Prospect, Inactive

Commodities and mineralogy

Main commodities Zn
Other commodities Cu
Ore minerals chalcopyrite; pyrite; pyrrhotite; sphalerite
Gangue minerals chlorite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-1
Latitude 63.3474
Longitude -144.0706
Nearby scientific data Find additional scientific data near this location
Location and accuracy The DG prospect crops out at an elevation of about 4,800 feet on the northeast side of the ridge 0.9 mile southeast of peak 6171. The prospect is about 0.6 mile north-northeast of the center of section 16, T. 18 N., R. 7 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The DG prospect is in the Tushtena Pass unit, largely metavolcanic rocks of Devonian age. Massive and semimassive sulfides occur in quartz-chlorite-sericite-feldspar schist. A single drill hole by Resource Associates of Alaska in 1977 intersected 7.8 feet of massive sulfides; the thickest layer was 1.5 feet thick. The mineralized layer appears to be eroded to the east, west, and north of the showing on the ridge; consequently, there is little tonnage potential (E. Hunter, unpublished data, 1998).
The DG massive sulfide is exposed at surface in a pyritic, quartz-sericite schist; it consists of highly contorted massive layers of pyrite, pyrrhotite, sphalerite, and chalcopyrite as much as a foot thick that are bordered by banded pyrite and banded coarse-grained pyrite and sphalerite. The mineralized zone is approximately 3 feet thick at surface (J.K. Muntzert and others, unpublished Resource Associates of Alaska, Inc. report, 1977).
A single drill hole tested a magnetic anomaly down-dip from the outcrop. Minor amounts of disseminated sphalerite were intersected over broad zones; mineralized intervals contained as much as 4.0 percent zinc and 0.13 percent copper over a thickness as much as 7.8 feet and no lead or precious metals (J.K. Muntzert and others, unpublished Resource Associates of Alaska, Inc. report, 1977).
The Tushtena Pass unit, which hosts the DG occurrence, is characterized by medium- to coarse-grained, calcareous, quartz-sericite-chlorite-schist, with local carbonate interbeds. In many places, sheared zones are the loci of pervasive iron-carbonate alteration, and they weather to a distinct reddish hue. Discontinuous bands of siliceous limestone and dolomite marble and black, weakly pyritic metasiltstones are common. The sequence is intruded by gabbroic sills and dikes; hornfels is locally developed in adjacent rocks (Dashevsky and others, 2003).
Geologic map unit (-144.0728553322, 63.3470284348216)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization Devonian, on the basis of the age of the host rocks.
Alteration of deposit Chlorite alteration in footwall.

Production and reserves

Workings or exploration This prospect was discovered in 1976. In 1977, Resource Associates of Alaska drilled one hole into the mineralized horizon. They penetrated 7.8 feet of 0.13 percent copper, 0.03 percent lead, and 4.0 percent zinc (E. Hunter, unpublished data, 1998).
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.