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TitleTrace element geochemistry of magnetite and its relationship to Cu-Bi-Co-Au-Ag-U-W mineralization in the Great Bear Magmatic Zone, NWT, Canada
AuthorAcosta-Góngora, P; Gleeson, S A; Samson, I M; Ootes, L; Corriveau, LORCID logo
SourceEconomic geology and the bulletin of the Society of Economic Geologists vol. 109, 2014 p. 1901-1928,
Alt SeriesEarth Sciences Sector, Contribution Series 20130173
PublisherSociety of Economic Geologists
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS85N; 85O; 86A; 86B; 86C; 86D; 86E; 86F; 86G; 86H; 86I/01; 86I/02; 86I/03; 86I/04; 86I/05; 86I/06; 86I/07; 86L/01; 86L/02; 86L/03; 86L/04; 86L/05; 86L/06; 86L/07; 86L/08; 86M/01; 86M/02; 86M/03; 86M/04; 86M/05; 86M/06; 86M/07; 86M/08; 85M
AreaGreat Bear; Coronation Margin; Hottah Terrane
Lat/Long WENS-120.0000 -114.0000 67.0000 63.0000
Subjectsgeneral geology; geochemistry; metallic minerals; industrial minerals; trace element geochemistry; iron; gold; copper; magnetite; indicator elements; mineral deposits
Illustrationslocation maps; stratigraphic columns; geological sketch maps; photographs; tables; photomicrographs; graphs
ProgramGEM: Geo-mapping for Energy and Minerals Iron-oxide Copper-gold (IOCG) / Multiple Metals - Great Bear Lake (NWT)
Released2014 08 27
AbstractThe Paleoproterozoic Great Bear magmatic zone is the focus of ongoing exploration for iron oxide copper-gold (IOCG) deposits and also hosts iron oxide-apatite occurrences. Examples of IOCG deposits in the Great Bear magmatic zone include Sue-Dianne and NICO, and other smaller prospects, including Damp, Fab, and Nori/Ra. The past-producing Terra mine property hosts significant IOCG-like alteration that contains dome-shaped, iron oxide-apatite bodies. Petrographic study has identified multiple generations of magnetite at NICO, Fab, and Nori/Ra and, for the most part, a single generation of magnetite at Sue-Dianne, Damp, and Terra. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) documents important geochemical differences in V, Ni, Cr, and Co concentrations within the magnetite. Variations of trace elements in magnetite from the Great Bear magmatic zone could be a result of (1) host rock-fluid equilibration during regional metamorphism, (2) postmetamorphic hydrothermal metasomatism of Treasure Lake Group metasedimentary rocks, (3) preferential solubility of Co over Ni within the Fe-rich fluids, (4) changes in oxygen fugacity (fO2), and (5) partitioning of elements into coprecipitating sulfides. Regionally, the Cr/Co ratio is higher in barren and pre-ore magnetite compared to magnetite coprecipitated with ore minerals and/or present in ore-rich veins and breccias. Locally, at the Nori/Ra prospect, the V/Ni ratio in magnetite differentiates between barren and ore-related magnetite, and at Damp and Sue-Dianne the Co/Ni ratio is extremely high and clearly different from that of other Great Bear magmatic zone magnetite samples. These results provide the first database for geochemically characterized magnetite from different stages of IOCG alteration and illustrate the potential use of magnetite as an indicator mineral in the exploration for IOCG deposits.
Summary(Plain Language Summary, not published)
An ancient volcanic belt in the Great Bear Lake region (Northwest Territories) hosts the NICO deposit (Au-Co-Bi-W). Research results presented here describe the behaviour of gold in the presence of bismuth which has the capacity to melt and to be easily remobilized entraining the gold with it. This is key information to understand the genesis of the gold mineralization in such deposit and understand ultimately if and where gold migrates and can form the highest ore grade. The work was undertaken as a PhD study at the University of Alberta with NRCan funding from the Research Affiliate Associate and Geomapping for Energy and Minerals programs within the IOCG-Great Bear project.

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