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TitleKimberlite indicator minerals and gold grains in till from the Great Bear magmatic zone and Wopmay metamorphic zone, Northwest Territories, Canada
AuthorNormandeau, P X; McMartin, I; Jackson, V; Corriveau, L; Paquette, J
SourceNorthwest Territories Geoscience Office, Yellowknife Geoscience Forum Abstracts Volume 2014, 2014 p. 97 (Open Access)
LinksOnline - En ligne (p.97)
Alt SeriesEarth Sciences Sector, Contribution Series 20140291
PublisherNorthwest Territories Geoscience Office
Meeting42nd Annual Yellowknife Geoscience Forum; Yellowknife; CA; November 25-27, 2014
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaGreat Bear Lake
Lat/Long WENS-120.0000 -112.0000 67.0000 64.0000
Subjectseconomic geology; surficial geology/geomorphology; kimberlites; indicator elements; mineral deposits; mineral occurrences; gold; mineralization; tills; till analyses; indicator minerals
ProgramUranium Ore Systems, Targeted Geoscience Initiative (TGI-4)
AbstractKimberlite indicator minerals (KIM) and gold grain counts from near surface till samples were collected as part of an applied Quaternary activity within the IOCG-Great Bear Multiple Metals GEM project in partnership with the South Wopmay Bedrock Mapping Project & Integrated Studies. Till sampling sites were designed primarily for an IOCG study focused on the Sue Dianne Cu-Ag-Au magnetite to hematite-group IOCG deposit (n=30), the Fab Lake U-Th-Cu magnetite-group IOCG showings (n=23) and the Au?Co?Bi?Cu NICO magnetite-group IOCG deposit (n=13) in the south GBmz but include 39 samples collected across the Great Bear magmatic zone (GBmz) and extending into the Wopmay metamorphic zone and Slave Craton.
Heavy mineral separation (S.G. >3.2) and indicator mineral picking was performed by Overburden Drilling Management Ltd. Potential KIM species identified include; Cr-pyrope garnet, chromite, Mg-rich olivine and Cr-rich diopside. All reported values are normalized to a 10 kg sample using the table feed value. The most common species is Cr-pyrope garnet found in 41 samples within the 0.25 to 0.5 mm fraction and in 4 samples within the 0.5 to 1 mm fraction. One Cr-pyrope garnet is present within the >1 mm fraction. Mg-Olivine, Cr-diopside and chromite grains are respectively found in 15, 11 and 8 samples within the 0.25 to 0.5 mm fraction and are rarely present within the 0.5 to 1 mm fraction. The maximum number of grains found in a single sample is 5.1 grains/10kg but 18 samples contain 2 grains/10 kg or more. Samples from the south GBmz are commonly enriched in potential KIM but high grain counts are also present throughout the study area.
The total visible gold grain counts vary from none to 34.6 grains/10kg with an average of 2.9. Modified gold grain counts reach a maximum of 12.3 grains/10kg with an average of 0.6. Reshaped gold grain counts reach a maximum of 14 grains/10kg with an average of 2. Eleven samples contain pristine gold grains (1 to 11.2 grains/10 kg), and these samples all have high contents of modified and reworked gold grains as well. While pristine and modified gold grains are rare, reshaped gold grain contents correlate well with known IOCG systems of the GBmz such as the NICO and Sue Dianne deposits and to some extent, the Fab Lake system in a context of short transport distances. This suggests that the reshaping of gold grains took place either rapidly during glacial transport or in situ caused by wave action from Glacial Lake McConnell. In either case, reshaping of the grains should not be used as an argument to support large transport distances and/or necessarily associating these grains with background values.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This poster presents the results and interpretation of kimberlite indicator minerals and gold grain counts picked from glacial sediments left during the last glaciation in the Great Bear Lake area. The work will help provide the geoscience knowledge required to develop effective mineral exploration methods in formerly glaciated terrain. Samples were collected as part the Geo-mapping for Energy and Minerals (GEM-1) Program and the research is continuing as part of the Targeted Geoscience Initiative 4.