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Vermilion Range - Soudan |
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Minnesota, USA |
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Fe
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Vermilion Range and the principal mine in the district Soudan are located approximately 50 km north of the Mesabi Range in northern Minnesota, USA.
The bulk of the major iron formations and ore deposits (Mesabi, Cuyuna, Gogebic, Marquette and Menominee Ranges districts - see separate records) of the Great Lakes region of North America are hosted by the Paleoproterozoic 2.2 to 1.75 Ga Animikie Group within the Penokean Animikie Basin which rests unconformably on Archaean basement of the Superior Craton.
The Vermilion Range deposits however, are hosted within the 2.75 to 2.6 Ga Neoarchaean Soudan banded iron formation (BIF) in the Ely greenstone belt of the Superior craton which has been infolded into the surrounding granitoid gneiss terrane.
The Soudan BIF is intercalated with basaltic to andesitic flows and tuffs and overlain by dacitic tuffs, agglomerates and other volcaniclastic members of the Lake Vermilion Formation. It comprises several varieties of fine grained ferruginous chert interbedded with finely crystalline tuffaceous rock, and less commonly metabasalt and epiclastic rocks.
The Vermilion Range extends over a distance of around 40 km, although the Soudan BIF is not continuously developed over the full length, having been complexly folded, metamorphosed and intruded by mafic dykes and sills and by granitic dykes.
The ferruginous chert is dominantly an oxide facies with jaspilites composed of thin inter-bedded or inter-laminated layers of chert or jasper and magnetite (or martite) and specular hematite. Massive chert interbands contain disseminate magnetite and/or specular hematite. Chert-siderite (carbonate facies) and chert-chlorite (silicate facies) are also present locally.
The package of rocks that make up the Soudan BIF are around 100 m thick and have an exploited strike length of approximately 2 km. Tabular and lenticular orebodies of magnetite and hematite occur in synclinal keels and adjacent to dykes that cut the BIF. Enriched orebodies were formed by the leaching of carbonates or silica minerals from the BIF.
The principal mine in the range is the Soudan underground operation which commenced operation in 1884 and was closed in 1977.
Total production over that period amounted to 104 Mt @ 59% Fe, 6.6% SiO2, 0.02% P2O5.
Resources remaining in 1970 were estimated to be of the order of 300 Mt of un-enriched BIF (Klemic, 1970).
The most recent source geological information used to prepare this decription was dated: 1991.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Klemic, H., 1970 - Iron ore deposits of the United States of America, Puerto Rico, Mexico and Central America: in Survey of World Iron Ore Resources, Occurrence and Appraisal, Department of Economic and Social Affairs, United Nations, New York, pp 411-477.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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