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Re-engineering the Elkon Deposit

Elkon in South Yakutia, East Russia, is the world’s largest known, undeveloped uranium deposit. It occurs as a series of narrow sub-parallel, steeply-dipping veins located within the Yuzhnaya fault zone, covering a strike length of some 20km and extending from about 100m to 1600m below surface. On average, the veins are 2 to 3m thick but vary between 12m to <1m in thickness. Along the strike, the veins pinch and swell significantly over short distances.

The deposit was identified in the 1960, and explored extensively in the 1960s and ‘70s, with more than 2300 boreholes drilled and 52km of underground exploration workings completed.

The entire Yuzhnaya mineralized zone is located within an old Precambrian fault zone, though the rocks inside the zone were altered and deformed during several progressive tectonic events, which resulted in structural reactivation. Gold-uranium and molybdenum-uranium mineralization is associated with alkaline dikes displaying hydrothermal-metasomatic alteration. The principal uranium mineral is brannerite, (U4+,Ca)(Ti,Fe3+)2O6, which requires more aggressive leaching than most uranium minerals, so, with the development of the Priagunsky deposit, Elkon was not developed.

Atomredmetzoloto (ARMZ), the Russian state uranium mining company, engaged SRK to re-evaluate the deposit and to develop a plan that would meet the requirements of international funding and investment. Knowing that the need for narrow-vein underground mining methods and expensive processing methods would challenge the project economics, SRK aimed to develop a plan that could bring to bear the potential economies of scale and the fact that ore-sorting had been demonstrated to be effective.

SRK created a computerized geological model using the Soviet geological interpretations and borehole data. The model was used to determine the natural rate for different mining options and to identify the impact of different cut-off grades on resources. Taking into account the morphology of the deposit defined by the underground workings and the rock strength data, SRK concluded that a long-hole, open-stoping mining variant, combined with unconsolidated back-filling with development waste, is likely to be the most appropriate solution.

SRK drew heavily on the existing test-work to recommend a base case of pressurised acid leaching for the initial project feasibility analysis and identified a number of additional tests, which will be completed during the summer of 2009, to assess whether the flow sheet can be optimized.

With all of the data in Russian and often available only as hard copies, SRK created a team of Russian and UK employees and associates and worked closely with the client’s own specialists and Russian design institutes to update the options and to re-engineer the operation to significantly reduce the overall costs-per-pound of U3O8 from previous studies. The studies are ongoing with further data collection and test-work scheduled for 2009 and a Feasibility Study to begin in September.

David Pearce:
Nikolai Yenshin:

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