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    A Bibliography of Published Research in Minnesota Related to the State’s Mineral Potential: June 2023
    (University of Minnesota Duluth, 2023-06) Hudak, George J
    The Minnesota Geological Survey (MGS) was provided funding from the United States Geological Survey (USGS) via the FY 2022 National Geological and Geophysical Data Preservation Program for the “FY22 Minnesota Geological and Geophysical Data Preservation Program.” The program included two priorities that collectively involved 10 separate projects: Priority 1: Data Preservation • Project 1: Preservation of MGS Field Data • Project 2: Seismic Database and Geophysical Compilation • Project 3: Preservation of MGS Cuttings, Phase Three • Project 4: Minnesota Drill Core Library Inventory, Phase Two • Project 5: Data Preservation Workshop Priority 2: Mineral Potential-Related Information • Project 6: State Compilation of Mineral Deposits / Districts • Project 7: Mapping for USGS Compilation of Earth MRI Focus Areas • Projects 8: State Compilation of Borehole Data • Project 9: Prepare For, and Attend, and Follow-Up Earth MRI Workshop • Project 10: Preservation Plan for Critical Minerals As a Component of Priority 2, Project 7, “Mapping for USGS Compilation of Earth MRI Focus Areas,” the Natural Resources Research Institute (NRRI) was subcontracted by the Minnesota Geological Survey (MGS) to prepare a bibliography indicating published geological, geochemical, and geophysical research specific to Minnesota that supports inference of Mineral potential. Matching funding was provided from the NRRI University of Minnesota Permanent University Trust Fund to complete this work. The publications that form the basis of this bibliography are included in NRRI Technical Summary Report “Duluth Complex Geological Bibliography” (Hauck, 2017), “A Bibliography of Published Research in Minnesota Related to the State’s Mineral Potential” (Hudak, 2020), “Minnesota Data Preservation Report for 2019/2020: Updated Data Inventory, Preservation of Pillsbury Hall Rock Collections and Documentation, Assembly of Mineral Potential Related Information” (Thorleifson, 2020), and “A Bibliography of Published Research in Minnesota Related to the State’s Mineral Potential: June 2022” (Hudak, 2022). The following bibliography has been organized utilizing the USGS Mineral Systems approach for critical minerals inventory, research and assessment (Hofstra, 2019; Hofstra and Kreiner, 2020). As Minnesota has a preserved geologic history that spans greater than 3.6 billion years, a wide variety of geological processes encompassing several mineral systems have been active within the State. These include Chemical Weathering, Placer, Meteoric Recharge, Marine Chemocline, Volcanogenic Seafloor, Orogenic, Metamorphic, IOA-IOCG, and Mafic Magmatic. This bibliography includes references specific to each of these mineral systems, as well as a list of references related to potential by-products, recycling, and carbon mineralization publications focused on—and/or referencing—Minnesota resources.
