Geologic description
This deposit is one of many of similar deposits (PA002 to PA018) scattered over an area of about 6 square miles at the head of Silver Bay (Bittenbender and others, 1999). The deposits are gold-quartz veins with sparse sulfides, usually only pyrite and arsenopyrite. Samples that have been analyzed with modern methods usually show anomalous arsenic even if arsenopyrite is not identified in the rocks, and several parts per million mercury. he veins are often parallel to the bedding of the host rock which is graywacke and argillite of the Sitka Graywacke of Cretaceous age (Loney and others, 1975). Many of the so-called veins in the early literature are actually fault zones with lenses of quartz or concentrations of quartz stringers along the fault zone. Prospecting began in the area in 1871. The Stewart Mine (PA012) was located in 1872 and it was the first lode-gold mine in Alaska. The Silver Bay area has been prospected intermittently to the present but the veins are relatively small and most are low grade. The area has produced relatively little gold, many of the properties have not been active since before 1900, and there has been no production since the early 1940s. This site consists of several previously undocumented workings, four trenches and a 20-foot adit, found by Bittenbender and others (1999). The workings extend for about a mile along the ridge that extends south and then east from the top of Lucky Chance Mountain. They expose several quartz veins with rare pyrite and arsenopyrite, in phyllite and graywacke. The veins generally strike northwest and dip steeply to the northeast and southwest. Precious metal values in samples are generally low but two hand-selected samples contained 4,840 and 2,330 parts per billion gold. |