|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||
The lower Gold Standard mine is at an elevation of less than 100 feet, about 0.15 mile inland from the southwest shore of Helm Bay, and about 5.3 miles from the mouth of the bay. The map site is in section 1, T. 72 S., R. 87 E., of the Copper River Meridian, and is accurate within 0.1 mile. It corresponds to loc. 28 in Elliott and others (1978), and to loc. 239 in Maas and others (1995, fig. 46 and p. 192). It also includes the Lone Jack prospect at Helm Bay (Maas and others, 1995, loc. 240). The upper Gold Standard mine (Maas and others, 1995) is in the Craig quadrangle about 0.4 mile west of this site, and is not described in this report.Also see Additional comments.
The country rocks near this site 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 strata nearby on Gravina Island.
The deposit consists of auriferous, pyritic quartz fissure veins in schistose metavolcanic (greenstone) and subordinate metapelitic rocks (Brooks, 1902, p. 59-60; Wright and Wright, 1908, p. 153-155; Cobb and Elliott, 1980, p. 46). There are two sets of veins: both sets strike N25W, parallel to the foliation of the schistose hostrocks, but dip in opposite directions. The older set dips 60-85 NE, parallel to the foliation, and contains the best ore, especially at the intersection of the two vein systems (Brooks, 1902, p. 59). The principal vein is 6 inches to 6 feet thick and has been traced along strike for more than 1000 feet. It consists of quartz, calcite, and chlorite, and, in addition to free gold, contains pyrite and minor tetrahedrite and galena. The walls of the vein are well defined by slickensides with gouge on the footwall side, and by a seam filled with calcite carrying free gold along the hanging wall. Locally, the wallrock next to the veins is bleached and impregnated with pyrite (Maas and others, 1995, p. 183).
Maas and others (1995, table 25) report the following average metal contents in their samples from the lower Gold Standard mine: 10.4 ppm Au, 99 ppm Cu, 7.4 ppm Pb, 48 ppm Zn, 2.3 ppm Te, and 9.6 ppm Sn. They also report (table 24) that the average gold content in quartz at two places on this property is 8.12 and 8.71 ppm, and that the average gold content in pyritic schist is 17.0 and 35.9 ppm. The sampling by Maas and others (1995, p. 184) shows a distinct northward plunge to the ore zone, which is cut off by a fault that strikes NE and dips 45SE. The continuation of the ore zone past this fault has not yet been determined.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||(-131.998684005274, 55.6486373087152)|
|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 is bleached and impregnated with pyrite.|
|Workings or exploration||
The deposit was discovered in 1897 and mined intermittently from 1898 to 1941. It was developed by a 150-foot shaft and 700 feet of drifts and tunnels on two levels. A ten-stamp mill on the site was installed in 1899 and was still operating at 20 tons per day in 1938. An average grade of $6.00 Au/ton was reported in 1922 (Brooks, 1922, p. 35).Maas and others (1995, p. 192) report a 1300-foot adit and two glory holes at the lower Gold Standard mine, and a nine-foot adit on the Lone Jack claim. They also report (p. 191) that the entire lower Gold Standard adit was sampled by private interests as recently as 1993, but the gold values were subeconomic.
|Indication of production||Yes; small|
|Production notes||Maas and others (1995, p. 192) report that the combined production from the lower and upper Gold Standard mines from about 1898 to 1941 was 310 kg or more of gold, and 33 kg or more of silver. They do not report the amount produced only from the lower Gold Standard. Judging from the assay values and the extent of the workings, production from each mine may have been about equal. In addition to the lode production, a little placer gold was mined in 1913 from near the main outcrop of the vein (Cobb and Elliott, 1980, p. 46).|
Additional commentsThe Gold Standard was the largest producer of gold and silver in the Helm Bay area. In early reports, it was also referred to as the Alaska and Free Gold claims (Cobb and Elliott, 1980, p. 46).
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.
Brooks, A.H., 1922, The Alaska mining industry in 1920: U.S. Geological Survey Bulletin 722-A, p. 1-74.
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||6/29/1999|