Browsing by Subject "Northeastern Minnesota"

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    Browse Availability, Bite Size, and Effects of Stand Age on Species Composition and Browse Density for Moose in Northeastern Minnesota
    (2014-05) Ward, Rachel Leigh
    Large ruminant herbivores like moose spend most of their time foraging and ruminating to acquire and process enough plant biomass to meet energy and nutrient requirements. In northeastern Minnesota, moose forage in a mosaic of forest stands with ages shaped by harvest and other disturbances. Distribution and abundance of browse species varies across the landscape and each browse species has unique growth patterns and a patchy distribution within and among different stand types. To estimate available and consumed biomass, we collected available twigs and created diameter-at-point-of-browsing-biomass regressions for each browse species. These relationships varied by canopy closure and were used to estimate biomass consumed on foraging paths. We also measured browse availability and use along foraging paths of GPS radio-collared moose and within randomly selected regenerating stands in northeastern Minnesota. We measured all sites using traditional methods and a method that simulates moose foraging behavior by measuring large feeding stations. We tested the hypotheses that (1) browse density is higher at large feeding stations than at random locations along a foraging path, (2) browse density is higher at large feeding stations than at randomly chosen feeding stations along a foraging path, and (3) browse density is higher at large feeding stations than along a straight transect. At each site we measured available species composition, available browse density, diet composition, and browse species selection. Combined with the use of GPS collars this method allowed us to compare the foraging path diet composition and browse selection of individual free-ranging moose. Paper birch, willow, and quaking aspen were common in young stands while hazel, mountain maple, and balsam fir (winter) or juneberry (summer) were common in older stands. Browse density also changed with stand age, but the changes in species composition and browse density were similar along foraging paths and within randomly selected regenerating stands indicating that moose habitat restoration projects can effectively create forage for moose. In areas with and without collared moose the simulated browsing method was an effective tool for measuring browse availability and use. We also provide evidence from the field that moose, and possibly other large herbivores, obtain most of their energy intake from small patches of high density browse.
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    Copper-Nickel Grade Maps for the Spruce Road Deposit, South Kawishiwi Intrusion, Duluth Complex
    (University of Minnesota Duluth, 2002-02) Peterson, Dean M
    This report describes the Cu-Ni mineralization of the Spruce Road area in the northern portion of the South Kawishiwi intrusion. The mineralization in the area is defined by > 9,500 assays from approximately 140,000 feet of core from 232 exploration holes drilled by INCO (220 holes), Bear Creek (6 holes), U.S. Bureau of Mines (3 holes), Hanna Mining (2 holes), and Wallbridge Mining (1 hole). Drilling in the Spruce Road area largely occurred during two time periods: the middle 1950s, following the original discovery of Cu-Ni mineralization, and from 1966 to 1973. Assay data from all of the drill holes within the South Kawishiwi intrusion have been compiled by the author into a comprehensive geological and geochemical database. Drill hole assays for the Spruce Road area have been exported out of this database and form the geochemical basis for this report. Preliminary analysis of the drill hole assay data for all of the deposits of the South Kawishiwi intrusion has led to the identification of two main styles of mineralization associated with the base of the intrusion. These mineralization types include: 1) “Open” – vertically extensive (> 450 meters) mineralization with moderate Cu-Ni grade and low Au+PGE grades. Examples of this open style include the Spruce Road, Serpentine, and Dunka Pit deposits. 2) “Confined” – vertically restricted (< 150 meters) mineralization with high Cu-Ni grades and moderate to very high (locally) Au+PGE grades. Examples of the confined style include the Maturi, Maturi Extension, and the Birch Lake deposits. Regional crosscutting relationships indicate that the “Open” style mineralization preceded the “Confined” style. Moreover, the curvilinear nature of the contact between the styles of mineralization is similar to the regional contacts of most of the intrusions of the Duluth Complex and adds further support to this theory.
