Geologic description
The placer gold in Yakataga-area beaches was discovered in 1897 or 1898,and small-scale mining started in 1899 (Maddren, 1914). Rocker and sluice operations continued to WW II. Drill prospecting of raised beaches occurred after WW II (Thomas and Berryhill, 1962), as did sporadic attempts at small-scale mining. Most of the post-WW II mining was west of Cape Yakataga (see BG005; Miller, 1971). The gold in the Yakataga area, naturally concentrated in heavy-mineral accumulations by storm waves, is fine and flat. Other heavy minerals include amphibole, garnet, chromite, native copper, hematite, magnetite, pyroxene, rutile, sphene, ilmenite, zircon, and probably some monazite (Maddren, 1914, Thomas and Berryhill, 1962; Foley and others, 1995).
The iron and titanium oxide contents of reconnaissance samples of beach sand from the Yakataga area were reported by Thomas and Berryhill (1962). These samples contained as much as 6.2 pounds of iron per ton but mostly less than 2 pounds of iron per ton. Their titanium oxide content was less than 2 pounds per ton in the magnetic fraction and as much as 7.3 pounds, but mostly less than 2 pounds, per ton in the non-magnetic fraction. Foley and others (1995) processed 94 samples from 51 locations, including some raised beaches, along this segment of the Yakataga shoreline. Spiral concentrates from these samples contained less than 0.028 grams (64 samples) to 0.790 grams gold per ton (one outlier sample was reported to contain 12.219 grams of gold per ton), 0.34 to 1.65 percent titanium, and 95 to 2029 ppm zirconium. Heavy-mineral concentrates from five samples (3.91 to 7.47 weight percent of the original samples) contained 0.001 to 0.031 percent magnetite, 0.106 to 0.232 percent ilmenite, 0.193 to 0.629 percent garnet, 0.001 to 0.032 percent rutile, and 3.32 to 7.22 percent other minerals. Flotation concentrates from two samples contained 7.253 and 15.86 grams of gold per ton, 0.008 and 0.0085 gram platinum per ton, and 0.017 and 0.056 gram of palladium per ton. The placer gold in the Yakataga beaches may be derived from reworking of marine-glacial deposits of the Cenozoic Yakataga Formation (Reimnitz and Plafker, 1976). |
