Browsing by Subject "Geologic exploration"

Now showing 1 - 7 of 7
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    Data Compilation of United States Steel Corporation (USSC) Exploration Records in Minnesota
    (University of Minnesota Duluth, 2007) Severson, Mark J; Heine, John J
    As a major landholder in Minnesota, United States Steel Corporation (USSC) conducted numerous exploration campaigns throughout the state. Until now, much of their explorationrelated information has been filed away in corporate files that were generally unavailable to the exploration community. With the recent sale of most of United States Steel’s mineral rights, this data is now the property of RGGS Land and Minerals, Ltd., L.P. The main objective of this proposal was to obtain permission from RGGS to acquire most of this exploration data, and then organize, compile, and summarize the data in a useable form that could then be transferred to, and open-filed, at the Minnesota Department of Natural Resources (MDNR) office in Hibbing, MN. Over 3,450 items were obtained from the exploration files that include: detailed geologic maps, maps with contoured geophysical results, geophysical profiles, maps showing soil sampling results, drill hole profiles with assay results, geologic cross-sections, and field books. A more complete inventory of these items is included with this report. Most of the data pertaining to 15 airborne surveys, flown for USSC, was acquired as part of this project. An additional four airborne surveys, flown for Marathon Oil Corp. and Kerr McGee Corp., were also acquired. Drill core, along with descriptive lithologic logs, for 24 drill holes was transferred from US Steel’s Minntac facilities to the MDNR. All of these items have been carefully inventoried and were transferred to the MDNR during May and June of 2007. Overall, United States Steel spent a great deal of effort exploring in Minnesota for iron, base metals, and precious metal deposits in the: Mesabi Iron Range; Vermilion Greenstone Belt; Duluth “Gabbro” Complex; Deer Lake Intrusive Complex of Itasca County; Emily Iron District; and portions of the Animikie Basin and Fold-and-Thrust Belt. This report is a dialog that describes not only the materials that were acquired and transferred to the MDNR, but also discusses, to a limited degree, the reasoning behind USSC’s exploration efforts and their end results. The exploration efforts of Marathon Oil in southwestern Minnesota, for uranium, are also discussed. When perusing all of these data, one may ask, “How successful was USSC in their exploration efforts?” Using hindsight, the authors suggest that USSC was moderately successful. They did find several bodies of mineable manganiferous iron ore in the Emily District, and they did find a large resource of oxidized taconite in the western portion of the Mesabi Range. However, both of these discoveries were overshadowed by development of the taconite facilities of Minntac, and they were relegated as less important at the time and subsequently shelved. USSC also found a low grade Cu-Ni deposit in the Duluth Complex that they called the Dunka Road deposit. This deposit was also put on hold during a regional Copper Nickel Study in the 1970s and was also shelved. This deposit, now referred to a the NorthMet deposit, is currently being actively developed by PolyMet Mining Corp., and is now in the environmental review stage prior to seeking mine-related permits. USSC also found several potential Fe-Ti deposits in the Duluth Complex, some of which are currently being looked at again as viable resources. The only areas where USSC failed to turn up anything economically significant are the: Vermilion greenstone belt; Deer Lake Complex of Itasca County; central portion of the Animikie basin (Meadowlands area); Fold-and-Thrust Belt (Aitkin-Carlton County); and west central Minnesota (Morris and Melrose blocks). However, even in these areas, interesting anomalies were located and the mapping and drilling that ensued eventually led to a better geological understanding of these poorly-exposed areas.
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    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.
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    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
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    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
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    The History of Gold Exploration In Minnesota
    (University of Minnesota Duluth, 2011) Severson, Mark J
    This report is more or less an atlas with regard to gold exploration in the Archean rocks of northern Minnesota. The main objective of this study is to compile all available information (maps, assays, reports, etc.) from the historical records to produce a “Guidebook” that describes “who did what, where, and how, and what did they find” regarding the gold exploration history of northeastern Minnesota. In essence, detailed “due diligence” checks have been performed in this report, and the results are described for 62 orogenic gold prospects as follows: western Vermilion District with 29 gold prospects; Cook area with nine gold prospects; northeastern Itasca County area with nine gold prospects; Rainy Lake area with four gold prospects; Virginia Horn area with ten prospects; and the Koochiching-Beltrami-Roseau-Lake of the Woods counties area (no significant prospects). Out of 23 gold prospects that were extensively drilled and/or trenched in the western Vermilion District, the best prospects that returned the highest gold values, and collectively the most mineralized zones, are located in the area bordered by the Vermilion Fault and Mud Creek Shear zone. Most of these prospects are associated with subsidiary shear zones and/or rheological contacts on the edges of iron-formation lenses. Shear zone-hosted gold was also explored for in some detail elsewhere in the western Vermilion District at Spaulding Bay, Murray, and Eagles Nest Shear zones. Exploration for gold took place the most extensively, and for the longest period, at the Shagawa Lake stock. There are very few conclusions that can be drawn from the data that are available for the Cook area. The data suggest that the best gold potential is present at the Linden Grove area, where several faults converge and structural preparation would be increased. A review of the gold prospects in Itasca County suggests that significant gold shows are associated with an iron-formation trend in the Wilson Lake sequence. In almost all cases, the high gold values are associated with iron-formation, especially structurally-prepared and sulfide-replaced zones. Glacial overburden sampling campaigns have reiterated this gold-to-iron-formation connection. A review of the exploration activities conducted at the gold prospects in the Rainy Lake area suggests that significant gold anomalies are present within both the “iron-formation” unit of Day (1990) and the Rainy Lake-Seine River Fault Zone. However, the gold values obtained during drilling generally occur as isolated values in a select number of drill holes. Exploration to the west of Rainy Lake in the Koochiching-Beltrami-Roseau-Lake of the Woods area is confined to scattered drill holes that targeted geophysical anomalies. Exploration in the Virginia Horn has to date identified a “small but low-grade” gold deposit associated with a hypabyssal quartzofeldspathic intrusion informally known as the Viking porphyry. Visible gold, often with associated arsenopyrite, is present in quartz veins in the porphyry. However, gold shows are also present in the surrounding rocks, and more drilling is needed to fully assess the potential of the Virginia Horn.
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    Non-ferrous Geology along the Highway 53 Relocation near Virginia, MN
    (University of Minnesota Duluth, 2015) Heine, John J; Patelke, Marsha Meinders; Post, Sara P; Maly, Craig C
    This report outlines the non-ferrous work done in the area of the Highway 53 relocation near Virginia, MN. At the request of the mineral lease holder (Vermilion Gold Inc.), an examination of the gold potential in the area of the new road was completed. Vermilion Gold Inc. located ten exploration diamond drill hole sites which they believed were necessary to characterize the area. Drilling occurred during fall 2013 and was conducted by Idea Drilling. The drilling and subsequent work by Natural Resource Research Institute, University of Minnesota Duluth (NRRI) was funded by the Minnesota Department of Transportation (Mn/DOT) as part of the relocation work for the highway. Logging and sample preparation were completed at the NRRI Coleraine Minerals Research Laboratory (CMRL) in Coleraine, MN.