Summary:
Deposit Type
The mineralization within the Project exists as roll-front uranium deposits. Roll-front deposits are hosted within sandstones that are intermittently interbedded with lenses of siltstone and claystone/mudstone. Uranium mineralization occurs as interstitial fillings between and coatings on the sand grains along “roll front” trends formed at geochemical reduction–oxidation (redox) boundaries within the host sandstone aquifers. The redox boundary typically has a “C”-shape with the point of the “C” (or nose) pointing down the hydrogeological gradient.
Uranium minerals in roll front deposits in the unoxidized zone are most commonly uraninite (UO2 ) and coffinite (U(SiO4 )1-x (OH)4x ).
Deposit Dimensions
In each of the Resource Areas, uranium is concentrated in typical roll front-type deposits and the concept of a single deposit with x-y-z dimensions is not applicable. Roll front deposits occur at the interface between oxidized and reduced sandstone (redox front) that forms as a result of oxidized groundwater flows down the hydrogeological gradient and oxidizes the host sandstone progressively downward. Redox fronts are typically very long and sinuous (Figure 6 5) and up to tens of miles in length. Recoverable deposits of uranium are sporadically concentrated along that front. Individual redox fronts are many miles long with discrete uranium deposits a few tens of feet thick and tens to a few hundreds of feet wide and a few hundreds of feet long scattered along the front. Thickness and width vary rapidly along strike contributing to the discontinuous nature of the deposits. In the Reno Creek Project, there are at least five levels in the stratigraphy that are favorable for formation of this type of deposit.
Mineralization in the Project area occurs in fluvial sandstones of the lower parts of the Eocene Wasatch Formation. Most of the upper Wasatch Formation has been eroded away. The sandstones are arkosic, fine- to coarse-grained with local calcareous lenses. The sandstones contain minor amounts of organic carbon that occurs as dispersed bits or as stringers. Unaltered sandstones are generally gray while altered sandstones are tan or pink, due to hematite or show yellowish coloring due to limonite (Utah International, 1971).
Pyrite occurs in several forms within the host sandstones. In unaltered sandstones, pyrite occurs as small to large single euhedral crystals associated with magnetite, ilmenite, and other dark detrital minerals. In altered sandstone, pyrite is typically absent, but locally occurs as tarnished, very fine-grained euhedral crystals. In areas of intense or heavy mineralization, pyrite locally occurs as massive, tarnished crystal aggregates (Utah International, 1971).
The Felix Coal seams are laterally continuous in the North and Southwest Reno Creek Resource Areas and extend northward into the Moore and Bing Resource Areas. The Felix Coal seams and the underlying Badger Coal seam provide important correlation points across the entire project area and are readily identified on uranium exploration logs and coal bed methane logs in this portion of the PRB.
RCH drilling, coupled with historical electric log datasets and coal bed methane gamma ray logs, enabled correlation of major uranium host sandstones and identification of continuous hydrostratigraphic units across the Project. UEC acquired lithologic logs for several hundred coal bed methane pilot holes. In total, UEC has data from approximately 10,151 uranium exploration holes and nearly 1,500 coal bed methane logs in the Project area.
Dips in the area are 1-2.5 degrees to the west. Faults have not been observed or reported in literature in any of the Resource Areas.
he overlying aquifer at North and Southwest Reno Creek, Moore, and Bing Resource Areas overlies the production zone and the Felix Coal marker across the entire area. This overlying aquifer/sandstone is regarded as a host for mineralization at the Pine Tree Resource Area, which does not have an overlying aquifer.
The overlying aquitard is a continuous confining mudstone unit providing isolation between the production zone aquifer and overlying aquifer in the North and Southwest Reno Creek, Moore, and Bing Resource Areas that includes the Felix Coal seams.
The production zone aquifer is the host for uranium deposits at the North Reno Creek, Southwest Reno Creek, Moore, Pine Tree, and Bing Resource Areas. At Pine Tree, the production zone aquifer includes the overlying aquifer and the overlying aquitard, and Felix coal seams are not present.
The underlying aquitard, the lower-most unit of the Wasatch Formation, is a continuous confining mudstone unit providing isolation between the production zone aquifer and underlying discontinuous sandstone units occurring above the Badger Coal seam. The aquitard is approximately 200-250 ft thick and consists of a laterally continuous sequence of undifferentiated mudstones and clays, with discontinuous and often lenticular sandstones. This confining unit is present under the entire Project area.