Explained by David A. Lindsey

On the choice of deposit models

Red-bed-type sediment-hosted copper deposits are lenticular, sandstone- and shale-hosted, and are associated with accumulations of plant and other organic matter in red-bed sequences. These characteristics are widespread in this tract and indicate classification as red-bed type. No information is available on tonnage and grade, but at least one deposit (Paoli, Oklahoma) was explored by drilling (Shockey and others, 1974); grade and tonnage curves for the worldwide red-bed-type sediment-hosted copper model were used.

On the delineation of permissive tracts

The tract encompasses the Lower Permian (Leonardian) mixed continental-marine strata of Kansas, Oklahoma, and northern Texas (Fischer, 1937) and includes the Ninnescah Shale and Wellington Formation.

Important examples of this type of deposit

Occurrences in the Ninnescah Shale and Wellington Formation, south-central Kansas, and north-central Oklahoma are typical of this tract and are the best-studied (Berendsen and Lambert, 1981; Waugh and Brady, 1976). The sandstone-hosted copper-silver deposit at Paoli, Oklahoma (Shockey and others, 1974) is probably the largest example assigned to this tract.

On the numerical estimates made

Only the Paoli deposit (Thomas and others, 1991) is known to have presented an attractive exploration target. However, numerous other occurrences are known, and at least two stratigraphic horizons are mineralized in southern Oklahoma and north Texas (Fischer, 1937). Many occurrences probably have not been sufficiently explored to determine whether median-size deposits exist. Probabilities of 1, 3, and 20 or more undiscovered deposits were assigned to the 90th, 50th, and 10th percentiles, respectively, consistent with the grade and tonnage model (Mark3 index 97), but more work is needed to determine the number and possible size of occurrences in north Texas.

References

Berendsen, P., and Lambert, M.W., 1981, Copper sulfides in the lower Permian red beds of south-central Kansas—Stratigraphy and host rocks lithology: Kansas Geological Survey Bulletin 223, pt. 1, 86 p.

Fischer, R.P., 1937, Sedimentary deposits of copper, vanadium-uranium, and silver in southwestern United States: Economic Geology, v. 32, no. 7, p. 906-951.

Shockey, P.N., Renfro, A.A., and Peterson, R.J., 1974, Copper-silver solution fronts at Paoli, Oklahoma: Economic Geology, v. 69, no. 2, p. 266-268.

Thomas, C.A., Hagni, R.D., and Berendsen, P., 1991, Ore microscopy of the Paoli silver-copper deposit, Oklahoma: Ore Geology Reviews, no. 6, p. 229–244.

Waugh, T.C., and Brady, L.L., 1976, Copper occurrences associated with Permian rocks in south-central Kansas, in Johnson, K.S., and Croy, R.L., eds., Stratiform copper deposits of the Midcontinent region, a symposium: Oklahoma Geological Survey Circular 77, p. 76-79.