Geology, Petrography, and Geoschemistry of Fisher Property Rocks and their Altered Equivalents, and Relationships to Auriferous Quartz Veins, Glennie Domain, Northern Saskatchewan
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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 secondary shear zones in the Pine Lake greenstone belt of the Glennie Domain. This region has a complex geological history related to accretionary episodes during the development of the Reindeer zone of the larger Trans-Hudson Orogen. The structures and lithological units, which host the Santoy and Seabee deposits, are interpreted to extend to the Fisher property, located to the southeast of the Santoy mine. However, the characteristics of the supracrustal and intrusive rocks that host the auriferous quartz veins in the Fisher property are not well known. Representative samples of these rocks were collected from 13 drillholes along an 8 km trend of the extension of the Santoy shear zone through the Fisher property. Petrographic, geochemical and mineralogical 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 intrusive rocks dominated by granites and diorites, that formed in a maturing arc. All rocks were subsequently metamorphosed to lower amphibolite grade conditions. Sampling of variably altered rocks, and auriferous quartz (+/- pyrite, chalcopyrite, pyrrhotite, arsenopyrite, sphalerite, native gold) veins from outcrop and drill core show evidence of a thin (~50 cm), proximal calc-silicate alteration halo and a distal biotite-sericite halo. The alteration assemblage consists of variable proportions of biotite, chlorite, and sericite (+/- calcite, clinozoisite, epidote, diopside, actinolite, tremolite, tourmaline, scheelite) in mafic rocks, and sericite (+/- biotite, chlorite, tourmaline, epidote, calcite) in granitoids. Basalts from the Fisher property were further discriminated based on their chromium content. High Cr basalts (HCrB; typically > 60 ppm Cr) have a transitional to calc-alkaline affinity and stronger depletions in the LREEs, especially Nb. Low Cr basalts (LCrB; typically < 60 ppm Cr) have a tholeiitic to transitional affinity and are relatively enriched in LREEs. Textural relationships from auriferous quartz veins observed in thin section analysis have been used to constrain a paragenetic sequence encompassing sulphides, precious metals, and alteration phases. Of note, brecciated textures, Bi-tellurides, and pyrite were associated with high-grade gold. Petrographic observations also noted variations in alteration minerals morphology, colour and structural location. The chemistry of these minerals was studied using microprobe analysis to identify any corresponding chemical changes which were notably observed in chlorite, where a Fe-endmember chlorite is typical of vein-hosted chlorites, but were absent in other phases, such as biotite. Molar Element Ratio diagrams and mass change plots suggest that gains in K and losses in Na reflect feldspar destruction and subsequent sericite and/or biotite/chlorite formation, which tend to be stronger in HCrB relative to LCrB. Zr-weighted enrichment/depletion plots show HCrB have stronger enrichments in K, Rb, Ba, Pb, As, Mo and depletions in Na. Principal Component Analysis identified element clusters reflecting primary igneous features and a possible Au or chalcophile-related signature of Pb, As, As, Mo, W + Bi, Te, and Sb. Fluid conditions were likely constrained by low salinities, made evident by low concentrations of base metals, and were likely boron-enriched . Gold mineralization at the Fisher property likely has a strong relationship with structures, however, HCrB, LCrB, granites and metasedimentary rocks all have potential as favourable host rocks.
DegreeMaster of Science (M.Sc.)
SupervisorAnsdell, Kevin M
CommitteePartin, Camille; Pan, Yuanming; Brueckner, Stefanie; Butler, Samuel
Copyright DateJune 2021
Orogenic Gold, Paleoproterozoic