| Basis for focus area |
Permissive focus area is bounded by the Mesoproterozoic Midcontinent Rift System on the west and east, Lake Superior to the north, and the Niagara suture zone to the south. |
| Identified resources |
Unknown. |
| Production |
Unknown. |
| Status |
Past exploration drilling by Prime Meridian near Wilson Creek prospect. |
| Estimated resources |
No data. |
| Geologic maps |
Cannon (1986), scale 1:250,000. |
| Geophysical data |
Recent adequate USGS-acquired aeromagnetic data in limited areas (<25%), otherwise inadequate; inadequate aeroradiometric coverage. |
| Favorable rocks and structures |
Multiple favorable rock types throughout the western Upper Peninsula, including early Proterozoic (1750-1680 Ma) gneiss dome structures and related metamorphic nodes. Post-Penokean orogeny retrograde hydrothermal overprinting related to doming produced trace Cu-Fe sulfide and REE-bearing fluor-apatite and monazite, diagnostic of a possible IOCG signature. |
| Deposits |
No data. |
| Evidence from mineral occurrences |
No data. |
| Geochemical evidence |
Prime Meridian core from the Wilson Creek area (Michigan) has veins of massive chalcopyrite with trace Au, Sn, and Bi, along with magnetite, fluorite, epidote, K-spar, tourmaline, albite, and chlorite alteration, mineral assemblages, and structural features characteristic of IOCG mineralization. Mineralization consists of disseminated and/or fracture controlled veinlets of chalcopyrite-pyrite and lesser scheelite (< 2%) with magnetite/hematite as well as trace molybdenite locally. |
| Geophysical evidence |
No data. |
| Evidence from other sources |
No data. |
| Cover thickness and description |
Covered by Paleozoic rocks in the east (assumed to be <1 km) and glacial materials and recent alluvium in most other areas. |
| Authors |
Laurel G. Woodruff. |
| New data needs |
New mapping, high resolution geophysics. |
| Geologic mapping and modeling needs |
Need new geologic mapping. |
| Geophysical survey and modeling needs |
Need aeromagnetic, radiometric, and gravity data collection. |
| Digital elevation data needs |
Lidar adequate. |
