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TitreThe Rainy River "atypical" Archean Au deposit, western Wabigoon Subprovince, Ontario
TéléchargerTéléchargement (publication entière)
AuteurPelletier, 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; par Dubé, B (éd.); Mercier-Langevin, P (éd.); Commission géologique du Canada, Dossier public 7852, 2015 p. 193-207,
ÉditeurRessources naturelles Canada
Documentdossier public
Mediaen ligne; numérique
Référence reliéeCette publication est contenue dans Dubé, B; Mercier-Langevin, P; (2015). Targeted Geoscience Initiative 4: Contributions to the understanding of Precambrian lode gold deposits and implications for exploration, Commission géologique du Canada, Dossier public 7852
SNRC52D/09; 52D/10; 52D/15; 52D/16; 52E/01; 52E/02
Lat/Long OENS -95.0000 -94.0000 49.2500 48.5000
Sujetsgéologie du substratum rocheux; caractéristiques structurales; Archéen; minéralisation; or; gîtes minéralogiques; roches ignées; roches volcaniques; altération; déformation; datations au uranium-plomb; Subprovince de Wabigoon ; stratigraphie; géologie structurale; géologie économique; géochronologie; Précambrien
Illustrationslocation maps; photographs; plots; photomicrographs
Bibliothèque de Ressources naturelles Canada - Ottawa (Sciences de la Terre)
ProgrammeÉtude des gîtes d'or, Initiative géoscientifique ciblée (IGC-4)
Diffusé2015 06 11
Résumé(disponible en anglais seulement)
The 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.