PP2

Prospect, Active

Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Ag; Au; Cu
Ore minerals arsenopyrite; chalcopyrite; galena; gold; magnetite; pyrite; pyrrhotite; sphalerite
Gangue minerals chlorite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.239
Longitude -144.0784
Nearby scientific data Find additional scientific data near this location
Location and accuracy The PP2 massive sulfide deposit crops out beneath a scree slope at an elevation of about 6,400 feet about 0.4 mile southwest of peak 7505. The prospect is approximately one-half mile south of the remnant glacier in the SE1/4 section 21, T. 17 N., R. 7 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The PP2 mineralized zone was identified at the surface by talus of massive pyritic boulders 2 to 4 feet in diameter that are scattered over the slope for a distance of about 100 feet (R.A. Blakestad and others, unpublished Resource Associates of Alaska, Inc. report, 1976). The PP2 prospect represents a second mineralized layer in the Lagoon unit. It occurs in the middle Lagoon unit about 800 to 1,000 feet stratigraphically beneath the DW-LP massive sulfide layer of the upper Lagoon unit. Although the layer that contains the PP2 deposit is dominated by metasedimentary rocks at this level, the mineralization is associated with a felsic volcanic sequence in the sedimentary rocks (Dashevsky and others, 2003). The middle Lagoon unit is a transitional sequence that marks the change from the carbonaceous-dominated sedimentary rocks of the lower Lagoon unit to the felsic volcanic rocks of the upper Lagoon unit, which is of Devonian age.
A total of 6,703 feet in 14 core holes has been drilled on the PP2 prospect. The drill intersections of the PP2 horizon indicate it is a remarkably planar body averaging 14 feet in true thickness and having a maximum thickness of 29 feet (American Copper and Nickel Company, unpublished data, 1998). An inferred resource of 5.9 million tons has been calculated; it averages 0.4 percent copper, 2.1 percent lead, 4.6 percent zinc, 71 parts per million (ppm) silver, and 1.7 ppm gold (Dashevsky and others, 2003).
Geologic map unit (-144.08064969386, 63.2386242088299)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization The Drum unit, which is part of the metamorphic sequence that includes the rocks at this deposit, has been dated at the Devonian-Mississippian boundary on the basis of one SHRIMP U-Pb zircon age of 359 +/- 6 Ma at the nearby DD South prospect (MH325).
Alteration of deposit Development of sericite, quartz, pyrite, and carbonate in the hanging wall; extensive chlorite and magnesium enrichment and sodium depletion in the footwall.

Production and reserves

Workings or exploration Extensive geological, geochemical, and geophysical surveys were conducted on the PP2 prospect from 1976 to 1981 by Resource Associates of Alaska and from 1994 to 1998 by American Copper and Nickel Company (S.S. Dashevsky, oral communication, 2002). Drilling of 6,703 feet of core in a total of 14 holes has been done here (American Copper and Nickel Company, unpublished data, 1998). An inferred resource of 5.9 million tons has been calculated for the prospect; it averages 0.4 percent copper, 2.1 percent lead, 4.6 percent zinc, 71 parts per million (ppm) silver, and 1.7 ppm gold (Dashevsky and others, 2003).
Indication of production None
Reserve estimates The PP2 prospect has an inferred resource of 5.9 million tons that averages 0.4 percent copper, 2.1 percent lead, 4.6 percent zinc, 71 parts per million (ppm) silver, and 1.7 ppm million gold. The resource calculation includes only those contiguous bodies with a true thickness greater than 8 feet and a gross metal value of greater than $80.00 per ton at 1998 prices (Dashevsky and others, 2003).

Additional comments

The unpublished data that is cited can be seen by contacting Grayd Resources Inc. in Vancouver, B.C., Canada (www.grayd.com), or Northern Associates Inc. in Fairbanks, Alaska.

References

References

Lange, I. M., Nokleberg, W.J., Newkirk, S. R., Aleinikoff, J.N., Church, S.E., and Krouse, R.H., 1993, Devonian volcanogenic massive sulfide deposits and occurrences, southern Yukon-Tanana terrane, eastern Alaska Range, Alaska: Economic Geology, v. 88, p. 344-376.
Reporters W.T. Ellis (Alaska Earth Sciences) and A.W. Wyatt and S.S. Dashevsky (Northern Associates Inc.)
Last report date 3/20/2003