Tsirku Silver Occurrences, Skagway District, Juneau District, Haines Borough, Alaska, USA
This page is currently not sponsored. Click here to sponsor this page.
Geology: Still and others (1991) informally named this occurrence 'Tsirku Silver'. They describe it as, '...scattered, narrow, discontinuous silver-bearing zinc-galena-quartz veins hosted in dolomite and limy slate.' A representative chip sample of the highest grade vein contained 0.48 ppm gold, 653.5 ppm silver, 18.4 % zinc, and 6.2 % copper. According to Gilbert and others (1987), the veins occur within a 6-square-mile area immediately east of the Tsirku River that is cut by a swarm of felsic, intermediate, and mafic dikes. The dikes are probably Tertiary in age, based on a 29.3 + 1 to 33.0 + 1 m.y. age of nearby quartz diorite and granodiorite bodies (MacKevett and others, 1974). The probable Devonian or Mississippian age of the host rocks (Gilbert and others, 1987) establishes a maximum age for the veins. More likely, the veins are the same inferred Tertiary age as the dikes.
Workings: This occurrence was discovered in 1986 during the Bureau of Mines study reported in Still and others (1991).
Age: The veins must be younger than the Devonian to Mississippian age of the host rocks (Gilbert and others, 1987) and are probably about the same age as the dikes in the area, which are inferred to be 29.3 + 1 to 33.0 + 1 m.y. based on the age of nearby quartz diorite and granodiorite (MacKevett and others, 1974).
Commodities (Major) - Ag, Cu, Pb, Zn; (Minor) - Au
Development Status: None
Deposit Model: Polymetallic quartz-sulfide veins (Cox and Singer, 1986; model 22c).
Mineral List
5 entries listed. 5 valid minerals.
The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to
visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders
for access and that you are aware of all safety precautions necessary.
References
Gilbert, W.G., and Redman, E.C., 1989, Lode deposits, prospects, and occurrences of the Porcupine mining area, southeast Alaska: U.S. Bureau of Mines Open-File Report 17-89, 1 sheet, scale 1:39,600. Gilbert, W.G., Burns, L.E., Redman, E.C., and Forbes, R.B., 1987, Preliminary bedrock geology and geochemistry of the Skagway B-3 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 87-2, 2 sheets, scale 1:36,200. 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, MacKevett, E.M., Jr., Robertson, E.C., and Winkler, G.R., 1974, Geology of the Skagway B-3 and B-4 quadrangles, southern Alaska: U.S. Geological Survey Professional Paper 832, 33 p., 1 plate. 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.
