Occurrence, Probably inactive
|Quadrangle map, 1:250,000-scale||SK|
|Quadrangle map, 1:63,360-scale||B-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This occurrence is at an elevation of approximately 3,500 feet on the east side of an unnamed headwater tributary to Porcupine Creek near the divide to Cottonwood Creek. It is in the the SW1/4, section 23, T. 29 S., R. 54 E. of the Copper River Meridian. It is shown as location 146 by Still and others (1987) and as site R by Gilbert and Redman (1989) who informally referred to it as the 'Porcupine Roof Pendant'.|
Geologic descriptionAccording to Still and others (1991), this occurrence is a mineralized, 400 foot by 1,000 foot, roof pendant surrounded by diorite. The pendant consists of metamorphosed slate and limestone that form bands of garnet and diopside at some locations. Samples from the pendant contained up to 0.068 ppm gold, 1.1 ppm silver, 192 ppm zinc, and 230 ppm copper (Gilbert and others, 1991), and a sample of gossan rubble with 20% pyrite collected 500 feet below the pendant contained 6.33 ppm gold, 18.2 ppm silver, and 515 ppm copper (Still and others, 1991). The metamorphosed slate and limestone are of probable Paleozoic age (MacKevett and others, 1974). The bands of garnet and diopside and the mineralization are probably due to to contact metasomatism by the surrounding Cretaceous diorite (MacKevett and others, 1974).
|Geologic map unit||(-136.281866214515, 59.3296576383794)|
|Mineral deposit model||Based on limited information, this is probably a skarn related occurrence (Cox and Singer, 1986; model 18b? or 18c?).|
|Mineral deposit model number||18b? or 18c?|
|Age of mineralization||Probably Cretaceous or younger based on the age of the surrounding diorite (MacKevett and others, 1974).|
|Alteration of deposit||Development of calc-silicate minerals.|
|Indication of production||None|
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., 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, Section A: Haines - Klukwan - Porcupine subarea, in U.S. Bureau of Mines, Mineral investigations in the Juneau Mining District, Alaska, 1984-1988: Volume 2 - Detailed mine, prospect, and mineral occurrence descriptions: U.S. Bureau of Mines Special Publication VOL. 2A, 214 p., 9 sheets.
Still, J.C., Gilbert, W.G., and Forbes, R.B., 1987, Final report of stream sediment, float, and bedrock sampling in the Porcupine mining area, southeast Alaska, 1983-1985: U.S. Bureau of Mines Open-File Report 36-87, 35 p., 8 sheets.
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.
|Reporters||T.C. Crafford (T. Crafford & Associates, Anchorage)|
|Last report date||2/4/2001|