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TitleThe Rainy River "atypical" Archean Au deposit, western Wabigoon Subprovince, Ontario
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AuthorPelletier, M; Mercier-Langevin, P; Dubé, B; Crick, D; Tolman, J; McNicoll, V J; Jackson, S E; Beakhouse, G P
SourceTargeted Geoscience Initiative 4: Contributions to the understanding of Precambrian lode gold deposits and implications for exploration; by Dubé, B (ed.); Mercier-Langevin, P (ed.); Geological Survey of Canada, Open File 7852, 2015 p. 193-207, https://doi.org/10.4095/296639
Year2015
PublisherNatural Resources Canada
Documentopen file
Lang.English
RelatedThis publication is contained in Dubé, B; Mercier-Langevin, P; (2015). Targeted Geoscience Initiative 4: Contributions to the understanding of Precambrian lode gold deposits and implications for exploration, Geological Survey of Canada, Open File 7852
ProvinceOntario
NTS52D/09; 52D/10; 52D/15; 52D/16; 52E/01; 52E/02
AreaRainy River
Lat/Long WENS-95.0000 -94.0000 49.2500 48.5000
Subjectsstratigraphy; structural geology; economic geology; geochronology; bedrock geology; structural features; Archean; mineralization; gold; mineral occurrences; igneous rocks; volcanic rocks; alteration; deformation; uranium lead dates; Rainy River Gold deposit; Wabigoon Subprovince; Rainy River greenstone belt; Precambrian
Illustrationslocation maps; photographs; plots; photomicrographs
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Location
 
Natural Resources Canada Library - Ottawa (Earth Sciences)
 
ProgramGold Ore Systems, Targeted Geoscience Initiative (TGI-4)
Released2015 06 11
AbstractThe Rainy River project, located in the western Wabigoon Subprovince in western Ontario, is an advanced Au exploration project with an estimated 6.2 Moz Au and 14.6 Moz Ag in reserves and resources (New Gold Inc). The bulk of the Au and Ag mineralization occurs with pyrite, chalcopyrite, and sphalerite in disseminated } stockwork form, and part of the ore is within quartz-sulphide-tourmaline-carbonate veinlets that are subparallel to the main east-trending, south-dipping penetrative foliation (S2). Folded and transposed veins of quartz, Fe-carbonate, and tourmaline contain higher Au values, with Au in its native form or as electrum. At deposit-scale, there is a relatively good correlation between Au and Ag values, and between Au and Zn contents. Mineralization is concentrated in six zones that are elongated parallel to the main foliation. Higher grade zones are aligned within the main foliation plane along a stretching lineation (L2) plunging to the southwest.
The deposit is hosted mainly within dacitic to rhyodacitic calc-alkaline volcanic domes, flows, and associated flow breccia. The rocks were regionally metamorphosed to greenschist facies. The proximal to immediate alteration consists of a sericite }Fe-carbonate overprinted to various degrees by chlorite. Manganiferous garnet, chloritoid, and kyanite are present locally, in proximity to, or within, mineralized zones.
There is a strong correlation between the spatial distribution of the mineralization and the sericite-dominated alteration. Moreover, there is a direct correlation of stronger alteration intensity, higher-grade and/or more extensive mineralization, and host rocks of higher initial porosity (i.e. fragmental units), suggesting an early Au-Ag mineralization controlled by volcanism-related hydrothermal activity. Cross-cutting field relationships, preliminary laser-ablation inductively coupled plasma mass spectrometry analyses (LA-ICP-MS) of pyrite grains, and U/Pb ID-TIMS zircon geochronology further support the hypothesis of a synvolcanic origin for at least part of the Au mineralization. Subsequent deformation and metamorphism are responsible for transposition of the mineralized zones and metals within the main foliation plane and the associated stretching lineation, and for the modification of the primary alteration mineralogy to its greenschist-facies metamorphic equivalent.
GEOSCAN ID296639