Wakefield

Prospect, Undetermined

Alternative names

Moira Copper

Commodities and mineralogy

Main commodities Au; Cu
Other commodities Ag
Ore minerals chalcopyrite; pyrite
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale A-1
Latitude 55.07436
Longitude -132.17823
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Wakefield prospect is at an elevation of about 1,300 feet, east of upper Lake Luelia. It is on the nose of the ridge that extends north-northwest from elevation 2577, and about 0.4 mile southeast of the center of section 29, T. 78 S., R. 88 E.

Geologic setting

Geologic description

As described by Wright and Wright (1906, 1908), the workings are a 50-foot shaft with mineralization exposed at the 25-foot level, and several open cuts. There was assessment work as late as 1915. The host rock is greenschist, slate and 'grits.' The deposit consists of a lenticular mass of chalcopyrite 10 feet thick in a 60-foot-thick mineralized layer in the schist that contains considerable pyrite, quartz, and epidote. The Wrights considered the deposit to be similar to the mineralization at the Niblack Mine (CR216). The prospect was examined by Maas and others (1992), who found a flooded shaft, a 17-foot adit, and some trenches. The workings expose a zone up to 100 feet wide of iron-stained, epidote-bearing, silicified greenschist that contains disseminations and layers of pyrite and chalcopyrite. Chip samples 1.3 to 4 feet long contained 221 to 656 parts per billion gold (ppb) and 851 to 7,566 parts per million (ppm) copper. A select sample contained 1,732 ppb gold, 47.2 ppm silver, and 6.57 percent copper.
The age of the rocks in the area has been variously interpreted. Eberlein and others (1983) mapped the strata as locally metamorphosed graywacke of Silurian or Ordovician age, near a large Paleozoic or Mesozoic granitic intrusion. Gehrels (1992) and Maas and others (1995) mapped them as pre-Ordovician metamorphosed volcanic and sedimentary rocks near a Silurian or Ordovician granitic intrusion. Brew (1996) called them Late Proterozoic and Cambrian Wales Group schist, phyllite, and marble, near a Tertiary granitic intrusion of intermediate composition. Most recently, Slack and others (2002) and S.M. Karl (oral communication, 2003) mapped the strata as Silurian and Ordovician, low-grade, regionally metamorphosed sedimentary and volcanic rocks.
Geologic map unit (-132.179882632818, 55.0740107243298)
Mineral deposit model Probably a Besshi-type, volcanogenic massive-sulfide copper deposit (Cox and Singer, 1986; model 24b).
Mineral deposit model number 24b
Age of mineralization Probably contemporaneous with the deposition of the Silurian or Ordovician host rocks.
Alteration of deposit Greenschist is iron stained and silicified.

Production and reserves

Workings or exploration Explored prior to WW I by a 50-foot shaft, a short adit, and several trenches.
Indication of production None

References

MRDS Number A101138

References

Slack, J.F., Shanks, W.C. III, Karl, S.M., Ridley, W.I., and Bittenbender, P.E., 2002, Geochemical and sulfur isotope compositions of Late Proterezoic and early Paleozoic volcanogenic massive sulfide deposits, Prince of Wales Island and vicinity, southeastern Alaska (abs.): Geological Society of America, Abstracts with Programs, v. 34 (6), p. 113.
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004