Geology of Lower Precambrian Rocks and Associated Sulfide Mineralization in an Area South of Indus, Koochiching County, Northern Minnesota
1978-08
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Geology of Lower Precambrian Rocks and Associated Sulfide Mineralization in an Area South of Indus, Koochiching County, Northern Minnesota
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1978-08
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The Indus area is located near the Canadian border approximately halfway between International Falls and Baudette in the southwestern part of the Wabigoon greenstone belt. This is an area of interbedded Archean volcanics, related intrusives and metasediments including iron-formation. An outcrop of disseminated to massive sulfides is associated with a felsic volcaniclastic unit. The outcrop of the Archean volcanics is located along the flanks of a northwesterly trending Middle-Precambrian mafic dike which has proved more resistant to weathering. The Archean volcanic units consist of a sequence of mafic, intermediate, and felsic units that were apparently deposited under deep, still water conditions. Studies of whole rock analyses indicate that these rocks are similar in composition to rocks in other areas of the Superior province. They may have been deposited in a geological environment similar to a modern island arc environment. The area was regionally metamorphosed during the Algoman orogeny and the Archean rocks now contain a mineral assemblage characteristic of the greenschist-amphibolite transition facies. Based on data from outside the study area, the major structure in the area consists of an overturned, isoclinally folded anticline with a general east-northeast trend. Lineaments observed in aerial photographs and apparent offsets of the mafic dike suggest that faulting has occurred in three places. Disseminated to massive sulfides which occur in felsic volcaniclastics are believed to be volcanogenic in origin with both the metals and sulfur being of magmatic derivation. The sulfides are almost entirely pyrite and pyrrhotite with only trace amounts of chalcopyrite and sphalerite. Textural evidence suggests that the sulfides were mobilized and redeposited in favorable sites by a later event, probably the same one producing the folding and metamorphism in the host rocks. Electro magnetic studies suggest that their pre sent form is that of small strata bound lenses. Trace element analyses show that base metal values are low in all cases. The number of analyses is insufficient to be statistically valid. A comparison of trace ele1nent ratios from the Birchdale and Indus areas shows a difference between the metal ratios of the two areas. The significance of the observed difference is not known.
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A Thesis submitted to the faculty of the Graduate School of the University of Minnesota by Leon Wayne Gladen in partial fulfillment of the requirements for the degree of Master of Science, August 1978. Plate 1 referenced in the thesis is also attached to this record.
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Gladen, Leon Wayne. (1978). Geology of Lower Precambrian Rocks and Associated Sulfide Mineralization in an Area South of Indus, Koochiching County, Northern Minnesota. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/220208.
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