GEOSCAN, résultats de la recherche


TitreA Paleoproterozoic Andean-type iron oxide copper-gold environment, the Great Bear magmatic zone, Northwest Canada
AuteurOotes, L; Snyder, D B; Davis, W; Acosta-Gongora, P; Corriveau, L; Mumin, A H; Gleeson, S A; Samson, I M; Montreuil, J F; Potter, E; Jackson, V A
SourceOre Geology Reviews vol. 81, pt. 1, 2016 p. 123-139,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20150397
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceTerritoires du Nord-Ouest
SNRC86L; 86K; 86C; 86D; 86E; 86F
Lat/Long OENS-120.0000 -116.0000 67.0000 63.0000
Sujetsoxydes de fer; or; cuivre; apatite; magmatisme; Terrane d'Hottah ; tectonique; minéralogie; minéraux métalliques; géochimie
Illustrationslocation maps; tables; photographs; diagrams; graphs; plots
ProgrammeÉtude des gîtes porphyriques, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
Iron oxide copper-gold (IOCG) and associated iron-oxide apatite (IOA) styles of metallic mineralization are recognized throughout the Paleoproterozoic Great Bear magmatic zone of the northwest Canadian Shield. The Great Bear magmatic zone was constructed between ca. 1876 and 1855 Ma on top of the older Hottah terrane, which preserves continental arc magmatism that began around ca. 2.0 to 1.97 Ga and continued between ca. 1.93 and 1.89 Ga. The Great Bear represents the final stages of ca. 150 million years of intermittent and pulsed magmatism related to an evolving continental orogenic belt. The preserved geology supports a dramatic geodynamic change in the subduction zone process at ca. 1875 Ma, a key driving mechanism for magma and metal mobilization, and was rapidly followed by a large-scale introduction of felsic-intermediate plutons. The overall tectonic setting is partially constrained from new and previously published geochemical data that show that the volcanic and plutonic rocks are high-K calc-alkaline to shoshonitic in nature (e.g., high K2O, Th/Yb, and Ce/P205). They also have suprasubduction-zone geochemical signatures, including primitive mantle normalized positive Th and negative Nb, P, and Ti anomalies. The data support the primary melts were derived from a GLOSS-modified mantle wedge. Three-dimensional rendering of geophysical datasets suggest that two (of four) preserved surfaces within the upper mantle lithosphere, at 70 to 120 km depths, represent frozen, subducted oceanic slabs, and likely were the drivers for the bulk of Hottah and Great Bear arc magmatism. The older slab is northwest-striking and dips 12° to 15° northeast, whereas the younger is deeper and north-striking, dipping 13° east. The geometry of the surfaces are comparable with 4D modeling, where a subduction zone is temporarily shut down due to plateau collision, and then steps oceanward and re-initiates; there is no need for polarity reversal of the subduction system. This new geometry and the related inferences about process should be the focus of future research in the region, but for the time-being it can be stated that these subduction and collisional processes were the first order control on lithospheric evolution, and therefore metallic mineralization. Overall, the Great Bear magmatic zone IOCG and related mineralization is not comparable to other Proterozoic IOCG belts, such as those in Australia. However, the complexity of mineralization styles, the spatial-temporal relationship between IOA and IOCG mineralization, the suprasubduction zone environment, and a major change in tectonic regime are features similar to Andean-type IOCG mineralization, as well as Cordilleran alkali porphyry Cu-Au deposits. This further establishes the linkages between subduction zone processes and IOCG formation, as well as relationships in the IOCG-porphyry deposit continuum model.
Résumé(Résumé en langage clair et simple, non publié)
Cette contribution RNCan du programme de l'Initiative géoscientifique ciblée fait partie d'une série d'articles scientifiques soumis pour un volume spécial sur les gîtes polymétalliques à oxydes de fer du Missouri et des Territoires du Nord-Ouest organisé par des chercheurs du USGS et de la Commission géologique du Canada. L'article optimise la géoscience régionale du programme de la Géocartographie de l'Énergie et des Minéraux dans la région du Grand lac de l'Ours. Les travaux ont été menés en collaboration avec le bureau géoscientifique des Territoires du Nord-Ouest, le secteur privé (Fortune Minerals Ltd), la communauté Tlicho de Gamètì et des universitaires.