Geologic descriptionBedrock in the area of this occurrence consists of andesitic volcanic rocks of Late Jurassic-Early Cretaceous age, and quartz latite volcanic rocks of Late Cretaceous age, both of which are intruded by the Late Cretaceous Hawk River quartz monzonite. The older andesitic volcanics are thermally metamorphosed in the vicinity of the Hawk River pluton. Numerous fine-grained, pyritiferous, felsic dikes cut both the andesitic and quartz latite volcanics throughout this area. Pyrite-bearing, milky-white, vuggy, quartz veins cut the volcanics in a northwest-trending belt about 6.5 miles long by 1.5 mile wide. This belt parallels a zone of prominent, northwest-trending lineations and faults. The veins are narrow, appear to strike NE and dip steeply to the north. Locally they contain irregular segregations of argentiferous galena along with lesser chalcopyrite and malachite. Pyrite occurs in cubes up to one inch on a side and is almost completely oxidized to limonite. The galena is fresh and fills vugs and fissures along the edges of the veins. No galena or chalcopyrite were found in the volcanics, although the andesitic wallrock locally contains abundant pyrite. Grab samples contained up to 200 ppm Ag, 0.3 ppm Au, 3,000 ppm Cu, 20,000 ppm Pb, and 1,500 ppm Zn (Miller and Ferrians, 1968). |