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    A Bibliography of Published Research in Minnesota Related to the State’s Mineral Potential: June 2022
    (University of Minnesota Duluth, 2022-06) Hudak, George J
    The Minnesota Geological Survey (MGS) was provided funding from the United States Geological Survey (USGS) via the FY 2021 National Geological and Geophysical Data Preservation Program for the “FY21 Minnesota Geological and Geophysical Data Preservation Program.” The program included two priorities that collectively involved 11 separate Projects: Priority 1: Data Preservation • Project 1: Preservation of MGS Field Data • Project 2: Preservation of MGS Cuttings • Project 3: Minnesota Drill Core Library Inventory, Phase I • Project 4: Data Preservation Workshop Priority 2: Mineral Potential-Related Information • Project 5: State Compilation of Mineral Deposits / Districts • Project 6: Contribute Data to USGS Map Compilation of Focus Areas • Projects 7 and 8: State Compilation of Borehole Data with Metadata to NDC • Project 9: Update Geologic Map Database • Project 10: USGS Critical Minerals Workshop • Project 11: Strategic Plan for Critical Minerals As a Component of Priority 2, Project 6, “Contribute Data to USGS Map Compilation of Focus Areas,” the Natural Resources Research Institute (NRRI) was subcontracted by the Minnesota Geological Survey (MGS) to prepare a bibliography indicating published geological, geochemical, and geophysical research specific to Minnesota that supports inference of Mineral potential. Matching funding was provided from the NRRI University of Minnesota Permanent University Trust Fund to complete this work. The publications that form the basis of this bibliography are in NRRI Technical Summary Report “Duluth Complex Geological Bibliography” (Hauck, 2017), “A Bibliography of Published Research in Minnesota Related to the State’s Mineral Potential” (Hudak, 2020), and “Minnesota Data Preservation Report for 2019/2020: Updated Data Inventory, Preservation of Pillsbury Hall Rock Collections and Documentation, Assembly of Mineral Potential Related Information (Thorleifson, 2020). Matching funding was provided from the NRRI University of Minnesota Permanent University Trust Fund to complete this work. The following bibliography has been organized utilizing the USGS Mineral Systems approach for critical minerals inventory, research and assessment (Hofstra, 2019; Hofstra and Kreiner, 2020). As Minnesota has a preserved Geologic history that spans greater than 3.6 billion years, a wide variety of geological Processes encompassing a number of Mineral Systems have been active within the State. These include Chemical Weathering, Placer, Meteoric Recharge, Marine Chemocline, Volcanogenic Seafloor, Orogenic, Metamorphic, IOA-IOCG, and Mafic Magmatic. This bibliography includes references specific to each of these Mineral Systems, as well as a list of references Related to potential by-products, recycling, and carbon Mineralization publications focused on Minnesota resources.
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    Research, Development, and Marketing of Minnesota’s Iron Range Aggregate Materials for Midwest and National Transportation Applications: Final Compendium Report to the Economic Development Administration
    (University of Minnesota Duluth, 2010-11) Zanko, Lawrence M; Fosnacht, Donald R; Hauck, Steven A
    From January 1, 2006 to June 30, 2010, a comprehensive taconite aggregate research and demonstration program was undertaken. The program’s main objectives were to: • identify new and economically viable uses for Minnesota Iron Range taconite aggregate material in road construction and repair projects; and • conduct demonstration projects inside and outside Minnesota, including targeted Upper Midwest States. To assure program success, a cooperative and collaborative research approach was taken using expertise from both public and private entities. The program proceeded in two major phases. The first phase aimed at assessing the resource and road construction market opportunity in terms of technical information on aggregate applications, unique properties and benefits, different mix designs and attributes, alternative products and technologies, and to build awareness and interest in the expanded use of taconite aggregate products at the regional and national scale. Material logistics and costs, and market opportunities and approaches to demonstrate taconite aggregate’s advantages were also assessed during this first phase. The second phase expanded on the first phase findings and used them as a guide for demonstrating the actual use of taconite aggregate products on a larger scale throughout Minnesota and the Midwest in potential construction applications. The geologic characteristics of potential aggregate materials on Minnesota’s Mesabi Iron Range were characterized on a broad basis during both phases.
