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TitleMagnetite composition applied to drift prospecting methods for IOCG exploration in the Great Bear magmatic zone, Canada: results from the NICO Au-Co-Bi deposit
AuthorMcMartin, I; Corriveau, L; Beaudoin, G; Jackson, S E; Normandeau, P X
SourceFinal programme and abstracts, 25th international applied geochemistry symposium; by Sarala, P (ed.); Ojala, V J (ed.); Porsanger, M -L (ed.); 2011 p. 90-91
Alt SeriesEarth Sciences Sector, Contribution Series 20110008
Meeting25th international applied geochemistry symposium IAGS; Rovaniemi; FI; August 22-26, 2011
ProvinceNorthwest Territories
NTS85N; 86C; 86D; 86E; 86F; 86K; 86L
AreaGreat Bear Lake; Lac la Martre; Hottah Lake
Lat/Long WENS-119.0000 -116.0000 67.0000 63.0000
Subjectseconomic geology; surficial geology/geomorphology; geochemistry; drift prospecting; prospecting techniques; magnetite; glacial deposits; iron oxides; copper; gold; mineralization; Great Bear magmatic zone
ProgramGEM: Geo-mapping for Energy and Minerals, Iron-oxide Copper-gold (IOCG) / Multiple Metals - Great Bear Lake (NWT)
AbstractAn applied Quaternary research activity was undertaken in the Great Bear magmatic zone, Northwest Territories, Canada, to provide a practical guide to geochemical and indicator mineral exploration for iron oxide copper-gold (IOCG) deposits in glaciated terrain. An orientation study was initiated in 2007 and continued in 2009 around the NICO Au-Co-Bi deposit, an atypical magnetite-group IOCG deposit with arsenopyrite mineralization within amphibolemagnetite- K-feldspar-biotite alteration in 1.88 Ga metasedimentary rocks. Bedrock (n=30) and till (n=20) samples were collected up-ice, proximal to, and down-ice from mineralization, host hydrothermal systems and least altered bedrock. The minor and trace element composition of sand-sized ferromagnetic minerals is used to evaluate whether the NICO deposit can be fingerprinted by drift prospecting using Fe-oxide composition.
The ferromagnetic fraction (0.25-2 mm) is abundant in most bedrock and till samples and consists of individual magnetite (dominant) or hematite grains, bedrock fragments with disseminated magnetite, non-ferromagnetic minerals with small magnetite inclusions, and magnetite-hematite mixtures. Electron microprobe analyses of grains demonstrate that the trace element signature of Fe-oxides is a prospective discriminator for IOCG exploration. Most Fe-oxide grains from bedrock and till collected at or near the NICO deposit have lower Ti+V concentrations compared to grains from samples collected from least-altered metasedimentary rocks up-ice of NICO. There is also a strong correspondence between the composition of grains from bedrock collected in altered NICO metasedimentary rocks and grains from till collected over or directly down-ice of NICO. Furthermore, preliminary in situ trace element analysis by LA-ICP-MS of magnetite grains from NICO bedrockand till samples show relatively high As-Bi-Cu- Sb-W-U-Zr-Ag-LREE concentrations. This distinct
element association is similar to the enrichments found in the bulk geochemistry of the <0.063 mm fraction of till collected over the NICO deposit, and reflects major differences in composition between the country/barren host rocks versus the mineralized rocks. Geochemical analysis of the pulverized ferromagnetic fraction of the till matrix will potentially show this signature. Further examination and analysis
of the ferromagnetic fraction will help to identify discrimination criteria for the different types of mineralization and host rocks. In addition, the examination of Fe-oxide grains from samples collected in the vicinity of the Sue-Dianne Cu-Ag-Au hematitegroup IOCG deposit, and additional showings across the Great Bear magmatic zone, will help to develop criteria that contribute vectors to a range of IOCG deposits. This work is part of the Geological Survey of Canada's Geomapping for Energy and Minerals Program aimed at improving mineral exploration effectiveness and discovery rates in Canada's North.