Browsing by Subject "Lithologic maps"
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Item Compile and Make Digital the Lithologies for all NRRI Drill Logs, with Emphasis on the Duluth Complex Drill Holes (An Addendum to an Earlier NRRI Database)(University of Minnesota Duluth, 2009) Severson, Mark J; Oreskovich, Julie A; Patelke, Marsha MeindersThis report and associated databases are updates on many of the holes that have been recently logged by the Natural Resources Research Institute (NRRI) in the Keweenawan Duluth Complex, the Paleoproterozoic Biwabik Iron Formation of the Mesabi Iron Range, and the Archean Deer Lake Complex of northeastern Itasca County, Minnesota. The main emphasis of this project was to update some of the databases that were presented in an earlier NRRI report (Patelke, 2003) with regard to lithologies in Duluth Complex drill holes that were logged by the NRRI since 2003 (and discussed in Severson and Hauck, 2008). To date, all of the publically available drill holes (except for around 30 drill holes) have now been logged in the Duluth Complex by the NRRI. These 30 holes are all that are missing from either the databases in this report or the databases in Patelke (2003). It is strongly suggested that the databases herein be combined, at the user’s discretion, with corresponding databases in Patelke (2003) in order to make an all- encompassing database for lithologies for all NRRI logged drill holes in the Duluth Complex. A secondary goal of this project was to present a header file database for all the holes that were recently drilled in the Duluth Complex (post-2003). Most of these holes are not yet publically available, but data regarding drill hole locations can be gleaned from abandonment files. Combining Duluth Complex header files in this report with the similar header file in Patelke (2003) could provide an all-encompassing database of locations for all of the holes drilled to date in the Duluth Complex (pre-2010 data). This combining of the data is left to the user’s discretion. Lastly, additional goals of this project (time permitting) were to present lithologic databases for all holes logged by the NRRI in the Mesabi Iron Range and, to a much lesser extent, holes logged by the NRRI in the Deer Lake Complex. The database for the Mesabi Iron Range contains information for almost 300 drill holes (over 5,947 lines of lithologic data) in regard to the lithologic picks pertaining to informal members and submembers of the iron-formation. The data in this file is about 80% complete in that not all of the iron-formation submembers are presented for holes drilled at the Keetac Taconite mine or in the Coleraine, MN, area (the latter holes are discussed in Zanko et al., 2003).Item Sedimentary Exhalative (SEDEX) Potential of the Cuyuna North Range, Cuyuna South Range, Emily District, and Portions of Aitkin County - Old Drill Log Searches(University of Minnesota Duluth, 2003) Severson, Mark J; Heine, John JMany 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.