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TitleThe Bousquet 2-Dumagami world-class Archean Au-rich volcanogenic massive sulphide deposit, Abitibi: Metamorphosed submarine advanced argillic alteration footprint and genesis
AuthorDubé, B; Mercier-Langevin, P; Kjarsgaard, I; Hannington, M; Bécu, V; Côté, J; Moorhead, J; Legault, M; Bédard, N
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 36, 2013 p. 87-88
Alt SeriesEarth Sciences Sector, Contribution Series 20130528
PublisherGAC MAC
Meeting GAC-MAC 2013; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Winnipeg; CA; May 22-24, 2013
Mediapaper; on-line; digital
File formatpdf
NTS32D/01; 23D/02; 32D/07; 32D/08
Lat/Long WENS -78.6033 -78.4111 48.2922 48.2242
Subjectsmetallic minerals; geochemistry; structural geology; Archean; gold; volcanogenic deposits; sulphide deposits; alteration; metamorphism; veins; breccias; pyrite; silver; copper; zinc; mineral assemblages; mineralization; exploration guidelines; lithology; volcanic rocks; mineral deposits; structural features; boudinage; folds; structural interpretations; lineations; deformation; foliation; hydrothermal alteration; electron probe analyses; metallogeny; Doyon- Bousquet-LaRonde mining camp; Abitibi greenstone belt; Massive Hangingwall zone; Zone 5; Precambrian
ProgramTargeted Geoscience Initiative (TGI-4), Volcanogenic Massive Sulfide Ore Systems
AbstractThe Bousquet 2-Dumagami deposit is an Archean Au-rich volcanogenic massive sulphide deposit (VMS) with a total production of ~4 Moz Au. The deposit is located within the Doyon-Bousquet- LaRonde mining camp in northwestern Quebec and hosted by the 2704- 2695 Ma Blake River Group, the world's most productive volcanic assemblage for Au-rich VMS deposits. The deposit consists of stacked, deformed and transposed semimassive to massive pyrite-rich lenses, breccia zones and associated sulphide veins and stringer zones hosted by the upper member of the Bousquet Formation. The main ore zone is known as the Massive Hangingwall Zone or as Zone 5. Another semimassive to disseminated pyrite-rich auriferous zone with coarsely recrystallized massive pyrite is present in the footwall. The Massive Hangingwall Zone is a Au-Ag-Cu-Zn sheet-like, semimassive to massive, pyrite-rich sulphide lens intermixed with vein and breccia zones. The dominant ore type consists of Au-Cu mineralization, but its upper and eastern parts are enriched in Zn. The ore consists of a complex assemblage of sulphides, sulphosalts and native gold, including abundant pyrite, sphalerite, a few percent of chalcopyrite, bornite, and galena, with some visible gold. The Massive Hangingwall Zone was formed by subsea-floor replacement of footwall calc-alkaline dacitic volcaniclastic rocks and hanging-wall blue quartz-phyric rhyolite. Despite significant N-S shortening and metamorphism, which was responsible for transposition, flattening, folding and recrystallization, a number of different metamorphic mineral assemblages can be mapped over several tens of meters from distal to proximal to the ore: (1) quartz-muscovite±Mn-garnet±biotite±chlorite; (2) quartzmuscovite± pyrite; (3) quartz-muscovite-andalusite-pyrophyllite-pyrite with topaz and diaspore; (4) massive quartz-pyrite. All metamorphosed alteration assemblages are characterized by strong progressive Na2O depletion. Gains in MnO, Fe2O3T, MgO, and CaO are recorded in the quartz-muscovite ± Mn-garnet ± biotite ± chlorite assemblage. In the quartz-muscovite-andalusite-pyrophyllite-pyrite and the proximal massive quartz-pyrite assemblages all oxides, except SiO2, Fe2O3T and TiO2, were strongly to almost entirely leached. The andalusite-kyanite-pyrophyllite-bearing aluminous assemblages are interpreted to represent metamorphosed equivalents of synvolcanic advanced argillic-style alteration, whereas the massive quartz-pyrite assemblage is similar to the massive silicic alteration. Gold emplacement is considered synvolcanic, coeval with the formation of the sulphide zones, and similar to the age of the host rhyolite (2697.8 Ma) and overlying felsic volcanic rocks (2697.5 Ma). The major Au endowment of the Doyon-Bousquet-LaRonde mining camp may be related to favourable source rock or Au reservoirs specific to the lower crust or upper mantle beneath the eastern Archean Blake River Group.