Geologic descriptionPlacer gold was discovered on Bear Creek as early as 1916 and mining was reported intermittently up to 1934 (Hoare and Coonrad, 1978). This site is the lower of two placer mine locations on Bear Creek shown by Cobb and Condon (1972). Harrington (1921) visited Bear Creek in 1919 and reported that initial mining had opened up a 15- by 50-foot pit, in which 2 to 3 feet of black, clayey muck overlay 2 to 5 feet of gravel. The gravel was post-glacial, and consisted mostly of locally derived, iron-stained and cemented sedimentary material; plutonic rock fragments were not present. Only a few very small colors were obtained in pans taken from the base of the gravels (not necessarily on bedrock). Fechner (1988) collected 4 samples of sediments in the Bear Creek drainage; these samples contained a trace to 0.624 ounce of gold per ton. A sample of felsic intrusive rock, apparently float (Fechner, 1988, sample 44), contained 725 ppb gold. Minor platinum was recovered with the gold from Bear Creek and some prospecting for platinum was completed here by the Goodnews Bay Mining Company (Mertie, 1969, p. 89). An analysis of PGE material recovered from Bear Creek showed it to contain 72.82 percent platinum, 15.58 percent iridium, 8.17 percent osmium, 2.29 percent ruthenium, 0.78 percent rhodium, and 0.36 percent palladium (Mertie, 1969, Table 38). Bedrock in the area includes Paleozoic and Mesozoic sedimentary and volcanic rocks locally intruded by Upper Cretaceous to Lower Tertiary granitic rocks and Jurassic mafic/ultramafic plutonic rocks (Hoare and Coonrad, 1978). |
