|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 U.S. prospect is at an elevation of about 250 feet, 0.4 mile northeast of the head of the falls at the mouth of Falls Creek. The site is in section 30, T. 72 S., R. 88 E., of the Copper River Meridian. It corresponds to loc. 258 in Maas and others (1995, fig. 46), and to loc. 37 in Elliott and others (1978). The location is accurate within 0.1 mile.|
The country rocks near this site include gray and green phyllite and semischist derived from intertonguing flysch and andesitic and basaltic volcanic rocks (Berg and others, 1988, p. 17-20); and gray felsic schist possibly derived from silicic tuff (Maas and others, 1995, p. 183 and fig. 46). Near Smugglers Cove, the bedded rocks are intruded by diorite that may be transitional to the andesitic and basaltic volcanic rocks. The bedded and intrusive rocks were regionally metamorphosed to greenschist grade in Late Cretaceous time (Brew, 1996, p. 27). Their premetamorphic age is uncertain. Berg and others (1988, p. 17) note that the intertonguing flysch and volcanic rocks closely resemble Upper Jurassic to mid-Cretaceous marine strata nearby on Gravina Island.
The deposit consists either of (1) auriferous, pyrite-bearing quartz that forms irregular lenses parallel to the foliation of pyritic chlorite schist (Wright and Wright, 1908, p. 157); or (2) an auriferous pyritic quartz vein 10-20 feet wide that strikes NW and dips 70 NE (Brooks, 1902, p. 57). The deposit was explored in the early 1900s by stripping and by a 6-foot-long adit.Maas and others (1995, p. 184 and tables 25 and 26) suggest that the U.S. deposit may be part of a belt of exhalative volcanogenic gold deposits (KC035) that extends along the northeast shore of Smugglers Cove and includes the Mary T. (KC036) and Blue Bucket (KC039) deposits. The average metal contents of their samples of the U.S. deposit are: 1.45 ppm Au, 0.15 ppm Ag, 45 ppm Cu, 67.8 ppm Pb, and 124 ppm Zn.
|Geologic map unit||(-131.970682855592, 55.5986373638696)|
|Mineral deposit model||Distal disseminated Ag-Au? (Bliss, 1992, model 19c)|
|Mineral deposit model number||19c?|
|Alteration of deposit||Pyritization of chlorite schist.|
|Workings or exploration||The deposit was explored in the early 1900s by stripping and by a 6-foot-long adit. The average metal contents of samples of the U.S. deposit collected in the early 1990s by the U.S. Bureau of Mines are 1.45 ppm Au, 0.15 ppm Ag, 45 ppm Cu, 67.8 ppm Pb, and 124 ppm Zn (Maas and others, 1995, table 25).|
|Indication of production||None|
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.
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|