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TitleIndicator mineral and till geochemical signatures of the Nico Co-Au-Bi deposit, Great Bear Magmatic Zone, NWT: Results and progress report
AuthorMcMartin, I; Corriveau, L; Beaudoin, G; Averill, S; Neale, K
Source36th Annual Yellowknife Geoscience Forum, Abstracts of talks and posters; by Jackson, V; Irwin, D; Northwest Territories Geoscience Office, Yellowknife Geoscience Forum Abstracts Volume vol. 2008, 2008 p. 43-44 (Open Access)
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20080421
Meeting36th Annual Yellowknife Geoscience Forum; Yellowknife; CA; November 18-20, 2008
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaGreat Bear Lake
Subjectssurficial geology/geomorphology; geochemistry; economic geology; indicator elements; glacial deposits; tills; till geochemistry; cobalt; gold; bismuth; mineralization; mineral occurrences; oxides; iron oxides; exploration; mineral exploration; geochemical surveys; geochemical analyses; sulphides; chalcopyrite; pyrite; molybdenite; arsenopyrite; Great Bear magmatic zone; Nico Deposit; indicator minerals
ProgramNorthern Mineral Development Program
AbstractTo establish a practical guide to geochemical and mineralogical exploration for Iron Oxide Copper-Gold±U (IOCG(U)) deposits in glaciated terrain, an orientation study around the NICO cobalt-gold-bismuth deposit in the Great Bear magmatic zone (GBMZ) of N.W.T. was initiated in 2007. This work is part of a joint government-industry-academia research project taking place under the government TGI-3 and SINED program umbrellas. Bedrock and till samples were collected at NICO over mineralization, host rocks and alteration zones, and in background terrain, to characterize the indicator mineral and alteration geochemical signatures of these domains.

Indicator mineral picking (0.18-2 mm, S.G.>3.2) from 27 bedrock samples indicates the presence of arsenopyrite, magnetite, tourmaline and ferroactinolite in various concentrations in the suite of ore/gangue/alteration heavy minerals, essentially in the 0.25-0.5 mm fraction. The magnetite occurs as individual grains but also disseminated in crushed bedrock fragments. When present, the tourmaline is very fine grained and intercalated with quartz so that few grains are heavier than S.G. 3.2 in the >0.18 mm fraction. Ferroactinolite is abundant in a few samples in association with arsenopyrite. Bismuthinite can also be present but is so fine-grained that it is recovered only in the pan concentrate or as inclusions in coarser-grained arsenopyrite. Gold is rarely present in the bedrock concentrates suggesting that most of the gold is encapsulated in the arsenopyrite. Very few mineral species present in the bedrock samples appear to have been preserved in the 13 till samples collected in the upper C-horizon soils. Indicators of mineralization are essentially restricted to samples collected near the Bowl Zone and consist of chalcopyrite, bismutite, gedrite and ferroactinolite. Pyrite and (rarely) pyrrhotite are present but only in the pan concentrate (<0.1 mm). Pristine gold grains are relatively abundant in till immediately down-ice (<200 m) of #2 Zone and #3 Zone. Electron microprobe analysis and examination of selected grains will help to develop criteria that contribute vectors to mineralization.

Lithogeochemistry and till geochemical methods are used in conjunction with indicator mineral methods to identify important pathfinder elements and extract geochemical criteria for IOCG(U) mineralization. Additional orientation studies in the GBMZ are planned to further develop reference rock and mineral indicator and geochemical databases.