PRECIOUS METALS AND CARBONACEOUS SUBSTANCE IN ORES OF THE SUKHOI LOG DEPOSIT (EASTERN SIBERIA, RUSSIA)

Abstract

A precious metal distribution in constituents of the dispersed carbonaceous substance (DCS) in ores from the Sukhoi Log gold deposit has been studied. Bitumens (soluble constituents) are hydrocarbons consisting of carbonic acid ethers and geopolymers (resins, asphaltens). Gold occurs in spirit-benzene bitumens and their asphalten fraction. Two modes of gold occurrences, i.e., chemically bound and free gold (amalgamated by mercury), are found in bitumens. Concentrates and analysis products such as suspension, percolate, and rock residuum, where gold was detected, were obtained using a special technique of fractionation of the insoluble carbonaceous substance (ICS) and the insoluble constituent of the DCS in ores. Three modes of gold occurrences, colloidal gold (suspension), soluble gold (filtrate), and that bound with a carbonaceous substance, were identified. Platinum was found in concentrates of the ICS obtained after decomposition of the carbonate-silicate fraction of ores only. Probably, native platinum does not occur in the carbon-rich substance. This is why the analytical problems of its determination in black shale-hosted deposits exist. Organic substance and fluid inclusion studies showed that a principal geochemical feature of the major ore-forming substage at the Sukhoi Log deposit is an interaction of nitrogen- and precious metal-rich deep-sourced fluids with a carbonaceous substance that is a geochemical barrier for ore components. An occurrence of metalloorganic precious metal species should be taken into account to elaborate the optimal technology for their recovery and avoid losses of valuable components.