Yukon

Prospect, Inactive

Alternative names

Mendeltna

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; W
Ore minerals bornite; chalcocite; chalcopyrite; covellite; malachite; tetrahedrite
Gangue minerals calcite; epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-6
Latitude 63.169
Longitude -146.9284
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is about 1.3 miles east of Clearwater Creek and about 1.5 miles above its junction with Pass Creek. It is at an elevation of 4,500 to 5,100 feet on the south flank of peak 5410 in the NW1/4 section 23, T. 20 S., R. 4 E., Fairbanks Meridian. The prospect probably includes locality 5 in figure 4 of Cobb (1979 [OFR 79-238]) and localities 4 and 5 in table 2 of Nokleberg and others (1991). It also includes locality 33 of Clautice and others (1989) about 2,000 feet north of the center of section 23; see also table A37 of Kurtak and others (1992).

Geologic setting

Geologic description

Bedrock in the area consists of propylitized basalt of the Nikolai Greenstone of Late Triassic age that is cut by mafic dikes (Nokleberg and others, 1991; Kurtak and others, 1992). The basalt is locally sheared and silicified and is cut by quartz-epidote-calcite-filled veinlets. Veinlets and vesicles are stained with malachite and contain chalcocite, tetrahedrite (?), and, less commonly, bornite and covellite (Kurtak and others, 1992, table A37). At the ridgetop, a 2-inch vein in amygdaloidal basalt consists mainly of chalcopyrite and malachite (Clautice and others, 1989, locality 33).
Mineralized zones are of moderately high grade but are small and discontinuous (Kurtak and others, 1992). Sample 3010 containing bornite and covellite in greenstone assayed 3.28 percent copper; sample 1411 assayed 0.41 ounce of silver per ton, 3.72 percent copper, and 50 parts per million (ppm) tungsten. A narrow vein sampled by Clautice and others (1989, locality 33) contained more than 1 percent copper and 24.6 ppm silver.
Geologic map unit (-146.9306632917, 63.1685573743325)
Mineral deposit model Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization The deposits are probably of either Cretaceous or early Tertiary age (see MH060 and MH100).
Alteration of deposit Silicification and propylitization of basalt.

Production and reserves

Workings or exploration The Mendeltna (Kardex site number KX68-79) claims were located by Atwater in 1957; the Yukon claims (Kardex site number KX68-28) were located by F.S. Pettyjohn, Jr., in 1961 (Kurtak and others, 1992; Heiner and Porter, 1972). State geologists found other copper veins in later reconnaissance work (Clautice and others, 1988, 1989). There are no significant workings at the site.
Indication of production None

Additional comments

Select samples contain high copper values, but the exposures are very small and discontinuous, and the prospect has low potential for commercial copper and silver deposits (Kurtak and others, 1992).

References

References

Heiner, L.E., and Porter, Eve, 1972, Alaska Mineral Properties, volume 2: University of Alaska, Mineral Industry Research Laboratory Report 24, 669 p.
Reporters W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 8/5/2001