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

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

Location: The Abo prospect is about 3.8 miles east-southeast of Mount Hecht. Mineralization has been found at three locations on the property. The coordinates reflect the more-or-less centrally-located showing. It is at an elevation of about 1,240 meters, about 0.4 mile southwest of the center of section 4, T. 30 N., R. 23 W., of the Fairbanks Meridian. The other two locations are approximately 3,000 feet northwest and southeast of the central prospect. The location is accurate.
Geology: The Abo prospect consists of zinc and lead mineralization in the upper portion of the Devonian, Skajit Limestone (Kurtak and others, 2002). The mineralization is generally near the contact between sandy, micaceous limestone, which constitutes the uppermost part of the Skajit Limestone in this area, and underlying massive, gray marble. The Skajit Limestone contains lenses or interbeds of dolomite, sandstone, quartzite, quartz-mica schist, and chlorite schist. The dolomitic rocks occur as irregular zones and as individual dolomite units within the gray marble. The Skajit Limestone is overlain by Upper Devonian, Hunt Fork Shale. There are three principal mineral showings (Kurtak and others, 2002). In two of the areas, stratabound sphalerite and galena occur in thin bands along the contact between sandy limestone and massive marble, and in a quartzose, dolomitic interbed in the marble. Individual bands of sulfide mineralization range in thickness from less than 1 inch to 2.5 feet. The extent of the mineralization along strike appears to be limited (in part due to overburden); the maximum traceable length is 175 feet. Selected samples of this mineralization contain up to 25% zinc and lead, and 2.4 ounces of silver per ton. More systematic sampling indicates the grades are generally less than 1% lead and 5% zinc over widths of a few tens of feet or less (Kurtak and others, 2002). Sphalerite, galena, and minor pyrite, form disseminations, stringers, and pod-like bodies in siliceous and/or dolomitic zones in one of the two areas described above, as well as in the third area. This mineralization, where it is stratabound, appears to be stratigraphically below the mineralization along the contact between the limestone and gray marble. The siliceous, mineralized bodies typically are 5 to 20 feet in length, and one is 150 feet long. Chip samples of this mineralization contain up to 13.5% combined zinc and lead, and 0.35 ounce of silver per ton. Two drill intercepts give values of 9.47% zinc, 0.96% lead, and 0.17 ounce of silver per ton over 15.5 feet;, and 0.44% zinc, 1.55% lead, and 0.14 ounce of silver per ton over 6 feet (Kurtak and others, 2002). A float sample contains 22.41% zinc, 1.8% lead, 0.34 ounce of silver per ton, and 77 ppb gold (Kurtak and others, 1999). A continuous chip sample of siliceous rock with abundant sphalerite contains 12.92% zinc, 0.34% lead, 2.7 ounces of silver per ton, and 19 ppb gold. Mining claims were staked in the mid-1970's (Grybeck, 1977). Extensive exploration has included geologic mapping, geochemical sampling, geophysics surveys, and diamond drilling (Kurtak and others, 2002).
Workings: Mining claims were staked in the mid-1970's (Grybeck, 1977). Extensive exploration has included geologic mapping, geochemical sampling, geophysics surveys, and diamond drilling (Kurtak and others, 2002).

Commodities (Major) - Ag, Pb, Zn
Deposit Model: Polymetallic replacement deposit (?) (Cox and Singer, 1986; model 19a)

Other Databases

Link to USGS - Alaska:	WI048

Other Regions, Features and Areas containing this locality

References