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TitleThe B26 Cu-Zn-Ag-Au project, Brouillan volcanic complex, Abitibi greenstone belt, part 2: hydrothermal alteration and mineralization
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorFayard, Q; Mercier-Langevin, P; Daigneault, R; Perreault, S; Wodicka, NORCID logo
SourceTargeted Geoscience Initiative 5: contributions to the understanding of Canadian gold systems; by Mercier-Langevin, P (ed.); Lawley, C J MORCID logo (ed.); Castonguay, SORCID logo (ed.); Geological Survey of Canada, Open File 8712, 2020 p. 109-125, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in Targeted Geoscience Initiative 5: contributions to the understanding of Canadian gold systems
File formatpdf
NTS32E/10; 32E/15
AreaAbitibi; Matagami
Lat/Long WENS -79.0000 -78.7500 49.8833 49.7167
Subjectseconomic geology; tectonics; igneous and metamorphic petrology; geochemistry; Nature and Environment; Science and Technology; Archean; mineral deposits; base metals; precious metals; gold; zinc; silver; copper; volcanogenic deposits; sulphide deposits; ore mineral genesis; mineralization; mineralization, primary; mineralization, secondary; hydrothermal alteration; mineral exploration; exploration guidelines; host rocks; bedrock geology; structural features; faults; shear zones; lithology; igneous rocks; intrusive rocks; felsic intrusive rocks; gabbros; volcanic rocks; andesites; dacites; rhyolites; lava flows; felsic volcanic rocks; mafic volcanic rocks; basalts; tuffs; volcano-sedimentary strata; sedimentary rocks; argillites; mafic rocks; iron formations; tectonic evolution; tectonic setting; magmatism; volcanism; intrusions; sills; domes; dykes; lenses; hydrothermal systems; metamorphism; deformation; foliation; lineations; mineral enrichment; alteration halos; sulphides; chalcopyrite; carbonates; veins; veinlets; mineral assemblages; gangue minerals; remobilization; zoning; marine environments; geometric analyses; Abitibi Greenstone Belt; Harricana-Turgeon Belt; B26 Property; Brouillan Volcanic Complex; Brouillan Group; Enjalran-Bapst Group; Brouillan Pluton; Selbaie Deposit; Precambrian
Illustrationslocation maps; geoscientific sketch maps; cross-sections; photographs; photomicrographs; tables; plots; lithologic sections; profiles; pie charts; schematic cross-sections
ProgramTargeted Geoscience Initiative (TGI-5) Gold ore systems
Released2020 06 11; 2023 03 17
AbstractThe B26 project is located in the northern Abitibi greenstone belt a few kilometres south of the past-producing Zn-Cu-Ag-Au Selbaie mine. It consists of a transposed Au-rich chalcopyrite stringer zone (Copper zone) overlain by concordant Ag-rich Zn-(Pb) sulphide lenses (Main Zinc zone) and disseminated to discordant sulphide vein- and veinlet-rich zones (Upper Zinc zone). The footwall rocks are affected by a wide and intense semi-conformable alteration halo mainly composed of sericite, chlorite, and quartz assemblages. Fe-Mn carbonate and quartz are common as gangue minerals in the sulphide lenses. The hanging-wall rocks are affected by a proximal K-feldspar-quartz and a more distal albite alteration with Fe-(Mn)-carbonate veins and replacement zones. The mineralized zones and host rocks have undergone major shortening during the main phase of regional deformation, which is responsible for transposition of the Cu-rich footwall stringers, flattening and stretching of the concordant semi-massive to massive sulphide zones, and local remobilization of precious metal-bearing phases into the south-dipping foliation and along the associated southwest-plunging stretching lineation.
Gold is directly associated with Cu, and also with Bi, Se, and Sn in the Copper zone as native gold, and Au-rich electrum with native Bi, bismuthinite, laitakarite, ikunolite, stannite, and cassiterite. Silver is present in the Main and Upper Zinc zones as freibergite, native silver, allargentum, acanthite, and pyrargyrite. Deposit-scale metal distribution and primary sulphide assemblages indicate that precious metals introduction was primary, although later local (metre-scale) remobilization occurred in response to deformation and metamorphism. Copper and Zn are decoupled at B26 and result from a strong vertical zonation in the system, suggesting an evolving geological environment with potentially a gradually shallowing seawater level. Shallow-water to subaerial conditions have been documented at the nearby Selbaie deposit, where they are considered responsible for the epithermal-style characteristics of the ore.
Summary(Plain Language Summary, not published)
The main objective of phase 5 (2015-2020) of Natural Resources Canada and Geological Survey of Canada's Targeted Geoscientific Initiative (TGI) program was to generate new knowledge, methodologies and models to enhance the exploration industry's ability to detect buried ore deposits. This synthesis volume contains 20 individual papers that discuss craton to deposit-scale characteristics of auriferous deposits, plus some support material pertaining to the TGI-5 Gold project.

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