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    A Bibliography of Published Research in Minnesota Related to the State’s Mineral Potential: April 2020
    (University of Minnesota Duluth, 2020-04) Hudak, George J
    The United States Geological Survey (USGS) provided funding via the FY 2019 National Geological and Geophysical Data Preservation Program (NGGDPP) for the project “Updated Minnesota Data Inventory: Preservation of Pillsbury Hall Rock Collections with Associated Additional Documentation: Assembly of Mineral Potential Related Information.” The three priority components of this project were as follows: • Priority 1: Collection Inventory and metadata record revision in the National Digital Catalog; • Priority 2: Preservation of Pillsbury Hall Rock collections with associated and additional documentation; and • Priority 3: Assemble information that supports identification of critical mineral resources in Minnesota. As part of Priority 3, the Natural Resources Research Institute (NRRI) was subcontracted by the Minnesota Geological Survey to prepare a bibliography briefly describing published research specific to Minnesota that supports inference of mineral potential on the basis of geological mapping, and a bibliography listing references for published literature on this topic. The NRRI provided matching funding to complete this work from the NRRI University of Minnesota Permanent University Trust Fund. The USGS has recently developed a new minerals system approach for critical minerals inventory, research and assessment (https://www.usgs.gov/energy-and-minerals/mineral-resourcesprogram/ science/systems-approach-critical-minerals-inventory?qt-science_center_objects=0#qtscience_ center_objects; Hostra, 2019). The following bibliography is organized utilizing this minerals system classification scheme. As Minnesota has a preserved geologic history that spans greater than 3.6 billion years, and as a wide variety of geological processes have been active over this geological history, mineral potential exists in many of the mineral systems, including Chemical Weathering, Placer, Meteoric Recharge, Marine Chemocline, Volcanogenic Seafloor, Orogenic, Metamorphic, IOA-IOCG, and Mafic Magmatic. As well, a short bibliography of potential By-Products/Recycling resources has been included with this bibliography.
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    Torrefaction of Ponderosa Pine Pellets
    (University of Minnesota Duluth, 2019-04) Young, Matthew; Hagen, Timothy S; Mack, Paul
    Oregon Torrefaction, LLC (OTL) and the US Endowment for Forestry and Communities (USFC) have formed Restoration Fuels, LLC (RF) to construct and operate a 12 ton/h kiln torrefier that targets approximately 100,000 tons of torrefied woody biomass production annually. The plant will be colocated at the Malheur Lumber Mill in John Day, Oregon. Biomass sourcing will be principally smalldiameter, low-value wood from surrounding or nearby national forests including the Malheur and the Ochoco National Forests. The bulk of the woody biomass will be ponderosa pine from the dry land forests that surround John Day. Biomass coming from national forest areas have been evaluated for compliance with the US National Environmental Policy Act (NEPA) and are termed “shelf ready” for treatment. Restoration Fuels is now in the process of acquiring biomass supply to feed the torrefier. Early discussions with potential domestic and off-shore customers points to the need to have torrefied, densified test samples available for their evaluation, and it is in OTL’s interest on behalf of RF to produce a test batch of torrefied biomass that would be representative of RF’s future fuel product and to make samples available to serve customer interests. The effort is funded by the USFC and US Forest Service. To accomplish the test sample production, the OTL provided five tons of wood pellets to the Biomass Conversion Lab (BCL) located in Coleraine, MN for a sustained torrefaction production run using ponderosa pine pellets as feedstock. The targeted heating value specification for the torrefied wood pellets as requested by OTL was 9,500 btu/lb (22.09 MJ/kg). The BCL torrefied and provided over 6,000 lbs (2,727 kg)of torrefied pellets to the OTL.
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    Test Sample Production Report Torrefaction of Ponderosa Pine Chips
    (University of Minnesota Duluth, 2019-03) Hagen, Timothy S; Young, Matthew; Mack, Paul; Grochowski, Jack; Kangas, Kevin W; Fosnacht, Donald R
    Oregon Torrefaction, LLC (OTL) and the US Endowment for Forestry and Communities has formed Restoration Fuels, LLC (RF) to construct and operate a 12 ton/h kiln torrefier which targets approximately 100,000 tons of torrefied woody biomass production annually. The plant will be colocated at the Malheur Lumber Mill, located in John Day, Oregon. Biomass sourcing will be principally small diameter, low-value wood from surrounding or nearby national forests including the Malheur and the Ochoco National Forests. The bulk of the woody biomass will be Ponderosa Pine from the dry land forests that surround John Day. Biomass coming from national forest areas have been evaluated for compliance with the US National Environmental Policy Act (NEPA) and are termed “shelf ready” for treatment. Restoration Fuels is now in the process of acquiring biomass supply to feed the torrefier. Early discussions with potential domestic and off-shore customers points to the need to have torrefied, densified test samples available for their evaluation, and it is in OTL’s interest on behalf of RF to produce a test batch of torrefied biomass that would be representative of RF’s future fuel product and to make samples available to serve customer interests. The effort is funded by the US Endowment and US Forest Service. To accomplish the test sample production, the OTL provided 32.8 tons of wood chips to the Biomass Conversion Lab (BCL) located in Coleraine, MN for a sustained torrefaction production run using ponderosa pine as feedstock. The targeted specification for the torrefied wood chips as requested by OTL was 9,500 btu/lb. The BCL successfully torrefied and provided over 14 tons of torrefied feed stock to the OTL that met this targeted specification.
