Browsing by Subject "Babbitt Minnesota"

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    The Babbitt Copper-Nickel Deposit: Part A: Digital Drill Hole Data Files for the Babbitt and Serpentine Copper-Nickel Deposits
    (University of Minnesota Duluth, 1994-09) Patelke, Richard L
    The main objective of this investigation is to assist Arimetco International, Inc. in their evaluation of establishing a non-ferrous mine in northeastern Minnesota. This portion of the report presents data compilation work done on the Babbitt and Serpentine Cu-Ni deposits by the NRRI. The purpose was to put all available copper-nickel-sulfur assays, precious metal assays, RQD (Rock Quality Designation) information, and down hole drill hole survey data into a uniform digital format.
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    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.
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    Geologic Mapping And Structural Analysis Of The Peter Mitchell Mine
    (University of Minnesota Duluth, 1996-02) Severson, Mark J
    At least 17 faults are located within the Peter Mitchell Mine. Most of the faults trend north to north-northeast; four faults trend northwest. The faults are near-vertical, with offsets ranging from <5 feet to >50 feet. Thirteen of the faults display a "scissors-type" offset in that the relative displacement along the length of the fault is more pronounced toward one end of the fault. In 10 faults, the amount of offset increases from north to south toward the Duluth Complex. Three faults exhibit increased amounts of offset away from the Duluth Complex. Collectively, the relative motion along the majority of the faults indicate that they were formed (and reactivated?) during emplacement of the Duluth Complex. Five basaltic dikes occur within the mine area. Only one of the dikes occupies a fault zone; the remainder are intruded along various joint sets. The age of the dikes is inferred to be late-Duluth Complex. Several large-scale folds also occur within the mine area. They trend northwest and diminish in intensity away from the Complex, indicating that folding was initiated during emplacement of the Complex.
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    Geology and Mineralization of the Serpentine Copper-Nickel Deposit
    (University of Minnesota Duluth, 1994-12) Zanko, Lawrence M; Severson, Mark J; Ripley, Edward M
    A geological model explaining the formation of mineralization at the Serpentine Cu-Ni deposit, located at the western edge of the Keweenawan (1.1 Ga) Duluth Complex near Babbitt, Minnesota, has been developed following detailed re-logging of drill core and compilation of geochemical (Cu-Ni-S) data. The model suggests that sulfide mineralization was influenced by a combination of factors, the most important being localized structural preparation of the Lower Proterozoic (1.8 Ga) Virginia Formation footwall. The drill core provides evidence that faulting and the emplacement of sills (both pre-and/or early-Duluth Complex) were responsible for this structural preparation. Both processes led to weakening and/or fracturing of the footwall, thereby allowing greater magma/footwall interaction to take place in a relatively confined area. This intimate interaction enhanced the genesis and distribution of Cu-Ni sulfide mineralization at the Serpentine deposit. A laterally extensive bedded pyrrhotite unit of the Virginia Formation is believed to have further contributed to the formation of semi-massive to massive sulfides present within the deposit by acting as a local source of additional sulfur (and minor additional Cu and Ni). Additional sulfur isotope work is necessary before an in situ sulfur source can be ruled out, however. A very general igneous stratigraphy has been determined for the Serpentine deposit, based on the idea that at least three distinct magmatic events and/or intrusive styles were responsible. The first (and earliest) contributed to the deposit's sulfide mineralization, due to its extensive interaction with the footwall; its rocks are a heterogeneous, gradational mixture of fine- to medium-grained troctolite, augite troctolite, and norite, loosely confined to the lowest one-half to two-thirds of the deposit. The second event produced rocks of greater homogeneity that are more plagioclase-rich, coarser grained, and relatively sulfide-poor; spatially, they tend to overlie those of the first. A third, but much less volumetrically significant, magmatic event and/or intrusive style probably occurred shortly after the second and was likely related to a faulting episode; it formed rocks that are predominantly ultramafic. Spatially, these ultramafic rocks are largely associated with the more homogeneous plagioclase-rich rocks, frequently occurring as linear sub-vertical bodies. Analytical work shows the platinum group element (PGE) potential of the Serpentine deposit is somewhat limited. The highest value (274 ppb rhenium) occurred in a massive sulfide sample. Only three samples contained more than 100 ppb palladium. Based on these results, the mechanisms and/or conditions for PGE enrichment that were present at the Local Boy deposit were lacking at the Serpentine deposit. A possible explanation is that the Serpentine deposit received additional sulfur from a local source, while the Local Boy deposit formed from a sulfide melt that: 1) formed elsewhere; 2) scavenged more PGEs from a more primitive(?) magma; and 3) moved an undetermined distance before being injected into structure zones, without the addition of local sulfur. Future investigations may shed more light on the apparent differences between these two deposits.