Influence of heavy minerals on in-process loss of gold in placer mining in Russian Far East

Abstract

Heavy metals in natural placers, as follows from the review of numerous reference sources and hands-on experience, greatly affects gold recovery, which, in the end, essentially raises interest in the final processing product and in dredge and sluice tailings dumps. The spatial cositing of geological structures of different ages, from the Archean to the Paleogene, and of various metallogeny, as well as the favorable geomorphological situation created conditions for the formation of gold placers with a wide range of associated components in the Far Eastern Region of Russia. The influence of heavy minerals during mining of such placers on the quality of precious metal extraction was studied. The significant impact of heavy minerals on complication of placer mining technologies and on the increased loss of gold was revealed. In this aspect, the analysis of the data obtained during three washing seasons at the experimental landfills of one of the unique placers in the Khabarovsk Krai is presented. It is found that the increased amount of heavy minerals in placer sands (from 10 to 30 %) conditions the increased loss of gold by more than 2 times. It is shown that the greatest losses of gold are observed when gold and accompanying valuable components in natural sands have the same (equivalent) sizes. To take into account the effect exerted on gold losses by such parameter as the content of heavy minerals in natural sands, it is recommended to use correction coefficients and, in some situations, to modify the mining and processing flowsheets. It is found that accumulation of valuable components in manmade waste placers formed in the course of natural placer mining significantly increases interest in the waste placers because of the high content of valuable components in such objects and owing to the increased gold losses in natural placer mining.