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
In southeast Alaska, Mesozoic and Paleozoic clastic, volcanic and some carbonate rocks that are intruded by scattered Cretaceous and Tertiary mesozonal to epizonal subduction- and post-subduction-related calcalkaline granitic plutons and dikes host numerous polymetallic vein deposits..
On the delineation of permissive tracts
This multi-part tract is delineated by outcrop areas of Mesozoic and Paleozoic sedimentary, volcanic, and metamorphic rocks that are intruded by Cretaceous and Tertiary granitic plutons, by numerous occurrences of polymetallic veins, and by favorable geochemical patterns (Brew and others, 1991; Brew, 1993).
Important examples of this type of deposit
Numerous deposits occur in the Hyder Mining District, including the Homestake and Riverside. The Lucky Nell, Puyallup, Dawson, Valparaiso, and Golden Fleece deposits are on Prince of Wales Island. Admiralty Alaska (Willoughby) and Alaska Dano are on Admiralty Island. The Hoadley and Goldstream occurrences are near Ketchikan, and the Lost Charlie Ross deposit is near the Whiting River.
On the numerical estimates made
Permissive rock types and associations, abundant known deposits, and appropriate geochemical patterns were the main basis for the estimates. The minimum number of undiscovered polymetallic vein deposits, consistent with the grade and tonnage model of Bliss and Cox (1986) was estimated to be:
Percentile 90 50 10 5 1
Estimated number of deposits 5 9 15 17 21
Bliss, J.D., and Cox, D.P., 1986, Grade and tonnage model of polymetallic veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 125-129.
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.