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    Electron Microprobe Analysis of Alteration Mineralogy at the Archean Five Mile Lake Volcanic Associated Massive Sulfide Mineral Prospect in the Vermilion District of Northeastern Minnesota
    (University of Minnesota Duluth, 2003-05) Hocker, Stephanie M; Hudak, George J; Heine, John J
    Alteration mineral assemblage mapping at the Five Mile Lake Prospect in the Vermilion District of northeastern Minnesota has identified two distinct types of alteration zones within 2.7 billion year-old volcanic and volcaniclastic rocks associated with volcanic-hosted massive sulfide (VHMS) mineralization (Hudak et al., in press; Odette et al., 2001a, 2001b; Peterson, 2001). Regional semi-conformable alteration zones are composed of various proportions of quartz + epidote ± amphibole ± chlorite ± plagioclase feldspar. These regional, semiconformable alteration zones are locally crosscut by several relatively narrow, northeast trending disconformable alteration zones composed of fine-grained chlorite and/or sericite that are closely associated with synvolcanic fault zones. Electron microprobe analyses of the various alteration mineral phases (epidote group minerals, chlorite, amphibole, white mica, and feldspar) have been conducted in an effort to better understand the hydrothermal processes associated with the development of the semiconformable and disconformable alteration zones at the Five Mile Lake Prospect. These analyses indicate that: a) epidote group minerals range in composition from oisite/clinozoisite to pistacite; b) chlorite is dominantly ripidolite; c) amphibole is primarily actinolite and ferroactinolite, with magnesio-hornblende and ferro-hornblende also present; d) sericite is finegrained muscovite; and e) feldspar is albite. This mineral chemistry suggests the presence of a complex, long-lived hydrothermal system that evolved from seafloor-proximal (hundreds of meters) to deeper subseafloor environments (~1-3 km) as the volcanic rocks were buried by rapid, dominantly effusive mafic to intermediate volcanism and associated sedimentation. Alteration mineral chemistry at the Five Mile Lake Prospect is remarkably similar to that from the Noranda VHMS mining camp of Canada as well as other VHMS orebodies. This mineral chemistry, combined with favorable volcanology and numerous untested geophysical targets, suggest that the Five Mile Lake Prospect, as well as the uppermost several hundred meters of the Lower Member of the Ely Greenstone, have excellent exploration potential for VHMS mineral deposits.
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    Electron Microprobe Analysis of Alteration Mineralogy at the Archean Five Mile Lake Volcanic Associated Massive Sulfide Mineral Prospect in the Vermilion District of Northeastern Minnesota
    (University of Minnesota Duluth, 2003-05) Hocker, Stephanie M; Hudak, George J; Heine, John J
    Alteration mineral assemblage mapping at the Five Mile Lake Prospect in the Vermilion District of northeastern Minnesota has identified two distinct types of alteration zones within 2.7 billion year-old volcanic and volcaniclastic rocks associated with volcanic-hosted massive sulfide (VHMS) mineralization (Hudak et al., in press; Odette et al., 2001a, 2001b; Peterson, 2001). Regional semi-conformable alteration zones are composed of various proportions of quartz + epidote ± amphibole ± chlorite ± plagioclase feldspar. These regional, semiconformable alteration zones are locally crosscut by several relatively narrow, northeasttrending disconformable alteration zones composed of fine-grained chlorite and/or sericite that are closely associated with synvolcanic fault zones. Electron microprobe analyses of the various alteration mineral phases (epidote group minerals, chlorite, amphibole, white mica, and feldspar) have been conducted in an effort to better understand the hydrothermal processes associated with the development of the semiconformable and disconformable alteration zones at the Five Mile Lake Prospect. These analyses indicate that: a) epidote group minerals range in composition from zoisite/clinozoisite to pistacite; b) chlorite is dominantly ripidolite; c) amphibole is primarily actinolite and ferroactinolite, with magnesio-hornblende and ferro-hornblende also present; d) sericite is finegrained muscovite; and e) feldspar is albite. This mineral chemistry suggests the presence of a complex, long-lived hydrothermal system that evolved from seafloor-proximal (hundreds of meters) to deeper subseafloor environments (~1-3 km) as the volcanic rocks were buried by rapid, dominantly effusive mafic to intermediate volcanism and associated sedimentation. Alteration mineral chemistry at the Five Mile Lake Prospect is remarkably similar to that from the Noranda VHMS mining camp of Canada as well as other VHMS orebodies. This mineral chemistry, combined with favorable volcanology and numerous untested geophysical targets, suggest that the Five Mile Lake Prospect, as well as the uppermost several hundred meters of the Lower Member of the Ely Greenstone, have excellent exploration potential for VHMS mineral deposits.
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    Field Guide for Maintaining Rural Roadside Ditches
    (2014) Brady, Valerie; Axler, Richard P.; Schomberg, Jesse
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    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.
