Browsing by Author "Hauck, Steven A"

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Airborne Imaging Scanner Survey of Northeastern Minnesota
(University of Minnesota Duluth, 1990-04) Hauck, Steven A; Ager, Cathy; Pastor, John; Zanko, Lawrence M; Aaseng, N
An airborne imaging scanner survey was flown over two areas in the Duluth Complex and one area along the Vermilion fault zone on September 12, 1988 to detect heavy metal induced stress in plants due to the presence of buried mineral deposits. The Duluth Complex flight lines covered copper-nickel and iron-titanium mineral deposits while the Vermilion fault flight line covered Archean gold mineralization sites. The 63 channel imaging scanner had a spatial resolution of about 9-10 meters and a flight path width of approximately 6.4-7.2 kilometers along three flight lines. Supervised, unsupervised, principal components and inverted principal components analysis and Chebyshev polynomial expansions were used on data collected over two test sites, i.e., the east end of the Archean flight line and the Dunka Pit area, to learn whether or not vegetative stress could be identified in areas with known metallic mineralization. Interpretation of the Dunka Pit test site was abandoned because: 1) the test site was too small; 2) much of the canopy was dead; and 3) the test site was overwhelmed by an adjacent, highly reflective mine dump. At the Archean site, ground spectroradiometer data was collected to assist with the interpretation of the imaging scanner data. The ground data indicated spectral shifts to both longer and shorter wavelengths in vegetation over mineralized compared with unmineralized sites. However, the imaging scanner data did not indicate any evidence of vegetative stress in mineralized areas. At this point, the imaging scanner survey data are useful mainly for discriminating different types of vegetation.
The Babbitt Copper-Nickel Deposit: Part B: Structural Datums
(University of Minnesota Duluth, 1994-09) Severson, Mark J; Patelke, Richard L; Hauck, Steven A; Zanko, Lawrence M
This portion of the investigation concentrated on determining specific structural and stratigraphic datums within the Babbitt Cu-Ni deposit of the Partridge River Intrusion, Duluth Complex, northeastern Minnesota. Structural datums and footwall lithologies were obtained by relogging the footwall portions of all surface drill holes (391) within the confines of the deposit. Specific lithologies recorded during relogging included depth to: 1) basal contact of the Duluth Complex with the footwall rocks; 2) distinctive units within the footwall Virginia Formation; and 3) top of the underlying Biwabik Iron-formation and the specific iron-formation submembers intersected in drill hole. In addition, 100 surface drill holes were relogged in detail and compared with 166 previously relogged drill holes. The top of Unit I, the main sulfide-bearing igneous unit of the Babbitt deposit, was determined for all 266 drill holes that were relogged. The top of the first significant sulfide-bearing zone (not always the top of Unit I) was also determined for the relogged drill holes. All these datum points are used to generate several contoured surface maps to gain a better understanding of the main structural features present within the Babbitt deposit. The contoured surface for the top of the Biwabik Iron-formation is an excellent means of displaying the major structural features, i.e., the Local Boy Anticline, Bathtub Syncline, and Grano Fault. These same features are evident in the contoured surface of the basal contact and indicate that pre-existing structures in the footwall were important to how the basal portion of the Duluth Complex was emplaced. Datum points within the upper portion of the Duluth Complex also suggest that these structures were reactivated throughout the emplacement history of the Duluth Complex (see discussion in Part C). Some of the structures were also important controls of Cu-Ni mineralization. A contoured surface of the bedrock ledge is also presented for the Babbitt deposit. Several structural features are outlined by the bedrock ledge. A crude subsurface geologic map is also portrayed for the bedrock ledge. In addition, an isopach map of glacial overburden thickness is included in this report.
