Derwent

Occurrences, Active

Commodities and mineralogy

Main commodities Zn
Other commodities Ag; Mo; U; V
Ore minerals azurite; chalcopyrite; malachite; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale CY
Quadrangle map, 1:63,360-scale A-3
Latitude 65.05
Longitude -142.3
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Derwent zone covers a large area along an east-northeast trend from section 11 in the northeast corner of T. 2 N., R. 26 E., of the Fairbanks Meridian to section 22, just southeast of the center of T. 3 N., R. 27 E., of the Fairbanks Meridian. The coordinates are for the approximate center of the zone, in section 32, T. 3 N., R. 27 N., of the Fairbanks Meridian. This prospect is located on Doyon, Limited selected or conveyed land. The location is accurate to within 1 or 2 miles.

Geologic setting

Geologic description

The Derwent zone of zinc geochemical anomalies is hosted by a northwest-trending belt of metasedimentary and possibly metavolcanic rocks. This belt lies between a granitic batholith and the Tintina fault (Doyon, Limited, 1998). The zone extends for 24 miles between the Seventymile and Charley Rivers. It is mostly underlain by Paleozoic phyllite, graphitic schist, chert, phyllite, and marble (Doyon, Limited, 1998).
The zone has been defined by soil samples containing zinc values greater than 5,200 ppm zinc. Some samples, especially ones from a color anomaly, are also weakly anomalous in copper, silver, molybdenum, vanadium, tungsten, and uranium. Soils contain greater than 5,200 parts per million Zn, 3.4 parts per million Ag, 3,000 parts per million V, 18 parts per million U, and 285 parts per million Mo.
All of the soil anomalies are probably due to elevated background concentrations in the metasedimentary rocks. Locally, the zone contains quartz veins and segregations that carry visible copper sulfides and oxides. Also, samples of graphitic schist breccia contain 920 parts per million Zn, 900 parts per million V, 85 parts per million Mo, 7 parts per million U, and 1.2 parts per million Ag (Doyon, Limited, 1986). The Derwent zone may be a fault-offset block from near the Anvil district that has been displaced 300 miles by the Tintina fault (Doyon, Limited, 1998).
This area has been examined by stream silt samples, panned concentrates, soil and rock sampling of the color anomalies, and regional reconnaissance since the mid-1970s (Doyon, Limited, 1998).
Geologic map unit (-142.302345919417, 65.0496800144503)
Mineral deposit model Shale-hosted Zn-Pb (Schmidt, 1997; Cox and Singer, 1986; model 31a).
Mineral deposit model number 31a
Age of mineralization Paleozoic?

Production and reserves

Workings or exploration Since the mid-1970s, this area has been examined by stream silt samples, panned concentrates, soil and rock sampling of the color anomalies, and regional geologic reconnaissance (Doyon, Limited, 1998).
Indication of production None

Additional comments

These prospects are located on Doyon, Limited selected or conveyed land. For more information, contact Doyon, Limited.

References

MRDS Number 10307399

References

Doyon, Limited, 1986, Mines, prospects, and geochemical anomalies on Doyon, Limited, regional overselection lands, Alaska: Fairbanks, Alaska, Doyon, Limited Report 86-01A, v. 1, 150 p. (Report held by Doyon, Limited, Fairbanks, Alaska.)
Doyon, Limited, 1998, Veta Prospects 1997 Volume 1: Doyon, Limited, unpublished report 98-10, 256 p. (Report held by Doyon, Limited, Fairbanks, Alaska.)
Schmidt, J.M., 1997, Shale-hosted Zn-Pb-Ag and barite deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska, 1997: Economic Geology Monograph 9, p. 35-65.
Reporters C.E. Cameron (ADGGS)
Last report date 4/7/2000