THE LITHOGEOCHEMICAL SIGNATURES OF HYDROTHERMAL ALTERATION FRAMING PALEOPROTEROZOIC AURIFEROUS QUARTZ VEINS, FISHER PROPERTY, SEABEE GOLD OPERATION, SASKATCHEWAN, CANADA

The Fisher property is part of the Seabee Gold Operation in northern Saskatchewan, which also includes the active Santoy mine and the recently decommissioned Seabee mine. These Paleoproterozoic orogenic gold deposits are hosted by shear zones in the Pine Lake greenstone belt of the Glennie Domain, which has a complex geological history related to accretionary episodes during the development of the Reindeer Zone of the Trans-Hudson Orogen. The structures and lithological units, which host the Santoy deposit are interpreted to extend to the Fisher property, located to the southeast of the Santoy mine. Representative samples of these rocks were collected from 8 drillholes along an 8 km trend of the Santoy shear zone through the Fisher property. Petrographic and geochemical characteristics were determined for these samples to test their correlation with rocks hosting the Santoy deposit. The host rocks are dominated by transitional to calc-alkaline basalts to dacites, with associated intrusives dominated by granodiorites and gabbros, which were subsequently metamorphosed to lower amphibolite grade conditions. Sampling of variably altered rocks, and auriferous quartz (+/- pyrite, chalcopyrite, pyrrhotite, arsenopyrite, native gold) veins from outcrop and drillcore show thin (~50 cm) alteration haloes. The alteration assemblage consists of variable proportions of biotite, chlorite, sericite, epidote, and calcite (+/- diopside, tremolite, rutile, ilmenite) in mafic rocks, and sericite (+/- rutile, epidote, calcite, zircon) in granitoids. High Cr basalts (HCrB; typically > 180 ppm Cr) have a more tholeiitic affinity and stronger depletions in the REEs. Low Cr basalts (LCrB; typically < 60 ppm Cr) have a more calc-alkaline affinity and exhibit enrichments in REEs. Density and Zr-weighted enrichment/depletion plots show HCrB’s have enrichments in Pb, As, Mo and depletions in Na, while LCrB have enrichments in P and depletions in Ni. Pearce Element Ratio and mass change plots suggest feldspar destruction and subsequent sericite formation is the major alteration type affecting both basalts, but is stronger in HCrB. Results thus far suggest HCrB are more favourable for hosting high grade Au mineralization and demonstrate the value in integrating various lithogeochemical methods into an exploration strategy.