New Analysis Method for Gold Occurrence in Carlin-type Gold Ore

Gold exists in the form of micro-super micro dispersed states in Carlin-type gold ores, which is in the form of rich organic matter. The gold occurrence state cannot be analyzed accurately or at best, can be roughly estimated by using the Mineral Liberation Analyzer (MLA) and the traditional chemistry method. In this study, carlin-type gold ore in Guizhou Huilong was analyzed systematically using MLA, and the results show that micro-super micro gold was mainly embedded in pyrite and arsenopyrite, and less was embedded in gangue minerals and other minerals. The separation degree of pyrite and arsenopyrite were 66% and 30% in minerals, respectively. As gold-bearing minerals are attached or embedded in other minerals, the separation of gold-bearing sulfides (GBS) is more difficult. The leaching orders regarding free gold (FG), gold-bearing carbonates (GBC), gold-bearing sulfides (GBS) and silicates (GBSi) were sequenced on the basis of the tradition method, gold occurrence state and high content of organic matter characteristics of Guizhou Huilong gold ore. Furthermore, according to the high content of organic matter in this deposit, the activated carbon was added in the process of leaching FG and GBC to restrain the adsorption to gold by organic carbon. The comparative studies between traditional methods (TM) and modified methods (MM) show that there is only a small effect on the detected value after adding activated carbon into the gold ores which contain about 1% of organic carbon. In MM, gold-bearing carbonates were leached prior to gold-bearing sulfides; results of every phase data were more accurate than those of TM. Along with the addition of activated carbon in MM, the contents of FG, GBS, GBC, GBSi in Guizhou Huilong gold ore were 1.25%, 84.17%, 11.46% and 3.13%, respectively, which was consistent with the results of processing experiments. This indicates that MM can be applied to analyze precisely the occurrence states of gold in carlin-type gold ores.