Abundance of Cadmium in Permian Dolostones in Japan

Abstract

Cadmium contents of 55 Permian dolostone samples collected from 6 localities in Japan were determined by flame atomic absorption spectrometry combined with ammonium pyrrolidinedithiocarbamate (APDC) -4-methyl-2-pentanone solvent extraction system. Positive correl ations exist among the Cd, Zn, Mn, Ni, and Cu contents of these samples, suggesting the similar geochemical behavior of these metals during the formation of dolostones. More Zn, Mn, Ni, and Cu are incorporated in dolostones than in limestones because of the similarity of ionic radius between these metal ions and Mg²⁺. No enrichment of Cd has however been observed in dolostones, probably due to large difference in ionic radius between Cd²⁺ and Mg²⁺. The geometric mean of Cd in Permian dolostone samples (n=81) including Kuzuu ones (n=26) was 0.43 ppm, which was almost the same as that (0.47 ppm) of Permian limestone samples (n=56) collected from the same localities. These values are somewhat high as compared with the geometric mean of Cd (0.07 ppm) of Quaternary limestone samples (n=94) taken from the Nansei Islands, southwestern Japan. These values are also higher than the abundance (0.09 ppm) of Cd in carbonate rocks compiled by Mason and Moore, suggesting the peculiarity of Cd contents of Permian carbonate rocks in Japan.