KINETICS OF SULFIDE OXIDATION AND THE SOLUTION OF GOLD

Abstract

The oxidation of the main gold carriers in sulfide deposits was studied by bubbling oxygen through suspensions of them. We used both natural and synthetic sulfides and, while growing the latter, added gold tagged with the radioisotope Au195. The gold content of these sulfides was: pyrite 192 ppm, pyrrhotite 180, chalcopyrite 50, arsenopyrite 133, galena 100. The highest gold concentrations in waters were recorded during oxidation of gold-bearing galena, chalcopyrite and arsenopyrite. Oxidation of pyrite and pyrrhotite yielded considerably less gold, despite its higher concentration in the starting samples. Such differences in the behavior of gold in solution can be explained by the fact that sulfide oxidation creates conditions differing in the extent to which they favor its solution and migration.