Data released on December 19, 2013
December 19, 2013 – DNR Open-File Project 392: Regional Survey of Gold in Till, Cook Area, St. Louis County
Summary and Data: The DNR is today releasing preliminary results from the processing and analysis of thirty-four (34) glacial sediment samples collected in Northern St. Louis County, at locations where State- or County-controlled surface ownership overlies State-owned or State-administered mineral rights. This is the latest data release for a DNR geological investigation that began in July, 2012, within an approximately 200 square mile area of historical gold and base metal exploration that lies between Cook and Tower. In this region, an Archean granite-greenstone terrane is overlain by relatively thin layers of Rainy Lobe till and other glacially-derived sediments. These are ideal geological conditions for using gold grain counts and heavy mineral geochemistry in glacial sediment samples to explore for proximal bedrock mineralization.
The 34 glacial sediment samples were collected in October 2013, and sent to Overburden Drilling Management, Ltd, (ODM) for heavy mineral concentrate (HMC) separation and gold grain counts. Sample locations were based on initial results from 105 glacial sediment samples that were collected within the project area in October 2012, processed by ODM, and assayed by Activation Laboratories Limited (ActLabs). The DNR released those results to the public on February 4, 2013 and July 2, 2013.
Today’s data release includes an ODM report dated December 5, 2013 that documents HMC separation and gold grain count work for the 34 new samples, a sample location map, and associated spreadsheet files. These documents, and a more detailed description of the project, are available below:
This laboratory reports from Overburden Drilling Management, Ltd, (ODM) documents total gold grain counts and magnetic/non-magnetic heavy mineral concentrate weights in 34 Rainy Lobe glacial sediment (till) samples that overlie an Archean greenstone belt in the Cook Area of Northern St. Louis County, Minnesota. These samples were collected on State-owned or State-administered mineral rights by Mn DNR in October, 2013. The approximately 200 square mile Cook Area is an area of historical gold and base mineral exploration, located in between areas of active gold exploration to the Northeast (Vermilion District) and West (Linden Grove Area). The Mn DNR has a contract with ODM to process the till samples that it collects.
Data table for 34 Phase 2 CATS samples with locations and normalized gold grain counts
This data table provides locations as UTM coordinates and normalized gold grain counts (10kg sample weight) for the 34 samples identified in the ODM report.
Attribute data table for 139 CATS series samples
This data table combines the field data and ODM results for the 34 samples collected in October 2013 with the results for the 105 Cook Area till samples collected in 2012 (see February, 2013 monthly data release.
Map of Cook Area sample locations and gold grain counts
This map displays sample locations, normalized total and pristine gold grain counts and areas of active and historic mineral exploration, overlain on a 2010 aerial photograph of the Cook Area. Results from the previous phase of till sampling (105 samples) are also shown. The State of Minnesota has a dominant land position within this accessible greenstone terrane.
Next data release: Geochemical analyses
ODM-prepared representative splits of the silt and clay fraction (<63 micron), the non-magnetic HMC and magnetic HMC have been forwarded to Activation Laboratories (ActLabs) for geochemical analysis. The results will be posted as a separate data release.