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    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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    Geology, Mineralization, and Geostatistics of the Minnamax/Babbitt Cu-Ni Deposit (Local Boy Area), Minnesota: Part I: Geology
    (University of Minnesota Duluth, 1991-06) Severson, Mark J
    The Minnamax Cu-Ni deposit (also called the Babbitt deposit) is situated within what has been informally referred to as the Partridge River intrusion (or Partridge River Troctolite) of the Duluth Complex (1.1 Ga), northeastern Minnesota. The deposit has been subdivided into five contiguous ore zones; the Local Boy area and Bathtub area are two ore zones described in this report. Within the deposit are a wide variety of troctolitic, ultramafic, and footwall rock types, and hornfelsed inclusions (both footwall and hanging wall). Many specific rock types are correlative between drill holes and can be grossly categorized into seven sub-horizontal troctolitic units, three types of hornfelsed inclusions, and a late cross-cutting pegmatitic phase. Also present are correlative units within the footwall rocks. All rock units were identified by detailed relogging of 61 surface drill holes (117,605 feet of core) and are portrayed on nine cross-sections that extend through various portions of the Minnamax deposit. Severson and Hauck (1990) described the stratigraphy of the troctolitic rocks of the Partridge River Troctolite to the west of the Minnamax deposit; the stratigraphy is referred to as the Partridge River Troctolite Series (PRTS). Most of the PRTS rock units defined at the Dunka Road Cu-Ni deposit (located to the immediate SW of Minnamax) by Severson and Hauck (1990) are present at Minnamax. However, the overall picture at Minnamax is more complicated than Dunka Road due to rock type changes that are manifested by: 1) pinch-out and reappearance of specific marker bed units; 2) down-strike gradational changes of ultramafic horizons; 3) extremely limited areal extent of some ultramafic horizons; and 4) gradational changes in the troctolitic rock types between drill holes. In some areas a particular marker horizon may "disappear" laterally and then reappear at the same stratigraphic level in another group of drill holes. In spite of these local difficulties, a gross stratigraphy of seven subhorizontal igneous units is present at Minnamax and consists of (from bottom to top): Unit I - heterogeneous, sulfide-bearing augite troctolite and troctolite with abundant metasedimentary inclusions; Unit II - homogeneous troctolite with a basal picrite horizon (Unit II is present only in the SW portion of the Minnamax deposit); Unit III - mottled textured anorthositic troctolite to troctolite with characteristic olivine oikocrysts (Unit III is present mainly in the SW portion of Minnamax and is enveloped by Unit I to the NE); Unit IV - mixed homogeneous troctolite and augite troctolite (augite troctolite is at the top of Unit IV in localized areas) with a semipersistent basal ultramafic horizon termed the "± picrite"; Unit V - homogeneous anorthositic troctolite that exhibits a gradational contact with Unit IV; and Units VI and VII - homogeneous troctolites with persistent basal ultramafic horizons. More abundant and thicker ultramafic horizons are present in Units VI and VII in the Bathtub area of the Minnamax deposit. Specific marker horizons utilized in drill hole correlations include: Unit III, "± picrite," "pocket picrite," top of Unit IV (augite troctolite), and the ultramafic base of Units VI and VII. The troctolitic stratigraphy is cut by pegmatitic orthopyroxenite and peridotite bodies that are referred to as OUI - Oxide-bearing Ultramafic Intrusions. Pegmatitic hybrid hornblendite and granophyre also cut the stratigraphy and are often related to the OUI bodies. Rusty chlorine-rich drops may commonly coat the core of the ultramafic horizons and OUI bodies. Several enigmatic hornfelsed inclusions are present in Units VI and VII at Minnamax. These are grouped in two categories that include: 1) CC-type inclusions that are similar to outcrops of the Colvin Creek hornfels; and 2) "pic"-type inclusions that are similar to nearby outcrops of basalt inclusions. Both inclusion types are similar in that they contain fine-grained plagioclase-filled ovoids or wisps that may represent vesicles, and they exhibit the same chemical signature. However, they exhibit a different mineralogy (the CC-type inclusions are oxide-rich). Their stratigraphic position in the troctolitic rocks suggests that they are probably hanging wall material (North Shore Volcanic Group). While these two inclusion types are readily correlative between drill holes, the nature of their different mineralogy remains unknown. Another enigmatic rock type is present within the lower portion of the Virginia Formation footwall rocks. The rock is unique in that it contains hornblende ± olivine and locally grades into serpentinized picrite with hornblende. It is generally concordant with the overall bedding of the Virginia Formation and is referred to as the sill(?) unit. Whole rock geochemistry indicates that this unit locally exhibits: high Cl contents that are similar to Cl values of ultramafic horizons in the troctolitic rocks; MG numbers that are more primitive than the ultramafic horizons; and high Cr contents that are much higher than anything sampled in the overlying troctolitic section. If the unit was a sill, it now exhibits gradational contacts with the metasedimentary rocks and is characterized by a granoblastic texture with superimposed euhedral hornblende. These data may indicate that the sill was intruded before, and hornfelsed during, emplacement of the majority of the Partridge River Troctolite Series.
