Characterization of Gold in Flotation Tailing by Metallurgical and Micro-Beam Techniques at the Sar Cheshmeh Porphyry Copper Mine

摘要

A trend which is emphasized, not only by the necessity of promotion the coordinated development of economy, resources, and the environment, but also by the new technical developments in the fields of mineral processing and metallurgical recoveries of mineral resources, is the increased importance of precious metals, particularly gold, in porphyry copper deposits. Meanwhile, the mode of occurrence and mineralogical characteristics of gold in most of the porphyry copper ores are not yet clear and frequently during the beneficiation process, a large amount of gold is lost to tailings. An evaluation of gold distribution in the mill products of Sar Cheshmeh porphyry copper shows that about 56% of the gold is lost to the tailing, which is currently worth over $8,500,000 per year (@ $600/oz). Considering the very low bulk concentration of gold (i.e., 34 ppb) and different mineralogical forms of gold occurrences in the Sar Cheshmeh tailing, a fundamental study of the nature and location of gold and its peculiarities are more complicate than a low grade gold ore. Accordingly, no single method or purely mineralogical approach can provide all the information needed. In this study a multi-disciplinary approach as well as thoroughly evaluation of the geological and process evidences was employed. The results of metallurgical experiments consist of sizing, heavy liquid separation, flotation, staged digestion, and cyanidation of the tailing in combination with the advanced mineralogical analysis techniques such as SEM, EPMA, and SIMS, enabled detection of gold in both "visible" and "invisible" modes of occurrence. It was also revealed that while a fraction of gold is present in solid solution and/or colloidal size within sulfides of the Sar Cheshmeh flotation tailing, "visible" gold is the principal form of gold with particle size in the range of 2-300 urn, but most of them less than 10 urn in diameters.