The greatest new uranium region in the Republic of Sakha (Russia)

More than ten uranium deposits have been discovered in the Elkon district on the Aldan Shield from 1960s to 1970s. Their total resources exceed 600000 tonnes of uranium. The Aldan Shield was granitized in the Lower Proterozoic and broken by faults directed NW. Tectonic-magmatic activity (TMA) manifested in the Cimmerian epoch. TMA is displayed by the renewal of ancient deep fault zones by formation of new faults, horst uplifts and volcanic depression and by intensive alkali magmatism. Uranium deposits of the Elkon region are metasomatite type. Deposits with ores of this type are almost completely composed of newly formed metasomatic minerals and the concentration of relict minerals of initial rocks is less than 10-15%. Potassic metasomatites are discovered in the Elkon district only. The host rocks are granite, migmatite and gneiss. The metasomatites are presented by potash feldspar (50-70%), quartz (15-20%), carbonate (7-12%), chlorite (5-10%), and gold-bearing pyrite (2-7%). Brannerite prevails in the ores. The metasomatite deposits are very large in size: up to 20 km along the strike, down to 2 km in depth, but only 10-50 m in thickness. The thickness of the ore bodies is rather small: from 1 to 5-7 m. From 2 to 5 ore vein-line bodies can be inside one metasomatic zone. Ore bodies do not have natural borders and are outlined by the cutoff grade of the uranium. A total of 13 deposits have been discovered in the Elkon region now. Identified resources of these deposits are 340000 tonnes of uranium. Only a few deposits are exploited now, because the average content of uranium is low in metasomatite deposits (0.08-0.20%). However, the use of new methods of extraction of uranium (radiometric enrichment, heap and block leaching) may change the situation. Metasomatite deposits will be the main source of uranium in future.