| 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. |
