Sedimentary Exhalative (SEDEX) Potential of the Cuyuna North Range, Cuyuna South Range, Emily District, and Portions of Aitkin County - Old Drill Log Searches
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Sedimentary Exhalative (SEDEX) Potential of the Cuyuna North Range, Cuyuna South Range, Emily District, and Portions of Aitkin County - Old Drill Log Searches
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2003
Publisher
University of Minnesota Duluth
Type
Technical Report
Abstract
Many SEDEX deposits, specifically those in Canada and Australia, are hosted by Proterozoic
sedimentary rocks that were deposited in intracratonic or intra-rift tectonic settings. Rocks of similar
age and tectonic settings are also found within east-central Minnesota. However, exploration for
SEDEX deposits has been very limited in Minnesota due to an almost complete lack of outcrop.
Also, while extensive drilling for iron-formation took place in these same areas, little drill core exists
for examination. In lieu of this absence of information, all of the old drill log descriptions, from
areas in Crow Wing and Aitkin Counties, were searched for any mention of “unique” features that
may be indicative of SEDEX mineralization. This report summarizes the results of those drill log
re-checks. In addition, core samples were also collected from select drill holes in the Cuyuna North
Range for thin-section inspection. The samples were collected from the Mahnomen Formation in
order to more fully document the spatial distribution of areas with, and without, tourmaline-bearing
rocks. Previous studies (Cleland et al., 1996) found that tourmaline-bearing rocks were present in
four widely-spaced holes and a large SEDEX hydrothermal system was envisioned to be present
somewhere in the Cuyuna North Range.
The lithologic drill log searches found some holes that contain descriptions of sulfide-bearing
rocks, and in a very few instances, descriptions were found that are suggestive of tourmaline, but
these are vague and uncertain (in all but a few instances, no drill core remains to conduct a further
check of these vague descriptions). Attempts to outline further areas with tourmaline-bearing rocks
in the Cuyuna North Range, by sampling and thin section inspection, were not successful as only
trace amounts of tourmaline were found in only one, out of the eleven, drill holes that were studied.
In essence, the thin section study, though limited in extent, indicates that tourmaline is not
abundantly present everywhere in the footwall rocks of the North Range; rather, tourmaline-bearing
rocks are present in at least three much smaller areas.
All of the data assembled for this investigation, when viewed collectively, suggests that some
SEDEX potential may be present in the Glen Township Sulfide - South Body of Aitkin County, and
in the Cuyuna North Range and Emily District of Crow Wing County. SEDEX potential may also
be present in the Cuyuna South Range, but review of the old lithologic drill logs was not
instrumental in uncovering any useful data.
Description
The files attached to this record include the report (TR-2003-13.pdf) and Appendix 1 (NRRI-TR2003-13 APPENDIX.pdf). While the report mentions a file ending with XLS (presumably a Microsoft Excel 97-2003 spreadsheet), the only appendix file on the disk in the back pocket of the report was this pdf version of the data.
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Severson, Mark J; Heine, John J. (2003). Sedimentary Exhalative (SEDEX) Potential of the Cuyuna North Range, Cuyuna South Range, Emily District, and Portions of Aitkin County - Old Drill Log Searches. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/187132.
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