BACKGROUND GEOECOLOGICAL CONDITIONS OF ELKON GOLD-URANIUM ORE REGION

The Elkon ore region is located in the southern part of Sakha Republic (the largest federal subject of the Russian Federation). Elkon gold-uranium fields have the richest deposits of uranium ore, but they have not been developed. Although the natural landscapes of mountain taiga are already changed due to about-century-long geological exploration, we have the last chance to fix the environmental conditions before the start of developing. The paper deals with the characteristics of distribution of radionuclides and element in soils, plants and water of El’kon region and is based on field works performed in 2007–2008 (immediately after the decision on exploration). The Elkon horst is the part of Aldan Shield, an exposed basement of the Siberian craton not covered by the latest sediments. The uranium mineralization is confined to igneous Mesozoic complexes. Weathering and erosion cause dispersion halo of elements and radionuclides which may become probable pollutants. The studied area is divided into four geological formations, but soil probes reveal no distinction in geochemistry specialization. So landscapes were divided into three groups by level, slope exposition and vegetation condition. Each group was measured by couple of samples. The main migration features were assessed by the distribution of elements and radionuclides (some local peaks were found for ⁹⁰Sr, As, Th, and Mo). The As, Pb (rarely Mn, Hg) contamination of soils is proved. The main co-locations were computated for soils. The total contamination was estimated acceptable to moderate rates, therefore, there were found local high-polluted areas in dump zones. The combined database could be used as a reference point for further environmental research.