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    Geology, Mineralization, and Geostatistics of the Minnamax/Babbitt Cu-Ni Deposit (Local Boy Area), Minnesota: Part II: Mineralization and Geostatistics
    (University of Minnesota Duluth, 1991-06) Severson, Mark J; Barnes, Randal J
    The Minnamax/Babbitt Cu-Ni deposit, located within the Partridge River Troctolite Series (PRTS) of the Duluth Complex, northeastern Minnesota, contains both troctolite-hosted disseminated ore and footwall-hosted massive sulfide ore. This report pertains to the massive sulfide ore zone, which is restricted to a small portion of the deposit, and is referred to as the Local Boy area. Studies conducted in the Local Boy area include: 1) detailed geologic relogging of drill core; 2) sulfide petrography and microprobe analysis; 3) assaying for Pt, Pd, Au, and Ag in the high-grade Cu ore zones; and 4) geostatistical analysis of the Cu-Ni ore (plus PGEs and precious metals). Detailed relogging of 76 underground drill holes, along with pertinent surface drill holes, has been completed within the Local Boy area (from drifts B, C, and D). The data indicates the highly undulatory nature of the basal contact of the Duluth Complex with the footwall Virginia Formation. Intrusive rocks of the Duluth Complex (Unit I of the PRTS) consist of augite troctolite, troctolite, and norite. All exhibit gradational contacts with each other, and all may occur at any stratigraphic position relative to the undulatory basal contact. However, norite is the most common rock type adjacent to sedimentary hornfels inclusions and at the basal contact due to contamination of the magma. The spatial configuration of the intrusive rocks indicates that Unit I was intruded as multiple pulses along bedding planes of the Virginia Formation. The Virginia Formation hosts the majority of the massive sulfide ores that are present within hornfels inclusions positioned above the basal contact, and within the footwall rocks at and below the basal contact. Massive sulfide ore is not as common within the intrusive rocks, and when present, is generally associated with, or in close proximity to, hornfels inclusions. Ore/host rock textures are extremely varied, but all are indicative of structural control in the footwall rocks. Overall, the massive sulfide ores are spatially distributed in a spotty manner in an east-west (EW) direction that corresponds to a major EW-trending anticline present within the footwall rocks. All these factors suggest that an immiscible sulfide melt was injected into structurally prepared footwall rocks along the anticlinal axis in a "vein-like" setting. At some later period, the footwall-hosted massive sulfide ore zone was re-intruded by multiple sills (which collectively make up a portion of Unit I) along bedding planes of the Virginia Formation. The end result is a disjointed zone of mineralized inclusions and mineralized footwall rocks separated by "barren" intrusive rocks. Sulfide textures indicate that the sulfides formed by cooling of a monosulfide solid solution (MSS) followed by limited replacement at very low temperatures. Minerals contained within the sulfide ore are dominantly pyrrhotite, chalcopyrite, cubanite, and pentlandite. Locally present are maucherite, sphalerite, bornite, talnakhite, mackinawite, and an unknown Cu-sulfide ("Cp"). Also present in minor amounts are native silver (primary and secondary), parkerite, chalcocite, covellite, godlevskite, violarite, magnetite, and zincian hercynite. Although no discrete PGE minerals were identified, analytical results of the high-grade (>1% Cu) massive sulfide ore confirms the presence of several anomalous PGE values. These spot values are mainly confined to an EW-trending zone that also roughly corresponds to the EW-trending anticline. Maximum values obtained within the Local Boy massive sulfide ores include: Pd = 11,100 ppb; Pt = 8,300 ppb; Au = 10,900 ppb; and Ag = 34 ppm. Native silver (primary) was found within several maucherite grains in this investigation, and PGE mineral inclusions have previously been found in maucherite (Ryan and Weiblen, 1984). Generally, the drill holes that contain the anomalous PGE values also contain the native silverbearing maucherite; whereas, homogeneous maucherite is more characteristic of drill holes with little to no anomalous PGE values. This suggests that PGEs were scavenged from the sulfide melt by early-formed maucherite, and thus the PGEs are related to a primary (magmatic) process. However, a hydrothermal origin for the PGEs