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. The 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. The Bauer prospect was staked in 1895 (Becker, 1897) and was active intermittently to 1923. By 1904, at least 850 feet of adit had been driven (Wright and Wright, 1905), and in 1912, 180 feet of drift was driven off the end of the adit Knopf, 1912). Bittenbender and others (1999) mapped and sampled what are probably all of the old workings. Most of the adit is in graywacke and phyllite. The drift at the end of the adit is along a fault zone marked by fine-grained quartz and quartz stringers with minor pyrite, arsenopyrite, and pyrrhotite. Samples contained low precious metal values. The highest value was in a sample across 1.5 feet of the fault zone; it contained 280 parts per billion gold. That sample also contained 716 parts per million (ppm) arsenic and 1.1 ppm mercury. Becker (1897) noted that there was a rich pay streak along the footwall of a quartz vein several feet thick. Wright and Wright (1905) said that the main vein averaged about $4.50 in gold (about 0.22 ounce of gold per ton). |