Explained by Frederic H. Wilson, Stanley E. Church, Richard W. Saltus, Lawrence J. Drew, and W. David Menzie.
On the choice of deposit models
The Aleutian Islands arc is a poorly mapped area containing volcanic and volcaniclastic rocks of Cenozoic age intruded by plutons of Oligocene, Late Miocene, and possibly other ages. The geologic setting is permissive for BC-Alaska type porphyry copper deposits as described by Menzie and Singer (1993).
On the delineation of permissive tracts
Large parts of the Aleutian Islands are considered permissive for porphyry copper-type deposits based chiefly on the well-known presence of porphyry-type deposits in other volcanic arcs throughout the world. The level of knowledge of the geology is very low and geophysical and geochemical data are virtually nonexistent. As more information becomes available, the tract can be restricted to areas near known or inferred intermediate to felsic plutons of Cenozoic age.
Important examples of this type of deposit
In the eastern Aleutian Islands, Unalaska Island has a number of mineralized areas and Rootok Island has a small mineralized area, both of which have potential for porphyry copper deposits (Christie, 1974; 1976).
On the numerical estimates made
The minimum number of undiscovered porphyry Cu deposits for this tract, consistent with the tonnage and grade model of Menzie and Singer (1993), has been estimated as:
Percentile 90 50 10 5 1
Estimated no. of deposits 0 1 4 4 4
Christie, J.S., 1974, Aleut‑Quintana‑Duval 1974 joint venture final report: Unpublished Quintana Minerals Corporation report available from The Aleut Corporation, 24 p., 3 appendices, 2 maps in pocket.
Christie, J.S., 1976, Aleut‑Quintana‑Duval joint venture 1975 report on drill programmes at the Tarasof and San Diego prospects and additional exploration on Rootok Island and Unalaska Island: Unpublished Quintana Minerals Corporation report available from The Aleut Corporation, 21 p., 1 appendix, 10 maps and figures in pocket.
Menzie, W.D., and Singer, D.A., 1993, Grade and tonnage model of Porphyry Cu deposits in British Columbia, Canada, and Alaska, U.S.A.: U.S. Geological Survey Open-File Report 93-275, 7p.