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    NRRI Evaluation of Starch-Based Binders for Agglomerating Red Oak
    (University of Minnesota Duluth, 2019-01) Young, Matthew; Hagen, Timothy S
    Cargill Industrial Starch (CIS) focuses on adding value to various starch fractionations through new market development. The purpose of this project is to identify the effect of different starch fractions on torrefied wood briquettes when blended at nominal 1% to 3% inclusion rates into torrefied red oak using the performance metrics of Kansas State Tumbling can durability and 24-hour moisture uptake. It was originally envisioned that conventional ring and die pelletizing could create testable 6.35 mm (¼ inch) pellets. However, after repeated failures and a multitude of die plugging issues, the decision was made to trial rotary briquetting as an alternative densification technique using a Komarek B220B briquetter. Previous batching trials conducted by the NRRI with the Komarek B220B using torrefied red oak as feedstock have yielded viable briquettes across a variety of binder types. Recent upgrades to the densification circuit have been made and include new grinding, larger batching and conveyance devices that enhance the safety and operational aspects of the system while allowing a variety of individual and unique densification equipment to be set in place and operated consistent with client needs across a variety of industries.
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    Avian Surveys for the St. Louis River Natural Areas Project: Submitted to Minnesota Land Trust
    (University of Minnesota Duluth, 2019-02) Liljenquist, Alexis L
    In 2018, researchers from the Natural Resources Research Institute (NRRI) at the University of Minnesota Duluth conducted bird surveys along the St. Louis River Estuary (SLRE) in nine project areas nominated for inclusion in the Duluth Natural Areas Program (DNAP). The DNAP was created in 2002 to manage Duluth’s environmentally significant areas to ensure the preservation of services and values, such as habitat diversity and water quality (Duluth Natural Areas Program Guidelines 2002). To assess the importance of the SLRE to birds, we conducted surveys throughout spring migration, the breeding season, and fall migration. In total, we documented 13,953 individuals of 169 species. We summarized bird use of the nine project areas based on abundance and diversity by guild classification within each season. All nine project areas in the nominated tract (i.e. SLRE) meet the conditions for ‘Important Bird Congregation Area’ based on nomination criteria outlined by DNAP. The western tip of Lake Superior is a well-known corridor for migrating birds, which funnel along the shore, using forests, wetlands, and shoreline habitat, to rest and refuel during both north and southbound migration. This study highlights the importance of the SLRE for breeding birds and as stopover habitat for a wide diversity of migratory birds, including 50 species of conservation concern.
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    Bayfield County Forest Breeding Bird Survey Modeling Report
    (University of Minnesota Duluth, 2019-02) Walton, Nicholas G; Kolbe, Stephen; Grinde, Alexis R
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    Duluth Complex Geological Bibliography
    (University of Minnesota Duluth, 2017-11) Hauck, Steven A
    This bibliography is meant to be a follow-up to the Hauck (1995) bibliography on the Midcontinent Rift System and this bibliography includes some, but not all, of the references in Cooper (1978) in the “Geology of the Copper-Nickel Study Area,” nor does it include the all geophysical and related data in Anonymous (1981), Czamanske et al. (1986), or other bibliographies, e.g., Swanson et al., (1987).
