Bonanza Prospects, Koyukuk Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Bonanza Prospects	Group of Prospects
Koyukuk Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

See also Bonanza (Beef Claims), (BV003) in the Beaver quadrangle.
Location: These prospects are approximately centered at an elevation of about 2,750 feet on a small hill informally called Windy Knob which is in about the center of the SW 1/4 of section 19, T. 21 N., R. 11 W. of the Fairbanks Meridian. The prospects are scattered over an area about 1.5 miles wide and 5.5 miles long (which extends into the adjacent Beaver quadrangle). The coordinates are the center of the Bonanza claim block, which is the locus of the principal mineral showings in the area. The location is accurate.
Geology: Clautice (1983) reports modest amounts of scheelite and molybdenite along the contact of the Cretaceous, Kanuti batholith with Paleozoic metasedimentary rocks. This 30-square-mile area extends into the Beaver quadrangle. The principal scheelite occurrences are near a feature informally named Windy Knob. Here, the highest grade tungsten mineralization occurs in pyrrhotite-rich, chalcopyrite-bearing, dark green tactite along the margin of biotite,quartz monzonite. A grab sample contains as much as 0.89% tungsten, 300 grams of silver per ton, and 0.65% copper. However, the scheelite most commonly occurs as disseminated grains in relatively sulfide-free pyroxene-garnet skarn. The skarn appears to form irregular pods. Scheelite also occurs on fracture surfaces in calc-silicate schist and less commonly in quartz veins. Molybdenite typically occurs as rosettes and small flakes in quartz veins in biotite, quartz monzonite and less commonly in aplite, pegmatite, and calc-silicate rock. Several select samples of skarn contain up to 1.44% tungsten, 24.3 ppm silver, 1,438 ppm zinc, and 936 ppm lead. (Kurtak and others, 2002). The Kanuti batholith is Cretaceous based on a K-Ar date of 90.6 Ma (Nokleberg and others, 1987).
Workings: Surface sampling, geologic mapping, and trenching.
Age: The Kanuti batholith is Cretaceous based on a K-Ar date of 90.6 Ma. (Nokleberg and others, 1987).
Alteration: Calc-silicate skarn.

Commodities (Major) - Mo, W; (Minor) - Cu
Development Status: None
Deposit Model: W skarn deposit (Cox and Singer, 1986; model 14a)

Other Databases

Link to USGS - Alaska:	BT009

Other Regions, Features and Areas containing this locality

References