Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Cu
Ore minerals arsenopyrite; chalcopyrite; gold; pyrite; pyrrhotite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale D-3
Latitude 60.872
Longitude -147.832
Nearby scientific data Find additional scientific data near this location
Location and accuracy The prospect is southwest of the head of Derickson Bay at an elevation of about 600 feet. It is in the N1/2 section 15, T. 9 N., R. 9 E., of the Seward Meridian. This is location 184 of Tysdal (1978 [MF-880-A]) and location S-123 of Jansons and others (1984). This location is accurate to within half a mile.

Geologic setting

Geologic description

The Eldorado prospect consists of a 12- to 48-inch-wide quartz vein in a shear zone. The vein is semi-concordant to the shear. It strikes N40E, dips 75NW, and is traceable for 400 feet along strike (Johnson, 1914 [B 592-G, p. 235]). The country rock is slate and quartzite of the Valdez Group of Late Cretaceous age (Cobb and Tysdal, 1980). The shear zone hosting the vein is related to the Contact Fault, a major regional structure that separates the Valdez Group from the younger Orca Group.
Overall, the vein is composed of bluish-gray quartz that contains calcite, arsenopyrite, chalcopyrite, pyrite, pyrrhotite, and gold. Grab samples assayed as much as $5 in gold (gold at 20.67 per ounce) (Johnson, 1914 [B 592-G, p. 235]). Johnson (1914 ) reported that 375 feet of workings had been completed in 1913. No other information about this prospect has been made public. In 1978 and 1979, the U.S. Bureau of Mines searched for this prospect, but no workings were found (Hoekzema and Sherman, 1983).
Geologic map unit (-147.834072188872, 60.8714714263601)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Oligocene or younger; the Contact Fault cuts Oligocene intrusive rocks northeast of this prospect.

Production and reserves

Workings or exploration Johnson (1914 [B 592-G, p. 235]) reported that 375 feet of workings had been completed in 1913. Johnson also reported that samples of blue-gray quartz from the shear zone were reported to contain $100 in gold per ton (gold at $20.67/ounce), and samples of the sheared material contained $4.00 to $5.00 in gold per ton.
Indication of production None



Reporters Jeff A. Huber ( Anchorage)
Last report date 1/1/2000