The DNR is testing the effectiveness of a proprietary geochemical exploration technique in an area of known copper-nickel mineralization in Aitkin County, Minnesota. In case studies outside of Minnesota, the soil gas hydrocarbon (SGH) procedure developed by Activation Laboratories, Ltd. (ActLabs) has delineated mineralized bedrock targets buried under thick layers of overburden by extracting and analyzing organic compounds trapped on surficial sediment. The goal of this MnDNR project is to test the method’s efficacy in an area of known bedrock mineralization that is overlain with layers of both saprolite and clay-rich glacial till. The project combines SGH surface soil sampling with detailed characterization of till and saprolite samples obtained from rotosonic drill cores.
A comparison of the targeting results of this blind SGH soil survey against the known footprint of subsurface bedrock mineralization may provide useful guidance on the effectiveness of this exploration technique in other areas of underexplored State-owned or State-managed mineral rights.
Project Manager: Don Elsenheimer
Summary and Data: The Minnesota Department of Natural Resources (MnDNR) is today releasing laboratory analytical results and associated files for saprolite samples from four (4) rotosonic borings in Northeastern Aitkin County, Minnesota. These rotosonic drill borings were completed by a mineral exploration company working on active State non-ferrous metallic mineral leases in the area.
These documents are available below. A previously released sample location map is available here.
Certificate of Analysis/Laboratory Report A14-06814, Activation Laboratories, dated October 14, 2014
This laboratory report provides analytical and quality control results for the multi-element analysis of bulk and silt+clay fractions (-63micron) from the 4 saprolite samples. Analytical packages included whole rock analysis of major elements, and ICP/MS trace element analysis. This laboratory report was dated and submitted by ActLabs to MnDNR on October 14, 2014.
Rare Earth Element Plot
This PDF figure, provided by ActLabs, plots rare earth element (REE) distributions for the bulk and silt+clay fractions of the four saprolite samples. These distributions are of scientific value only; there is no significant economic value associated with the plotted concentrations.
Laboratory Data Spreadsheet
This spreadsheet, provided by ActLabs, reports the laboratory data in tabular spreadsheet form. The data table identifies analytical methods and method detection limits for each analyzed element.
Data table with locations
This MnDNR generated MS-Excel spreadsheet adds sample locations as UTM coordinates to the multi-element geochemical analysis of the bulk and -63micron portions of the four saprolite samples. Information provided in the ActLabs data table on analyte detection limits, units of measure, and analytical methods was stripped from this data table in order to create a format suitable for import into ArcGIS. The “less than” non-detect values reported in the ActLabs data table are replaced by values that are one-half the method detection limit. “Greater than” values are replaced by values that are 1 unit greater than the maximum detection limit (i.e. “> 10000” replaced by 10001). The original ActLabs data table and QC results are archived in this file as separate sheets.
Combined Analytical Results, Rotosonic Samples in NE Aitkin County
This MnDNR generated MS-Excel spreadsheet combines the new analytical data with previously-released results from MnDNR sampling of material from rotosonic drill cores in Northeastern Aitkin County. This single attribute table has a format suitable for import into ArcGIS. It combines analyses on bulk samples, silt and clay fractions, and heavy mineral concentrates from samples of till and saprolite from fifteen (15) rotosonic drill cores. The results were obtained using different analytical methods that have different method detection limits. “Less than” non-detect values are replaced by values that are one-half the method detection limit, while “greater than” values are replaced by values that are 1 unit greater than the maximum detection limit (i.e. “> 10000” replaced by 10001). More information regarding the methodology, detection limits, and QA/QC results may be obtained by clicking on the links that are tied to PDF versions of the original laboratory reports.
Click on bars to expand each past data release.
Data released on September 17, 2014
Summary and Data: The MnDNR is today releasing drill core logs, cross-sectional depictions, and associated files for fifteen (15) Rotosonic borings in Northeastern Aitkin County, Minnesota. These documents are available below:
Rotosonic Drill Core Descriptions and Interpretation of Glacial Sediment and Saprolite, Northeastern Aitkin County, Minnesota
This document includes fifteen (15) drill core descriptions, based on the observations made by the Minnesota Department of Natural Resources (MnDNR) geologists during their review of rotosonic drill cores obtained by a mineral exploration company working on active State non-ferrous metallic mineral leases in Northeastern Aitkin County, Minnesota.
In March 2013, the MnDNR collected twenty-two (22) samples of saprolite and till from eleven (11) existing rotosonic drill cores within the project area. These samples were submitted to Overburden Drilling Management Ltd (ODM) for heavy mineral concentrate and silt+clay fraction separations. These processed materials were then sent by ODM to ActLabs for third-party geochemical analysis. These analytical results were released to the public in June and July of 2013.
