| Basis for focus area |
Geophysical expression indicates a very large volume of mafic/ultramafic rocks; geophysical expression is also consistent with large volume of alkaline rocks, including carbonatites and large alkaline complexes. |
| Identified resources |
None known. |
| Production |
No known production. |
| Status |
Limited past exploration (4 boreholes). |
| Estimated resources |
No data. |
| Geologic maps |
Sims and others (1991), scale 1:1,000,000. |
| Geophysical data |
Inadequate Rank 5 aeromagnetic data with poor ground gravity coverage in central and western North and South Dakota. Inadequate Rank 3 aeromagnetic data in coverage areas of northern and southern MN. Inadequate aeroradiometric coverage. |
| Favorable rocks and structures |
Large volumes of mafic/ultramafic intrusive rocks, significant portion of these may be alkaline complexes, including perhaps carbonatites. Located at the intersection of two major crustal-scale (lithospheric-scale?) fault zones: the Belle Plaine and Fayette structural zones. Possible rock type and presence of major structural zone permissive for occurrence of critical minerals, although none are known. |
| Deposits |
No data. |
| Evidence from mineral occurrences |
No data. |
| Geochemical evidence |
No data. |
| Geophysical evidence |
Gravity highs and complex aeromagnetic anomalies. |
| Evidence from other sources |
No data. |
| Cover thickness and description |
Total cover is variable from 0-1000 feet; The most common overburden is Quaternary glacial sediment (till) which can range from 0-over 500 feet thick. Patchy Mesozoic (Cretaceous) and Paleozoic strata up to ~300 feet thick are locally present beneath glacial sediments. Locally saprolite of several tens of feet covers solid Precambrian bedrock. |
| Authors |
Benjamin J. Drenth, Amy Block. |
| New data needs |
New mapping; high resolution geophysics. |
| Geologic mapping and modeling needs |
Basement geologic map needed. |
| Geophysical survey and modeling needs |
Need Rank 1 aeromagnetic data and more ground gravity data over the northern half of focus area. |
| Digital elevation data needs |
Lidar in progress or planned for the area, but not needed (concealed). |
