U.S.

Prospect, Undetermined

Commodities and mineralogy

Main commodities Au
Ore minerals gold; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale C-6
Latitude 55.599
Longitude -131.969
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.

Geologic setting

Geologic description

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.

Production and reserves

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

References