Genesis of the Island Gold Deposit, Ontario, Canada: Implications for Gold Mineralization in the Wawa Subprovince of the Superior Province

The Island Gold deposit represents an uncommon example of known economic mineralization in the Wawa subprovince, which has been tectonically correlated with the neighboring Abitibi subprovince that hosts world -class orogenic gold deposits. The Island Gold deposit is hosted in dacite, gabbro, and tonalite-trondhjemite, and accompanied D-2 deformation. The main ore zone dips steeply toward the south and consists of early shear-hosted laminated quartz veins and late extensional veinlets; both vein sets host gold mineralization. A set of shallowly dipping extensional quartz veins in the Goudreau zone located north of the main ore zones also host economic gold mineralization. Multiple sulfur isotope analysis of pyrite associated with gold-bearing alteration envelopes in the main ore zone indicates no involvement of sulfur affected by mass-independent fractionation, which rules out sulfur (+/- gold) sourced from nearby banded iron formation or metasedimentary material. However, a single analysis of pyrite from an auriferous Goudreau zone vein indicates the involvement of sulfur that underwent mass-independent fractionation, which suggests a different fluid source. Zircon U-Pb geochronology of pre-and postmineralization rock samples at Island Gold restricts the timing of mineralization to between ca. 2724 and 2672 Ma. Including previous results of detrital zircon geochronology, gold mineralization occurred between ca. 2680 and 2672 Ma. This age range is similar to the timing of gold mineralization at the Hemlo deposit in the Wawa subprovince but is slightly older than the bulk of orogenic gold mineralization in the neighboring southern part of the Abitibi subprovince. Multiple sulfur isotopes indicate that gold mineralization at Island Gold results from fluids of igneous affinity associated with second-generation transpressional deformation. The ore-controlling structures were developed in bends in regional shear zones focused around relatively competent premineralization plutons.

Automated summary

The Island Gold deposit is a rare example of economic mineralization in the Wawa subprovince, with similar tectonic characteristics as the neighboring Abitibi subprovince. It is hosted in dacite, gabbro, and tonalite-trondhjemite, and associated with second-generation transpressional deformation. The age range of gold mineralization is similar to other events in the Wawa subprovince.