is also indicated. Anomalous PGE values are commonly associated with Cl-drop encrusted massive sulfide drill core. The spatial distribution of the Cl-drop encrusted drill core also coincides with the EW-trending anticline. Presence of the Cldrops indicates that the rocks of the Local Boy area were invaded by Cl-bearing solutions that may have been capable of transporting and concentrating PGEs. Therefore, both primary/magmatic (sulfides injected into a "vein-like" setting) and later secondary/hydrothermal processes appear to have been factors in controlling PGE distribution in the Local Boy area. However, it is difficult to separate the primary and secondary processes. This is due to the coincidence of several features within the EW-trending zone, which include: 1) anticline in the footwall rocks; 2) overall massive sulfide spatial distribution; 3) spatial distribution of anomalous PGE values; and 4) spatial distribution of Cl-drop encrusted core. Reactivation of structures that controlled the initial "vein-like" massive sulfide distribution could have been responsible for channeling later hydrothermal solutions. Geostatistical analysis of the underground drill holes (Drifts B, C, and D), and pertinent surface drill holes, yields five main conclusions: 1) the top of the Biwabik Iron-formation (BIF) is a critical datum, with the higher grade Cu-material located between 100 and 400 feet above the BIF (mainly within the Virginia Formation near the basal contact); 2) inter-variable correlations between Cu and Ni are high, indicating that selective mining of Cu and Ni is physically possible; but, selection on ore grade Cu and Ni will not necessarily capture all the ore grade PGEs and other precious metals; 3) the available drilling gives a spacial range of geologic influence of about 150 feet; 4) potentially economic ore reserves do exist in the Local Boy area; and 5) the property is under-valued due to the inclusion of many "barren" (unassayed) intervals into the compositing process. A coarse block model, and in situ geologic reserves, are presented for the Local Boy area.
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    Imagining Scientific Realities Deep Underground: Utilizing Knowledge and 3-D Geological Modeling, Fundamental Tenets of The University of Minnesota’s Proposed Institute for Underground Science and Soudan Dusel
    (University of Minnesota Duluth, 2007-03) Peterson, Dean M
    The ultimate goal of scientific research is to enhance knowledge, thus allowing one (or all) to imagine reality. The most renowned physicists, e.g., Nicholas Copernicus, Galileo Galilei, Isaac Newton, Max Planck, Albert Einstein, and Niels Bohr, and geologists, e.g., Nicholas Steno, William Smith, Charles Lyell, Louis Agassiz, Alfred Wegener, Harry Hess, and J. Tuzo Wilson, all used their individual imaginations to open the door to new scientific realities that we as a society now realize. Quite possibly the greatest scientific reality ever imagined is Charles Darwin’s theory of Natural Selection (“On the Origin of Species,” published in 1859). The National Science Foundation’s (NSF) goal of scientific research at a U.S. Deep Underground Science and Engineering Laboratory (DUSEL) is to enhance our collective knowledge of physics, geology, biology, and engineering through dedicated research in a deep underground setting. This short report highlights some of the geological features and their relationships to future science opportunities associated with the University of Minnesota’s most recent (January 9, 2007) DUSEL proposal to the NSF (Marshak et al., 2007). In this proposal, the University plans to develop the Institute for Underground Science (IUS) at the University of Minnesota and expand the current Soudan Underground Laboratory down to a depth of 1500m, i.e., 4125 meters of water equivalent (MWE) immediately southeast of its current location. The IUS would be a widely-collaborative, multidisciplinary institute with a mission to facilitate a coherent theoretical and experimental program in underground science and technology. Previous University of Minnesota DUSEL proposals (Marshak et al., 2003, 2005) have outlined the opportunities for deep underground science at the Soudan Mine near Tower, Minnesota, though an interdisciplinary science vision was not yet developed in the 2003 proposal, and the location of a Soudan DUSEL in the 2005 proposal was approximately one mile east (and thus largely hosted within a different stratigraphic sequence of rocks) than the recently proposed site at Soudan.
