Unnamed Occurrence (ARDF - SO038; tributary to Clear Creek), Koyuk Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - SO038; tributary to Clear Creek)	- not defined -
Koyuk Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: This occurrence is on the second north tributary to Clear Creek upstream from the confluence of Clear Creek and the Tubutuluk River. It is 1.2 miles upstream from the tributaries confluence with Clear Creek and at about 275 feet elevation. This is sample locality 2983 of West (1953, Plate 1) and locality 132 of Cobb (1972, MF 445; 1978, OF 78-181).
Geology: Heavy-mineral concentrate (concentration ratio of 1,100:1) from stream gravels at this locality contain 0.086% equivalent uranium. Minerals identified in the heavy-mineral concentrates include hematite, ilmenite, garnet, topaz, allanite, sphene, an unidentified uraniferous titanium niobate, and trace cassiterite and scheelite. This is the farthest downstream sample in this drainage (West, 1953) and it is located near the eastern contact of the Darby pluton with metasedimentary rocks (Till and others, 1986). Clear Creek and its north tributaries have headwaters in the Darby pluton. Many of the heavy minerals in the concentrates from stream sediments in the area are known accessory minerals in the Darby pluton. The widespread elevated Nb values in stream sediments (Miller and Grybeck, 1973) and in heavy -mineral concentrates (West, 1953) of the Clear Creek-Vulcan Creek area may indicate specific mineralized zones of disseminations in late, felsic phases of the Darby pluton (Miller and Grybeck, 1973). The Darby pluton is a mid-Cretaceous granodiorite and granite that has elevated background levels of uranium and thorium (Miller and others, 1972; Miller and Bunker, 1976; Johnson and others, 1979). This pluton is considered the bedrock source of uranium that was mobilized and deposited in the Death Valley sandstone uranium deposit (in the Bendeleben quadrangle to the north) during the Eocene (Dickinson and others, 1987). K/Ar ages for the Darby pluton are 88.3 +/- 1.5 and 92.8 +/- 2.6 Ma (Berry and others, 1976).
Workings: There are no known workings; exploration in the region may have included reconnaissance stream sediment sampling and radiometric surveys.
Age: The heavy mineral concentrates are from Holocene surficial materials but these have been primarily derived from the nearby bedrock of the Darby pluton. The Darby pluton is mid-Cretaceous; K/Ar ages for the Darby pluton are 88.3 +/- 1.5 and 92.8 +/- 2.6 Ma (Berry and others, 1976).

Commodities (Major) - REE, Sn, U, W
Development Status: None
Deposit Model: Disseminated; uranium- and rare-earth-bearing minerals are probably accessory ph

Other Databases

Link to USGS - Alaska:	SO038

Other Regions, Features and Areas containing this locality

References