Mascot-Jefferson City Zinc 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 Polygon for area enclosing Zn mines, prospects, and occurrences from MRDS.
Identified resources Identified resources and historical production of zinc.
Production Between 1850 and 1964, the Mascot-Jefferson City district produced about 1.5 Mst of recoverable Zn (Crawford and Hoagland, 1968). Production continues to this time.
Status Past mining at a number of mines, and current mining of Zn at the Young, Coy, and Immel mines.
Estimated resources Reserves (in 2018) for the East Tennessee complex operated by Nyrstar were: Proven and Probable reserves of 5.61 Mst with grade of 4.4% Zn; Measured and Indicated reserves of 7.49 Mt with grade of 4.4% Zn; Inferred reserves of 24.41 Mt with a grade of 3.7% Zn.
Geologic maps Miller and others (2004), scale 1:24,000; Bridge (1945), scale 1:31,680; all 7.5-minute (scale 1:24,000) geologic quadrangle maps have been completed for this area.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures The Lower Ordovician Kingsport and Mascot Formations, part of the Knox Group, host the majority of the ore. Most ore occurs in altered limestone beds in the lower and middle members of the Mascot Dolomite, the uppermost Formation in the Knox Group within dissolution collapse breccias and caverns (Potra and Moyers, 2017).
Deposits Young, Immel, Coy, New Market (MRDS dep_id: 10251351), Mascot-Jefferson City district (MRDS dep_id: 10084093), North Friends Station, Grasselli.
Evidence from mineral occurrences MRDS.
Geochemical evidence Mineralogy is simple-sphalerite is the only primary metallic mineral of economic value, and generally contains less than 0.5% Fe (Crawford and Hoagland, 1968).
Geophysical evidence Unknown.
Evidence from other sources Exploration, diamond drilling.
Comments Sphalerite has low concentrations of Fe (below 0.4%) and Cd (below 0.96%); Cu is either below the detection limit or very low (below 0.19.%); Mn was below the detection limit (Peevler and others, 2003). A wealth of information about Zn mining in Tennessee is available at:
Cover thickness and description Surface to <800 feet.
Authors Laurel G. Woodruff, Peter J. Lemiszki.
New data needs Geophysical data.
Geologic mapping and modeling needs Geologic mapping adequate.
Geophysical survey and modeling needs High resolution geophysical coverage. Note that the timing of the deposits is uncertain; they may have been transported on thrust sheets.
Digital elevation data needs Lidar adequate.