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    Utilization of Minnesota Clays to Produce New Clay Products: Initial Research
    (University of Minnesota Duluth, 1989-11) Hauck, Steven A; Toth, Thomas A
    NRRI's mission was to evaluate the geologic, geochemical, mineralogical and physical characteristics of clays throughout the state of Minnesota. During the project period, the 499 clay samples collected represented primary and secondary kaolinitic clays, Cretaceous shales, glacial tills, loess and lake clays, Precambrian argillites and shales, and Paleozoic shales. In addition, detailed geologic mapping of existing clay mines was conducted to document the three dimensional relationships between the different types of samples.
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    Precious Metals (Pt-Pd-Au-Ag) in Three Copper-Nickel Deposits in the Duluth Complex
    (University of Minnesota Duluth, 1989-11) Hauck, Steven A
    The research work on the precious metals in the three copper-nickel deposits centered on: 1) defining the lateral and vertical extent of the precious metals; and 2) the controls on mineralization, e.g., lithology, structure, etc. While these objectives were the same for each deposit, the methods of investigation at each deposit were dependent upon the amount and quality of previous data available.
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    Erie Pier Dredge Material Beneficial Use Study Final Report February 25, 2013
    (University of Minnesota Duluth, 2013-02-25) Patelke, Marsha Meinders; Levar, Thomas E; Zanko, Lawrence M; Oreskovich, Julie A; Maly, Craig C
    A two-year (2011-2012) study was undertaken by the University of Minnesota Duluth Natural Resources Research Institute (NRRI) to conduct lab and field demonstrations – as well as concurrent testing and monitoring – related to the beneficial use of federal navigation channel dredge material removed from the Duluth-Superior Harbor and stored at the Erie Pier facility in Duluth, MN. Much of the groundwork for the 2011-2012 study was done in prior years, but especially in 2009 and 2010, through ongoing collaborative efforts of the U.S. Army Corps of Engineers’ (USACE) Detroit District, its Engineering Research and Development Center (ERDC) in Vicksburg, MS, its Duluth Area Office, and public and private entities in Minnesota and Wisconsin. Examples of the latter include: the Duluth Seaway Port Authority; the Duluth-Superior Metropolitan Interstate Council (DSMIC); the Harbor Technical Advisory Committee (HTAC) and its members; city, county and state officials and agency personnel; engineering firms and contractors; and Minnesota taconite mining operations.
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    The Economics and Logistics of Transporting Taconite Mining and Processing Byproducts (Aggregate): Minnesota and Beyond
    (University of Minnesota Duluth, 2007-10) Zanko, Lawrence M
    Every year, Minnesota’s taconite mining industry generates over 125 million tons of mining byproducts, a figure that is more than double the entire state’s annual aggregate usage. Since 2000, the Natural Resources Research Institute (NRRI), University of Minnesota, Duluth, has been investigating how these vast quantities of taconite mining byproducts can be used for construction aggregate purposes on an expanded basis. However, if taconite-based aggregate is to be competitive beyond the Mesabi Iron Range, cost-effective rail transport options will be needed, and rail-related economic and logistical barriers must be identified, quantified, and overcome. The reality is, lower value/higher volume commodities like construction aggregates are often economically limited by their distance to market, due to the cost of transportation. Consequently, this study is focusing on rail transport by reviewing/identifying transportation networks, logistics, equipment availability, costs, and potential difficulties associated with moving taconite aggregate through that network. Truck, barge, and Great Lakes shipping are also being addressed. By identifying the key transportation and market-related issues, this study will give potential end-users inside and outside Minnesota a better understanding of how taconite aggregate could be an important alternative to “conventional” aggregate sources. Likewise, taconite producers will have a better understanding of the relative ease or difficulty of marketing and/or moving various types of aggregate, and the potential economic benefit(s) thereof. By improving our understanding of what the supply, demand, and movement dynamics are (and how they interrelate), the prospect for expanded use of taconite aggregate will be enhanced - a development which will ultimately be important for both the economy and the environment, a dual benefit measurable in both a dollars (economic) and tons (resource conservation) sense. This Technical Summary Report describes project activities and progress through October of 2007.
