Geologic description
The RC East prospect is the eastern extension of the Rock Candy massive sulfide layer or unit. The prospect consists of massive and semimassive pyrite bands with distinctive sphalerite-galena banding and chalcopyrite along fractures. Hydrothermal quartz-pyrite-arsenopyrite-stibnite veins and veinlets are widely distributed throughout the area (R.A. Blakestad and others, unpublished Resource Associates of Alaska, Inc. report, 1979). The average grade of RC East massive sulfide is 0.3 percent copper, 0.9 percent lead, 1.6 percent zinc, 34.2 parts per million silver, and no gold (Lange and others, 1993). The average of 14 surface samples of the veins was 8.48 percent lead, 5.03 percent zinc, 25.43 ounces of silver per ton, 0.62 ounce of gold per ton, 15.75 percent arsenic, and 1.57 percent antimony (R.A. Blakestad and others, unpublished Resource Associates of Alaska, Inc. report, 1978). This occurrence is in the Devonian Jarvis Creek Glacier subterrane (Nokleberg and others, 1992). Rocks at the prospect consist of a complex sequence of volcaniclastic sedimentary rocks, predominantly of intermediate composition. The unit includes felsic and mafic metavolcanic and metasedimentary rocks including calcareous schist, dolomite, limestone, siltstone, quartzite, and black carbonaceous schist. The rocks are typically thin bedded, strike northwest, and dip moderately southwest. The schistosity and folds in the area are generally parallel to the regional strike, but there are local exceptions (R.A. Blakestad and others, unpublished Resource Associates of Alaska, Inc. report, 1976). |
