Quartz-Tourmaline Veins in the Northern Sierra Nevada Area

Tourmaline-bearing quartz veins and replacement deposits, commonly copperand gold-bearing, are found in unusual concentration in northwestern Nevada and adjacent northeastern California in Triassic and Jurassic arc rocks and in the Cretaceous plutons that intrude them. Mines and prospects that exploit the tourmaline-bearing deposits are found in a zone approximately 70 miles long and 50 miles wide. Many copper-bearing quartztourmaline veins contain appreciable gold ñ silver, but early miners were commonly discouraged by the difficult-to-treat sulfide ores encountered below the free-milling gold ore in the oxidized zone. Tourmaline-bearing aplite/pegmatite dikes, associated with Late Cretaceous plutons are also relatively common in the area, suggesting a genetic relationship between plutons and mineralization. A group of copper-bearing veins in the Genesee mining district near Taylorsville, California is probably also a related mineralization type. Tourmaline is known to occur in only a few of these mines, but there has been little recent work on them, and more widespread tourmaline may not have been recognized by early workers.