Midcontinent Rift layered Ti-Fe in the Duluth Complex

Region Central, North Central
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Titanomagnetite-ilmenite in layered mafic intrusions in the Duluth Complex, Minnesota, related to the 1.1 Ga Midcontinent Rift System.
Identified resources Identified iron and titanium resources.
Production No known production.
Status In 1947 the Office of the Commissioner of Iron Range Resources and Rehabilitation Board (IRRRB) funded 10 drill holes to check thickness and continuity of the Poplar Lake layered intrusion.
Estimated resources Estimate of 91.6 million tons of low grade material in 14 bodies ranging in size from 1 million to 19 million tons. Some layers are 35% Fe and 18% TiO2 (Grout and others, 1959).
Geologic maps Jirsa (2010), scale 1:24,000; Miller and others (2001), scale 1:200,000 and 1:500,000.
Geophysical data Adequate aeromagnetic coverage; inadequate aeroradiometric coverage.
Favorable rocks and structures Poplar Lake Intrusion is a series of olivine gabbro layers grading to peridotite layers, with intervening thick segregations of magnetite-ilmenite oxides.
Deposits Tucker Lake deposit (MRDS dep_id: 10082794).
Evidence from mineral occurrences MRDS.
Geochemical evidence Analyses from drill holes reported in Grout and others (1959).
Geophysical evidence No data.
Evidence from other sources No data.
Comments Mineralogy reported as titaniferous magnetite. Grout and others (1959) suggest that the resource estimate is overly optimistic due to unfavorable mineralogy and discontinuous nature of the layers.
Cover thickness and description Thin glacial cover.
Authors Laurel G. Woodruff.
New data needs New mapping, high resolution geophysics.
Geologic mapping and modeling needs Additional mapping as Jirsa (2010) map only covers the northern part of the layered intrusion.
Geophysical survey and modeling needs Rank 1 aeromagnetic coverage may reveal additional geologic and structural detail.
Digital elevation data needs Lidar in progress.