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TitleOre mineralogy, pyrite chemistry, and S isotope systematics of magmatic-hydrothermal Au mineralization associated with the Mooshla Intrusive Complex (MIC), Doyon-Bousquet-LaRonde mining camp, Abitibi greenstone belt, Québec
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LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorNeyedley, K; Hanley, J J; Mercier-Langevin, P; Fayek, M
SourceTargeted Geoscience Initiative 5: grant program final reports (2018-2020); by Targeted Geoscience Initiative Coordination Office; Geological Survey of Canada, Open File 8755, 2021 p. 129-148, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in Targeted Geoscience Initiative 5: grant program final reports (2018-2020)
File formatpdf
NTS32D/02NE; 32D/07SE
Lat/Long WENS -78.5903 -78.5011 48.2822 48.2489
Subjectseconomic geology; mineralogy; geochemistry; tectonics; Science and Technology; Nature and Environment; mineral exploration; mineral deposits; gold; copper; base metals; volcanogenic deposits; sulphide deposits; vein deposits; porphyry deposits; epithermal deposits; ore mineral genesis; mineralization; pyrite; isotopic studies; isotopes; sulphur; greenstone belts; tectonic setting; magmatism; intrusions; hydrothermal systems; fluid dynamics; petrographic analyses; mineral assemblages; sulphides; trace element geochemistry; bulk composition; mass spectrometer analysis; mineral occurrences; Archean; Mooshla Intrusive Complex; Doyon-Bousquet-LaRonde Mining Camp; Abitibi Greenstone Belt; Precambrian
Illustrationslocation maps; geoscientific sketch maps; tables; photographs; digital images; photomicrographs; plots
ProgramTargeted Geoscience Initiative (TGI-5) Knowledge Management Coordination
Released2021 10 27
AbstractThe Mooshla Intrusive Complex (MIC) is an Archean polyphase magmatic body located in the Doyon-Bousquet-LaRonde (DBL) mining camp of the Abitibi greenstone belt, Québec. The MIC is spatially associated with numerous gold (Au)-rich VMS, epizonal 'intrusion-related' Au-Cu vein systems, and shear zone-hosted (orogenic?) Au deposits. To elucidate genetic links between deposits and the MIC, mineralized samples from two of the epizonal 'intrusion-related' Au-Cu vein systems (Doyon and Grand Duc Au-Cu) have been characterized using a variety of analytical techniques.
Preliminary results indicate gold (as electrum) from both deposits occurs relatively late in the systems as it is primarily observed along fractures in pyrite and gangue minerals. At Grand Duc gold appears to have formed syn- to post-crystallization relative to base metal sulphides (e.g. chalcopyrite, sphalerite, pyrrhotite), whereas base metal sulphides at Doyon are relatively rare. The accessory ore mineral assemblage at Doyon is relatively simple compared to Grand Duc, consisting of petzite (Ag3AuTe2), calaverite (AuTe2), and hessite (Ag2Te), while accessory ore minerals at Grand Duc are comprised of tellurobismuthite (Bi2Te3), volynskite (AgBiTe2), native Te, tsumoite (BiTe) or tetradymite (Bi2Te2S), altaite (PbTe), petzite, calaverite, and hessite.
Pyrite trace element distribution maps from representative pyrite grains from Doyon and Grand Duc were collected and confirm petrographic observations that Au occurs relatively late. Pyrite from Doyon appears to have been initially trace-element poor, then became enriched in As, followed by the ore metal stage consisting of Au-Ag-Te-Bi-Pb-Cu enrichment and lastly a Co-Ni-Se(?) stage enrichment. Grand Duc pyrite is more complex with initial enrichments in Co-Se-As (Stage 1) followed by an increase in As-Co(?) concentrations (Stage 2). The ore metal stage (Stage 3) is indicated by another increase in As coupled with Au-Ag-Bi-Te-Sb-Pb-Ni-Cu-Zn-Sn-Cd-In enrichment. The final stage of pyrite growth (Stage 4) is represented by the same element assemblage as Stage 3 but at lower concentrations. Preliminary sulphur isotope data from Grand Duc indicates pyrite, pyrrhotite, and chalcopyrite all have similar delta-34S values (~1.5 ± 1 permille) with no core-to-rim variations.
Pyrite from Doyon has slightly higher delta-34S values (~2.5 ± 1 permille) compared to Grand Duc but similarly does not show much core-to-rim variation. At Grand Duc, the occurrence of Au concentrating along the rim of pyrite grains and associated with an enrichment in As and other metals (Sb-Ag-Bi-Te) shares similarities with porphyry and epithermal deposits, and the overall metal association of Au with Te and Bi is a hallmark of other intrusion-related gold systems. The occurrence of the ore metal-rich rims on pyrite from Grand Duc could be related to fluid boiling which results in the destabilization of gold-bearing aqueous complexes. Pyrite from Doyon does not show this inferred boiling texture but shares characteristics of dissolution-reprecipitation processes, where metals in the pyrite lattice are dissolved and then reconcentrated into discrete mineral phases that commonly precipitate in voids and fractures created during pyrite dissolution.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques, which will result in more effective targeting of buried mineral deposits. This compendium is the result of the TGI Grant Recipients 2018-2020.

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