San Juan

Prospect, Undetermined

Commodities and mineralogy

Main commodities Au
Ore minerals pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale A-1
Latitude 55.15065
Longitude -132.18182
Nearby scientific data Find additional scientific data near this location
Location and accuracy The San Juan prospect is east of the head of Kitkun Bay at an elevation of about 400 feet. It is 1.0 mile west-southwest of hill 1305 and about 0.1 mile northeast of the center of section 32, T. 77 S., R. 88 E.

Geologic setting

Geologic description

The San Juan prospect was discovered prior to 1902 and was explored intermittently until 1913 (Brooks, 1902; Wright and Wright, 1908; Smith, 1914). The rocks in the vicinity consist of greenschist and marble of the Wales Group of Late Proterozoic and Cambrian age (Eberlein and others, 1983; Brew, 1996). Maas and others (1991) describe a tunnel 320 feet long and another 20 feet long, neither of which exposes ore. A higher adit, 165 feet long, cuts a fault zone up to 10 feet thick with fragments of gouge, sericite schist, quartz-schist-marble breccia, and quartz, all with varying amounts of pyrite. Samples from the fault zone contained 16 to 860 parts per billion gold; a dump sample of milky quartz contained 6.68 parts per million gold. Based on a grid of soil samples, Hedderly-Smith (1999 [Inventory]) defined a stratabound epithermal breccia deposit as much as 4 feet thick that can be traced for over 700 feet. Based on numerous chip samples, he estimated that the average grade is less than 0.03 to 0.1 ounce of gold per ton.
Geologic map unit (-132.183482588773, 55.1502951609014)
Mineral deposit model Low-sulfide gold-quartz vein (breccia) (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization The deposit is younger than the Late Proterozoic or Cambrian host rocks.

Production and reserves

Workings or exploration The workings consist of a 20 foot and a 320-foot tunnel, neither of which cuts mineralization. A 165-foot tunnel cuts a mineralized fault zone. There was considerable sampling by government and private geologists in the the late 1980s and 1990s.
Indication of production None

References

References

Hedderly-Smith, D.A., 1993, Report of the 1992 work in the Brennan Bay-Kitkun Bay area-Sealaska minerals reconnaissance project: Sealaska Corporation, 24 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1993, Report of the 1993 work in the Brennan Bay-Kitkun Bay area-Sealaska minerals reconnaissance project, Sealaska Corporation, 45 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1996, Report of the 1994 and 1995 work in the Kitkun Bay area-Sealaska minerals reconnaissance project: Sealaska Corporation, 83 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1997, Report of 1996 work in the Kitkun Bay area-Sealaska minerals reconnaissance project: Sealaska Corporation, 29 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1999, Inventory of metallic mineral prospects, showings and anomalies on Sealaska lands, 1988 through 1998: Sealaska Corporation, Juneau, Alaska, 217 p. (internal report held by Sealaska Corporation, Juneau, Alaska).
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004