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Abstract:

The Archean Côté Gold deposit (8.3 M oz) is a low-grade, high-tonnage Au(-Cu) deposit located within the 2741 Ma Chester Intrusive Complex (CIC) on the southeast limb of the Swayze Greenstone Belt (SGB) in the Abitibi Subprovince of northern Ontario. Steeply-dipping, auriferous sheeted veins that form part of the mineralized setting can be interpreted as either orogenic in origin and associated with the formation of the proximal Ridout deformation zone or as older and intrusion-related. Structures that overprint CIC are similar to those of the RDZ and are interpreted to post-date the intrusion and mineralized veins. A geochemical study of an alteration profile related to a mineralized vein reveals elemental enrichment in K, Rb, Li, Cs, Ba, Na, F, S and LREEs with a Au-Cu-Te-Pb-Bi-S association. In situ SIMS analysis of δ34S and δ18O are consistent with a magmatic signature for the fluid with a minor component of seawater, and supports the previously proposed high-level, subaqueous setting for the deposit. The combination of temporal, spatial, and geochemical characteristics of the sheeted veins suggests an intrusion-related origin.