Environment of the zinc deposits of the Mascot-Jefferson City District, Tennessee

Abstract

Alteration and solution of lime-stone along early faults and joints within the Kingsport Formation in the Mascot-Jefferson City district formed structures that were later mineralized by zinc-bearing solutions. The degree of permeability within a structure is related to the amount of limestone dissolved. The yellow sphalerite and its associated gangue minerals were emplaced probably before the Appalachian orogeny, and they were removed from their original site of emplacement by thrusting during that orogeny.Ore-bearing structures are grouped into four physical types: (1) V-shaped, (2) high-domal, (3) low-domal, and (4) manto. The V-shaped ore structures that occur in the eastern part of the district show moderate alteration and minor solution thinning within the thin U-bed limestone. The high-domal ore structures, which are typical of the middle part of the district, show extensive solution and alteration of the S-bed lime-stone and the overlying R bed and are major collapse breccias. The low-domal ore structures, present in the western part of the district, show variable alteration and minor amounts of dissolution within a thinner S-bed limestone. The manto-ore structures show moderate alteration and varying amounts of solution thinning and are found in very thin R-bed limestones in the central and eastern parts of the district.