Geologic description
The 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 deposit was discovered in 1899. It is in hornfels, and consists of 5 widely-spaced, pyrite-rich quartz veins and of altered zones that contain pods of pyrite. The veins are up to 0.5 foot thick, and the altered zones are up to 50 feet thick. A nearby, half-mile-long, iron-stained zone in siliceous limestone contains 5-10% pyrrhotite (Brew and others, 1978). A select grab sample of one of the quartz veins contained 1,500 ppm copper, 150 ppm cobalt, 150 ppm nickel, and a trace of gold (MacKevett and others, 1971). |