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TitreIntegrated geodatabase study of the complexly deformed U-hosting Paleoproterozoic Amer Group, Nunavut
AuteurCalhoun, L; White, J C; Jefferson, C W; Patterson, J; Tschirhart, V
SourceCommission géologique du Canada, Présentation scientifique 19, 2014, 26 pages, (Accès ouvert)
ÉditeurRessources naturelles Canada
Documentpublication en série
Mediaen ligne; numérique
Référence reliéeCette publication est reliée Calhoun, L J; White, J C; Jefferson, C W; Tschirhart, V; Patterson, J G; (2012). Integrated geodatabase study of the complexly-deformed U-hosting Paleoproterozoic Amer Group, Nunavut, Association géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 35
Formatsppt; pdf
SNRC66H/06; 66H/07; 66H/08; 66H/09; 66H/10; 66H/11
Lat/Long OENS-97.1167 -96.2833 65.6167 65.4167
Sujetsanalyses stratigraphiques; corrélations stratigraphiques; caractéristiques structurales; interpretations structurelles; analyses structurales; levés géophysiques; levés aéromagnétiques; interprétation aéromagnétique; uranium; granites; failles; syenites; lithostratigraphie; Archéen; Groupe d'Amer ; Bassin de Thelon ; minéraux radioactifs; stratigraphie; géologie structurale; géophysique; Protérozoïque; Précambrien
Illustrationsstratigraphic columns; photographs; location maps; block diagrams
ProgrammeUranium, GEM : La géocartographie de l'énergie et des minéraux
Diffusé2014 01 23
Résumé(disponible en anglais seulement)
The uranium-hosting Paleoproterozoic Amer Group, central Nunavut, comprises four dominantly sedimentary sequences (Ps1 through Ps4) deposited unconformably on Archean basement of the Rae sub-province. Ps1 is characterized by Ayagaq fm. quartzites formed in a stable cratonic and/or marine setting, with minor conglomerate and/or a distinctive schist at its base. PS2 is a sharply transgressive sequence of graphitic siltstone (Resort Lake fm.) shallowing up to dolostone (Aluminium River fm.) and intercalated to overlying porphyritic basalt (Five Mile Lake fm.). Ps3 comprises three units recording an overall coarsening- then shallowing-upward sequence involving siltstone to feldspathic arenite (Three Lakes, Oora Lake and Showing Lake formations). Ps3 is the primary host of U-mineralization in this region. Ps4 arkose (Itza Lake fm.) is preserved as isolated occurrences above a profound unconformity. The Amer Group is intensely deformed. D1 produced multiple transposition (three fold generations) and displacement along discrete detachments resulting in sub-horizontal axial surfaces and tectono-stratigraphy. D2 generated the regional, generally upright synclinoria, and is separated from D1 by the Ps3-Ps4 unconformity. Late D3 folds with sub-horizontal axial surfaces are rare. The region is transected by arrays of ENE- and NW- trending faults.
Elucidation of the structure of Ps3 units is central to determining the distribution of U-mineralization in the Amer Group. The difficulties of dealing with a polydeformed terrane are exacerbated by the absence of exposure in critical areas. This problem has been overcome by integrating detailed outcrop examination with high-resolution aeromagnetic data, and legacy drill hole data. The analysis is dependent on the strong, but distinct magnetic responses of the euhedral disseminated magnetite-bearing fine siliciclastic Three Lakes and Showing Lakes formations that, in preserved stratigraphic sequences, are separated by the Oora Lake fm. The aforesaid approach has enabled identification of a consistent, yet distinctly different geometry for the Amer Group "basins". In contrast to the apparent straightforward structure of the regional D2 synclinoria, it is demonstrated that the D1 tectono-stratigraphy forms large, regional recumbent structures masked by the lack of outcrop, but for which evidence occurs at all scales and within separate data sets i.e. field, geophysics, drill hole. The occurrence in some areas of elongate "cigar-shaped" mineralized zones reflects U-concentration within D1 hinge zones coaxially overprinted by D2. The success of this study in integrating diverse data bases, especially high-resolution geophysics and detailed outcrop mapping, argues for the future extension of such approaches.
Résumé(Résumé en langage clair et simple, non publié)
Le Groupe d'Amer du Paléoprotérozoïque, qui renferme de l'uranium, est situé à quelque 150 km de Baker Lake, au Nunavut. Il comporte quatre séquences sédimentaires (Ps1 à Ps4), dont la séquence Ps2 qui renferme du basalte tholéiitique. Le socle archéen et les séquences Ps1 à Ps3 ont subi anciennement une déformation, une dislocation et des plissements isoclinaux de translation à plusieurs phases, y compris des plis en fourreau orientés vers le nord-est. Plusieurs déformations subséquentes ont affecté la séquence Ps4 et les roches plus anciennes, alors que D2 créait des structures à l'échelle macroscopique. Les plis et les linéations D1 et D2 présentent la même orientation à plusieurs endroits, et les zones uranifères prometteuses disséminées, en forme de cigares, présentent également une attitude plongeante vers le sud-ouest.