PECULIARITIES OF FREE GOLD OF THE GUMESHEVSKOYE DEPOSIT: MORPHOLOGY, COMPOSITION, ZONAL DISTRIBUTION

The relevance of research is determined by the need for a detailed study of the composition and changes of free gold in conditions of hypogene-supergene processes within the Gumeshevskoye deposit. The methods of investigation are X-ray spectral microanalysis, scanning electron microscopy. Purpose of the study was to obtain data on the granulometric, morphological and chemical composition of free gold to identify vertical zoning in its distribution within the upper part of the deposit. Results of the research. The study of free gold from regolite of ore-bearing karst (Cu, Au) and argillizated rocks of the Gumeshevskoye copper-skarn deposit (Middle Urals) was carried out. Variations in the granulometric, morphological and chemical composition of gold at different depth levels of the tested section of the productive ore zone are considered. The signs of vertical zonation in the distribution of gold by granulometric and chemical compositions, as well as in the ratio of its main morphotypes, are revealed. It is shown that with the general predominance of fine gold (< 0.15 mm) at all levels, the average grain size of gold increases with depth. There is a significant variation in gold fineness from 591 ‰ to ≥ 980 ‰; most of gold is high-grade. Low-grade gold and electrums are found only in the upper part of the section (up to 35 m). By the ratio of these impurities there are three geochemical types of free gold: gold-silver, gold-silver-copper, and gold-copper. The most frequent in the deposit is Au-Ag-Cu type, which is 47% in the upper part of the ore zone to 70% at depths of more than 50 m. Pure Au-Cu natural alloys are much less common, amounting to no more than 5%. From 25 to 51% is accounted for Au-Ag alloys. Conclusions. The morphological and geochemical types of gold were identified, and data were obtained on their distribution in the deposit section