| Titre | The Westwood deposit, southern Abitibi greenstone belt, Canada: An Archean Au-rich polymetallic magmatic-hydrothermal system Part 2. Hydrothermal alteration, mineralization, and geological model |
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| Auteur | Yergeau, D; Mercier-Langevin, P; Dubé, B; McNicoll, V J; Jackson, S E; Malo, M; Savoie, A |
| Source | Economic Geology vol. 117, no. 3, 2022 p. 577-608, https://doi.org/10.5382/econgeo.4879 |
| Image |  |
| Année | 2022 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20180399 |
| Éditeur | Society of Economic Geologists |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.5382/econgeo.4879 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Québec |
| SNRC | 32D |
| Lat/Long OENS | -80.0000 -78.0000 49.0000 48.0000 |
| Sujets | altération hydrothermale; mécanique des fluides; métamorphisme; enrichissement des minéraux; minéralogie; géologie générale; Précambrien |
| Illustrations | cartes de localisation; échelles stratigraphiques; cartes géologiques généralisées; photographies; tableaux; photomicrographies; profils géochimiques; graphiques |
| Programme | Initiative géoscientifique ciblée (IGC-5) Systèmes aurifères |
| Diffusé | 2022 05 01 |
| Résumé | (disponible en anglais seulement)
The Westwood deposit, located in the Archean Doyon-Bousquet-LaRonde mining camp in the southern Archean Abitibi greenstone belt, contains 4.5 Moz (140 metric t)
of gold. The deposit is hosted in the 2699- 2695 Ma submarine, tholeiitic to calc-alkaline volcanic, volcaniclastic, and intrusive rocks of the Bousquet Formation. The deposit is located near the synvolcanic (ca. 2699-2696 Ma) Mooshla Intrusive
Complex that hosts the Doyon epizonal intrusion-related Au ± Cu deposit, whereas several Au-rich volcanogenic massive sulfide (VMS) deposits are present east of the Westwood deposit. The Westwood deposit consists of stratigraphically stacked,
contrasting, and overprinting mineralization styles that share analogies with both the intrusion-related and VMS deposits of the camp. The ore zones form three distinct, slightly discordant to stratabound corridors that are, from north (base) to
south (top), the Zone 2 Extension, the North Corridor, and the Westwood Corridor. Syn- to late-main regional deformation and upper greenschist to lower amphibolite facies regional metamorphism affect the ore zones, alteration assemblages, and host
rocks. The Zone 2 Extension consists of Au ± Cu sulfide (pyrite-chalcopyrite)-quartz veins and zones of disseminated to semimassive sulfides. The ore zones are spatially associated with a series of calc-alkaline felsic sills and dikes that crosscut
the mafic to intermediate, tholeiitic to transitional, lower Bousquet Formation volcanic rocks. The metamorphosed proximal alteration consists of muscovite-quartz-pyrite ± gypsum-andalusitekyanite- pyrophyllite argillic to advanced argillic-style
tabular envelope that is up to a few tens of meters thick. The North Corridor consists of auriferous semimassive to massive sulfide veins, zones of sulfide stringers, and disseminated sulfides that are hosted in intermediate volcaniclastic rocks at
the base of the upper Bousquet Formation. The Westwood Corridor consists of semimassive to massive sulfide lenses, veins, zones of sulfide stringers, and disseminated sulfides that are located higher in the stratigraphic sequence, at or near the
contact between calc-alkaline dacite domes and overlying calc-alkaline rhyodacite of the upper Bousquet Formation. A large, semiconformable distal alteration zone that encompasses the North Corridor is present in the footwall and vicinity of the
Westwood Corridor. This metamorphosed alteration zone consists of an assemblage of biotite-Mn garnet-chlorite-carbonate ± muscovite-albite. A proximal muscovite-quartz-chlorite-pyrite argillicstyle alteration assemblage is associated with both
corridors. The Zone 2 Extension ore zones and associated alteration are considered synvolcanic based on crosscutting relationships and U-Pb geochronology and are interpreted as being the distal expression of an epizonal magmatic- hydrothermal system
that is centered on the upper part of the synvolcanic Mooshla Intrusive Complex. The North and Westwood corridors consist of bimodal-felsic Au-rich VMS-type mineralization and alteration produced by the convective circulation of modified seawater
that included a magmatic contribution from the coeval epizonal Zone 2 Extension magmatic-hydrothermal system. The Westwood Au deposit represents one of the very few documented examples of an Archean magmatichydrothermal system-or at least of such
systems formed in a subaqueous environment. The study of the Westwood deposit resulted in a better understanding of the critical role of magmatic fluid input toward the formation of Archean epizonal intrusion-related Au ± Cu and seafloor/subseafloor
Au-rich VMS-type mineralization. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Cette contribution présente de nouvelles données et informations sur la géologie du gisement d'or Westwood dans la ceinture de roches vertes de
l'Abitibi dans le nord-ouest québécois. Le focus est sur la description du minerai et des alterations hyddrothermales associées. La genèse du gisement et les implications sur les modèles d'exploration pour les gisements d'or sont dicsutées. |
| GEOSCAN ID | 313649 |
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