The Babbitt Copper-Nickel Deposit: Part C: Igneous Geology, Footwall Lithologies, and Cross-Sections
(University of Minnesota Duluth, 1996-03) Severson, Mark J; Patelke, Richard L; Hauck, Steven A; Zanko, Lawrence M
Twenty-five cross-sections are presented that display the detailed igneous geology for several areas of the Babbitt Cu-Ni deposit. Shown in the cross-sections are the stratigraphic relationships of at least seven major igneous units - Units I through VII of the Partridge River Troctolite Series (PRTS). However, not all seven units are equally present throughout the deposit due to "pinch-out" relationships and lateral gradational rock type changes. In addition to these seven units, three new units are briefly discussed and include the: 1) Bathtub Layered Series (BTLS) of Hauck (1993); 2) Basal Ultramafic Unit (BU Unit) of Severson (1994); and 3) Upper Layered Series (ULS). Small plug-like bodies of Oxide-bearing Ultramafic Intrusions (OUIs) are also locally present within the Babbitt deposit. They intrude the rocks of the PRTS and are often positioned adjacent to, or within, fault zones. Rock types found within the footwall rocks beneath the Complex at the Babbitt deposit are also described. Metamorphic textural variations are described for select units within the Virginia Formation (RXTAL, DISRUPTED, and BDD PO units). These textural variations indicate that the effects of structural deformation, recrystallization, and partial melting are more pronounced than previously thought. The exact origin of the textures is unknown, but is believed to be associated with early stages of Duluth Complex emplacement. Also present within the basal portion of the Virginia Formation are early intrusive rocks that predate emplacement of the Partridge River intrusion (PRI). These early intrusive rocks are referred to as the Virg Sill and "Massive Gray" Unit ("MG" Unit); both are interrelated and are submembers of a single composite sill. At least three major structural features are present in the footwall rocks and include the: Local Boy Anticline, Bathtub Syncline, and Grano Fault (for a more detailed discussion see Part B - Severson et al., 1994). During intrusion of the Partridge River intrusion, specifically during emplacement of the lowest unit (Unit I), the Local Boy Anticline and Bathtub Syncline were important factors controlling how the base of the Complex was formed (see Part B). In addition, these same structures also appear to have been repeatedly reactivated during continued emplacement of the Complex and affected the distribution of specific units within overlying Unit III and the BTLS. Also, the distribution of the "MG" and Virg Sill units are affected by these same two structures. These relationships suggest that reactivation of the structures created "void spaces" into which specific PRTS units were emplaced. The exact details and of this complicated emplacement history have yet to be unraveled.
Bedrock Geochemistry of Archean Rocks in Northern Minnesota
(University of Minnesota Duluth, 1991-07) Southwick, David L; Welsh, James L; Englebert, Jayne A; Hauck, Steven A
The primary purpose of this project is the geochemical evaluation of Archean bedrock in northern Minnesota. The rocks included are both the greenstone/granite and gneissic terranes but exclude the Archean rocks of the Minnesota River Valley. The emphasis is on the characterization of the greenstone portions of the Archean subprovinces. A total of 15 counties with geochemistry pertinent to this project were included: Beltrami, Clay, Hubbard, Becker, Itasca, Cook, Lake, Lake of the Woods, Marshall, Koochiching, Roseau, St. Louis, Polk, Todd, and Norman. The first portion of this project consisted of the development of an archival geochemistry data base that contains all analyses available for Archean rocks through December 1, 1990. This data base consists of data from a number of sources, including published material, unpublished dissertations and theses, and data contained within the abandoned-lease files at the Department of Natural Resources - Minerals Division office in Hibbing, Minnesota. The data base contains 12,451 complete or partial analyses of drill core and bedrock outcrop rock samples that are divided into files by county and sorted by their township-range-section location. Planimetric digital county maps showing locations of samples and drill holes were constructed using AutoCAD software. An additional 219 samples were submitted to X-Ray Assay Laboratories for analysis as part of this project in order to cover areas lacking sufficient data and also to aid in current mapping projects. The second portion of this project consisted of evaluating the data base in terms of quality and completeness of the analyses. The total number of "quality" analyses was reduced to 1,477, and these were then separated into their respective subprovince or area. The divisions consist of the: 1) eastern Vermilion district (which includes Ranges 4 to 11 West of the Wawa-Shebandowan Subprovince); 2) western Vermilion district (which includes Ranges 12 to 17 West of the Wawa Shebandowan Subprovince); 3) western Wawa-Shebandowan Subprovince (Range 18 and west); 4) Giants Range batholith; 5) Wabigoon Subprovince; and 6) Quetico Subprovince. The analyses for each of these areas were then used to geochemically characterize the Archean subprovinces of Minnesota. The eastern Vermilion district is a greenstone terrane, largely volcanic in nature, and generally tholeiitic in composition. The western Vermilion district is more variable and contains both tholeiitic and calc-alkaline volcanics. The rest of the western