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MINERALOGICAL FORMS OF OCCURRENCE OF FINE-DISPERSED GOLD

Gulnara Omarova

Abstract

The present study aims to develop methodological approaches for the investigation of fine-dispersed gold in ores from primary (bedrock) deposits and placers, with the objective of improving recovery efficiency. The type of gold under investigation exhibits a number of distinctive characteristics that substantially differentiate the conditions of its concentration, distribution within ore horizons and bodies, and the reliability of its analytical determination using conventional methods from those applicable to small-grained gold and, in particular, coarser gold fractions. To develop a research methodology for fine-dispersed gold from deposits in Kazakhstan, a total of 78 samples were collected: 32 from primary (bedrock) sources and 46 from placer deposits. Samples from placer deposits were subjected to comprehensive mineralogical-technological investigations, including the analysis of beneficiation products for gold content. Research into the development of a technology for the recovery of fine and ultrafine gold was carried out through the processing of large-volume samples under laboratory conditions according to the following scheme: wet screening with classification into 11 size fractions, separate beneficiation of each size class using concentration equipment to obtain concentrates and tailings, followed by mineralogical examination of the concentrates. Following sample processing, scintillation and thermoactivation analyses revealed the presence of gold particles of micron and submicron dimensions. Samples from primary deposits were examined using the automated mineralogical system TESCAN TIMA. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) was employed for surface analysis of geological specimens in order to characterise their composition and structure. Gold micrograins were studied using the integrated Solver Spectrum system (NT-MDT, Russia), which incorporates an optical microscope, a Raman spectrometer, and an atomic force microscope. The following analytical techniques were additionally applied: X-ray diffraction analysis (for determination of mineral composition); phase chemical analysis of ores for gold compounds; as well as fire assay and scintillation analyses. The sequential application of these analytical methods enabled not only the identification of all gold micrograins and their alloys present in the samples, but also the precise characterisation of their elemental composition.

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