In August 2014, MnDNR geologists gained access to four additional Rotosonic drill cores. The unconsolidated sediments and saprolite layers within each drill core were visually logged, and the sediments were associated with distinct glacial advances (as characterized in Figure 5 of Jennings and Kostka, 2014 ). Samples of saprolite were collected from each of these drill cores. These samples will be shipped to ActLabs for geochemical analysis; the pending analytical laboratory results will be provided in a future data release.
These drill core descriptions and glacial lobe associations were made for the purpose of classifying the samples of saprolite and glacial sediments for the geochemical survey. This review was also made in order to construct cross-sections and identify specific intervals of clay-rich sediments that might have influenced the results obtained by collecting overlying surface sediment samples for the SGH survey. These cursory observations are not intended for other purposes.
Rotosonic drill core location map
This PDF map image depicts the relative locations of the 15 rotosonic drill cores reviewed by MnDNR geologists, and identifies the drill cores used to construct North-South and West-East cross sections.
This PDF document includes North-South and West-East cross-sectional depictions of the glacial sediments and saprolite layers identified by MnDNR geologists during their visual review of the 15 rotosonic drill cores. Specific intervals within each core are roughly associated with distinct glacial advances (as characterized by Jennings and Kostka, 2014). Note that these schematic depictions are not drawn to scale. A copy of the rotosonic drill core location map is attached for viewer convenience.
Rotosonic drill core sample information
This spreadsheet provides rotosonic drill core collar information for the 15 drill cores reviewed by MnDNR geologists in 2013 and 2014.
ArcGIS Shapefile (all_sonic_locations.zip)
This ArcGIS shapefile (allsonic_locations.shp) encapsulates the geospatial information included within the drill core sample information spreadsheet.
Data released on January 31, 2014
In October 2013, the DNR collected surface materials from 152 sample locations and sent them to ActLabs for SGH analysis and interpretation. The samples were located within a grid that was proximal to a previously sampled grid (see July 3, 2013 data release). ActLabs performed the analysis, and provided the DNR the results in an interpretive report dated January 27, 2014. The DNR is publically releasing the following associated documents:
Data released on July 2, 2013
The MnDNR is releasing the following field and analytical data associated with the test of the Soil Gas Hydrocarbon (SGH) Soil Survey Method. A discussion and analysis of these results will be included within a future open-file report.
In May 2013, the MnDNR collected surface samples from 179 points in a grid that covered the project area with 65 meter spacing. These surface materials were submitted to ActLabs for SGH analysis. The results of this analysis were provided to MnDNR by ActLabs on June 27, 2013.
ActLabs has completed geochemical analysis of the silt+clay fraction separations from twenty-two (22) samples of saprolite and till from eleven (11) existing rotosonic drill cores (see June 18, 2013 data release for sample collection and processing data). While these samples of till and saprolite from the base of the overburden layer are not part of the SGH soil survey, the results obtained from these samples using conventional methods of analysis provide valuable background information.
ActLabs has completed geochemical analysis of the magnetic and non-magnetic fractions of the heavy mineral concentrate (HMC) from twenty-two (22) samples of saprolite and till from eleven (11) existing rotosonic drill cores (see June 18, 2013 data release for sample collection and processing data). While these samples of till and saprolite from the base of the overburden layer are not part of the SGH soil survey, the results obtained from these samples using conventional methods of analysis provide valuable background information.
Map of Rotosonic Drill Hole Locations
Click for full size PDF
Data released on June 11, 2013
June 11, 2013 laboratory reports from Overburden Drilling Management, Ltd:
These laboratory reports from Overburden Drilling Management, Ltd. (ODM) provide processing data associated with the collection of silt+clay fractions and Heavy Mineral Concentrates (HMC) from twelve (12) samples of saprolite and ten (10) samples of overlying till within eleven (11) existing rotosonic drill cores. Samples were collected by MnDNR in March, 2013. From each submitted sample, ODM isolated a <63 micron sieve fraction (silt+clay), and obtained HMC (S.G.>3.3) from a pan concentrate. The HMC was subjected to a magnetic separation, and ODM made general identifications of the metallic minerals present within the pan concentrate. Gold grain counts were also obtained (note that gold was not a targeted mineral in this project). The DNR has a contract with ODM to process these types of samples that it collects.
The silt+clay fractions and magnetic/non-magnetic HMC splits from each sample were sent by ODM to Activation Laboratories, Ltd. (ActLabs) for geochemical analysis. These analytical results are pending.
This excel table provides locations as UTM coordinates and normalized gold grain counts (10kg sample weight) for the 22 samples of till and saprolite identified in the ODM report. This data is combined with the ODM processing report data in a single spreadsheet file that is formatted for import into ArcGIS.
This map displays the location of the eleven rotosonic drill locations that produced the core from which the 22 samples of till and saprolite were obtained. These drill holes locations are all on actively-leased State-managed mineral rights in Section 3 of T48N R22W, Aitkin County.
For more information:
Project Leader - Don Elsenheimer, Ph.D
500 Lafayette Road
St. Paul, Minnesota 55155-4045
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