Geologic description
Most of Gold Dust Creek flows within the Upper Quartzite and Upper Schist units described by Wiltse and others (1995). The Upper Schist is a mixed unit of variably garnetiferous pelitic quartz-muscovite schist, muscovite-quartz schist, chlorite-quartz-muscovite schist, and layers tens of meters thick of garnetiferous, calcareous albite-porphyroblastic muscovite-chlorite schist. The Upper Quartzite unit is a porphyroblastic albite-chlorite-muscovite-quartz schist.
Gravel clasts in the creek are subangular to subrounded and are commonly as much as 30 cm in diameter. The area of mined gravel is approximately 70 m wide for most of the creek length, with an average gravel thickness of 4 m. Average gold values were 0.007 to 0.01 ounces per cubic yard (Menzie and others, 1983). Concentrates include ilmenite granules up to 0.5 cm, hematite nodules up to 2 cm, along with pyrite and scheelite (Menzie and others, 1983). Galena-bearing boulders have been found in previously placer mined creek gravels by John Mitchell in the late 1980s. Mining was reported shortly after drilling in 1936 (Mertie, 1938, p. 231). There were two active placer operations during 1975, but little is known about productivity (Eberlein and others, 1977, p. 20). Simple sluicebox operations used in the early 1980s were moderately to highly efficient in recovering coarse gold, but low in recovering fine gold. As a result, research by the local miners led to the use of a sophisticated washing plant with jigs. Gold in the 120 to 400 mesh range was routinely recovered with the new system (Yeend, 1991). In 1995, Alpine Exploration Co. conducted 1400 feet of reverse circulation drilling to explore veins found during earlier placer mining (Bundtzen and others, 1995). About 8 km of the ll km long creek has been mined, but the upper 3 km has a steep gradient and contains little gravel, and so it remains unmined (Yeend, 1991). |
