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TitleGeologic evolution of the world's most prolific Archean VMS-bearing sequence: the Blake River Group, Abitibi Greenstone Belt, Canada
AuthorGoutier, J; McNicoll, V; Mercier-Langevin, P; Dion, C; Ross, P -S
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 34, 2011 p. 78
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130569
MeetingGAC-MAC-SEG-SGA Joint Annual Meeting 2011; Ottawa; CA; May 25-27, 2011
File formatpdf
NTS32D/03NE; 32D/06; 32D/07
AreaRouyn Noranda; Lac Chassignolle; Malartic
Lat/Long WENS-79.5000 -78.5000 48.5000 48.1667
Subjectseconomic geology; igneous and metamorphic petrology; mineral occurrences; mineral deposits; mineral potential; mineralization; gold; volcanogenic deposits; sulphides; sulphide deposits; lithogeochemistry; greenstone belts; greenstones; igneous rocks; volcanic rocks; tholeiites; basalts; andesites; lithostratigraphy; Archean; Abitibi Greenstone Belt; Laronde Penna Deposit; Blake River Group; Bousquet Deposit; Doyon Deposit; Precambrian; Proterozoic
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
AbstractThe Blake River Group (BRG) hosts the world's largest Archean VMS cumulative tonnage with 371 Mt of ore (production and reserves) from 30 deposits. It contains almost half of the entire Abitibi greenstone belt VMS tonnage (806 Mt). The 2704-2695 Ma BRG represents the youngest episode of abundant submarine volcanism in the Abitibi. Recent research conducted in the BRG shows that VMS-forming events occurred about every m.y. and that Au-rich VMS deposits were formed during two distinct events (Horne and Quemont at 2702-2701 Ma, and Bousquet 2-Dumagami and LaRonde Penna at 2698-2697 Ma). Precise U-Pb geochronology, lithogeochemistry and volcanology indicate that the BRG is not the result of a simple gradual succession of tholeiitic to calc-alkaline volcanic units, a "layercake" succession of cycles, or a submarine megacaldera complex. Instead, the BRG was created by the simultaneous formation of different styles of volcanic edifices and settings associated with major extension and subsidence. Developed on a komatiitic-tholeiitic substratum (2710-2702 Ma Tisdale-Malartic-type units), the BRG construction started with the formation of a tholeiitic lava plain coeval with the development of bimodal volcanic centers (stage 1). The oldest VMS deposits of the BRG are associated with felsic centres of this stage (e.g. Horne and Quemont). This was followed by major extension and tholeiitic to transitional, maficdominated bimodal volcanism in the central part of the BRG where a graben structure was developed, and by transitional to calc-alkaline intermediate to felsic volcanism in the eastern and western parts of the BRG (stage 2). The typical Noranda-type VMS deposits (e.g. Amulet and Millenbach) are associated with the stage 2 graben and mafic-dominated bimodal rocks, whereas the Au-rich VMS deposits of the Doyon-Bousquet-LaRonde mining camp (e.g. Bousquet 2-Dumagami and LaRonde Penna) are associated with intermediate-felsic centres in the eastern part of the BRG. The last stage of volcanism is characterized by a new tholeiitic episode comprising abundant rhyolitic rocks, a large mafic-intermediate volcaniclastic basin, and local intermediatefelsic centres of transitional to calc-alkaline magmatic affinity hosting the youngest VMS deposits of the BRG (e.g. Bouchard- Hebert). When compared to the other volcanic units of the Abitibi, the BRG shows a greater variety of volcanic styles and settings, which may explain its unique VMS endowment. The BRG was most probably formed in a back-arc basin setting and the associated arc, if it existed, may have been located north of the BRG.