Illinois-Kentucky Fluorspar District

Region Central, South Central
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Focus area outline of the Illinois-Kentucky Fluorspar District from Denny, Goldstein and others (2008).
Identified resources Historical production of cadmium, lead, silver, and zinc.
Production Since 1939 the district has yielded more than 135,000 tons (122,000 tonnes) Zn and more than 60,000 tons (54,000 tonnes) Pb. Additionally, small amounts Ag and Cd were recovered as part of the Pb and Zn. The ores of the area furnish a significant amount of the Cd produced in the United States (Pinckney, 1976).
Status Past mining and one currently operating mine in Kentucky.
Estimated resources The mineral potential of the Illinois-Kentucky mining district is considered to be very large (Pinckney, 1976).
Geologic maps Denny, Nelson and Devera (2008), scale 1:24,000; Martin and others (2007), scale 1:100,000.
Geophysical data Adequate Rank 1 aeromagnetic and radiometric coverage collected as part of Earth MRI Phase 1 (McCafferty and Brown, 2020a).
Favorable rocks and structures Major fault systems; Paleozoic carbonates. Most of the barite veins are in the Carters limestone, but some veins also are in the overlying and underlying limy rocks. The limestones are locally sandy, shaley, or dolomitic. Most of the deposits are within 20 miles of the junction of DeKalb, Smith, and Wilson Counties, but others are in Rutherford, Cannon, Williamson, Trousdale, and Putnam Counties.
Deposits Old Jim mine (MRDS dep_id: 10242273), Huston mine, Patrick mine (MRDS dep_id: 10083017), Hickory Cane mine, Minerva No. 1.
Evidence from mineral occurrences MRDS.
Geochemical evidence Silver and Sn are concentrated in galena (compared to sphalerite) and show a marked zonal patter within the district. Sphalerite is high in Cd, Ga, and Ge. This pattern differs from other MVT deposits, for example in the Upper Mississippi Valley Zn-Pb district (Hall and Heyl, 1968). Old Jim mine, Huston mine, Patrick mine, Hickory Cane mine all contained high-grade Zn ores. Davis-Deardorf mine reported crude ore 50-60% CaF2, 12-14% Zn, 3-5% Pb. Concentrate contained 0.33% Cd and enough Ga to adversely affect further processing of the Zn concentrate. Lead concentrate contained 7.38 oz/t Ag. Minerva mine was a major producer of fluorite. In 1945 the Minerva No. 1 mine mill feed averaged 35% CaF2 and 4.2% Zn (Weller and others, 1952); Zn concentrates averaged 1% Cd and 0.25% Ge (Grogan and Bradbury, 1968).
Geophysical evidence New airborne magnetic survey shows elongate high amplitude magnetic anomalies associated with Permian dikes. Circular, high amplitude magnetic highs occur over Arkoma Dome, Coefield anomaly and several other inferred ultramafic igneous centers associated with dikes (McCafferty and Brown, 2020a).
Evidence from other sources Exploration industry interest.
Comments MVT deposits in this district are of two types: 1) narrow, vein-mineral deposits that extend vertically and horizontally for hundreds of feet and consist of fluorite, sphalerite, calcite, barite, and galena, and 2) strata-bound or bedded deposits containing fluorite and possibly bedded sphalerite. A mineral deposit with substantial barite reserves is at the southern end of the Stewart sub-0district. It was not mined due to the low price of barite. Illinois State Geological Survey has reserve estimates of this deposit in scanned Ozark Mahoning documents.
Cover thickness and description Exposed to thin cover.
Authors Albert H. Hofstra, Warren C. Day, Anne E. McCafferty.
New data needs Mapping (Phase III); Geophysics (Phase I-II); Geochemistry (Phase III).
Geologic mapping and modeling needs Detailed geologic mapping to follow on new high resolution geophysical survey.
Geophysical survey and modeling needs Entire district has been flown with modern and uniform coverage for magnetics and radiometrics in 2019.
Digital elevation data needs Lidar adequate.