Home – Home – Jornals – Russian Geology and Geophysics 2018 number Неопубликованное

Using the laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) complex, with the involvement of X-ray photoelectron spectroscopy (XPS), new data were obtained on the distribution features and concentration levels of “invisible” gold on the natural surface of arsenopyrite crystals from the Natalka gold deposit (North-East of Russia). It was found that the distribution of Au contents on the surface of the studied sulfide and its concentration levels are closely related to the conditions of the deposit formation. The highest Au concentrations are confined to the surface of arsenopyrite crystals of the hydrothermal stage of ore formation, and the minimum ones are found at the early metamorphic stage. The extreme instability of the gold distribution profile and its content even within the surface of a single crystal is especially pronounced in arsenopyrite of vein and veinlet-vein ores, which is due to the instability of the physicochemical parameters of the hydrothermal ore formation processes at later stages of the deposit formation. Basically, these are oxidation processes that lead to a change in the composition of the primary (as-grown) non-autonomous phases and the redistribution of gold in the surface layer of the crystal, containing highly charged forms of arsenic – As⁵⁺ and As³⁺. The complex and long-term metamorphogenic-magmatic genesis of the giant gold ore deposit Natalka is confirmed. High concentrations of “invisible” gold in the easily destroyed surface layer of sulfides during enrichment are of significant practical interest in the extraction of gold from “refractory” ores, increasing the quality and value of the extracted raw materials.