Geologic description
The RC West occurrence consists of multiple bands and lenses of pyrite-rich sulfides in a sequence of quartz-chlorite-sericite schist, quartz-sericite schist, dolomite, calcareous schist, limestone, and black carbonaceous schist. For about 100 feet, pyrite, galena, sphalerite, and minor chalcopyrite occur as multiple bands and disseminations as much as 6 inches thick over a total thickness of 8 to 10 feet. Three grab samples contained 0.08 to 0.71 percent copper, 0.81 to 5.8 percent lead, 1.4 to 10.6 percent zinc, 2.04 to 21.2 ounces of silver per ton, and less than 0.003 ounce of gold per ton (R.A. Blakestad and others, unpublished Resource Associates of Alaska, Inc. report, 1976). This occurrence is in the Jarvis Creek Glacier subterrane of Devonian age (Nokleberg and others, 1992). It consists 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in the area are generally parallel to the regional strike, but there are local exceptions (R.A. Blakestad and others, unpublished Resource Associates of Alaska, Inc. report, 1976). |
