PG West

Occurrence, Inactive

Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Ag; Au; Cu
Ore minerals chalcopyrite; galena; pyrite; pyrrhotite; sphalerite
Gangue minerals ankerite; carbonate; chlorite; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-1
Latitude 63.3424
Longitude -144.4722
Nearby scientific data Find additional scientific data near this location
Location and accuracy The PG West occurrence is 0.2 mile southwest of peak 7630 and in the NW1/4 section 16, T. 18 N., R. 5 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The PG West occurrence is a massive sulfide deposit with chalcopyrite, galena, pyrite, and sphalerite in a quartz-ankerite gangue. The deposit is in altered and brecciated quartz sericite schist and carbonaceous schist. Fine to very coarse grained quartz arenite and quartzite units underlie the occurrence, which is above a mafic intrusive body below the PG West occurrence. A gray siltstone composed of quartz, sericite, and graphite forms the hanging wall of the deposit; the overlying rocks consist of chloritic phyllites and intermediate to felsic schists thought to have originally been volcanic sediments and rhyolite tuffs (J. K. Muntzert and others, unpublished Resource Associates of Alaska Inc. report, 1977).
The occurrence was originally described as a volcanogenic massive sulfide deposit. Subsequent examination by American Copper and Nickel in 1994 indicated that the sulfides may be related to skarn developed beside a mafic intrusive (W. Shalosky, written communication, 1994).
Resource Associates of Alaska Inc. drilled one core hole in 1977 after finding pyritic massive sulfides in talus. Some pyrite was was intersected in a 1-foot interval in the core; it contained 0.1 percent copper, 0.8 percent lead, 1.5 percent zinc, 27.8 parts per million (ppm) silver, and 0.1 ppm gold (E. Hunter, unpublished data, 1998).
Geologic map unit (-144.47444997055, 63.3420219688953)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization The enclosing Drum unit has been dated at the Devonian-Mississippian boundary on the basis of one SHRIMP U-Pb zircon age of 359+/- 6 Ma determined at the DD South deposit (MH325) (Dashevsky and others, 2003).
Alteration of deposit Strong enveloping pyrite; ankerite; regional carbonate alteration (Lange and others, 1993).

Production and reserves

Workings or exploration Surface sampling and mapping that found the massive sulfide float led to Resource Associates of Alaska Inc. drilling one core hole in 1977.
Indication of production None

Additional comments

Unpublished data cited is available for viewing 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), A.S. Wyatt and S.S. Dashevsky (Northern Associates, Inc. ), and Nokleberg, W.J., (USGS)
Last report date 3/20/2003