-wide, multi-stage orogenic gold system. Finally, we report new geochronology for a ca. 1842 Ma granodiorite intruding the Porky Lake Group, refining previous age constraints.