|Quadrangle map, 1:250,000-scale||KC|
|Quadrangle map, 1:63,360-scale||C-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This site, in section 18, T. 72 S., R. 87 E., of the Copper River Meridian, is at an elevation of about 1000 feet on the north flank of Gold Mountain, about 0.8 mile due west of the south tip of Forss Island in Helm Bay. The site is at the approximate center of a mile-square area on Gold Mountain, and represents a group of claims, including Annie, Mountain Top, Starry Banner, Fannie, Gold Dollar, Jewel, Gertrude, and Annex no. 1 (Wright and Wright, 1908, p. 156 and fig. 14; Cobb and Elliott, 1980, p. 45, 145-146), and Lone Jack (Gold Mountain) (Maas and others, 1995, fig. 46 and p. 192). The site corresponds to loc. 29 in Elliott and others (1978). The location is accurate within about 0.1 mile.|
The country rocks in the area of Gold Mountain are marine, andesitic and basaltic metavolcanic rocks that are gradationally interbedded with flyschlike metasedimentary rocks (Berg and others, 1988, p. 18). The strata were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time (Brew, 1996, p. 27). The depositional age of the strata is uncertain. Berg and others (1998, p. 17) report that they closely resemble Upper Jurassic to mid-Cretaceous marine strata nearby on Gravina Island.
The deposits at this site are in basaltic or andesitic metavolcanic rocks (greenschist), and consist of quartz-calcite fissure veins and stringer lodes that contain pyrite, chalcopyrite, galena, and free gold, locally in pockets of bonanza ore (Brooks, 1902, p. 58-59; Wright and Wright, 1908, p. 156). Telluride minerals have also been reported. The sulfides, along with some gold, also are disseminated in the country rocks adjacent to the veins. The deposits vary in width and structural attitude. A quartz stringer lode on the Annie claim is 10.5-20 feet wide and strikes N30W, parallel to the foliation of the greenschist hostrock; some veins in this lode are as much as one foot thick. Maas and others (1995, p. 184) report that the ore at the Annie mine is concentrated in distinct shoots controlled by vertical warps in the faults that carry the veins, rather than evenly distributed in the veins. An 8-inch quartz vein on the Starry Banner claim also strikes northeast, parallel to the foliation. On the Mountain Top claim, an 8-inch vein that strikes N25W and dips 25 NE crosscuts the foliation of the greenschist. The country rocks near this vein contain calcite and epidote veinlets, and, near the surface, the sulfide minerals are oxidized. Maas and others (1995, p. 183) report that the wallrock near some of the veins are bleached and pyritized.Fluid inclusion studies of quartz vein material from several of the Helm Bay lodes suggest that the veins formed at temperatures and pressures consistent with conditions during the Late Cretaceous greenschist-grade regional metamorphism (Maas and others, 1995, p. 184).
|Geologic map unit||(-131.990683386572, 55.6266369022932)|
|Mineral deposit model||Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a)|
|Mineral deposit model number||36a|
|Age of mineralization||Late Cretaceous.|
|Alteration of deposit||Locally, the wallrock next to the veins are bleached and pyritized.|
|Workings or exploration||
The Gold Mountain deposits were explored in the early 1900s by various underground workings accumulating more than 600 feet (Wright and Wright, 1908, p. 156). On the Annie claim, a 20-foot shaft was sunk on an ore pocket around 1900, and a 450-foot tunnel with a 50-foot winze and drift was completed by about 1906. The Mountain Top claim was explored by shallow shafts and opencuts; and the Starry Banner was explored by a 225-foot tunnel. Maas and others (1995, table 26) describe the following workings on several of the properties. Annie: two adits, 380 and 360 feet long, and two shafts; Lone Jack (Gold Mountain): two adits, 36 and 72 feet long; Mountain Top: two flooded shafts; Jewel: one 160-foot adit.Assays reported by the owners in the early 1900s ranged in gold values from $4 to several thousand dollars per ton (Au at $20.67/oz.) (Brooks, 1902, p. 58-59). Maas and others (1995, table 25) report the following average metal contents in their samples from several of the properties at this site. Annie: 4.92 ppm Au, 0.92 ppm Ag, 82 ppm Cu, 10.4 ppm Pb, and 88 ppm Zn. Lone Jack (Gold Mountain): 1.0 ppm Au, 0.27 ppm Ag, 125 ppm Cu, 8.1 ppm Pb, and 78 ppm Zn. Mountain Top: 0.45 ppm Au, 0.2 ppm Ag, 45 ppm Cu, 5.0 ppm Pb, and 57 ppm Zn. Jewel: 6.73 ppm Au, 0.97 ppm Ag, 73 ppm Cu, 6.0 ppm Pb, and 61 ppm Zn.
|Indication of production||Yes; small|
|Production notes||Maas and others (1995, table 26) report production in the early 1900s of 7.9 kg of gold from the Annie lode.|
Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map I-1807, 27 p., scale 1:250,000.
Brew, D.A., 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 1 sheet, scale 1:250,000.
Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p.
Cobb, E.H., and Elliott, R.L., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 80-1053, 157 p.
Elliott, R.L., Berg, H.C., and Karl, S.M., 1978, map and table describing metalliferous and selected non-metalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-73-B, 17 p., 1 sheet, scale 1:250,000.
Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p.
|Reporters||H.C. Berg, USGS|
|Last report date||6/30/1999|