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TitreGeologic evolution of the world's most prolific Archean VMS-bearing sequence: the Blake River Group, Abitibi Greenstone Belt, Canada
AuteurGoutier, J; McNicoll, V; Mercier-Langevin, P; Dion, C; Ross, P -S
SourceAssociation géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 34, 2011 p. 78
Année2011
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130569
Éditeurgac
RéunionGAC-MAC-SEG-SGA Joint Annual Meeting 2011; Ottawa; CA; mai 25-27, 2011
Documentpublication en série
Lang.anglais
Mediapapier
Formatspdf
ProvinceQuébec
SNRC32D/03NE; 32D/06; 32D/07
Lat/Long OENS-79.5000 -78.5000 48.5000 48.1667
Sujetsgîtes minéralogiques; gisements minéraux; potentiel minier; minéralisation; or; gîtes volcanogènes; sulfures; gîtes sulfureux; lithogéochimie; ceintures de roche verte; roches vertes; roches ignées; roches volcaniques; tholéiites; basaltes; andésites; lithostratigraphie; Archéen; Ceinture d'Abitibi Greenstone ; Dépôt de Laronde Penna ; Groupe de Blake River ; Dépôt de Bousquet ; Dépôt de Doyon ; géologie économique; pétrologie ignée et métamorphique; Précambrien; Protérozoïque
ProgrammeÉtude des gîtes d'or, Initiative géoscientifique ciblée (IGC-4)
LiensOnline - En ligne
Résumé(disponible en anglais seulement)
The 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.
GEOSCAN ID296043