Wawa- Shebandowan Subprovince has less exposure and is covered in most areas by thick glacial deposits. It appears to be largely tholeiitic in composition and also contains the Deer Lake Complex, ultramafic and mafic tholeiitic differentiated sills in Itasca County. The rocks of the Wabigoon Subprovince are predominantly sedimentary in origin. What little volcanic suites are present appear to be principally tholeiitic in composition, with a minor suite of calc-alkaline rocks. The majority of the samples from the Quetico Subprovince are calc-alkaline felsic intrusives or high-grade amphibolites and gneisses. Additionally, lamprophyres from all of these areas were broken out and considered as a separate package. They were scrutinized more closely due to the recent interest in the lamprophyre/gold association. The third part of this project involved a more intensive geochemical study of a portion of the Wawa-Shebandowan Subprovince described as the Soudan-Bigfork area (Plate 16). The purpose was to further characterize this area due to recent geological mapping projects by the Minnesota Geological Survey and also due to the high exploration activity in the area. This area is defined as Township 59 to 62 North and Range 14 to 27 West. It consists of 16 packages of rocks including: 1) granitoid plutons, scattered throughout the area and intrusive into the other packages; 2) the Giants Range batholith, marking the southern boundary of the area; 3) the Lake Vermilion Formation, generally sedimentary in nature; 4) iron-formations, interbedded within volcanic and sedimentary units throughout the region; 5) the Sherry Lake-Upper Ely Greenstone sequence, tholeiitic pillowed basalts; 6) the Bear Lake-Lower Ely Greenstone sequence, composed of both tholeiitic and calc-alkaline volcanics; 7) the Joy Lake sequence, with sedimentary and mafic to felsic volcanics; 8) the Deer Lake sequence, including differentiated gabbroic sills of the Deer Lake Complex and associated volcanics, both tholeiitic in composition; 9) the Thistledew Lake sequence, consisting of mafic volcanic rocks chiefly of Fe-tholeiite composition and a unit composed of graywacke, slate, and dacitic tuff; 10) the Wilson Lake sequence, with several units composed of mafic to felsic volcanic and sedimentary rocks; 11) the Cook sequence, composed of two units, a graywacke and argillite unit, and a unit consisting of mafic volcanic rocks tholeiitic in composition; and 12) mafic intrusions, a variety of separate intrusions that form dikes and sills in supracrustal sequences throughout the region. Of the original 1,477 "quality" analyses used in part two of this project, 572 samples fell within this area and were divided into these sequences for further detailed geochemical analysis that supports the tholeiitic-calc-alkaline descriptions given previously. Part four of this project involved a detailed geochemical analysis of the Virginia Horn area of northeastern Minnesota. The Virginia Horn area is located in the Virginia-Eveleth area of the Mesabi Range. It is comprised predominantly of metavolcanic and metasedimentary supracrustal rocks of Archean age that are similar to those found in the Vermilion district of northeastern Minnesota, from which it is separated by the Giants Range batholith. Both tholeiitic and calcalkaline suites of metavolcanic rocks occur here; the relationship between them is unclear. However, the occurrence of both suites of rocks without the presence of obvious structural or stratigraphic discontinuities may suggest a geologic setting similar to modern immature island arcs. The area additionally includes quartz-feldspar porphyries, probably altered dacites or rhyodacites, associated with anomalous gold values. These values are related to more intensely-altered zones within the porphyries.
Ceramic Tile And Lightweight Aggregate Product Development Using Minnesota Clays
(University of Minnesota Duluth, 1993-12) Hauck, Steven A
The kaolinite-rich clays found in the St. Cloud area are currently used on a small-scale basis for ceramics by a local university. Testing of a specific clay bulk sample (MAQ) from Meridian Aggregates Company's granite quarry shows that these clays are heterogeneous and not suitable in a raw form for commercial use. However, selective mining and processing could provide a uniform commercial material. While inferior to the commercial kaolin to which it was compared, MAQ's properties can be enhanced by the addition of various controlling substances. Additives tested include ball clay, feldspar, and flint flour, all common to tile body formulation. Tests comparing Springfield C4 ball clay and Silver Bay anorthosite to commercial equivalents indicate desirable properties that would allow their substitution for existing additives in ceramic tile. The Springfield C4 ball clay increases plasticity and workability while reducing shrinkage and absorption, although it does increase the crossover point slightly. The crossover point (used as an indicator of maturity in a fired clay body) is the point on a graph where the shrinkage and absorption curves intersect. The Silver Bay anorthosite acts as a color lightener and retards shrinkage; however, absorption and crossover point can be increased significantly. When used in conjunction with ball clay, the crossover point is reduced. A flowchart showing the equipment necessary to produce ceramic tiles on a small-scale was developed, along with consideration for sufficient space and other supplies. Although the clay resources in the St. Cloud area are presently not developed, the establishment of a light industry ceramic tile processing operation is feasible.
