Abundance and distribution of Pb, Zn, Cu and Cd in the Downeys Bluff Limestone, Minerva Mine No. 1, Cave-In-Rock District, Illinois
Englishman, Donald Ellsworth
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Trace amounts of Pb, Zn, Cu, and Cd in diamond drill cores from the Downeys Bluff Limestone (one of the host rocks for fluorite-sphalerite ore) in Minerva Mine No. 1, Cave-in-Rock, Illinois, were determined by atomic absorption spectroscopy. An attempt was made to find the abundance and distribution of these elements, and to determine the extent of their dispersion halos (if any) within the host rock. The amounts of Fb, Cu, and Cd present in the non ore-bearing portions of the Downeys Bluff Limestone were below the detection limits of this study and are reported as <1.5 parts per million (ppm), <1.0 ppm, and <0.25 ppm, respectively. The content of Zn varied between 0 and 50 ppm, with an average of 20 ppm, which is in agreement with average crustal abundances for Zn in carbonate rocks. The Pb and Cu abundances reported by this study are much lower than the average crustal abundances for carbonate rocks. Fluorite-sphalerite ore gave detectable Cd contents when the Zn content was greater than 4000 ppm; Cu and Pb were not detected in the ore. Sampling and analyzing core samples from six lateral diamond drill holes at 2 and 5-foot intervals did not reveal any dispersion halos for Pb, Zn, Cu, or Cd.