Browsing by Subject "Highway 169"

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    An Addendum to: Geology and Sulfide Content of Archean Rocks Along Two Proposed Highway 169 Relocations to the North of Sixmile Lake, St. Louis County, Northeastern Minnesota and Geologic Investigations in the Armstrong Lake Area
    (University of Minnesota Duluth, 2012) Severson, Mark J; Heine, John J
    This report summarizes the geochemical results pertaining to the sulfur contents of rock samples collected in the Sixmile Lake area, and thusly, serves as an addendum to a previous report by Severson and Heine (2010). Geologic mapping in the Sixmile Lake area was initiated at the request of the Minnesota Department of Transportation (Mn/DOT) and concentrated on areas where Highway 169 could potentially be re-routed. The second purpose of this addendum is to provide the appropriate GIS-related shape files that were omitted from the initial report by Severson and Heine (2010). These shape files have been finalized and are provided in this report. In addition, reconnaissance geologic mapping took place along other Highway 169 relocations in the Armstrong Lake/McComber Mine area. The results of that endeavor are provided in this report. The results of sulfur analyses for samples collected from the Sixmile Lake area show that most of the samples with ≥ 0.15% analyzed sulfur contents were correctly mapped as “anomalous sulfide zones” by Severson and Heine (2010). However, there were several instances where the visually-estimated pyrite contents did not compare well with the actual sulfur contents due to a “nugget effect” variation in the third dimension. This “nugget effect” variability is troublesome and suggests that some form of drilling should take place in the areas of future road cuts in order to obtain more representative S% values. Examination of rock exposures and recent drilling of the iron-formation in the vicinity of Shaft #2 in the McComber Mine area indicates that pyrite is present in much higher amounts when compared to Sixmile Lake. Thus, additional drilling will be needed in the McComber Mine/Shaft #2 subarea, and possibly in the Clear Lake subarea, in order to obtain a better understanding of the amount of pyrite present.
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    MnDOT Highway 169 2015 Drilling Project
    (University of Minnesota Duluth, 2017-06) Heine, John J; Patelke, Marsha Meinders; Buschette, Michael; Leu, Adam; Maly, Craig C; Gordee, Sarah M; Chlebecek, Sara; Lee, Aubrey; Post, Sara P
    The Natural Resources Research Institute (NRRI) Economic Geology Group was contracted by the Minnesota Department of Transportation (MnDOT) [Project Number 0005269] to provide onsite drilling supervision, core logging and sampling, and geochemical studies related to proposed construction along Highway 169 east of Soudan, Minnesota. The goal of this project was to provide MnDOT the data required to produce a mitigation plan for the Highway 169 Eagles Nest project. MnDOT, working with the Minnesota Department of Natural Resources (DNR) and Golder Associates, was responsible for developing the guidelines for this work with the help of the Highway 169 Technical Working Group (Minnesota Pollution Control Agency, Minnesota Department of Health, US Corps of Engineers, Environmental Protection Agency, and NRRI). Golder Associates (Seattle, WA office) was responsible for developing the mitigation plan for bedrock roadcuts along the reroute. This work was a continuation of the studies by Severson and Heine (2010, 2012) and Heine (2015) which examined the bedrock outcrops along three proposed Highway 169 reroutes and alternatives. Severson and Heine (2012) concluded that drilling would be needed in the potential bedrock roadcuts along the reroute corridor to fully characterize the geology as required in the mitigation plan.
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    A Second Addendum To: Geology and Sulfide Content of Archean Rocks Along Two Proposed Highway 169 Relocations to the North of Sixmile Lake, St. Louis County, Northeastern Minnesota
    (University of Minnesota Duluth, 2015-08) Heine, John J
    This second addendum to GEOLOGY AND SULFIDE CONTENT OF ARCHEAN ROCKS ALONG TWO PROPOSED HIGHWAY 169 RELOCATIONS TO THE NORTH OF SIXMILE LAKE, ST. LOUIS COUNTY, NORTHEASTERN MINNESOTA (Severson and Heine, 2010) examines the bedrock outcrops in the western part of the area along the existing Highway 169 alignment. This area is the western part of the identified “Northern Alignment” alternative. Outcrops were examined to determine rock type, sulfide content, and structural features. Samples were collected of both representative rock types and any rock types with elevated sulfides present. Twenty-six samples were collected during this project, and an additional sixteen samples collected during the 2010 work were included from the area where the areas overlapped. The current map area contains generally higher visual pyrite content and higher sulfur analyzed by Leco technique (AcmeLabs, Canada) than observed along the “Southern Alignment” in Severson and Heine (2010). This elevated sulfur content is due to a number of factors: 1. The presence of the upper black cherty Soudan Iron-Formation, which contains syngenetic disseminated and bedded pyrite (FeS2); 2. The presence of faults in the central part of the area and increased localized shearing; and 3. The new rock units that include the Gray Basalt and Gafvert Lake Sequence, which both contain elevated sulfides. Observed sulfide mineral contents and chemical concentrations are higher in the Northern Alignment than the Southern Alignment, suggesting that based on sulfide mineral contents and sulfur concentrations alone, the Southern Alignment would be the preferred alignment; however, consideration of other factors beyond the scope of this report are also required for determining the final location for the highway. Additionally, should this route be chosen, additional drilling would be needed to supplement the outcrop information in areas with less exposure.