Characterization of New and Traditional Clay Products using Wrenshall, Springfield, and St. Cloud Area Clays
(University of Minnesota Duluth, 1990-11) Toth, Thomas A; Oreskovich, Julie A; Hauck, Steven A; Bresnahan, Richard
Clays and clay minerals from Wrenshall, Springfield, and the St. Cloud area show potential for use as industrial minerals. The Wrenshall clays are Pleistocene glacial lake clays, the Springfield clays are Late Cretaceous non-marine and marine shales, and the St. Cloud area clays are primary and secondary kaolins and Late Cretaceous non-marine shales. This project includes a characterization of the physical properties of these clay raw materials and their finished products. Specialty bricks can be made from the Wrenshall clays using coloring additives, paint rock, taconite concentrate, and wild rice hulls as additives. Springfield non-marine shales can be used as fillers in a tile body to improve plasticity to the body. Springfield marine shales, which bloat upon firing, can be used as lightweight aggregate. The primary kaolins from the St. Cloud area are capable of being used as floor and wall tile and as a ceramic clay. The secondary kaolins can also be used for tile and ceramics, but sufficient quantities have not been found. The non-marine shales in the St. Cloud area (Avon) are currently being used for ceramic pieces. This project characterizes these clays and clay minerals based on evaluation of the shrinkage, absorption, and color of the fired products. These clay deposits can be used as industrial minerals for the products tested.
Comparative Geology, Stratigraphy, and Lithogeochemistry of the Five Mile Lake, Quartz Hill, and Skeleton Lake VMS Occurrences, Western Vermilion District, NE Minnesota
(University of Minnesota Duluth, 2002-12) Hudak, George J; Heine, John J; Newkirk, Trent; Odette, Jason; Hauck, Steven A
Compressed Air Energy Storage (CAES) in Northern Minnesota Using Underground Mine Workings and Above Ground Features
(University of Minnesota Duluth, 2015) Fosnacht, Donald R; Wilson, Elizabeth J; Marr, Jeffrey D; Carranza-Torres, Carlos; Hauck, Steven A; Teasley, Rebecca
The goal of this research project is to determine the potential viability, environmental sustainability, and societal benefits of CAES, as a vital, enabling technology for wind turbine based power generation. The intent of this research is to provide a clear roadmap for CAES development in Minnesota. This project is multifaceted and draws resources across the University System and from key industrial partners: Great River Energy and Minnesota Power. The results from the project will provide vital information to decision makers on the potential of CAES and give guidance on how the technology can be implemented using the unique assets of the Minnesota’ various Iron Ranges (Mesabi and Cuyuna) or in other areas, so that renewable mandates and greenhouse gas reduction can be effectively accomplished. The results show that the topography and water resources exist at various sites that could allow a 100 to 200 MW facility to be constructed if the overall economic, mineral rights, and environmental issues associated with a given site can be properly managed. This report delves into the possibilities and outlines selection criteria that can be used for site selection. Other information is developed to compare the potential economic impact of implementation of the project within the constraints of the factors that can be monetized using the current policy environment. Finally, potential life cycle, regulatory, environmental, and permitting issues that are associated with implementation of the concept are discussed.
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).
Federal Prison Metallurgical Project: Optical Inspection of Spot Weld
(University of Minnesota Duluth, 1986-11-24) Power, Barry; Hauck, Steven A
This report examines the quality of the we'tded joints in wire postal baskets being made at the Duluth Fedenal Prison Camp. The report also addresses probable causes for the defects and possible solutions. The done wor k h,as at the nequest of ilr. Thomas stabe of the Federa't prison camp.
Finish Logging of Duluth Complex Drill Core
(University of Minnesota Duluth, 2007-10) Severson, Mark J; Hauck, Steven A
From 1988 through 2005, NRRI personnel had logged 955 drill holes from the basal zone of the Duluth Complex. The major result of all this effort was the establishment of igneous stratigraphic packages, which in turn, were used to improve our understanding of the mineralization controls on the Cu-Ni deposits and the distribution of Platinum Group Elements (PGE). However, at the beginning of the biennium there were still over 220 drill holes (226,000 feet of core) that remained to be re-logged from portions of the Partridge River and South Kawishiwi intrusions. The main objective of this proposal was to complete a logging campaign of these remaining holes and establish a complete stratigraphic section for these two intrusions of the Duluth Complex. To date, 224 holes have been relogged for this project totaling 198,979 feet of drill core. This total includes several holes that were recently drilled in the Maturi Extension/Nokomis deposit by Duluth Metals, and several recently found drill cores from the Dunka Pit deposit. All of the newly logged holes, see appendix, are located in eight deposits within the Partridge River and South Kawishiwi intrusions; including a few scattered holes in the Cloquet Lake and Tuscarora intrusions. The vast majority of relogged holes were from the Babbitt/Mesaba deposit due to the incredibly large number of drill holes drilled there in the first place. While this project made a significant dent in the total amount of holes logged at the Babbitt deposit, there are still about 20 holes that yet remain to be logged. In an addendum to this report, these drill holes at the Babbitt deposit will be logged, and an unknown number of additional drill holes at the Maturi Extension will be logged.
