Pennsylvanian Phosphate, Black Shale, Underclay

Region Central, South Central
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area All states listed here have Pennsylvanian black shales, but the nature of the rocks are different across this large focus area. Some parts of the Pennsylvanian have minor Zn mineralization, whereas others do not; thus the prospectivity for critical minerals from this mineral system is variable for states included in this focus area. Cleat and clastic dikes in Middle Pennsylvanian coal beds from certain areas of the Illinois and Forest City Basins have many occurrences of a separate zinc sulfide phase in small-scale structural features that are possible indicators of Mississippi Valley-type mineralization. Areas of interest are the subcrop and outcrop of the Pennsylvanian.
Identified resources None.
Production None.
Status Unknown.
Estimated resources Unknown.
Geologic maps Horton and others (20107), scale 1:500,000.
Geophysical data Inadequate coverage; majority of the area is Rank 4 and 5, whereas central Illinois, southwest Indiana, and eastern Ohio are Rank 3. Some rank 3 in southwestern Missouri.
Favorable rocks and structures Middle Pennsylvania coals of the mid-continent, recognized in the surface exposures and margins of the Illinois and Forest City Basins.
Deposits None.
Evidence from mineral occurrences None.
Geochemical evidence Coals in Iowa have high Zn and Cd, and are enriched (relative to other coals in the United States) in Sn, Co, Cu, Ph, Mo, Ni, and Ag (Hatch and others, 1976).
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Comments The Iowa Geological Survey has 8 cores (1970s coal project) and 100s of water wells with cuttings into the Pennsylvanian. Areas of interest are the subcrop and outcrop of the Pennsylvanian.
Cover thickness and description Variable; polygon shows the extent of subcrop and outcrop.
Authors Laurel G. Woodruff.
New data needs Geochemistry, isopach maps.
Geologic mapping and modeling needs Geologic mapping of specific coal beds.
Geophysical survey and modeling needs High resolution aeromagnetic and aeroradiometric coverage.
Digital elevation data needs Variable lidar quality; some complete, some planned/funded, some inadequate.