Geologic description
The host rocks of these occurrences are mainly lower Paleozoic, black, carbonaceous limestone and subordinate interbedded argillite (Clough and Redman, 1989). These rocks are intruded by equigranular to slightly porphyritic andesite dikes. The deposits consist of thin, quartz-calcite veins that cut the sedimentary rocks and locally contain pyrite, galena, sphalerite, and chalcopyrite. Several fault zones up to 2 miles along, are marked by elevated metal values (Clough and Redman, 1989). U.S. Bureau of Mines samples of fault gouge contained up to 30 ppm silver, 0.7 ppm gold, 9,200 ppm zinc, 4,070 ppm lead, and 210 ppm copper. Their samples of quartz-calcite veins contained up to 1.2 ppm gold, 1,500 ppm copper, 7,500 ppm lead, and 3,800 ppm zinc. They also noted anomalous gold values in samples of black argillite. Salisbury and Associates explored for massive sulfide deposits in the area in the late 1980s (Clough and Redman, 1989). The rocks in the general area are deformed and metamorphosed Silurian or Devonian carbonate, clastic, and volcaniclastic rocks that have been intruded by Upper Jurassic and Lower Cretaceous granitic and dioritic rocks (Brew and others, 1992). The rocks immediately west of the occurrence are metamorphosed Silurian and Devonian graywacke and argillite that have been intruded by foliated Cretaceous granitic rocks (Brew and others, 1978). |
