Letlhakane Uranium Project, Botswana
The ore body consist of three ore types, namely: calcrete, secondary mineralized and primary mineralized material. The scoping study only considered the calcrete and secondary ore, as additional testwork for the primary material is ongoing.
Two process options were considered: a heap leach pad and tank leaching with an associated tailings facility for the Whittle optimization runs. The optimization runs were also undertaken at two uranium prices of USD55/lb and USD80/lb U3O8, reflecting a lower and upper bound price range. SRK also considered two production rates, namely: 20,000 and 40,000 tonnes per day.
Following the optimization step, the tank leach option was not taken forward to develop a cost estimate. The scoping study proposes conventional open pit mining using excavators and trucks. The calcrete ore at Mokobaesi was assumed to be free-dig, while the secondary ore in the mudstones will require drill and blasting.
SRK provided A-Cap with ongoing advice with regard to metallurgical testwork that was, and is still, being undertaken.
Separate from the scoping study work, SRK undertook the resources estimation for the project. In preparing the new resource estimate, SRK used a more geologically-appropriate modelling technique to better constrain the estimate. Using a combination of Leapfrog and GOCAD software SRK built a stratigraphic S-Grid model of the resource in GOCAD and used Ordinary Kriging to estimate the grade within appropriate stratigraphic horizons.
These techniques resulted in a more rapid construction of the geological model constraints and mineralization shells. The techniques employed also produced an improved head grade of some 30% higher U3O8 than previous poorly (geological) constrained estimates. The technique took only those samples in a specific stratigraphic horizon into account, rather than averaging across horizons as had previously been the case. SRK now has the capability of modelling thin stratabound mineralisation horizons relatively accurately and effectively, across large distances in three dimensions.
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