| This paper investigates the concentrations and distributions of copper (Cu), zinc (Zn), silver (Ag), and lead (Pb) in the Keystone mining waste rock mound. This study employs flame atomic absorption spectrometry for the analysis of ore samples that were totally dissolved, water leaches of ore samples, and dissolved plant material. This study suggests that the Keystone mound contains low grade ore of about 0.08%, or approximately one fifth of the 0.4% established by the mining operations during the 1930s as unprofitable ore. The data show that Cu, Zn and Ag concentrations increase from the top of the mound to the bottom of the mound. The average concentrations are as follows (top and bottom, respectively): Cu - 590 ppm and 920 ppm, Zn - 25 ppm and 75 ppm, Ag - 1.8 ppm and 2.8 ppm. Lead, however, is fairly constant throughout the mound, around 48 ppm. The change in concentration levels for Cu, Zn, and Ag are probably due to natural leaching and past heap leaching during mining activities. The soil pH is acidic with a pH level of 3 to 4 throughout the mound. This low pH has mediated the transport of Cu, Zn, and Ag down the mound. The data for the plants show that the concentration of Cu, Zn, and Ag are elevated in plants growing on the mound. |
