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TitleThe direct indicator mineral concept and QEMSCAN® applied to exploration for carbonatite and carbonatite-related ore deposits
AuthorSimandl, G J; Mackay, D A R; Ma, X; Luck, P; Gravel, J; Akam, C
SourceIndicator minerals in till and stream sediments of the Canadian Cordillera; by Ferbey, T (ed.); Plouffe, AORCID logo (ed.); Hickin, A S (ed.); Geological Association of Canada, Special Paper vol. 50, 2017 p. 175-190
Alt SeriesMineralogical Association of Canada, Topics in Mineral Sciences 47
PublisherGeological Association of Canada
PublisherMineralogical Association of Canada
RelatedThis publication is contained in Ferbey, T; Plouffe, A; Hickin, A S; (2017). Indicator minerals in till and stream sediments of the Canadian Cordillera, Geological Association of Canada, Special Paper vol. 50
ProvinceBritish Columbia
NTS93J; 93K; 93N; 93O; 94B; 94C
AreaAley Creek; Wicheeda Lake; Granite Creek
Lat/Long WENS-126.0000 -122.0000 57.0000 54.0000
Subjectseconomic geology; surficial geology/geomorphology; geochemistry; mineral deposits; mineral exploration; prospecting techniques; carbonatites; carbonatite complexes; stream sediment samples; x-ray fluorescence analyses; geochemical analyses; scanning electron microscope analyses; pyrochlore; columbite; geochemical anomalies; grain size analyses; grain size distribution; monazite; Canadian Cordillera; Aley Deposit; Wicheeda Deposit; Lonnie Deposit; British Columbia Alkaline Province; carbonate-hosted deposits; indicator minerals; high field strength elements (HFSE); rare earth elements (REE); QEMSCAN®; geochemical signatures; niobate; Phanerozoic; Cenozoic; Mesozoic; Paleozoic
Illustrationsgeoscientific sketch maps; tables; bar graphs; photographs; flow diagrams; photomicrographs; plots; ternary diagrams; diagrams
ProgramTargeted Geoscience Initiative (TGI-5), Specialty metal systems
ProgramTargeted Geoscience Initiative (TGI-4)
Released2017 01 01
AbstractIndicator minerals have long been used in diamond exploration and the approach has been expanded to search for other commodities. Orientation surveys using stream sediment samples collected from the drainages of three carbonatite-related deposits in the Canadian Cordillera (Aley, Lonnie, Wicheeda) establish that a number of carbonatite indicator minerals contain elevated concentrations of high field strength elements (HFSE), including rare earth elements (REE) and Nb. These elements are detectable by traditional geochemical or portable X-ray fluorescence (XRF) analyses of stream-sediment samples even if only a few indicator mineral grains are present. We refer to these minerals, which are rich in carbonatite pathfinder elements, as direct carbonatite indicator minerals (e.g., REE-fluorocarbonates, REE phosphates, pyrochlore supergroup minerals, and columbite-iron). These direct indicator minerals can also be effectively identified by QEMSCAN® (Quantitative Evaluation of Minerals by SCANning electron microscopy), a fully automated micro-analysis system that is widely available at commercial laboratories. There is a strong link between high concentrations of direct carbonatite indicator minerals and high concentrations of HFSE in stream sediments draining known carbonatites and related deposits. This relationship is the basis of the direct indicator mineral concept; only samples identified as geochemically anomalous by traditional laboratory or portable XRF analyses need to be examined for carbonatite indicator minerals by QEMSCAN®. Advantages of QEMSCAN® over traditional indicator mineral processing and analysis include the capability to: 1) identify minerals that are too small for hand picking; 2) provide automated, simultaneous indicator mineral grain counts and weight % equivalents; 3) perform detailed grain-size analysis on a mineral-by-mineral basis; 4) quantitatively assess abundances of free and polymineralic grains; and 5) identify mineral species within polymineralic grains. Because all samples are first geochemically analysed for carbonatite pathfinder elements, only those with concentrations above background need to be evaluated for carbonatite indicator minerals, thereby reducing costs. The direct indicator mineral concept in combination with QEMSCAN® analysis is an effective mineral exploration approach because it combines traditional geochemical analysis with the interpretative power of modern indicator mineral surveys. This approach may have exploration applications for deposits other than those that are carbonatite-hosted.

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