SELF-PURIFICATION OF THE PRODUCTIVE HORIZON AT THE SITE OF THE TWO-HOLE IN SITU LEACHING EXPERIMENT AT THE DOBROVOLNOE URANIUM DEPOSIT (KURGAN REGION)

Abstract

The relevance of the topic is caused by the need to determine the nature of the elevated uranium content in sediments at the site of the two-hole in situ leaching experiment, to monitor the quality of groundwater, to identify its potential for self-restoration of natural equilibrium and conditions for self-purification of the ore-bearing horizon without the need for special reclamation. The purpose of the research is to determine the neutralizing properties of ore-hosting rocks in relation to the technogenic components entering the subsoil during in situ leaching; study of changes in the concentration of polluting components in groundwater and the mineral composition of ore-bearing rocks at the site of the two-hole in situ leaching experiment. Object is ore-bearing sediments and groundwater of the Taborinsky suite of Middle-Upper Jurassic age (J2-3tb), studied at the site of the two-hole in situ leaching experiment (check borehole 224) within the Dobrovolnoe deposit. Methods. Groundwater composition was studied directly at the drilling site of the check borehole; mineralogical and analytical studies were performed using traditional and precision methods in the laboratories of the All-Russian Scientific-Research Institute of Mineral Resources named after N.M. Fedorovsky, the studies were carried out using the JEOL JHA 8100 X-ray microanalyzer, equipped with an INCA energy dispersive prefix and a scanning electron microscope with the most representative sample in order to study the chemical composition, morphology and detailed pattern of the uranium mineralization distribution. Radioisotope studies were performed by gamma-spectrometric method using «ORTEC-65195-P/DSPecPlus» according to the methodology developed by All-Russian Scientific-Research Institute of Mineral Resources named after N.M. Fedorovsky. In order to study the effect of the vital activity of microorganisms on the physico-chemical properties of the medium, microbiological studies were carried out at the S.N. Vinogradsky Institute of Microbiology of the Russian Academy of Sciences. Results. Uranium concentrations remaining after the two-hole in situ leaching experiment were identified; uranium redeposition intervals were determined. It was found that 30 years after the experiment, groundwater at the Dobrovolnoe deposit was restored almost to original state. It is confirmed that uranium in situ leaching at the Dobrovolnoe deposit is environmentally sound, and the burial of man-made components introduced into the ore-bearing horizon occurs in the immediate vicinity of the mining site.

Keywords

• in situ leaching
• uranium
• dobrovolnoe deposit
• redeposition
• neutralizing properties
• exploration