Finish Logging of Duluth Complex Drill Core (and a Reinterpretation of the Geology at the Mesaba (Babbitt) Deposit)
(University of Minnesota Duluth, 2008) Severson, Mark J; Hauck, Steven A
This project was undertaken with the objective to finish logging all drill holes from the basal contact zone of the Duluth Complex. Logging of Duluth Complex holes by Natural Resources Research Institute (NRRI) personnel began in 1989, when Severson and Hauck (1990) defined the igneous stratigraphy for most of the Partridge River intrusion (PRI). During the ensuing years the NRRI logged a total of 955 holes and defined igneous stratigraphic sections for several more intrusions of the Duluth Complex. As of 2005, a remainder of over 220 holes had yet to be logged. At the end of this project, 295 holes, which include some recently-drilled holes, were logged with about 20 holes still to be logged from the far eastern end of the Mesaba deposit. Lithologic logs for most of the holes that have been logged since 1989 are now available on the NRRI Geology Group’s website at www.nrri.umn.edu/egg/. The vast majority of holes that were logged for this project were from the Mesaba (Babbitt) Cu-Ni±PGE deposit, and thus, this report deals mostly with that deposit. A result of logging a large number of holes at the Mesaba deposit indicates that most of the deposit does not exhibit a stratigraphic package that has been recognized within the nearby Partridge River intrusion. This suggests that most of the deposit is situated within another sub-intrusion, informally called the Bathtub intrusion (BTI). The BTI appears to have been fed by a vent in the Grano Fault area on the east side of the Mesaba deposit. Forty-two cross-sections from the Mesaba deposit, showing the geology in over 450 surface holes, are presented in this report. Another 26 cross-sections, showing the geology in 219 underground holes, are also presented for the Local Boy ore zone of the Mesaba deposit. All of these cross-sections are utilized to define the igneous stratigraphy of the BTI and adjacent PRI at the deposit. All publically-available drill holes have now been logged from the Dunka Pit Cu-Ni deposit located in the South Kawishiwi intrusion (SKI). Nineteen cross-sections through the deposit are presented in this report. These cross-sections show the geology, potential Cu-Ni ore zones in the holes, and the down dip extent of potential mineable zones of the Biwabik Iron Formation at depth. Additional areas in the SKI where holes were logged for this project include the Maturi, Spruce Road, and Nokomis deposits. Cross-sections and hung stratigraphic sections are presented, and they show the geology intersected in these newly-logged holes relative to previously-logged holes. Drill holes from two Oxide-bearing Ultramafic Intrusions (OUI) were also logged for this investigation. These logs include ten holes from the Longnose deposit and ten holes from the Water Hen deposit. Six cross-sections through the Longnose deposit are presented in this report. In summary, the holes logged in this investigation have added greatly to our understanding of the geology of basal portions of the Duluth Complex. In some cases, the previously defined igneous stratigraphic sections for the various intrusions have held up remarkably well as additional holes are drilled and logged. Of course, there are always some exceptions to the rule. In other cases, e.g., the Mesaba deposit, as more holes were logged and/or drilled, the igneous stratigraphy had to be modified in order to explain differences in a group of holes that were situated in the BTI versus the nearby PRI. This change serves as an example that definition of igneous units, and modes of mineralization, in the Duluth Complex is an iterative process and has to be continuously refined as more data, in the form of new drill holes, are generated.
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.
Geological and Geochemical Reconnaissance for Rare Earth Element Mineralization in Minnesota
(University of Minnesota Duluth, 2014) Hauck, Steven A; Heine, John J; Severson, Mark J; Post, Sara P; Chlebecek, Sara; Monson Geerts, Stephen D; Oreskovich, Julie A; Gordee, Sarah M
Geological Mapping of the Needleboy Lake – Six Mile Lake Area, Northeastern Minnesota: a Summary of Volcanogenic Massive Sulfide Potential
(University of Minnesota Duluth, 2002-09) Hudak, George J; Heine, John J; Hocker, Stephanie M; Hauck, Steven A
The Needleboy Lake and Six Mile Lake areas has focused on evaluating the stratigraphic succession, hydrothermal alteration, and synvolcanic and post-volcanic structures in an effort to better understand the VHMS potential in this region of the Lower Ely Greenstone. Field mapping in the Needleboy Lake area (performed during August, 2001) investigated all outcrops within a 100 to 200 meter perimeter of the Lake. A north-south section was also completed from the north-central shoreline of Five Mile Lake to the western shoreline of Needleboy Lake. Field mapping in the vicinity of Six Mile Lake (performed August-September, 2002) included three detailed north-south traverses (Fig. 4). Traverse 1 extended from the northwestern shoreline of Needleboy Lake to the western shoreline of Six Mile Lake. Traverse 2 extended from the northeastern shoreline of Needleboy Lake to approximately 200 meters north of Six Mile Lake. Traverse 3 extended from the southeastern part of Needleboy Lake to approximately 500 meters northeast of Six Mile Lake. In addition, all outcrops occurring along roads in the study area were investigated.
