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TitleOrigins of kimberlite indicator minerals on Banks Island, NWT: Evidence for unknown arctic kimberlite(s) and the potential of bedrock inheritance
AuthorSmith, I RORCID logo
Source2016 Yellowknife Geoscience Forum, abstract and summary volume; by Irwin, D; Gervais, S D; Terlaky, V; Northwest Territories Geological Survey, Yellowknife Geoscience Forum Abstract and Summary Volume 2016, 2016 p. 70-71 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 1.72 MB)
Alt SeriesEarth Sciences Sector, Contribution Series 20160178
PublisherNorthwest Territories Geological Survey (Yellowknife, Canada)
Meeting44th Annual Yellowknife Geoscience Forum; Yellowknife; NT; November 15-17, 2016
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS88B/04; 88B/05; 88B/11; 88B/12; 88B/13; 88B/14; 88B/15; 88C; 88D/05; 88D/12; 88F; 97G; 97H; 98A; 98B; 98C; 98D; 98E; 98F
AreaBanks Island
Lat/Long WENS-126.0000 -115.0000 74.7500 71.0000
Subjectseconomic geology; surficial geology/geomorphology; geochronology; geochemistry; mineral deposits; kimberlites; diamond; mineral assemblages; chromite; garnet; geological history; glaciation; modelling; glacial deposits; ice transport directions; sediment dispersal; dispersal patterns; source rocks; Pliocene; Upper Cretaceous; bedrock geology; lithology; fluvial deposits; granitic rocks; radiometric dating; isotopes; hafnium; ilmenite; Beaufort Formation; Isachsen Formation; Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous
ProgramGEM2: Geo-mapping for Energy and Minerals Western Arctic Sverdrup Basin
Released2016 01 01
AbstractSince 1996, exploration for diamond-bearing kimberlite by Monopros, Diamonds North and Rio Tinto has occurred on Banks Island, NWT. There have been 3 aeromagnetic survey programs, and 2 field-based exploration activities. The aeromagnetic surveys have yielded only weak-moderate anomalies. The stream and surface sediment sample collections have yielded generally low abundances (n<20), but nonetheless diverse kimberlite indicator mineral (KIM) assemblages (predominantly chromites), and include rare G10 and G10D garnets. To date, no kimberlite body has been identified on Banks Island although many are known regionally from east-central Victoria Island, Darnley Bay, and mainland NWT (north and east of Great Bear Lake). The GSC's Geo-mapping for Energy and Minerals (GEM) Program study was devised to re-examine industry-reported data using a new model of glaciation, and to assess the potential for hosting diamond-bearing kimberlites on Banks Island. Sediment samples were collected over two summer field seasons, and were designed to test different terrains and specific glacial deposits for KIM contents, and assess the potential for down-flow glacial dispersal using the new ice flow model in areas where industry had previously recovered KIMs. Fieldwork as part of this study identified numerous scattered outliers of Beaufort Formation gravelly-sands on upper pediment surfaces on northeastern Banks Island. Previously, Beaufort Formation strata were only reported from central and western Banks Island. Many of the catchments where industry had recovered KIMs on northeast Banks Island were recognized to contain these Beaufort Formation outliers. Because the Beaufort Formation is a Pliocene fluvial deposit, known to contain rare granitic material (hence have a potential Shield-derived component), it was targeted for KIM sampling. Results indicate that the Beaufort Formation deposits represent a potential bedrock-inherited KIM source. The Upper Cretaceous Isachsen Formation is another fluvial unit on Banks Island, also known to contain rare granites, and was the subject of field sampling this past summer. Geochemically distinguishing KIMs from either of these two bedrock units from local/distally glacier transported KIMs is important to resolving the kimberlite story on Banks Island.
Hafnium isotope dating of non-crustal ilmenites was used to discriminate potential KIM sources. If the ilmenite hafnium ratios matched those of known regional kimberlites, then it would support glacial dispersal of distally-sourced KIMs onto Banks Island. Analytical results to be presented identify an ilmenite age that is not in accordance with any of the known regional kimberlites. They do, however, match other kimberlites situated far south of Banks Island, but is incongruous with our understanding of glacial dispersal were that the mechanism by which they were transported onto Banks Island. Evidence thus exists of unknown kimberlite(s) on or proximal to Banks Island.
Summary(Plain Language Summary, not published)
Presentation of significant new kimberlite (diamond) exploration results is being released to an audience of industry, exploration companies, and scientific researchers who are most directly involved with natural resource development in Canada¿s north. Application of a new dating technique using ilmenite mineral grains recovered from Banks Island sediment samples has revealed an Eocene (~55 Ma) age. This is discordant with all known regional kimberlites, suggesting the presence of an unknown kimberlite(s), possibly on northwest Victoria Island. A published summary of known diamondiferous kimberlites in northern Canada reveal that this time period (Eocene) is correlated with the highest value deposits. Release of these research findings could promote renewed diamond exploration in this region.

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