PGX

Prospect, Active

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-1
Latitude 63.3252
Longitude -144.4047
Nearby scientific data Find additional scientific data near this location
Location and accuracy The PGX prospect is located about 0.2 mile east of a small glacier in section 23, T. 18 N., R. 5 E., Copper River Meridian. The prospect is 0.8 mile southeast of peak 7886 and in the SW1/4 section 23, T. 18 N., R. 5 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The PGX prospect is 1.5 miles southeast of the PG occurrence (MH259) and consists of two poorly exposed semimassive bands of sulfide within highly altered felsic metavolcanic rocks of the Drum unit. The bands are discontinuous, about 10 feet apart, and less than 1 foot thick. The upper band assayed 0.11 percent copper, 0.24 percent lead, 0.14 percent zinc, 15 parts per million (ppm) silver, and 300 parts per billion (ppb) gold. The lower band assayed 0.64 percent copper, 0.25 percent lead, 0.60 percent zinc, 23 ppm silver, and 840 ppb gold. In 1997, massive sulfide float was found in the valley southeast of the PGX prospect; it probably came from a layer in the Drum unit. This float contained higher values than found in outcrop at the PGX prospect, and higher grade massive sulfides may be present beneath the talus-covered slopes. A 2-foot boulder assayed 0.02 percent copper, 4.6 percent lead, 3.34 percent zinc, 4 ounces of silver per ton, and 800 ppb gold. A float sample 1,000 feet away assayed 0.24 percent copper, 5.1 percent lead, 5.7 percent zinc, 10 ounces of silver per ton, and 1,805 ppb gold (E. Hunter, unpublished data, 1998).
The Drum unit that hosts the PGX prospect consists of white to pale-gray green, rusty weathering, quartz-sericite(-chlorite-pyrite) schist with minor gray to black carbonaceous phyllite and rare interbeds of chloritic phyllite. The schist commonly contains 1 to 5 percent quartz eyes but may contain more. The protoliths of the schist are about two-thirds of volcanic origin and one-third of sedimentary origin. The schist has a phyllitic parting in many places.
Geologic map unit (-144.40694955468, 63.3248225326156)
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), approximately 6 miles to the southeast (Dashevsky and others, 2003).

Production and reserves

Workings or exploration Reconnaissance work began on the PGX prospect in 1976 with the collection of rock and stream-sediment samples (Rodney A. Blakestad and others, Resource Associates of Alaska, Inc., unpublished report, 1976). One hole drilled in 1977 intersected disseminated pyrite. Geophysical grids were established by Resource Associates of Alaska, though a systematic survey was not possible due to extremely rugged terrain.
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) and A.W. Wyatt and S.S. Dashevsky (Northern Associates Inc.)
Last report date 3/20/2003