Phase I fuzzy-logic GIS modeling to evaluate the occurrences of mineral systems in Minnesota
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Phase I fuzzy-logic GIS modeling to evaluate the occurrences of mineral systems in Minnesota
Published Date
2022-12
Publisher
University of Minnesota Duluth
Type
Technical Report
Abstract
Eight mineral systems potentially present in Minnesota have been evaluated using fuzzy-logic modeling
utilizing ArcMap® software. Data used from the models was derived from the Natural Resources
Research Institute Assembling Minnesota dataset. The eight mineral systems modeled include: 1) Placer;
2) Marine Chemocline; 3) Volcanogenic Seafloor; 4) Orogenic; 5) Metamorphic; 6) Alkalic Porphyry; 7)
Magmatic REE; and 8) Mafic Magmatic. Inference nets have been developed to illustrate the fuzzy logic
and components of each of the mineral system models.
Results of the modeling are summarized below by mineral systems:
Placer Mineral System: Based on the modeling, the highest probabilities for the presence of a Placer
mineral system occur in northeastern Minnesota and in southwestern Minnesota. These regions
correlate with the presence of the Biwabik Iron Formation, metasedimentary rocks associated with the
Penokean Orogeny, and the margins of the Sioux Quartzite.
Marine Chemocline: Based on the modeling, the highest probabilities for the presence of Marine
Chemocline mineral systems occur in northeastern and north-central Minnesota in rocks associated with
the Animikie Basin and Penokean Orogeny strata. As well, the model indicates high probabilities for the
presence of the Marine Chemocline mineral system in western and southwestern Stearns County
associated with interlayered volcanic, volcaniclastic, sedimentary, and hypabyssal intrusive rocks that
comprise the Mille Lacs Group, North and South Range Groups, and Glen Township Formation.
Volcanogenic Seafloor: High potential for the presence of Volcanogenic Seafloor mineral systems were
identified in both the Abitibi-Wawa and Wabigoon subprovinces. In the Abitibi-Wawa subprovince, this
includes the Vermilion district and the Wilson Lake sequence (Jirsa, 1990). Within the Wabigoon
subprovince, enhanced potential for Volcanogenic Seafloor mineral systems occurs in east-central Lake
of the Woods County and in northwestern Beltrami County. A single region of high potential for the
presence of a Volcanogenic Seafloor mineral system also occurs in north-central Marshall County.
Orogenic: The highest probabilities for Orogenic mineral system-associated gold deposits occur within
the Abitibi-Wawa and Wabigoon subprovinces within the northernmost one-third of Minnesota. These
regions are closely-associated with regional-scale shear zones. The modeled regions correlate well with
the six areas of gold exploration identified by Severson (2011), as well as a weights of evidence model
developed by Hartley (2014).
Metamorphic: Several regions occur where elevated potential for Metamorphic mineral systems exist in
Minnesota. The highest modeled potential for such a system exists in east-central St. Louis County and
northwestern Lake County; however, this region of modeled high potential may be a false positive due
to anomalously high contents of nickel (and perhaps vanadium) within Mesoproterozoic rocks in the
area. Other areas with modeled high potential occur within northeastern Koochiching County and are
associated with Quetico subprovince high-grade metamorphic rocks in proximity to the Rainy Lake –
Seine River Fault, and in northeastern Itaca County, in proximity to the Coon Lake Pluton.
Alkalic Porphyry: Modeling conducted for this study indicates several regions where elevated potential
for Alkalic Porphyry mineral systems exist. The areas with the highest modeled probability for having
Alkalic Porphyry mineral systems occur in northeastern Minnesota with Lake, St. Louis, and Itasca
counties.
Magmatic REE: Regions with the highest modeled potential for Magmatic REE mineral systems occur in
south-central Lake County, north-central and northwestern St. Louis County, northeastern Itasca
County, east-central Koochiching County, southeastern Marshall County, and east-central Stearns
County. These are associated with Neoarchean syenite, monzodiorite, granodiorite, and diorite and
granite-rich migmatites, Neoarchean gabbro, peridotite, pyroxenite, lamprophyre and metamorphic
equivalents, and Paleoproterozoic porphyritic granites.
Mafic Magmatic: Fuzzy-logic modeling indicates the highest probability for the presence of Mafic
Magmatic mineral systems occurs in northeastern Lake County, east-central St. Louis County, and within
eastern Aitkin County. The model identified known disseminated-to-massive Cu-Ni-PGM deposits that
occur in troctolitic rocks at the base of the Duluth Complex in Lake and St. Louis counties, as well as Ti-Voxide
deposits and prospects associated with oxide ultramafic intrusions (peridotites, pyroxenites) that
occur along the western margin of the Duluth Complex in central St. Louis County. As well, the model
identified the location of the Tamarack intrusion in eastern Itasca County, the host of the Tamarack Ni-
Cu-Co deposit.
Description
There are 8 appendix folders attached to this record, along with the pdf report file. Each zipped appendix folder contains shapefiles and model calculations for one of the mineral system models.
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The United States Geological Survey via the FY 2021 National Geological and Geophysical Preservation Program (NGGDPP), the Minnesota Geological Survey, and the University of Minnesota Permanent University Trust Fund
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Suggested citation
Hudak, George J; Nixon, Kristi; Thakurta, Joyashish; Bartsch, Will. (2022). Phase I fuzzy-logic GIS modeling to evaluate the occurrences of mineral systems in Minnesota. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/254377.
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