Stratigraphy, structure and lode gold system at the Central Manitoba mine trend, Rice Lake greenstone belt, Archean Superior Province, Manitoba, Canada

Abstract

The Central Manitoba mine trend is one of the most important lode gold districts in the Rice Lake greenstone–granitoid belt of the western Uchi subprovince within western Superior Province, Manitoba, Canada. Neoarchean host rocks consist of a south-facing metavolcano-sedimentary succession (2.75–2.73Ga) intruded by voluminous gabbroic sills and tonalitic–granodioritic plutons (2.73–2.72Ga), as well as late aplite dikes (2.73–2.72Ga) and quartz-feldspar porphyry dikes (2.73–2.71Ga). Five generations (G1–G5) of deformation structures have been recognized through detailed geological mapping. The entire succession was folded during G1 and G2 prior to rare late aplite dike emplacement. All fault-fill veins and extension veins cut all lithologic units, and are structurally governed by late (G3 and G4) conjugate shear zones. Main gold mineralization occurs within fault-fill veins hosted by west-trending steeply-dipping (G4) dextral brittle–ductile and ductile shear zones, which occur along or across contacts of metabasalt, metagreywacke and metagabbro or entirely within metagabbro. Microstructural and paragenetic analyses on main gold-bearing veins have revealed that gold is intimately associated with quartz, pyrrhotite and tellurobismuthite. Main gold introduction is interpreted to have taken place contemporaneously with pyrrhotite and tellurobismuthite deposition early during G4 shearing. These results in structural and mineralogical aspects at the Central Manitoba mine trend provide new constraints on structural evolution and gold mineralization of the southeastern Rice Lake belt, and can be used to improve exploration models for gold deposits in Archean terranes.