Unnamed Occurrences (ARDF - SK025; near Tukgahgo Mountain), Skagway District, Juneau District, Haines Borough, Alaska, USA
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Location: The location of this occurrence is in the approximate center of an area that includes Tukgahgo Mountain, the ridge extending to the east from Tukgahgo Mountain, and VABM 4520 ('Chilly'), to the southwest of Tukgahgo Mountain. It is within the area of anomalously high samples 804 to 817 shown on sheet 2 of Gilbert and others (1991). The occurrences were informally named 'Chilly' by Still and others (1991).
Geology: The following description is from Still and others (1991). The geology of the area consists of roof pendants of metabasalt and amphibolite surrounded by hornblende diorite, granodiorite and monzonite. Sporadic narrow and discontinuous quartz veins occur in the area, mostly near the northwesterly trending, Tukgahgo Mountain fault. A sample collected across a vein with visible molybdenite contained 1,240 ppm molybdenum. Seven samples analyzed for platinum and palladium contained from nil to 0.09 ppm platinum and from 0.004 to 0.07 ppm palladium. The source of the platinum and palladium may be ultramafic rocks that crop out several miles to the southeast of this area. Descriptions of samples collected from this area by Gilbert and others (1991) include numerous references to quartz veins with pyrite; chalcopyrite, malachite, and molybdenite are also mentioned in some descriptions. Samples contained up to 0.824 ppm gold, 2.70 ppm silver, and 2,140 ppm copper. The intrusive rocks are part of the Mount Kashagnak pluton (Redman and others 1984). It's mid-Cretaceous age establishes a maximum age for the mineralization.
Age: Mid-Cretaceous or younger based on the age of the Mount Kashagnak pluton that hosts the deposits (Redman and others, 1984).
Commodities (Major) - Ag, Au, Cu; (Minor) - Pd, Pt
Development Status: None
Deposit Model: Polymetallic veins (?) (Cox and Singer, 1986; model 22c?).
5 entries listed. 5 valid minerals.
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Gilbert, W.G., Still, J.C., Burns, L.E., Wier, K.R., and Redman, E.C., 1991, Geochemistry of Haines-Klukwan-Porcupine area, southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 91-5, 75 p., 2 sheets, scale 1:63,360, Redman, E.C., Retherford, R.M., and Hickok, B.D., 1984, Geology and geochemistry of the Skagway B-2 Quadrangle, southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 84-31, 34 p., 4 sheets, scale 1:40,000. Still, J.C., 1991, Bureau of Mines mineral investigations in the Juneau mining district, Alaska, 1984-1988; Volume 2, Detailed mine, prospect, and mineral occurrence descriptions, Section A, Haines-Klukwan-Porcupine subarea: U.S. Bureau of Mines of Mines Special Publication, 214 p. Still, J.C., Hoekzema, R.B., Bundtzen, T.K., Gilbert, W.G., Wier, K.R., Burns, L.E., and Fechner, S.A., 1991, Economic geology of Haines-Klukwan-Porcupine area, southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 91-4, 156 p., 5 sheets, scale 1:63,360.