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U-Pb geochronology of the Blake River Group, Abitibi greenstone belt, Quebec, and implications for base metal exploration.

McNicoll, Vicki; Goutier, Jean; Dubé, Benoît; Mercier-Langevin, Patrick; Ross, Pierre-Simon; Dion, Claude; Monecke, Thomas; Legault, Marc; Percival, John; Gibson, Harold L. (2014). U-Pb geochronology of the Blake River Group, Abitibi greenstone belt, Quebec, and implications for base metal exploration. Economic Geology , vol. 109 , nº 1. p. 27-59. DOI: 10.2113/econgeo.109.1.27.

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Résumé

The 2704 to 2695 Ma Blake River Group in the southern Abitibi greenstone belt comprises a well preserved submarine volcanic sequence that hosts a large number of VMS and important Au-rich VMS deposits, including the world-class Horne and LaRonde-Penna deposits. Establishing precise chronostratigraphic control on the VMS deposits within the Blake River Group is critical because numerous distinct events took place within a period of 9 m.y. Nineteen new high-precision U-Pb ages temporally constrain the host rocks of many polymetallic VMS deposits and associated synvolcanic intrusions, demonstrating that these VMS deposits formed throughout the protracted volcanic evolution of the entire group. Ages on host rocks of the Horne (2702.2 ± 0.9 Ma), Quemont (2702.0 ± 0.8 Ma), and Fabie (2701.9 ± 0.9 Ma) deposits reveal that they are among the oldest VMS deposits in the Blake River Group. The giant Horne Au-rich VMS deposit had already formed when the Cu-Zn deposits of the Noranda mine sequence, including Millenbach and Amulet, were generated at ~2698 Ma and is thus unrelated, consistent with its different volcanological setting and metal content. Large Au-rich VMS deposits of the Bousquet Formation, including LaRonde Penna and Bousquet 2-Dumagami, were formed at 2698 to 2697 Ma and are distinctly younger than the Horne and Quemont deposits. There were, therefore, two major time-stratigraphic intervals within the Blake River Group that were favorable for the formation of Au-rich VMS deposits. Rhyolite hosting the large Bouchard-Hébert VMS deposits yielded an age of 2695.8 ± 0.8 Ma. Important mineralizing events in the Blake River Group occur at ca. 2-m.y. intervals apart and are associated with major magmatic episodes. Recognition of specific time-stratigraphic intervals for different styles of mineralization and geologic settings is essential to improve exploration models within the Blake River Group and for similar volcanic assemblages elsewhere in the Archean.

Type de document: Article
Mots-clés libres: exploration model; geologic settings; greenstone belts; high-precision; metal content; U-Pb geochronology; volcanic assemblages; volcanic evolution
Centre: Centre Eau Terre Environnement
Date de dépôt: 18 avr. 2018 13:34
Dernière modification: 18 avr. 2018 13:34
URI: http://espace.inrs.ca/id/eprint/3774

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