|Quadrangle map, 1:250,000-scale||PE|
|Quadrangle map, 1:63,360-scale||B-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This long-known prospect is in and just above the intertidal zone near Wedge Point on Woronkofski Island. It is about 0.6 mile west of the center of section 7, T. 63 S., R. 84 E. The location is accurate.|
Geologic descriptionThe Exchange prospect was first staked in 1900 and has been described several times in similar terms (Wright and Wright, 1908; Roehm, 1945; Still and others, 2002). The workings include open cuts and two short adits. Two of the claims were restaked in 1974, were active through at least 1982, and were probably still active in 1996. Karl and others (1999) map the rocks in the area as part of the Jurassic or Cretaceous Seymour Canal Formation which is mainly graywacke. However, the prospect is in intrusive rocks that are probably similar to the Cretaceous tonalite that makes up much of Woronkofski Island (Still and others, 2002). The deposit consists of an irregular quartz vein that strikes north and dips 30W; it is up to 16 feet thick and can be traced for 250 feet. The vein contains small amounts of galena and pyrite. Still and others (2002) collected nine samples. The highest grade was a 5-foot sample across the vein; it contained 923 parts per billion gold, 26.6 parts per million (ppm) silver, and 944 ppm lead.
|Geologic map unit||(-132.535492730795, 56.4215535136899)|
|Mineral deposit model||Gold-quartz vein.|
|Age of mineralization||Probably Cretaceous or younger based on the probably age of the intrusive host rocks.|
|Workings or exploration||The property was first staked in 1900 and developed by surface trenches and two short adits. Two of the claims were restaked in 1974, were active through at least 1982, and were probably still active in 1996.|
|Indication of production||None|
|Production notes||No record of production.|
Brew, D.A., 1997, Reconnaissance geologic map of the Petersburg B-2 quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report 97-156-D, 21 p., 1 sheet, scale 1:63,360.
Cobb, E.H., 1972, Metallic mineral resources map of the Petersburg quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-415, 1 sheet, scale 1:250,000.
Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Petersburg quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-870, 53 p.
Grybeck, D.J., Berg, H.C., and Karl, S.M., 1984, Map and description of the mineral deposits in the Petersburg and eastern Port Alexander quadrangles: U.S. Geological Survey Open-File Report 84-837, 86 p., 1 sheet, scale 1:250,000.
Karl, S.W., Haeussler, P.J., and McCafferty, A.E., 1999, Reconnaissance geologic map of the Duncan Canal-Zarembo Island area, southeastern Alaska: U.S. Geological Survey Open-File Report 99-0168, 30 p., 1 sheet, scale 1:150,000.
Roehm, J.C., 1945, Preliminary report of investigations and itinerary of J. C. Roehm in the Wrangell and Petersburg precincts, Alaska: Alaska Territorial Department of Mines Itinerary Report 195-37, 13 p.
Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002, Mineral assessment of the Stikine area, central Southeast Alaska: U.S. Bureau of Land Management Technical Report 51, 560 p.
U.S. Bureau of Mines, 1980, Claim map, Petersburg quadrangle, Alaska: U.S. Bureau of Mines Map 117, 1 sheet, scale 1:250,000.
Wright, F.E., and Wright, C.W., 1905, Economic developments in southeastern Alaska, in Brooks, A.H., Report on Progress of Investigations of Mineral Resources of Alaska in 1904: U.S. Geological Survey Bulletin 259, p. 47-68.
|Reporters||D.J. Grybeck (Port Ludlow, WA)|
|Last report date||4/8/2007|