|Quadrangle map, 1:250,000-scale||KC|
|Quadrangle map, 1:63,360-scale||B-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||
The Goldstream mine is at sea level on southeastern Gravina Island, opposite Pennock Island. The old workings are 1.0-3.0 miles north of Gravina Point, in section 6, T. 76 S., R. 91 E., of the Copper River Meridian. The site includes loc. 69 in Elliot and others (1978), and loc. 286 (1-3) in Maas and others (1995). The location is accurate within 0.1 mile.Also see Additional comments.
The country rocks on southeastern Gravina Island are Upper Jurassic or Cretaceous marine andesitic or basaltic volcanic rocks interbedded with subordinate flyschlike sedimentary rocks (Berg, 1973; Berg and others, 1988). These strata were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. The country rocks are cut by a high-angle fault along Tongass Narrows that displays about 4 miles of right-lateral offset.
Wright and Wright (1908, p. 177-178) describe two types of lode deposits at the Goldstream mine. The main deposit consists of apparently stratiform massive sulfides in two or more layers of greenschist or quartz-sericite schist that strike NW and dip NE, and which are separated by layers of relatively barren schist. The sulfide-rich layers in the main deposit are 4-8 feet thick and have been traced on the surface and in underground workings for 1000 feet or more. Zones of lower-grade ore are as much as 40 feet thick and several hundred feet long. The principal ore minerals in the stratiform deposits are pyrite, chalcopyrite, galena, arsenopyrite, and native gold, small particles of which accompany the sulfides and also occur in quartz seams. The other type of deposit consists of quartz-calcite fissure veins that carry galena and sphalerite, and which crosscut the massive-sulfide-bearing layers. Both types of deposits are cut by barren quartz stringers and by an altered diabase dike several feet wide that strikes N10W and dips 75NE. Several thousand tons of ore were produced in the early 1900s from the Goldstream mine, mainly from a 5-foot-long, steeply-pitching oreshoot in the main deposit (Cobb and Elliott, 1980, p. 47). Maas and others (1995, p. 201) report cumulative production of 8.1 kg Au and 15 kg Ag.
Maas and others (1995, p. 197) report that a 4-foot sample across quartz lenses in talc schist contained 4.7 ppm Au, 74.4 ppm Ag, 0.8% Cu, and 6.28% Zn.Maas and others (1995, p. 201) suggest that the massive-sulfide-bearing layers are of stratiform volcanogenic origin. If so, The Goldstream deposit probably can be classified as a metamorphosed Besshi massive sulfide deposit, possibly of Late Jurassic age. The sulfide-bearing quartz fissure veins that cut the stratiform deposits probably formed by remobilization, during or following Upper Cretaceous regional metamorphism.
|Geologic map unit||(-131.630684343053, 55.304653900382)|
|Mineral deposit model||Besshi massive sulfide?; Polymetallic veins (Cox and Singer, 1986; models 24b, 24c)|
|Mineral deposit model number||24b?, 22c|
|Age of mineralization||Late Jurassic? (stratiform sulfides); Late Cretaceous or younger (quartz fissure veins).|
|Workings or exploration||
The Goldstream deposit was discovered in 1897 and worked mainly in the early 1900s. Some gold was also produced by reworking dump material in the 1930s. Development of the main deposit in the early 1900s included a 115-foot shaft with 2 levels (50 and 100 feet deep), and between 400 and 600 feet of drifts. The veins were developed at that time by two 50-foot shafts, opencuts, and trenches. Maas and others (1995) report that the two 50-foot shafts are plugged.Maas and others (1995, p. 197) report that a 4-foot sample across quartz lenses in talc schist contained 4.7 ppm Au, 74.4 ppm Ag, 0.8% Cu, and 6.28% Zn.
|Indication of production||Yes; small|
|Production notes||Several thousand tons of ore were produced in the early 1900s from the Goldstream mine, mainly from a 5-foot-long, steeply-pitching oreshoot in the main deposit (Cobb and Elliott, 1980, p. 47). Maas and others (1995, p. 201) report cumulative production of 8.1 kg Au and 15 kg Ag.|
Additional commentsThe Goldstream mine was the most productive of the early mines in the Ketchikan area. In some early reports, the property was also referred to as Bell, or Miller (and Phillips) (Brooks, 1902, p. 62; Cobb and Elliott, 1980, p. 47, 145). In 1925, two of the Goldstream claims, the Goldstone and Goldstring, were patented (Maas and others, 1995, p. 194).
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.
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||7/2/1999|