Lillie; and unnamed Prospects (south of Dry Pass), Ketchikan District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA

Location: Prospects, occurrences, and claims in an area of several square miles on northern Kosciusko Island, south of Dry Pass. Coordinates are for the approximate center of activity. Locality 50 and 51 of Grybeck, Berg, and Karl (1984).
Geology: Several mineral deposits occur near the contact of a Cretaceous quartz monzonite pluton bordered by Cretaceous marble metamorphosed from Silurian Heceta Limestone (Brew, and others, 1984); all the deposits are probably related to this contact zone. At the Lillie prospect (Denny, 1961; Herreid and Kaufman, 1964) a band of tactite about 100 feet wide in diorite contains joint coatings and disseminated irregular masses, less than a half-inch in diameter, of molybdenite and subordinate powellite, chalcopyrite, pyrite, and magnetite. At another unnamed occurrence, a band of magnetite about 3 feet wide follows the contact between a diorite dike and marble. At another, samples of hornfels, marble, and diorite collected from a dump outside a short caved adit contain variable amounts of magnetite, molybdenite, chalcopyrite, pyrrhotite, pyrite, and galena. Quartz veins near the adit contain scheelite and a 5-foot chip sample of the vein contained 1.4% WO3. Quartz-rich rock near a marble-diorite contact also carry disseminated scheelite. These and additional showings of molybdenite, pyrite, and chalcopyrite in the contact zone of the pluton suggest the possibility of a porphyry copper or molybdenum deposit as well as more contact metamorphic deposits in the vicinity. Also see 'Workings/exploration'.
Workings: Old prospects and occurrences on which little recent work apparently has been done beyond minor surface exploration and a short adit (said to be 100 feet long). Twenty-seven lode claims were staked in the area in 1961 (U. S. Bureau of Mines, 1980) and an even bigger block is shown on the 1995 Alaska land status map. Extent and type of work done on these claims in recent years is unknown.
Age: Cretaceous based on probable genetic relationship to nearby pluton.
Alteration: Contact metamorphic/metasomatic alteration with development of calcsilicate minerals in marble at periphery of the pluton at Dry Pass.
Production: None
Reserves: None

Commodities (Major) - Cu, Mo, Pb, W
Development Status: None
Deposit Model: Various types of skarn deposits (Cox and Singer, 1986; models 14a, 18a, 18b, 1

References:
Brew, D.A., Ovenshine, A.T., Karl, S.M., and Hunt, S.J., 1984, Preliminary reconnaissance geologic map of the Petersburg and parts of the Port Alexander and Sumdum 1:250,000 quadrangles, southeastern Alaska: U.S. Geological Survey Open-File Report 84-405, 43 p., 2 sheets, scale 1:250,000. Cobb, E.H., 1972, Metallic mineral resources map of the Petersburg quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-415, 1 sheet, scale 1:250,000. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Petersburg quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-870, 53 p. Denny, R.L., 1961, Lillie, Hawkins, and Eichner Moly prospect (Koscuisko Island): Alaska Territorial Department of Mines Prospect Evaluation 117-7, 3 p Grybeck, D.J., Berg, H.C., and Karl, S.M., 1984, Map and description of the mineral deposits in the Petersburg and eastern Port Alexander quadrangles: U.S. Geological Survey Open-File Report 84-837, 86 p., 1 sheet, scale 1:250,000. Herreid, G.H., and Kaufman, M. A., 1964, Geology of the Dry Pass area, southeastern Alaska: Alaska Division of Mines and Minerals Geologic Report 7, 12 p. U.S. Bureau of Mines, 1980, Claim map, Petersburg quadrangle, Alaska: U.S. Bureau of Mines Map 117, 1 sheet, scale 1:250,000.