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    A Brief History of the Use of Taconite Aggregate (Mesabi Hard RockTM) in Minnesota (1950s – 2007)
    (University of Minnesota Duluth, 2007-10) Oreskovich, Julie A
    Taconite aggregates (collectively termed Mesabi Hard Rock™) have been used as construction aggregate in Minnesota for nearly 50 years, dating back to the early days of the taconite industry. Coarse taconite tailings are a ready-made, free-draining, fine aggregate equivalent suitable for use as select granular and fine filter aggregates. Their angular interlocking form, when placed with water and covered with Class 5, produces sound embankment fill material. Their hardness, strength and durability produce superior wear and friction properties in bituminous mixes. This, coupled with 100% fractured faces, makes them ideal for Superpave mixes. Their cleanness (very low -200 mesh) makes them a valuable tool for adjusting volumetric properties in bituminous mix design. Crushed taconite rock brings the same hardness, strength and durability to the coarser aggregate size fractions, making it ideal for crushing to desired specifications for use as fill, filter material and the coarse aggregate component in bituminous and concrete mixes. Historically, taconite aggregate products have been used most when road construction, maintenance, and repair projects are in close proximity to the taconite operations, i.e., on the Mesabi Range. The 1970s and 1980s saw the use of coarse taconite tailings spread to the Twin Cities metropolitan area, as well as to the southern and western reaches of the state for use in bituminous overlays and surfacing. The 1990s and 2000s saw taconite aggregates become a staple of Duluth area bituminous contractors and road constructors, to the degree that they are used in some capacity in nearly every project. Millions of tons of taconite byproducts are produced every year in the mining and pellet production process. Couple this with nearly 50 years of production and the enormous size of this resource becomes obvious. While much of this material is consumed by the taconite mines for day to day operations (haul roads, tailings dams, shovel pads, drill hole stemming, etc.), much remains stockpiled and available for use. Infrastructure already in place for shipment of pellets (roads, railroads, and Lake Superior docks and ship-loading facilities) can be accessed for shipment of aggregates throughout the United States and beyond. This report is a historical narrative of the highlights of taconite aggregate usage as road construction aggregates in Minnesota. It documents how taconite byproducts have evolved from stockpiled "wastes" to become premium "in-demand" aggregates suitable for meeting today's infrastructure needs.
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    Cost Comparison of Underground and Surface Mining Options for Potential Western Mesabi Range Iron Ore Resources
    (University of Minnesota Duluth, 2011-05) Zanko, Lawrence M
    This summary report compares capital and operating costs associated with hypothetical underground and surface mining operations located on Minnesota’s Western Mesabi Iron Range. Spreadsheet cost models developed by the author are used for generating the comparative cost data.* The models are based in part on underground and surface mine cost information provided in InfoMine USA, Inc. Mining Cost Service. Model output is intended to provide only an approximation of capital and operating costs associated with both underground and surface mining, and should be viewed accordingly. “Ore” is considered to be restricted to sub-members Lower Cherty 4 and Lower Cherty 3 (LC-4 and LC-3). Note that the stripping ratio increases from about 4:1 to 6:1 approximately one mile to the south of the Biwabik Iron Formation’s southern subcrop extent. Currently, the stripping ratio at active Minnesota iron ore (taconite) surface mining operations is at about 1:1. Based on the Biwabik Iron Formation’s overall dip of 5-10° to the south in the area of interest, for every mile that mining progresses down-dip, the depth to ore increases by about 700 feet. Therefore, the ore zone (LC-4 and LC-3) of any mine developed more than one mile to the south of historic iron ore mining activity will be more than 1,000 feet below ground surface.
