Geologic description
The Greisen prospect consists of an elongate zone which contains axinite, tourmaline, and sulfides in an igneous breccia at the contact between dacite of the Horn Mountains volcanic field and the Horn Mountains pluton (Bundtzen and others, 1998). The greisen zone is about 300 feet long and about 50 feet wide; it contains about 5-8 percent axinite, 15-20 percent tourmaline, and 1-2 percent sulfides. Disseminated galena was recognized in some hand specimens. The zone strikes roughly north-south. One grab sample of sulfide-rich greisen contained 6,800 parts per billion (ppb) silver, 119 parts per million (ppm) copper, 2,302 ppm lead, 401 ppm zinc, 924 ppm arsenic, 321 ppm antimony, 32 ppm tin, and 13.43 ppm mercury (Bundtzen and others, 1998) This is the best example of a greisen deposit in the Horn Mountains. The Greisen prospect is in an area marked by anomalous stream sediment and panned concentrate sample sites (Gray and others, 1994; Theodorakos and others, 1992). Stream sediment samples from this area contained up to 26 ppb gold, 950 ppb silver, 290 ppm arsenic, 57 ppm antimony, 4.0 ppm mercury, 6.4 ppm bismuth, and 0.6 ppm tellurium. Panned concentrate samples contain up to 30 ppm gold, 5 ppm silver, 1,500 ppm bismuth, 500 ppm lead, 200 ppm antimony, 1,000 ppm tungsten, and 1,000 ppm boron. The panned concentrates also contained up to 1.0 percent scheelite. |
