Neoarchean Greenstone Belts of Minnesota, North Dakota and South Dakota

Region Central, North Central
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

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).