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Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 2. Origin, geochemistry, and geochronology

Ross, Pierre-Simon; McNicoll, Vicki; Goutier, Jean; Mercier-Langevin, Patrick; Dubé, Benoît (2011). Basaltic to andesitic volcaniclastic rocks in the Blake River Group, Abitibi Greenstone Belt: 2. Origin, geochemistry, and geochronology Canadian Journal of Earth Sciences , vol. 48 , nº 4. p. 757-777. DOI: 10.1139/E10-090.

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Résumé

In the Archean Blake River Group, mafic to intermediate fragmental units have controversially been proposed to have formed during the collapse of a giant submarine caldera. This paper describes and interprets these rocks, summarizing their physical characteristics, inferred origins, age relationships, and geochemical signatures. The widespread Stadacona member, south of Rouyn-Noranda, consists of several hundred meters of bedded volcaniclastic rocks interpreted to have been mostly deposited from aqueous density currents fed directly by explosive eruptions. The magmas involved in these eruptions were plagioclase-phyric tholeiitic to transitional basalts. The similarly widespread D’Alembert tuff, in the northern part of the Blake River Group, shares many physical characteristics with the Stadacona member and is thought to have a similar origin. However, the D’Alembert tuff is approximately six million years younger than the Stadacona member. It is composed mostly of transitional to calc-alkaline andesites and basaltic andesites with very distinct trace element profiles. Volcaniclastic rocks from other areas, such as Tannahill Township in Ontario and the Monsabrais area in Québec, are interpreted to represent mostly in situ to remobilized hyaloclastite, with no explosive eruptions involved in their genesis. Our observations and interpretations are not compatible with models in which the volcaniclastic units are emplaced during a catastrophic event in relation with the collapse of a giant caldera. Instead, the fragmental rocks were produced by various mechanisms at many distinct times during the evolution of the Blake River Group.

Type de document:
Mots-clés libres: unités volcanoclastiques mafiques; Groupe archéen de Blake River; géochimie; aves sous-marines mafiques; roches volcanoclastiques; Rouyn-Noranda; Stadacona
Centre: Centre Eau Terre Environnement
Date de dépôt: 17 déc. 2013 21:53
Dernière modification: 17 déc. 2013 21:53
URI: http://espace.inrs.ca/id/eprint/1904

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