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    Land Application of De-Inking Residue
    (University of Minnesota Duluth, 1996-04) McCarthy, Barbara J; Monson Geerts, Stephen D
    Pulp facilities which recycle office waste paper generate a large amount of waste by-products in the process of producing high-grade pulp. The paper-like substance, called de-inking residue, was evaluated for use as a soil amendment on land used for crop production in northeast Minnesota. Research plots were established in the fall of 1993 in Grand Rapids, Minnesota. The 10- by 20-foot plots were arranged in a randomized block design with 3 replications consisting of 3 levels of de-inking residue, 3 nitrogen rates, 1 manure rate, and 2 crops commonly produced in the region, for a total of 19 treatment combinations. Thirty-six lysimeters were installed to monitor changes in subsurface water quality. Soils were evaluated to determine impacts of de-inking residue on soil chemical properties. Crop yields and plant nutrient levels were determined in the late summer and early fall of 1994. De-inking residue was not a significant source of plant nutrients and cannot be classified as an Agricultural Liming Material (ALM). De-inking residue had a minimal impact on the chemical properties of soils and on subsurface water quality. The highest alfalfa yields typically occurred with the application of the following treatment combinations: 1) only nitrogen fertilizer, 2) nitrogen fertilizer with manure, 3) nitrogen fertilizer, manure, and 10 ton/acre de-inking residue, 4) 150 lb/acre nitrogen with 10 ton/acre de-inking residue applied in the fall, and 5) 300 lb/acre nitrogen with 10 ton/acre de-inking residue applied in the spring. The highest corn silage yields occurred with the application of the following treatment combinations: 1) no nitrogen, manure, or de-inking residue, applied in the spring, 2) only nitrogen fertilizer, 3) nitrogen fertilizer with manure, 4) spring application of 300 lb/acre nitrogen fertilizer with 10 ton/acre de-inking residue, 5) nitrogen fertilizer, manure and 10 ton/acre de-inking residue, and 6) 150 lb/acre nitrogen with 10 ton/acre de-inking residue applied in the fall. The alfalfa and corn plant analyses indicated that both nutrient and metal levels were within published sufficiency ranges, with few significant differences due to treatment effects.
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    M-195 Bedrock Geology of the Marr Island and Hovland Quadrangles, Cook County, Minnesota
    (2013-11-01) Boerboom, Terrence J.; Green, John C.
    Bedrock geologic map of Marr Island and Hovland Quadrangles, northeastern Minnesota, northshore of Lake Superior.
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    Mineland Reclamation using Office Waste Paper De-Inking Residue
    (University of Minnesota Duluth, 1994-03) McCarthy, Barbara J; Monson Geerts, Stephen D; Johnson, Kurt W; Malterer, Thomas J; Maly, Craig C
    Pulp facilities which recycle office waste paper generate a large amount of waste by-products in the process of producing high-grade pulp. The paper-like residue, called de-inking residue, was evaluated for use in the restoration of vegetation on coarse taconite tailings in NE Minnesota. The mineland reclamation rules specify that a 90 percent vegetative cover shall be established on tailings after three growing seasons, however this level of cover on coarse tailings has not been consistently achieved in Minnesota using standard restoration practices. Research plots were established in 1992 at Eveleth Mines arranged in a randomized block design with three replications using five levels of de-inking residue, five levels of fertilization and two plant mixes. A total of twenty-five treatment combinations were assigned to 2.5m- by- 4.0m plots and lysimeters were installed to monitor changes in sub-surface water quality. Coarse tailings were evaluated to determine the effects of de-inking residue on their chemical properties. Vegetative cover was measured in July and September in 1992 and 1993 and nutrient levels were determined in plant samples. Fertilization and de-inking residue amendments had significant effects on the vegetative cover of both introduced and native plant species. De-inking residue had a minimal impact on the chemical properties of coarse tailings at rates up to 80 dry ton/acre and on sub-surface water quality at a depth of four feet. Vegetative cover for introduced species increased from no cover, to 49 percent the first growing season, to 90 percent at the end of the second growing season on tailings fertilized at the highest level and amended with residue at 10 ton/acre. At the same fertilizer and de-inking residue rate, vegetative cover for native plants increased from no cover to 7 percent the first growing season, to 69 percent at the end of the second growing season. Alfalfa had lower levels of boron, magnesium, and manganese on residue amended plots in 1992 and 1993. Bluestem had higher levels of calcium and zinc, but lower levels of magnesium and manganese on residue amended. plots. Cadmium, chromium, copper, nickel, lead, and zinc in alfalfa and bluestem did not accumulate to toxic levels. Deinking residue appears to have benefited vegetative growth after two growing seasons using deinking residue applied at 10 dry ton/acre with fertilizer applied at 160 lb/acre of nitrogen and 359 lb/acre of phosphorus.
