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to the east, west, and north of the showing on the ridge; consequently, there is little tonnage potential (E. Hunter, unpublished data, 1998).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 The mineralized zone is approximately 3 feet thick at surface (J.K. Muntzert and others, unpublished Resource Associates of Alaska, Inc. report, 1977).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and 0.13 percent copper over a thickness as much as 7.8 feet and no lead or precious metals (J.K. Muntzert and others, unpublished Resource Associates of Alaska, Inc. report, 1977).The Tushtena Pass unit, which hosts the DG occurrence, is characterized by medium- to coarse-grained,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).