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TitleTectonomagmatic evolution of the southern Great Bear magmatic zone (Northwest Territories, Canada) : Implications on the genesis of iron oxide-alkali-altered hydrothermal systems
AuthorMontreuil, J F; Corriveau, L; Davis, W J
SourceEconomic geology and the bulletin of the Society of Economic Geologists vol. 111, 2016 p. 2111-2138,
Alt SeriesEarth Sciences Sector, Contribution Series 20150285
PublisherSociety of Economic Geologists
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS86C; 86D; 86E; 86L; 86K
AreaSouthern Great Bear Magmatic Zone
Lat/Long WENS-119.0000 -116.0000 67.8333 63.0000
Subjectsgeochemistry; geochronology; potassium; orogenies; magmatism; iron oxides; copper; gold; mineralization; deformation; Southern Breccia; Lou assemblage; Mazenod assemblage; Bea assemblage; Sue-Dianne deposits
Illustrationslocation maps; geological sketch maps; diagrams; stratigraphic columns; graphs; plots; photographs; tables
ProgramTargeted Geoscience Initiative (TGI-4), Uranium Ore Systems
Released2016 11 16
AbstractThe Great Bear magmatic zone in northwestern Canada is a Paleoproterozoic volcano-plutonic belt of high K, calc-alkaline to shoshonitic affinity interpreted as a continental arc that formed between 1.87 and 1.85 Ga following the short-lived Calderian orogeny. Tectonomagmatic evolution of this magmatic zone favored the formation of multiple iron oxide and alkali alteration systems within a time frame of 10 m.y., as constrained geochronologically within error between 1875 and 1865 Ma. This illustrates a temporal and genetic relationship between shoshonitic to high K, calc-alkaline continental arc magmatism and the formation of iron oxide-rich deposits and alkali alteration associated with iron oxide-copper-gold (IOCG) mineralization. Early rhyolitic magmatism formed the basal sequence of the Lou assemblage under a compressive (or transpressive) tectonic regime. Between 1872 and 1867 Ma, an apparent higher magmatic production is linked to a marked change in composition of the volcanic and plutonic rocks, from rhyolite to intermediate/felsic and locally mafic. Compositional homogeneity of the intrusive and volcanic rocks of the Mazenod and Bea assemblages, termination of ductile to brittle-ductile deformation along the main deformation zones, and transition to widespread brittle fracturing and breccia formation are interpreted to reflect a change in the regional stress regime, from compressional/transpressional to extensional/transtensional. This change in stress regimes is associated with iron oxide-rich mineralization that initially formed the NICO Au-Bi-Co deposit, followed by IOCG mineralization in the NICO and Sue-Dianne deposits as well as albitite-hosted U mineralization in the Southern Breccia.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This contribution of the Targeted Geoscience Initiative program is part of a series of scientific papers submitted for a special issue on polymetallic iron oxide deposits of Missouri and the Northwest Territories organized by USGS and Geological Survey of Canada scientists. The paper uses the regional geoscience outcomes of the former Geomapping for Energy and Minerals program in the Great Bear Lake region. The research was conducted in collaboration with the Northwest Territories Geoscience Office, private sector exploration companies (Fortune Minerals Ltd), the Tlicho community of Gamètì, and academia.