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    MnDOT Highway 169 2015 Drilling Project
    (University of Minnesota Duluth, 2017-06) Heine, John J; Patelke, Marsha Meinders; Buschette, Michael; Leu, Adam; Maly, Craig C; Gordee, Sarah M; Chlebecek, Sara; Lee, Aubrey; Post, Sara P
    The Natural Resources Research Institute (NRRI) Economic Geology Group was contracted by the Minnesota Department of Transportation (MnDOT) [Project Number 0005269] to provide onsite drilling supervision, core logging and sampling, and geochemical studies related to proposed construction along Highway 169 east of Soudan, Minnesota. The goal of this project was to provide MnDOT the data required to produce a mitigation plan for the Highway 169 Eagles Nest project. MnDOT, working with the Minnesota Department of Natural Resources (DNR) and Golder Associates, was responsible for developing the guidelines for this work with the help of the Highway 169 Technical Working Group (Minnesota Pollution Control Agency, Minnesota Department of Health, US Corps of Engineers, Environmental Protection Agency, and NRRI). Golder Associates (Seattle, WA office) was responsible for developing the mitigation plan for bedrock roadcuts along the reroute. This work was a continuation of the studies by Severson and Heine (2010, 2012) and Heine (2015) which examined the bedrock outcrops along three proposed Highway 169 reroutes and alternatives. Severson and Heine (2012) concluded that drilling would be needed in the potential bedrock roadcuts along the reroute corridor to fully characterize the geology as required in the mitigation plan.
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    The MnDRIVE Transdisciplinary Project Implementation of Smart Bioremediation Technology to Reduce Sulfate Concentrations in NE Minnesota Watersheds
    (University of Minnesota Duluth, 2017-07-14) Hudak, George J; Estepp, Lisa; Schoff, Patrick K
    This report opens with an Executive Summary, which briefly describes the project’s major accomplishments to date. The body of the report is constructed in sections focused on five related project efforts: 1) Bioreactor Design, Operation, and Performance, 2) Power Management, 3) Microbiology, 4) Chemical Treatments, and 5) Economic Aspects of Sulfate Reduction. Each of these sections, in turn, starts with a brief summary, which is followed by a detailed report. Additional materials concerning bioreactor design, construction, and operation, as well as experimental design, rationale, methods, and data are included in appendices. In addition, the MnDRIVE Project Accountability metrics, which contain a breakdown of particular project tasks, are included as appendices.
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    Northeast Minnesota Industry Cluster Study
    (2001) Munnich, Lee W; Chatfield, Nathan; Schrock, Greg; Lichty, Richard W; McIntosh, Chris; Wittrock, Tiana
    This major study explored factors contributing to the economic competitiveness of northeastern Minnesota communities and counties. It has a strong focus on economic and industrial development. The study focuses on four “clusters”: forest products, tourism, health services and information technology. The first two clusters are assumed to require an adequate supply of water, and are assumed to greatly influence the quality and quantity of water available for multiple uses. Summary: "This regional study sought to understand the issues shaping the competitiveness of Northeast Minnesota’s industry clusters. The study follows the Michael Porter 'industry cluster' approach to understanding competitiveness. The project identified four clusters for the region: 1) forest products, 2) tourism, 3) health services, and 4) information technology. Focus groups and individual interviews with local business leaders and economic development professionals offered insight into the industries. The study region encompassed a twelve-county area of northeastern Minnesota that centered on the city of Duluth (St. Louis County). Also included are Aitkin, Carlton, Chisago, Cook, Isanti, Itasca, Kanabec, Koochiching, Lake, Mille Lacs, and Pine Counties.”
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    NRRI Collection of Miscellaneous Reports Pt. 3
    (University of Minnesota Duluth, 2000) University of Minnesota Duluth. Natural Resources Research Institute
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    OFR10-04, Preliminary Bedrock Geologic Map of Part of the 2007 Ham Lake Fire Area: Portions of Conners Island, Gillis Lake, Long Island Lake, and Munker Island 7.5-minute quads, northeastern Minnesota, and Ontario, Canada
    (Minnesota Geological Survey, 2010) Jirsa, M.A.
