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Volcanology and metallogeny of a sector of the Blake River Group, Abitibi subprovince, Québec and Ontario / Volcanologie et métallogénie d'un secteur du Groupe de Blake River, Sous-province de l'Abitibi, Québec et Ontario.

Rogers, Russell (2010). Volcanology and metallogeny of a sector of the Blake River Group, Abitibi subprovince, Québec and Ontario / Volcanologie et métallogénie d'un secteur du Groupe de Blake River, Sous-province de l'Abitibi, Québec et Ontario. Mémoire. Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en sciences de la terre, 170 p.

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Résumé

A promising approach to enhance volcanogenic massive sulfide (VMS) exploration in regions outside of mining camps is to simultaneously (1) combine physical volcanology with chemo-stratigraphy to establish the location of effusive centers in the volcanic units; and (2) combine pyrite geochemistry in sulphide-bearing stratified horizons with whole-rock geochemistry in the underlying volcanic units to identify hydrothermal up-flow zones. These concepts are illustrated by a study in the Archean Blake River Group within the Abitibi Subprovince of Quebec and Ontario. The Blake River Group contains numerous VMS deposits, yet large segments of it remain underexplored, including the area west of Lake Hébécourt. Five main tholeiitic units are identified in the Hébécourt Formation there: the Hébécourt basalt, the Hébécourt basaltic andesite, the main rhyolite (divided into low-Ti and high-Ti subunits), the upper rhyolite and the McDiarmid dacite. Even though the same units are present in both the east and the west, the stratigraphic order of these units is different. In addition, in the eastern region there are thin units of calc-alkaline geochemistry, which are similar to the younger Reneault-Dufresnoy Formation, intercalated within the units of the Hébécourt Formation. The more detailed information available in the east allowed likely emplacement mechanisms and effusive centers to be identified, using physical volcanology, for three felsic units and a basaltic andesite unit. The low-Ti subunit was emplaced as an extrusive submarine lava dome from a single vent, while the high-Ti subunit was emplaced as submarine lava flows or domes from two separate vents. The upper rhyolite was emplaced as lava flows or domes in several episodes from separate vents and the basaltic andesite was emplaced as pillowed flows from a single vent. Vents in the west could not be located. Known Zn-Cu mineralization includes sulphide stringers and disseminations located within the flank breccia of the low-Ti rhyolite dome, predominantly forming as replacement of the pore spaces of the fragmental units. Higher in the stratigraphy, this sector corresponds to the inferred volcanic vent area for the basaltic andesite unit. Laser Ablation Induced Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis of pyrite grains sampled from several sulphide-bearing stratified horizons in the eastern stratigraphy indicates two broad regions of higher Cu, Zn Au and Ag contents. The same peaks were identified using two methods: (1) using all samples regardless of Stratigraphic position and (2) using only samples from a single horizon, which could be correlated. The eastern region corresponds to known volcanic vents and mineralization. The western region also indicates up-flow of Cu-bearing hydrothermal fluids, and corresponds to a possible effusive centre for the high-Ti rhyolite. This western sector does not contain known mineralization at lower stratigraphic positions but it has not received significant exploration efforts yet.

Type de document: Mémoire
Directeur de mémoire/thèse: Ross, Pierre-Simon
Co-directeurs de mémoire/thèse: Mercier-Langevin, Patrick
Mots-clés libres: volcanologie; chimico-stratigraphie; géochimie; roche; géologie; métallogénie; Blake river; Abitibi
Centre: Centre Eau Terre Environnement
Date de dépôt: 20 févr. 2014 14:40
Dernière modification: 16 mars 2016 20:10
URI: http://espace.inrs.ca/id/eprint/1955

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