Explained by T.L. Klein

On the delineation of permissive tracts

West-central Georgia and a small part of the east-central Alabama Piedmont contain massive sulfide deposits in the New Georgia and Sandy Springs Groups. These two rock units are dominated by volcanic rocks, immature volcanic-derived sedimentary rocks, and iron formation (Abrams and McConnell, 1984); they underlie the Dahlonega and Carroll County gold belts, and they define this permissive tract in Georgia and Alabama (see German, 1989). These multiply-deformed rock units, retrograded to greenschist-facies from amphibolite metamorphic-grade, were last deformed in a transpressive structural setting between the high-grade metamorphic rocks of the Richard Russell and Tallulah Falls thrust sheets (Albino, 1989). Approximately a dozen abandoned mines that produced primarily pyrite occur in this tract.

On the numerical estimates made

For the 90th, 50th, and 10th percentiles, respectively, the team estimated 2, 5, and 10 deposits consistent with the Phanerozoic kuroko model.

References

Abrams, C.E., and McConnell, K.I., 1984, Geologic setting of volcanogenic base and precious metal deposits of the West Georgia Piedmont—A multiply deformed metavolcanic terrain: Economic Geology, v. 79, no. 7, p. 1521–1539.

Albino, G.V., 1989, Gold deposits of the Dahlonega belt, northeastern Georgia, in Cook, R.B., ed., Economic mineral deposits of the southeast—Metallic ore deposits: Georgia Geologic Survey Bulletin 117, p. 85–120.

Franklin, J.M., Lydon, J.W., and Sangster, D.F., 1981, Volcanic-associated massive sulfide deposits, in Skinner, B.J., ed., Economic Geology Seventy-Fifth Anniversary Volume, 1905–1980: Lancaster, Pennsylvania, Economic Geology Publishing Company, p. 485–627.

Gair, J.E., and Slack, J.F., 1980, Stratabound massive sulfide deposits of the U.S. Appalachians, in Vokes, F.M., and Zachrisson, Ebbe, eds., Review of Caledonian-Appalachian stratabound sulphides: Geological Survey of Ireland Special Paper No. 5, p. 68–81.

German, J.M., 1989, Geologic setting and genesis of gold deposits of the Dahlonega and Carroll County gold belts, Georgia: Economic Geology, v. 84, no. 4, p. 903–923.

McConnell, K.I., and Abrams, C.E., 1984, Geology of the greater Atlanta region: Georgia Geologic Survey Bulletin 96, 150 p.

Neathery, T.L., and Hollister, V.F., 1985, Models for volcanogenic sulfide exploration in the southernmost Appalachians, in Misra, K.C., ed., Volcanogenic sulfide and precious metal mineralization in the southern Appalachians: Knoxville, University of Tennessee, Studies in Geology 16, p. 97–112.

Shearer, H.K., and Hull, J.P.D., 1918, A preliminary report on a part of the pyrites deposits of Georgia: Georgia Geologic Survey Bulletin 33, 229 p.

Singer, D.A., and Mosier, D.L., 1986, Grade and tonnage model of kuroko massive sulfide, in Cox, D.P., and Singer, D.A., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 190–197