    This map describes bedrock geology along the Gunflint Trail in a part of the area burned during the Ham Lake forest fire in 2007. The map covers only a portion of the fire area because much of the burn lies in Canada, or within plutonic rocks that generally lack significant mappable variations. Only the southeastern corner of the map area was not burned—the burn extends to the north and east beyond the map sheet. The western edge of the map is coincident with the area of the 2006 Cavity Lake fire, which was mapped previously by Jirsa and Starns (2008).
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    Origin and Occurrence of Platinum Group Elements, Gold and Silver in the South Filson Creek Copper-Nickel Mineral Deposit, Lake County, Minnesota
    (University of Minnesota Duluth, 1990-03) Kuhns, Mary Jo P; Hauck, Steven A; Barnes, Randal J
    The South Filson Creek Cu-Ni-PGE-Au-Ag mineral occurrence is located on the western margin of the Duluth Complex in Lake County, northeastern Minnesota. The occurrence of primary magmatic and late-stage, structurally controlled mineralization is located in the South Kawishiwi intrusion of the Duluth Complex, approximately 2200 feet above the basal contact. The primary host rock for the mineralization is a medium-grained augite troctolite. Petrographic studies indicate that there were at least two episodes of mineralization. Deposition of primary, coarse-grained, interstitial pyrrhotite, pentlandite, and chalcopyrite occurred in "cloud zones". Primary mineralization was followed by the introduction of hydrothermal fluids along fracture zones, as evidenced by the formation of hydrous minerals, sulfide replacement textures and geochemical signatures suggestive of remobilization. These late-stage fluids deposited secondary sulfides at redox boundaries created by the primary sulfides. The secondary assemblage includes chalcopyrite, bornite, chalcocite, digenite, covellite, violarite, sphalerite, mackinawite, valleriite, and the platinum group minerals, all which occur in extremely fine, discontinuous veinlets that are rarely recognizable in hand specimen. The veinlets were created by hydrofracturing of silicate minerals due to a volume increase initiated by serpentinization of olivine. These veinlets are always proximal to highly serpentinized fractures and are possibly associated with a proposed NE-trending fault zone along the south branch of Filson Creek. The copper-nickel ratio for the deposit is about 3:1. Platinum + palladium correlates with high copper and sulfur. Also, high inter-element correlation between Cu, Ni, Pd, Pt and Au suggests that secondary enrichment of these elements is local in extent and related to faulting and redox boundaries. Statistical analysis suggests, given the available data, that infill drilling could discover a significant quantity of mineralization. The alteration assemblage associated with the secondary mineralization is serpentine, biotite, stilpnomelane, iddingsite, chlorite, sericite, and clay minerals. The alteration is very subtle and is best recognized in thin section. Both alteration and mineralized zones range in thickness from less than one foot to 90 feet.
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    Performance of a Textile Filter, Polishing Sand Filter and Shallow Trench System for the Treatment of Domestic Wastewater at the Northeast Regional Correction Center
    (University of Minnesota Duluth, 2001-11) McCarthy, Barbara J; Monson Geerts, Stephen D; Axler, Richard P; Henneck, Jerald
    An estimated half million households in Minnesota are not connected to public sewer systems. Along with the growing use and expansion of lakeshore cabins and resorts, many have the potential to degrade surface and groundwater resources as they depend primarily on individual sewage treatment systems (ISTSs) for the treatment and dispersal of domestic wastewater. Unfortunately, many are in noncompliance with state standards or are hydraulically failing to the surface. Effective treatment options are needed for the thousands of locations with restrictive soil and site conditions. Many of these sites occur along lakes and streams, creating a potential health hazard to swimmers and others using surface water for drinking water and recreation, leading to increased algal blooms, aesthetic nuisances and degraded fish habitat. Packed bed textile filters, coupled with a site-specific soil dispersal system, were one of several options evaluated in Minnesota. Other systems tested in northeast Minnesota have included sand filters (single pass and recirculating), peat filters (in-ground and module), subsurface flow constructed wetlands, aerobic treatment unit, standard trenches, gravel filter and drip distribution (McCarthy et al., 1997, 1998, 1999, 2001; Anderson and Gustafson, 1998; Henneck et al., 1999, 2001; Axler et al., 1999, 2000; Monson Geerts et al., 2000, 2001; Pundsack et al., 2001; Christopherson et al., 2001). This paper provides an overview of the operation and performance of a recirculating packed bed textile filter, polishing sand filter and shallow gravelless trenches at the northern Minnesota research facility.