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    Generalized Mineral Potential of the Mesabi Purchase Area, Northern Minnesota
    (University of Minnesota Duluth, 2012-10) Severson, Mark J; Hauck, Steven A; Heine, John J; Fosnacht, Donald R
    Most of the Mesabi Purchase is underlain by granitic rocks of the Giants Range Batholith that exhibit an extremely low mineral potential to host a metallic deposit. This low potential is demonstrated by the lack of mineral exploration and other core holes drilled in the area by mineral exploration companies. In fact, the vast majority of drill holes shown in the area are associated with scientific holes drilled by the Minnesota Geological Survey for mapping purposes as a follow-up of regional geophysical interpretations. The copper-nickel-PGE mineralization located to the east in the Duluth Complex does not occur in the Mesabi Purchase area. The various types of geologic terrains, and their mineral potential, albeit low in almost all cases, are listed below: • Giants Range Batholith granitic rocks (pink, purple, and orange units on map): 1. Rare Earth Elements (REEs - unknown, but most likely low to moderate potential in spatially-limited deposits; currently being investigated by NRRI throughout Minnesota); 2. Gold along fault zones or contact zones with Greenstone Belt (unknown potential, but unlikely in spatially-limited deposits); 3. Road Aggregate (crushed rock); and 4. Dimension Stone • Greenstone Belt (North Half of Block – green, pale green, and yellow units on map): 1. Copper-Zinc associated with Volcanic Hosted Massive Sulfide deposits (very low potential overall, with moderate potential in T.61N., R.17W.); 2. Gold associated with shear zones and faulted rock (very low potential overall, with weak potential in T.61N., R.17W.); • Small granitic to syenitic plutons associated with a Greenstone terrain (circular pink units on map) with a low to moderate potential of hosting Rare Earth Elements; 2 • Virginia Horn Greenstone Belt (extreme southeastern corner): 1. Gold associated with a syn-volcanic Quartz Feldspar Porphyry (very low potential that has been tested by three drill holes); and • Mesabi Iron Range (red unit on extreme southern fringe of block): 1. Magnetic Taconite ores (the potential of these ores are negligible as most of the rock has already been mined out at the Minntac West Pit, Minntac East Pit, and Minorca Pit); and 2. Road Aggregate (crushed rock – also negligible as in the above category). 3. Mine tailings for various aggregates, bridge deck surfaces, etc. Detailed Township and Range Descriptions T.61N., R.21W. Metasedimentary rocks of a Greenstone terrain are dominant and exhibit no known, or expected, mineral potential. Small syenitic plutons are present and may have a REE potential, but these are largely unexposed and mostly known from limited outcrops and a single drill hole (scientific/mapping drill hole). No known exploration for any type of mineral deposit has occurred in this township. T.61N., R.20W. Metasedimentary rocks of a Greenstone terrain with no known, or expected, mineral potential. Small syenitic plutons are present and may have a REE potential, but these are largely unexposed. No known exploration for any type of mineral deposit has occurred in this township. T.61N., R.19W. Mostly metasedimentary rocks of a Greenstone terrain (no known potential) with a small amount of mafic volcanic rocks that may have a weak potential of hosting a Cu-Zn or gold deposit. Small syenitic plutons are present and may have a REE potential, but these are largely unexposed. No known exploration for any type of mineral deposit has occurred in this township. T61N., R.18W. Both metasedimentary and mafic volcanic rocks of a Greenstone terrain are the dominant rock types. No known exploration for any type of mineral deposit has taken place in either of these rock types, and the expected mineral potential is extremely low. Granitic rocks of the Giants Range Batholith are present and exhibit a very low potential of hosting a REE deposit. Also present in the western half of the township is the Lost Lake Pluton that has been unsuccessfully explored for gold in the adjacent eastern township. The REE potential of the Lost Lake Pluton is unknown, and this pluton has been recently sampled by the NRRI. T.61N., R.17W. Both metasedimentary and mafic volcanic rocks of a Greenstone terrain are the dominant rock type. Limited exploration for gold deposits has taken place with unsuccessful results (two exploration drill holes with no follow-up). Granitic rocks of the Giants Range Batholith are present and exhibit a very low potential of hosting a REE deposit. Also present in the township is the eastern half of the Lost Lake Pluton that has been unsuccessfully explored for gold (two drill holes), but may exhibit REE potential. 