Geology and Cr-PGE Mineralization of the Birch Lake Area, South Kawishiwi Intrusion, Duluth Complex
(University of Minnesota Duluth, 1997) Hauck, Steven A; Severson, Mark J; Ripley, Edward M; Goldberg, Steven A; Alapieti, Tuomo
Geology and Mineralization in the Dunka Road Copper-Nickel Mineral Deposit, St. Louis County, Minnesota
(University of Minnesota Duluth, 1990-03) Monson Geerts, Stephen D; Barnes, Randal J; Hauck, Steven A
The Dunka Road Cu-Ni deposit is within the Partridge River Intrusion (T. 60 W., R. 13 W.), which is part of the Duluth Complex, and is approximately 1.1 b.y. (Keweenawan) in age. Relogging of 46 drill holes at the Dunka Road Cu-Ni deposit identified four major lithologic units and several internal ultramafic subunits that can be correlated over two miles. The ultramafic subunits (layers of picrite to peridotite) exhibit relative uniform thicknesses and are present at the same relative elevation within the major lithologic units. The major lithologic units, the same as delineated by Severson and Hauck (1990), and upward from the basal contact are: Unit I, a fine- to coursegrained a sulfide-bearing troctolite to pyroxene troctolite (450 ft. thick) with associated ultramafic layers I(a), I(b), and I(c); Unit II, a medium- to coarse-grained troctolite to pyroxene troctolite (200 ft. thick) with a basal ultramafic layer II(a); Unit III, a finegrained, mottled textured troctolitic anorthosite to anorthositic troctolite (150 ft. thick) with one minor ultramafic layer III(a); and Unit IV, a coarse-grained troctolite/pyroxene troctolite to anorthositic troctolite with associated ultramafic layers IV(a) and IV(b). Most sulfide mineralization occurs within Unit I. Within Unit I the sulfide mineralization is both widespread but variable in modal percentage (rare to 5%), continuity and thickness (few inches to tens of feet). Sulfide mineralization is somewhat related with proximity to: hornfels inclusions, the basal contact with the footwall Virginia Formation, and some of the internal ultramafic layers within Unit I. Precious metal mineralization (Pd+Pt+Au) is associated with fracturing and alteration of the host rocks. The alteration assemblage is chlorite, bleached plagioclase, serpentine and uralite. Pd+Pt values range from 100 to >2400 ppb over 10 foot intervals. These intervals can occur independently as 10 to 50 foot zones, or as part of a larger correlatable occurrence/horizon. Two mineralized subareas within the Dunka Road deposit are: 1) an area which is peripheral to a highly anomalous Pd occurrence (reported by Morton and Hauck, 1987; 1989) herein termed the "southwest area", and 2) the "northeast area" which contains several drill holes that have near surface intercepts of >1% Cu. There are four somewhat large mineralized occurrences within the study area that carry >300 ppb combined total Pt+Pd+Au. These mineralized zones appear to be stratigraphically controlled by the ultramafic subunits within Unit I. Three of the four correlatable zones are found within the southwest area, and range from 40 to 130 feet thick. High Pd values within these zones range from 10 to 20 feet thick with values of 800 to 1650 ppb Pd. In the northeast area, the fourth mineralized zone appears continuously throughout Unit I. This zone ranges from 120 to 300 feet thick. High Pd values within this zone range from 10 to 40 feet thick with values of 800 to 1500 ppb Pd. Many 5 to 30 foot intersections of >1 ppm Pd+Pt+Au occur throughout the mineral deposit. Geostatistical analysis based on 72 vertical holes and 12 angle holes suggests: 1) the base of the complex is a critical datum with the higher grade intercepts located between 100 and 400 feet above the base; 2) high inter-element correlations support local redistribution/concentration of primary mineralization by a secondary hydrothermal process and thus, polymetallic mining selectivity is possible; 3) the available drilling gives a spacial range of geologic influence at 400 foot centers, but sufficient angle drilling is not available to assess the potential of high grade, steeply dipping mineralized zones; 4) additional vertical in-fill drilling will almost certainly not discover any additional quantity of ore within the volume of rock studied; but 5) additional angle drilling to assess the potential of high grade, steeply dipping, mineralized zones would benefit a more complete geostatistical analysis.
