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TitleThe Archean Westwood Au deposit, southern Abitibi: telescoped Au-rich VMS and intrusion-related Au systems
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AuthorYergeau, D; Mercier-Langevin, P; Dubé, B; Malo, M; McNicoll, V J; Jackson, S E; Savoie, A; La Rochelle, F
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. 177-191, (Open Access)
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
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
File formatpdf
AreaDoyon; Bousquet; LaRonde; Abitibi
Lat/Long WENS -78.5000 -78.0000 48.2500 48.0000
Subjectseconomic geology; mineralogy; mineral deposits; mineralization; mineral occurrences; gold; silver; copper; zinc; lead; sulphides; sulphide deposits; alteration; hydrothermal alteration; volcanogenic deposits; Archean; lithogeochemistry; deformation; metamorphism; Doyon-Bousquet-LaRonde mining camp; Westwood Deposit; Abitibi Greenstone Belt; Bousquet Formation
Illustrationslocation maps; photographs; plots; tables
ProgramGold Ore Systems, Targeted Geoscience Initiative (TGI-4)
Released2015 06 11
AbstractThe Westwood deposit (3.74 Moz Au) is part of the Doyon-Bousquet-LaRonde mining camp. The deposit is hosted in the 2699-2996 Ma Bousquet Formation that forms a moderately to highly-strained, steeply south-dipping and east-west-trending, upper greenschist/lower amphibolite facies, homoclinal volcano-plutonic sequence that faces south.* The Westwood deposit consists of three east-west-trending and steeply south-dipping mineralized corridors that are stacked from north to south: the Zone 2 Extension, the North Corridor, and the Westwood Corridor. The Zone 2 Extension consists of transposed centimetre- to decimetre-wide pyrite } chalcopyritesphalerite- rich quartz veins and disseminations whereas the North Corridor consists of centimetre- to decimetre-wide quartz-pyrite-chalcopyrite } sphalerite-galena-pyrrhotite veins and disseminations as well as thin, semi-massive to massive sulphide veins. The Westwood Corridor consists of discontinuous stratabound polymetallic semi-massive to massive sulphide lenses, veins and disseminations.
The Westwood and North corridors are associated with a large, semi-conformable to discordant Mn-rich garnet and biotite distal alteration halo that hosts a zone of more proximal sericite-dominated alteration. The Zone 2 Extension is characterized by a 2-10-m wide zone of intense biotite and sericite (} gypsum) alteration and local alteration zones composed of an assemblage of quartz-andalusite-kyanite-pyrophyllite. Mapping and 3-D modeling of the alteration zones strongly suggests that the Zone 2 Extension alteration overprints that of the North and Westwood corridors.
The Westwood and North corridors are considered to be subseafloor to seafloor (VMS-type) mineralization, whereas the Zone 2 Extension vein system is proposed to represent the eastward extension of the intrusion-associated Doyon Au deposit located less than 1.5 km west of Westwood. The Doyon system is rooted in, and possibly genetically related to, the polyphase Mooshla synvolcanic intrusive complex. The three mineralized corridors at Westwood were probably formed in a ?2 Ma time span, as indicated by U-Pb zircon geochronology. By analogy with telescoped porphyry-epithermal systems, the three mineralized corridors of the Westwood deposit may represent various components of a submarine Archean auriferous synvolcanic magmatic-hydrothermal system, providing a unique opportunity to improve and expand metallogenic and exploration models for Archean greenstone belts.