3 T.60N., R.21W. Granitic rocks of the Giants Range Batholith are the most prevalent and may show a very low potential of hosting a REE deposit. A glacial drift covered Greenstone Belt is present along the western edge of the township – it exhibits a low mineral potential as this belt has never been explored by minerals companies (except further to the west). T.60N., R.20W. Granitic rocks of the Giants Range Batholith are the most prevalent. These rocks may exhibit a moderate potential of hosting a REE deposit (geochemistry results are pending in samples collected from three scientific/mapping drill holes). No known exploration for any type of mineral deposit has occurred in this township. T.60N., R.19W. This township is entirely underlain by granitic rocks of the Giants Range Batholith. These rocks may exhibit a moderate potential of hosting a REE deposit (geochemistry results are pending in samples collected from two scientific/mapping drill holes). No known exploration for any type of mineral deposit has occurred in this township. T.60N., R.18W. Granitic rocks of the Giants Range Batholith are the most prevalent. These rocks may exhibit a moderate potential of hosting a REE deposit (geochemistry results are pending in samples collected from two scientific/mapping drill holes). No known exploration for any type of mineral deposit has occurred in this township. T.60N., R.17W. About 70% of this township is underlain by granitic and schistose rocks of the Giants Range Batholith with a moderate potential of hosting a REE deposit (one scientific/mapping drill hole is present). The remaining 30% of the township is underlain by metasedimentary rocks of a Greenstone terrain with a no known, or expected, mineral potential. No known exploration for any type of mineral deposit has occurred in this township. T.59N., R21W. Granitic rocks of the Giants Range Batholith are the most prevalent, but have shown a low potential of hosting a REE deposit to date. A glacial drift covered Greenstone Belt is present in the extreme southern portion of the township – it exhibits a low mineral potential as this belt has never been explored by minerals companies (except further to the west). T.59N., R.20W. This township is entirely underlain by granitic rocks of the Giants Range Batholith. These rocks may exhibit a moderate potential of hosting a REE deposit (outcrop samples have been collected from some exposures to help ascertain this assessment). No known exploration for any type of mineral deposit has occurred in this township. 4 T.59N., R.19W. This township is entirely underlain by granitic rocks of the Giants Range Batholith. These rocks may exhibit a moderate potential of hosting a REE deposit (outcrop samples have been collected from some exposures to help ascertain this assessment). No known exploration for any type of mineral deposit has occurred in this township. T.59N., R.18W. This township is largely underlain by granitic rocks of the Giants Range Batholith. These rocks may exhibit a moderate potential of hosting a REE deposit. A wedge of highly metamorphosed Greenstone is present to the north of the Mesabi Range (on USS owned lands) and may exhibit an extremely low potential of hosting a gold deposit. No known exploration for any type of mineral deposit has occurred in this township. Mined out taconite (USS Minntac Mine) is present along the southern fringe of this township. T.59N., R.17W. This township is largely underlain by granitic rocks of the Giants Range Batholith. These rocks may exhibit a moderate potential of hosting a REE deposit. A wedge of highly metamorphosed Greenstone is present to the immediate north of the Mesabi Range and may exhibit an extremely low potential of hosting a gold deposit. No known exploration for any type of mineral deposit has occurred in this township. Mined out taconite is present along the southernmost fringe of this township (Minntac West Pit, Minntac East Pit, and Minorca Mine). T.59N., R.16W. About 85% of this township is underlain by granitic rocks of the Giants Range Batholith with a moderate potential of hosting a REE deposit. The remaining 15% of the township is underlain by mixed metasedimentary and volcanic rocks of a Greenstone terrain referred to as the “Virginia Horn.” Gold mineralization has been documented in the Virginia Horn in the township to the immediate southwest (T.58N., R.17W.). There has been limited exploration for gold in T.59N., R.16W with unsuccessful results (three drill holes). T.58N, R.19W. About 90% of the township is underlain by the Mesabi Iron Formation and the overlying Virginia Formation. The remaining 10% is underlain by igneous rocks of the Giants Range Batholith with low mineral potential.