Geology and Mineralization of a Cyclic Layered Series, Water Hen Intrusion, St. Louis County, Minnesota
(University of Minnesota Duluth, 1990-03) Strommer, James; Morton, Penelope; Hauck, Steven A; Barnes, Randal J
The Water Hen intrusion is an oxide-bearing (ilmenite + magnetite) ultramafic intrusion (OUI) that is emplaced along a pre-basement fault into the troctolitic series rocks of the Duluth Complex. The intrusion consists of medium-grained dunite and peridotite and local pegmatitic pyroxenite approximately 1,600 ft. x 500 ft. x 700 ft. in size. Oxide (>90% ilmenite) composes from 5-50% of the various lithologies. Sulfides are minor, about 2-5%, and are predominantly pyrrhotite with minor cubanite, chalcopyrite and pentlandite. Concentrations of 5-80% graphite also occur within the intrusion. Surrounding the Water Hen intrusion is a zone of mixed lithologies (Mixed Zone) consisting of the host rock troctolites, apophyses of OUI and local inclusions of footwall rocks. The Mixed Zone (M) is dominated by >60% troctolitic rocks with OUI composing the remainder. The OUI apophyses vary from 1-50 ft. thick and have sharp contacts with the country rock. The troctolitic host rocks for the Water Hen intrusion consist of medium- to coarsegrained troctolite to anorthositic troctolite (TA unit) and a troctolitic cyclically layered series (TL unit). The cyclically layered series is similar to troctolitic layered rocks at Bardon Peak. The individual cyclic layers are 6 in. to 10 ft. in thickness and the entire unit is over 300 ft. thick. The An content decreases from An80 at the bottom of the unit to An60 near the top of the unit. The individual cyclic layers are composed of ilmenite-dunite at the base and grade upward to anorthositic troctolite. The bottom contacts are sharp and each successive layer within the individual unit is identified by the occurrence of biotite or clinopyroxene. In the bottom olivine-rich layer, the oxides (<5%) are ilmenite >> magnetite. The sulfides in this same layer (3-5%) are coarse-grained with cubanite > chalcopyrite > pentlandite >> pyrrhotite. In the more feldspathic layers, the sulfides (1-3%) are fine-grained with chalcopyrite >> pentlandite = cubanite + pyrrhotite. The oxides (1- 5%) are also fine-grained with ilmenite >> magnetite. The footwall rocks in the Water Hen area consist of very fine-grained metamorphosed Virginia Formation and fine-grained hornfelsed basalt and/or troctolite. There are >100 ft. of basalt or chilled margin rocks within the footwall. This mafic hornfels commonly occurs between the Virginia Formation and the TA unit. Orthopyroxenite dikes and dikelets also occur in the mafic hornfels. These dikes contain anomalous PGEs and secondary sulfide mineralization. The copper-nickel sulfides are primary igneous sulfides associated with the troctolitic rocks. Violarite, pyrite and secondary magnetite in cross-cutting veinlets and other secondary sulfides indicate that the primary sulfides were altered and remobilized by a later event. Cu:Ni ratios have a bimodal distribution that is not followed by the PGEs. However, Cu, Ni, Ag, Au, Pt, Pd are all highly correlated with each other. This high interelement correlation suggests that the late-stage (secondary) remobilization locally redistributed and reconcentrated these elements.
Geology and SEDEX Potential of Early Proterozoic Rocks, East-Central Minnesota
(University of Minnesota Duluth, 2003) Severson, Mark J; Zanko, Lawrence M; Hauck, Steven A; Oreskovich, Julie A
Geology, Geochemistry, and Stratigraphy of a Portion of the Partridge River Intrusion
(University of Minnesota Duluth, 1990-03) Severson, Mark J; Hauck, Steven A
Detailed relogging of drill holes (83 holes totalling 100,630 feet of core) and reconnaissance mapping have delineated three major rock groups within a portion (T.58-59 N., R.13-14 W.) of the Partridge River intrusion (PRI), Duluth Complex, Northeastern Minnesota. These have been informally designated as the Partridge River Troctolitic Series (PRTS), Partridge River Gabbro Complex (PRGC) and Oxide-bearing Ultramafic Intrusions (OUI). The PRTS consists of at least eight major igneous units which are correlatable in drill holes over an indicated eleven mile strike length extending (NE to SW) from the Dunka Road Cu-Ni deposit to the Wyman Creek Cu-Ni deposit. From the base up, these units are characterized by: Unit I - sulfide-bearing augite troctolite with minor picrite to peridotite layers; Unit II - troctolite and augite troctolite, with abundant picrite to peridotite layers (Wetlegs Cu-Ni area) and/or minor sulfide-bearing zones; Unit III - mottled textured anorthositic troctolite exhibiting a highly irregular olivine oikocryst distribution; Unit IV -augite troctolite with a picritic base and grading upwards into Unit V; Unit V - coarse-grained anorthositic troctolite; Unit VI - augite troctolite to anorthositic troctolite with a picritic base; and Unit VII - augite troctolite with a well-bedded peridotite-picrite base. Field mapping suggests that an eighth unit (Unit VIII) and possibly additional units are present above Unit VII. Unit VIII consists of troctolite to anorthositic