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Location: 90 km SW from Rapid City, South Dakota, United States
310 2nd Ave.EdgemontSouth Dakota, United States57735
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Uranium deposits in the Dewey-Burdock Project are sandstone, roll front type. This type of deposit is usually “C” shaped in cross-section, with the down gradient center of the “C” having the greatest thickness and highest tenor. The “tails” of the “C” are usually much thinner and essentially trail the “roll front” being within the top and bottom of the sandstone unit that is slightly less permeable.These “roll fronts” are typically a few tens of feet wide and often can be thousands of feet long. Uranium minerals are deposited at the interface of oxidizing solutions and reducing solutions. As the uranium minerals precipitate, they coat sand grains and partially fill the interstices between grains. As long as oxidizing groundwater movement is constant, minerals will be solubilized at the interior portion of the “C” shape and precipitated in the exterior portion of the “C” shape, increasing the tenor of the orebody by multiple migration and accretion. Thickness of the orebody is generally a factor of the thickness of the sandstone host unit. Mineralization may be 5 to 12 ft thick within the roll front while being 1 to 2 ft thick in the trailing tail portions. Deposit configuration determines the location of well field drillholes and is a major economic factor in ISR mining.Ore mineralogy consists of uraninite, pitchblende and coffinite with associated vanadium in some deposits. Typical alteration in the roll-front sandstone deposit includes oxidation of iron minerals up- dip from the front and reduction of iron minerals down-dip along advancing redox interface boundaries.Probable sources of uranium in the sandstone deposits are Oligocene volcanic ash and/or Precambrian granite (2,900–2,600 Ma). Mineralizing solutionsin the sandstone are oxygenbearing groundwater. Uranium mineralization of the sandstone deposits began with inception of Laramide uplift (approximately 70 Ma) and peaked in Oligocene. Size and shape of individual deposits can vary from small pod-like replacement bodies to elongate lobes of mineralization along the regional redox boundary.Historical drillhole data (electric and lithology logs), along with Azarga’s confirmatory drilling results confirm that the mineralization at Dewey-Burdock is a roll front type uranium deposit. This is determined by the position of the uranium mineralization within sandstone units in the subsurface, the configuration of the mineralization and the spatial relationship between the mineralization and the oxidation/reduction boundary within the host sandstone units.
