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TitleInterpretation of airborne geophysical data for the Thor Lake area, Northwest Territories
DownloadDownload (whole publication)
AuthorCharbonneau, B W; Legault, M I
SourceStudies of rare-metal deposits in the Northwest Territories; by Sinclair, W D (ed.); Richardson, D G (ed.); Geological Survey of Canada, Bulletin 475, 1994 p. 17-31, (Open Access)
PublisherNatural Resources Canada
Mediapaper; on-line; digital
RelatedThis publication is contained in Sinclair, W D; Richardson, D G; (1994). Studies of rare-metal deposits in the Northwest Territories, Geological Survey of Canada, Bulletin no. 475
File formatpdf
ProvinceNorthwest Territories; Nunavut
NTS85I/01; 85I/02; 85I/03; 85I/04; 76C; 76F; 75N; 76N; 56M; 56N; 27C; 85K; 85L; 85M; 85N; 86C; 86D; 86E; 86F
AreaGreat Slave Lake; Thor Lake
Lat/Long WENS-120.0000 -116.0000 66.0000 62.0000
Lat/Long WENS-110.0000 -108.0000 66.0000 63.0000
Lat/Long WENS-110.0000 -108.0000 68.0000 67.0000
Lat/Long WENS-96.0000 -92.0000 68.0000 67.0000
Lat/Long WENS-72.0000 -70.0000 70.0000 69.0000
Lat/Long WENS-113.0000 -112.0000 62.2500 62.0000
Subjectsgeophysics; geochemistry; e m surveys, airborne; e m interpretations; e m surveys; geophysical interpretations; magnetic surveys, airborne; magnetic interpretations; magnetic surveys; gamma-ray surveys; uranium; thorium; potassium; uranium thorium ratios; uranium potassium ratios; thorium-potassium ratios; v l f surveys, airborne; v l f interpretations; rare earths; beryllium; geophysical surveys; magnetic anomalies; v l f surveys; yttrium; niobium; tantalum; gallium; zirconium; alteration; analyses; major element analyses; trace element analyses; geochemical analyses; Archean; Blatchford Lake Intrusive Suite; Grace Lake Granite; Thor Lake Syenite; Caribou Lake Gabbro; Precambrian
Illustrationssketch maps; analyses; photomicrographs
ProgramCanada-Northwest Territories Mineral Development Agreement, 1987-1991
Released1994 05 01
AbstractRadiometric, magnetic, and electromagnetic patterns detected over the Blatchford Lake Intrusive Suite were investigated on the ground in order to gain a better understanding of this complex and the related Thor Lake rare-metal deposits (beryllium, yttrium, rare-earth elements, niobium, tantalum, zirconium, gallium). Bedrock radioelement concentrations in the Grace Lake Granite and Thor Lake Syenite, two major units of the Blatchford Lake complex, average 4.6% K2O (3.8% K), 3 ppm equivalent uranium, and 18 ppm equivalent thorium. Principal radioactive minerals in these rocks are zircon and bastnaesite with minor REE-rich apatite and monazite. Although the radioactivity of the Thor Lake deposits is typically one to two orders of magnitude higher than surrounding rocks, there is no apparent halo of uranium or thorium around the deposits. Felsic dykes within the Grace Lake Granite and Thor Lake Syenite are one order of magnitude more uraniferous or thoriferous than host rocks and are enriched in elements found in the Thor Lake deposits. A prominent magnetic anomaly in the western part of the complex is related to the Caribou Lake Gabbro. Two significant magnetic anomalies are present in the eastern part of the complex. One occupies the western half of the Thor Lake Syenite, and the other forms a crescent-shaped feature within the Grace Lake Granite. These two anomalies are related to magnetite produced by alteration of ferromagnesian minerals. The alteration may be either autometasomatic or related to fenitization by a nepheline syenite body which underlies the rare-metal deposits. The electromagnetic patterns relate primarily to conductive lake bottom material and faults.