troctolite with a well-bedded peridotite base. Most of the upper units (III-VIII) represent single cooling units in that they are floored by a bedded ultramafic member; whereas, other units (I and II) near the footwall exhibit an overall heterogeneous nature and contain abundant internal members reflecting continuous magma replenishment. Some of the units also exhibit downcutting relationships and lateral "facies" changes along strike indicating a complex intrusive history. Structural studies of the basal contact of the Partridge River intrusion have indicated more structure than previously recognized. Structure contour maps of the footwall rocks at the basal contact of the Duluth Complex and on the top of the Biwabik Iron-Formation, and isopach maps of the Virginia Formation beneath the PRI indicate that pre-existing folds in the basement rocks at both Minnamax and Dunka Road exerted a strong control over the form of the base of the intrusion. Cross-sections illustrating the internal "stratigraphy" indicate that in both the Dunka Road and Wetlegs areas, numerous NE-trending normal faults parallel to the Mid-continent Rift are present. These faults support the halfgraben model (Weiblen and Morey, 1980) which envisions a step-and-riser geometry at the base of the Duluth Complex due to extensional tectonics. However, most of the faults delineated show corresponding offsets in both the troctolitic and footwall rocks and are, thus, not true half-graben faults as envisioned in the model. The only exception is within the Wetlegs area where a NE-trending fault exhibits substantial offset in the footwall rocks, but no offset is present in the overlying troctolite rocks. An inferred window of Biwabik Iron- Formation is in direct contact with the PRI along this fault. Three late-stage Oxide-bearing Ultramafic Intrusions (OUI) are also located along this zone that suggests they may be genetically related to areas where massive iron-formation assimilation has occurred. The OUIs are later pegmatitic intrusives consisting of dunite, peridotite, clinopyroxenite, and lesser picrite and melagabbro; all are oxide-bearing (> 10%) and contain semi-massive to massive oxide horizons. These bodies are intrusive into the PRTS and include the Longnose, Longear, Section 17, Wyman Creek, and Skibo Fe-Ti prospects. The PRGC is situated at the southeastern portion of the investigated area and consists dominantly of oxide-bearing gabbroic and troctolitic rocks; both locally exhibit excellent modal bedding, which may be related to magmatic density currents. The Colvin Creek "Gabbro" (CCG) is part of the PRGC and was originally interpreted to be a hornfelsed basalt. However, reconnaissance mapping indicated that similar fine-grained CCG-type "gabbro" is present within the coarse-grained rocks of the Powerline Gabbro and vice versa. Because the Powerline Gabbro is located near the CCG, the two bodies may be intricately related. Within the Colvin Creek "Gabbro" are several unusual sedimentary-like structures that are not indicative of typical North Shore Volcanic basalts. However, textures resembling vesicles/amygdules are locally present. The unusual sedimentary-like structures suggest a magmatic density current origin but the exact origin of these textures is enigmatic. Also within the Colvin Creek "Gabbro" is a mile-long 1,000 foot-thick belt of cross-bedded rocks. Several internal features of these cross-bedded rocks, e.g., lack of rock fragments, no quartz, are not indicative of typical interflow sandstones and their relationship to the surrounding rocks suggests they may have also been deposited by magmatic density currents. The unmineralized portions of all the units were sampled (155 samples) in order to establish background geochemical levels and lithogeochemical signatures for each unit and to investigate possible origins for the different units. Background Pd, Pt, and Au values in the major rock groups average 10 ppb, 20 ppb, and 5 ppb, respectively. However, slightly elevated background values are associated with Unit II (15 ppb, 24 ppb, and 9 ppb, respectively), and the OUI rock group (15 ppb, 24 ppb, and 17 ppb respectively). In the course of sampling unmineralized rock (<1% sulfides), five anomalous samples (>200 ppb combined Pd and Pt) were revealed with a maximum of 910 ppb. The OUI units are the most geochemically unique in that they have elevated background values for TiO2, V, Cr, Co, Cu, Cd, C, Be, Sc, Sb, Pb, Te, Au, and W relative to the other igneous units. Geochemical data support the various rock units identified during relogging of the PRI. Units I and II exhibit a markedly different geochemical signature when compared to the other PRTS units. One interpretation of this difference is that magma contamination due to assimilation of footwall material was important in their genesis. All rock units of the PRGC have the same geochemical signature and, in turn, this geochemical signature is similar to the geochemical signature for the lower half of Unit I. The OUI units exhibit a markedly different geochemical signature when compared to all the other PRI units.

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