Geologic descriptionThe general area is underlain by deformed and metamorphosed Silurian or Devonian carbonate, clastic and volcanic clastic rocks that have been intruded by Upper Jurassic and Lower Cretaceous granitic and dioritic rocks (Brew and others, 1992). This occurrence was discovered in 1976 by the U.S. Geological Survey (Brew and others, 1978). It consists of widely-spaced quartz veins parallel to the bedding in limestone. A series of sills and ankerite layers up to 10-feet-thick also appear to be parallel to the bedding. One vein is in the footwall of an andesite sill; others are in the limestone. The veins contain ankerite, biotite, chlorite, albite-orthoclase, sericite, calcite, pyrite, chalcopyrite, and malachite. The veins can be traced for hundreds of feet. Channel samples of the veins contained 0.42 to 1.5 percent copper and traces of silver (Brew and others, 1978). |
