Structural control of ore bodies in the Jefferson City area, Tennessee

The zinc deposits of the Jefferson City area are confined to the lower half of the Kingsport formation of the Knox group of rocks. They are on the southeast flank of a northeast-trending anticline which is partially overridden from the southeast by the Bays Mt. thrust sheet. The beds show low dips. The area is transected by a series of high angle strike-slip faults having relatively small displacement and striking essentially parallel to the dominant northeast structure. Minor cross folds running transversely to the regional structure are numerous. Three sets of fractures trending N. 45-50 degrees W., N. 30-40 degrees E., and N. 60-70 degrees E. are well developed.

The ore bodies are irregular but generally have a distinct elongation. The vertical extent may be limited to a single bed or may include several beds, depending upon local structural conditions. All ore bodies are confined to zones of pre-mineral deformation. The linear trends of the ore bodies show a remarkable parallelism to the axes of the cross folds. Ore occurs on any part of the flexures but maximum concentration is on the anticlinal crests and synclinal troughs: the ore attains greatest thickness on the anticlines. Fractures associated with the folding exhibit local ore control. Faults are poor sites for ore, but fracturing and drag folding accompanying faulting produce conditions favorable to ore deposition.