7-mile Gold prospect, Prince of Wales Island, Ketchikan Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi

Regional Level Types
7-mile Gold prospect	Prospect
Prince of Wales Island	Island
Ketchikan Mining District	Mining District
Prince of Wales-Hyder Census Area	Census Area
Alaska	State
USA	Country

Location: The 7-Mile Gold prospect, which is exposed in road cuts and a borrow pit, is about 0.8 miles (1.29 km) southeast of hill 1360, and near the northeast corner of section 17, T77S, R89E.

Geology: The 7-Mile Gold prospect is one of the deposits in the Kael-7 Mile Trend (CR188), a belt of mineralization about 4 miles (6.44 km) long and 0.5 miles (0.8 km) wide. The rocks in the area consist mainly of marble and minor chlorite schist, cut by greenstone dikes and sills. They are part of the Wales Group of Late Proterozoic and Cambrian age (Eberlein and others, 1983; Brew, 1996). The mineralization is stratiform and consists of breccia veins or zones (Hedderly-Smith, 1993, 1999 [Inventory]). The clasts in the breccia vary from fresh marble to ferroan(?) dolomite to silicified marble. The matrix is mainly quartz; locally the matrix may contain up to 50 percent pyrite and chalcopyrite, but it generally contains only a few percent of sulfides. The mineralization in the Kael-7 Mile Trend was discovered in 1988 by a Sealaska geologist. The discovery (CR 186) was soon leased to the American Copper and Nickel Company, who mapped and sampled the belt, and drilled 26 shallow holes in 1990 and 1991, mainly on geochemical anomalies. At least one hole was drilled on the 7-Mile Gold prospect. Three holes totaling 2,837 feet (ca. 865 m) were drilled in 1994, one at the Roy Creek prospect (CR191) at the east end of the belt, and two at the west end. As described by Maas and others (1991), the deposit at this prospect is a 30-foot-thick, silicified marble-breccia zone with masses and blebs of pyrite and chalcopyrite. The zone trends N55-80E. The mineralization is exposed in road cuts and a borrow pit, but the best mineralization is in large blocks of sulfide-rich marble in rubble in the cuts and on the pit floor. Maas and others (1991) collected several sets of samples: 1) 4 samples, 6 to 10 feet (ca. 3 m) long, of the footwall and hanging wall of the mineralized zone contained 18 to 165 parts per billion (ppb) Au and 17 to 154 parts per million (ppm) Cu; 2) 7 samples, 2 to 8 feet (2.44 m) long, of the silicified breccia contained 105 to 566 ppb Au and 11 to 182 ppm Cu; and 3) 2 sulfide-rich samples of rubble in the pit contained 0.388 and 0.784 ounce (29.63 g) of Au per ton, 5.5 and 14.5 ppm Ag, and 1.0 and 2.18 percent Cu.

Workings: Extensive sampling of mineralized road cuts and a borrow pit by government and industry geologists. At least one shallow hole drilled in 1990.

Age: Younger than the Late Proterozoic or Cambrian host rocks.

Alteration: Silicification and dolomitization of marble.

Commodities (Major) - Au, Cu

Development Status: None

Deposit Model: Stratiform Au-Cu breccia zones in marble.

Other Databases

Link to USGS - Alaska:	CR190

Other Regions, Features and Areas containing this locality

References