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TitleThe Westwood deposit, southern Abitibi greenstone belt: a “hybrid” or “transitional” Archean gold deposit
AuthorYergeau, D; Mercier-Langevin, P; Dubé, B; Malo, M; Wright-Holfeld, A; Bernier, C; Savoie, A; Houle, H; Simard, P
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 35, 2012 p. 154
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130593
Meeting2012 GAC-MAC-SEG-SGA Joint Annual Meeting; St-Johns; CA; May 27-29, 2011
File formatpdf
AreaRouyn-Noranda; Doyon; LaRonde; Abitibi; Bousquet
Lat/Long WENS-78.5000 -78.0000 48.2500 48.0000
Subjectsmetallic minerals; volcanic rocks; mineral deposits; mineralization; Archean; volcanogenic deposits; sulphide deposits; hydrothermal alteration; hydrothermal deposits; Westwood gold deposits; Precambrian
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
AbstractThe Westwood deposit (~3.7 Moz of Au) is part of the Doyon-Bousquet- LaRonde mining camp that is located in the eastern part of the Blake River Group in the southern Abitibi greenstone belt. The deposit is hosted in the volcanic rocks of the 2699-2696 Ma Bousquet Formation, which forms a steeply south-dipping, east-trending homoclinal sequence that faces south. The Bousquet Formation, which is interpreted as the remnants of a stratovolcano, has been divided in a lower member composed of mafic to felsic volcanic rocks of tholeiitic to transitional affinity and an upper member dominated by intermediate to felsic volcanic rocks of transitional to calc-alkaline affinity. The study area is metamorphosed to the greenschist-amphibolite facies transition and the deformation is regionally heterogeneous with highly strained corridors. The deposit consists of three distinct mineralized corridors that are stacked from north (base) to south (top): (1) Zone 2 Extension; (2) North Corridor; and (3) Westwood-Warrenmac Corridor. Mineralization in the Zone 2 Extension consists of cm- to dm-wide pyrite- and chalcopyrite-rich auriferous quartz veins. The North Corridor mineralization consists of cm to dm-wide auriferous quartz-pyrite-chalcopyrite ± sphalerite veins as well as thin, semi-massive to massive sulphide veins. The veins and alteration halo of these two corridors are slightly discordant to the stratigraphy and main foliation and are possibly associated with the Mooshla synvolcanic pluton located west of Westwood. Finally, the Westwood-Warrenmac Corridor mineralization consists of discontinuous, stratabound Au-rich polymetallic semi-massive to massive sulphide lenses and disseminations. The Warrenmac lens, which is representative of the VMS-type Westwood-Warrenmac Corridor mineralization, is characterized by pyritesphalerite- chalcopyrite ± galena-pyrrhotite massive sulphides overlain by a highly transposed pyrite-sphalerite ± chalcopyrite stringer zone. The footwall of the lens is characterized by a volcaniclastic dacite cut by a massive andesite sill (?), whereas the hangingwall composition is variable and consists of andesite, volcaniclastic dacite-rhyodacite, and quartzphyric rhyolite. Sericite, quartz, Mg-chlorite and Mn-garnet define the main proximal alteration assemblage (metamorphic equivalents of primary alteration-related minerals) to the Warrenmac lens. Studying the Westwood deposit and its environment represents a unique opportunity to test the working hypothesis of a continuum between vein-type mineralizations associated with a synvolcanic intrusion and auriferous massive sulphide lenses, and therefore contribute to a better understanding of Archean auriferous magmatic-hydrothermal systems. The knowledge gained in this project will help improve the current exploration models for Au and VMS deposits in the Abitibi greenstone belt and elsewhere.