Yakima Prospect, Juneau District, Juneau Borough, Alaska, USA

Location: The Yakima prospect is at an elevation of approximately 500 feet on the north bank of Ready Bullion Creek on Douglas Island. It is in the NW1/4SE1/4 section 1, T. 42 S., R. 67 E. of the Copper River Meridian. The location is accurate.
Geology: The Yakima prospect was discovered in the early 1880's and was developed by a 175-foot shaft, a 500-foot crosscut and a 500-foot drift at the bottom of the shaft, a 60-foot adit, and another shallow shaft (Redman and others, 1989). The prospect was explored by Occidental Petroleum and Noranda in the 1970's and 1980's, and was drilled by Hecla Minerals in 1990 and 1991(Bundtzen and others, 1991; Swainbank and others, 1991). The host rocks at this prospect are quartz-sericite phyllite and interbedded volcanic metaconglomerate. The phyllite contains 1 to 3 percent disseminated pyrite, with traces of galena and sphalerite, and concordant layers and seams of galena and sphalerite up to 0.25 inch thick (Redman and others, 1989). The phyllite is also cut by quartz veins that contain albite, pyrite, galena, and sphalerite. The deposit is approximately 3000 feet long and 1000 feet wide. U.S. Bureau of Mines samples contained up to 11.3 ppm gold, 11.0 ppm silver, 830 ppm copper, 1,120 ppm lead, and 3160 ppm zinc (Redman and others, 1989). Newberry and others (1997), have interpreted the Yakima prospect as a Cretaceous volcanogenic massive sulfide deposit. The deposit is geologically similar to the Alaska Treasure Mine (JU228), Red Diamond (JU232), Mammoth (JU229), and Homestake prospects (JU231)(Redman and others, 1989). The rocks in the general area are Upper Jurassic or Cretaceous marine argillite and graywacke, interbedded with andesite or basalt (Brew and Ford, 1985). The bedded rocks are regionally metamorphosed to prehnite-pumpellyite or greenschist grade, and cut by diorite or gabbro dikes and sills.
Workings: The Yakima prospect was discovered in the early 1880's and was developed by a 175-foot shaft, a 500-foot crosscut with a 500-foot drift at the bottom of the shaft, a 60-foot adit, and another shallow shaft (Redman and others, 1989). The prospect was explored by Occidental Petroleum and Noranda in the 1970's and 1980's, and was drilled by Hecla Minerals in 1990 and 1991.
Age: Newberry and others (1997), have interpreted the Yakima prospect as a Cretaceous volcanogenic massive sulfide deposit.

Commodities (Major) - Ag, Au, Cu, Pb, Zn
Development Status: No
Deposit Model: Metamorphosed Kuroko massive sulfide deposit (Cox and Singer, 1986; model 28a)

References:
Bundtzen, T.K., Swainbank, R.C., Wood, J.E., Clough, A.H., 1991, Alaska's Mineral Industry 1991: Alaska Division of Geological & Geophysical Surveys, Special Report 46, 89 p. Newberry, R.J., Crafford, T.C., Newkirk, S.R., Young, L.E., Nelson, S.W., and Duke, N.A., 1997, Volcanogenic massive sulfide deposits of Alaska, in Goldfarb, R.J. and Miller, L. D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 120-150. Redman, E.C., Maas, K.M., Kurtak, J.M., and Miller, L.D., 1989, Bureau of Mines Mineral Investigations in the Juneau Mining District, Alaska, 1984-1988, Volume 2--Detailed mine, prospect, and mineral occurrence descriptions, Section D, Juneau Gold Belt Subarea: U.S. Bureau of Mines Special Publication, 424 p. Swainbank, R.C., Bundtzen, T.K., and Wood, J.E., 1991, Alaska's mineral industry, 1990: Alaska Division of Geological and Geophysical Surveys Special Report 45, 78 p.