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Research about Minnesota

Source-linked reports with geographic coverage including Minnesota.

At least 937 records · Page 52Linked to original sources
USGS1958

Titaniferous sedimentary rocks in the Cuyuna district, central Minnesot

The ore-yielding main iron-formation of the Cuyuna district is strati-graphically overlain by approximately 300 feet of titaniferous sedimentary rocks, and a field test for titahia has been an effective supplement to customary stratigraphic studies. The titanium is in leucoxene. The sedimentary rocks of the district are highly folded, and the main iron-formation serves as the reference for relative stratigraphic position. The strata older than the main iron-formation are light-gray argillite and siltstone with local lenses of quartzite near the upper contact; the older strata contain about 0.5 percent titania. The main iron-formation is a persistent layer of chemically precipitated ferruginous sediments that contain about 0.2 percent titania. The strata younger than the main iron-formation are gray or black argillite, partly carbonaceous, partly ferruginous, and are transitional into lenses of lean upper iron-formation. At the base of the younger strata, 250-350 feet of argillite and slate contain 1-3.7 percent titania and average 2.0 percent. This titaniferous argillite is similar to argillite higher in the younger sequence which contains less than 1.5 percent titania and averages about 1 percent. There are weathered rocks interpreted as tuffs and basalt flows locally interlayered near the bottom of the titaniferous zone. The basalt contains 1-2 percent titania. The high titania content of the 250-350-foot zone suggests a volcanic origin; the argillite probably is reworked basaltic pyroclastics. A few titaniferous bodies have been found in rocks below, within, and above the main iron-formation and thin titaniferous argillaceous layers occur within the main iron-formation.

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USGS1958

Bedrock geology of the southwestern part of the North Range, Cuyuna district, Minnesota

The Cuyuna manganiferous iron-ore district is in central Minnesota in Morrison, Crow Wing, and Aitkin Counties. The length of the district is about 68 miles, extending northeastward from a point near Randall, in Morrison County, to a point 11 miles east of the community of Hassmann in Aitkin County; the maximum known width is about 25 miles near the center of the district. Current mining activity is confined to a much smaller area, commonly called the North range, about 10 miles long and 3 miles wide near Crosby and Ironton in Crow Wing County. The average annual production of iron ore and manganiferous iron ore during 1940-50 was slightly less than 3 million tons.

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