Geoscience and Exploration

Stream Sediment Geochemistry and Heavy Minerals, Southern Mackenzie, NT

Thursday, November 22, 2018 - 12:20 to 12:39 Theatre 1


S.J.A. Day (Presenting)
Geological Survey of Canada

I.R. Smith
Geological Survey of Canada

R.C. Paulen
Geological Survey of Canada

R.D. King
Memorial University of Newfoundland

Stream sediments have long been used as a mineral prospecting tool and is an effective method to quickly evaluate the prospectivity of an area. Government stream sediment and water surveys date back to the early 1970s and have been carried out in all ten provinces and three territories. Under the Southern Mackenzie Surficial Mapping Activity of Geological Survey of Canada’s GEM-2 Program (Mackenzie Project), a multi-year stream sediment and water study was initiated in 2017 and continued in 2018.

Past mineral resource assessments carried out by the Northwest Territories Geological Survey, as part of the Protected Areas Strategy (PAS) in the Trout Lake and Kakisa areas, revealed the presence of elevated levels of chalcopyrite (CuFeS2), sphalerite ((Zn,Fe)S) and galena (PbS) in the heavy mineral concentrate (HMC) fraction of till samples. Preliminary isotopic analysis of these base metal indicator minerals (GSC OF 8449) has shown that those PAS sulphide grains are not derived from Pine Point. Stream sediment samples collected in 2017 substantiated the presence of chalcopyrite while revealing additional significantly elevated sphalerite and galena grain counts in several locations where there are no known subcropping mineral occurrences. Past producer, Pine Point lead-zinc Mine, lies ~75 km to the east-northeast of the nearest stream sediment site with elevated sphalerite and galena grain counts, and is not likely the source as samples between these sites have only background-level grain counts.

The 2018 stream sediment sampling strategy was designed to augment existing samples, resample a few of the 2017 sites with elevated grain counts, and target a number of coincident till and stream sediment sites in proximity to those with elevated grain counts. A total of eight bulk stream sediment and water samples were collected northeast and southwest of Fort Providence. Planned 2018 stream sediment sampling in the Hay River area was not feasible as a consequence of high water levels.

Stream sediment and water samples were collected in accordance to the Geological Survey of Canada’s former National Geochemical Reconnaissance (NGR) methodology. At every site possible, three samples were collected: bulk stream sediment for the heavy mineral fraction, silt-size sediment and a water sample. The bulk sediment was processed to obtain indicator mineral grain counts, while the silts and waters underwent geochemical analyses. Diligent NGR QA/QC practices facilitate data compatibility and compilation, whether it be from the early NGR surveys or recent GEM drainage geochemical studies. After publication, all data will be uploaded into the GSC’s Canadian Database of Geochemical Surveys.