Explained by David A. Brew, Cliff D. Taylor, Robert C. Jachens, Richard D. Koch, Donald Grybeck, James L. Drinkwater, David F. Barnes, and Larry J. Drew
On the choice of deposit models
Paleozoic and upper Proterozoic intermediate, felsic, and mafic volcanic rocks occur in heterogeneous units on Prince of Wales Island. Local altered areas are present. Geochemical patterns and mineral occurrences suggest kuroko massive sulfide deposits as described by Singer (1986).
On the delineation of permissive tracts
This multi-part tract is delineated mainly by the distribution of volcanic and metavolcanic units, the distribution of known deposits and occurrences, and the distribution of favorable geochemical patterns (Brew and others, 1991; Brew, 1993).
Important examples of this type of deposit
Big Harbor and Niblack on Prince of Wales Island are examples of kuroko massive sulfide deposits in this tract (Berg, 1984; Brew and others, 1991).
On the numerical estimates made
Permissive rock types and associations, appropriate geochemical patterns, and the occurrence of known deposits were the main basis for the estimates. The mineral resource team estimated the minimum number of undiscovered deposits, consistent with the grade and tonnage model of Singer and Mosier (1986), to be:
Percentile 90 50 10 5 1
Estimated number of deposits 0 0 2 2 4
Berg, H.C., 1984, Regional geologic summary, metallogenesis, and mineral resources of southeastern Alaska, U.S. Geological Survey Open-File Report 84-572, 298 p.
Brew, D.A., 1993, Regional geologic setting of mineral resources in southeastern Alaska, in Godwin, L.H., and Smith, B. D., eds., Economic mineral resources of the Annette Islands Reserve, Alaska: U.S. Dept. of the Interior, Bureau of Indian Affairs, Division of Energy and Mineral Resources Publication, p.13-20.
Brew, D.A., Drew, L.J., Schmidt, L.M., Root, D.H., and Huber, D.F, 1991, Undiscovered locatable mineral resources of the Tongass National Forest and adjacent areas, southeastern Alaska: U.S. Geological Survey Open-File Report 91-10, 370 p., 15 maps at 1:250,000, 1 map at 1:500,000, 11 figs.
Singer, D.A.., 1986, Descriptive model of kuroko massive sulfide, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 189-190.
Singer, D.A., and Mosier, D.L., 1986, Grade and tonnage model of kuroko massive sulfide deposits, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 190-197.