The Madaouela deposits exhibit classic characteristics of uranium sandstone deposits common the world over (Cuney and Kyser, 2009).

Sandstone-hosted uranium deposits are defined as epigenetic concentrations of uranium minerals occurring as impregnations and replacements primarily in fluvial, lacustrine, and deltaic sandstone formations. They occur in permeable medium- to coarse grained sandstone, usually deposited in continental fluvial or marginal marine sedimentary environments. Impermeable shale or mudstone are inter-bedded in the sedimentary sequence, and often occur above and below the mineralization.

The source of uranium is usually igneous or volcanic rocks (alkaline tuffs, granitic intrusion) either in close proximity to or inter-bedded with the sandstone units. The uranium mineralization typically precipitates from oxidizing fluids, under reducing conditions caused by a variety of reducing agents including: carbonaceous material (detrital plant debris and amorphous humate), sulfides accompanying organic matter decay, hydrocarbon, and inter-bedded mafic volcanic rock with abundant ferro-magnesian minerals. The reducing agent for Madaouela is most likely in-situ organic material (lignite) or hydrocarbons transported along major fault.

The main primary uranium minerals are uraninite and coffinite with minor secondary uranium minerals being noted in exposed (weathered) mineralization.

The mineralogy of uranium in the deposit is dominated by pitchblende and coffinite. The overall paragenesis could be divided in three stages: (1) early sulfides; (2) uranium on organic matter such as wood fragments; (3) carbonates and barite.

GoviEx drilling has established connections between the mineralization at Marianne and Marilyn, once separate deposits. The Marianne Marilyn deposit is a nearly flat tabular body of mineralization that spans approximately 5 km (N70E direction) by 2 km across in plan, and the deposit thickness varies from 0.2 to over 2 m (average thickness of about 1 m).

Drilling in the southern part of Madaouela I has thus far defined three individual pods of mineralization in the same stratigraphic setting and with similar grade, depth (100 m to 140 m), and thickness of mineralization to that at Marianne-Marilyn. The main body of the largest of the three pods of mineralization, Madaouela south northeast (“MSNE”), extends approximately 4 km east-west, by approximately 6 km north-south.

The mineralization occurs at depths from about 30 m on the eastern end of Marilyn, to approximately 60 m in depth in the middle of the Marianne-Marilyn deposit, up to 120 m in depths on the west extensions of Marianne; below the relatively flat topographic surface. The stratigraphy gently dips to the southwest, with local minor domal features. Mineralization at MSNE is similar in depth (about 100 to 140 m deep), grade, and thickness, although not yet drill-defined as large as the Marianne-Marilyn deposit is in plan.

The MSNE deposit occurs to the south of Marianne-Marilyn and is approximately 140 m deep. It occurs on the same redox front as Marianne-Marilyn (Figure 7-23) and the deposit is approximately 2.7 km long and 2.3 km.

Maryvonne deposit is located to the north of MSNE deposit and is approximately 100 m deep. The length of the deposit is 1.2 km and the width is 0.75 km

Miriam deposit is situated 8 km to the south of MSNE deposit and is dipping from 65 m to 120 m deep. The deposit is 2.4 km in length and 0.8 km wide.

Mining schedules have been developed including open pit mining at the Miriam deposit, and room and pillar mining with decline access at a combined 4,020 tonnes per day production rate from Marianne-Marilyn, MSNE and Maryvonne deposits.

The Madaouela deposits being considered for mining comprise four distinct deposits:
• Marianne-Marilyn (M&M);
• MSNE;
• Maryvonne; and
• Miriam.

Miriam is to be mined using open pit methods due to the larger mineralised thicknesses and proximity to the surface.

The engineered final pit design for the Miriam deposit is based on the selected pit shell. Where possible, ramps are located where practical within the constraints of the location of the waste dumps and run of mine (“RoM”) stockpile.

The final Miriam pit design is approximately 1,400 km long, 550 m wide and reaches a maximum depth of 120 m.

The open pit life of mine (“LoM”) plan is based on the final pit design and three pushback pit shells. The key scheduling parameters were as follows:
• Plant feed target of 1,400 ktpa;
• Limit total material movement ex-pit to 19.5 Mtpa;
• Two years of pre-production waste stripping;

Marianne-Marilyn (M&M) and MSNE-Maryvonne deposits are mined by room and pillar mining methods.

Due to the shallow depth of mineralisation, which is typically around 100 metres below the surface for the Madaouela deposits, decline access has been adopted.

There are two basic options for underground excavation; drill and blast or mechanical excavation.

The underground Life of mine plan (LoMP) combines production from Marianne-Marilyn and MSNE-Maryvonne into a single schedule. The schedule assumes one development crew in operation at any time. All panel and infrastructure development in Marianne-Marilyn is scheduled to be completed before the decline access to MSNE-Maryvonne commences. The underground LoMP is independent of the proposed open pit mining at Miriam.

The base case mineral processing design is crushing, radiometric sorting, ablation and two-stage tank acid leaching, solvent extraction, with dry stack tailings. Utilizing Cyanex 600 resin allows both uranium oxide yellow cake and by-product molybdenum oxide to be produced as commercial products with acceptable quality for sale.

Mined ore from Marianne and Marilyn is crushed underground (80 % < 306 mm) prior to transport and is received on surface at the transfer point at the discharge of the inclined conveyor from the mining operation. From here material is transferred to the ROM stockpile via the stockpile feed conveyor. Facility is also provided to receive primary crushed ore from other mining operations or from static stockpiles around the plant area into a feed receipt bin by road truck or front end loader (“FEL”).

Feed preparation effectively consists of two stage crushing with intermediate screening. Ore from the stockpile is reclaimed by 3 apron feeders and routed to a secondary jaw crusher operating in open circuit with the product screened and the oversize routed to a tertiary cone crusher with the product returned to the sizing screen. Product from the crushing circuit is nominally < 20 mm (80 % passing).

The primary crushed ore from the stockpile is routed to ROS where fines are screened out and routed directly to fine crushing with the coarse fractions (+20 mm) subject to preconcentration by ROS. The accept product only is routed to fine crushing while the rejects are routed to a waste stockpile.

Accept product from the ROS is secondary crushed and mixed with water to create 20% slurry, which is fed into the Ablation stage, in which one or more set of two jets of slurry site opposite each other to create a high energy impact zone. The high energy impact zone causes a break down of the ore material into coarse and fine particles, which are separated by screening and gravity. The uranium is predominately in the fine particles and this fine material slurry is thickened prior to feeding into the acid leach tanks. The coarse material, which is predominately sand, is thickened and sent to the tailings dam. An additional recovery step involves gravity separation of residual uranium and heavy mineral particles from the coarse material that is then fed back into the Ablation product. This improves overall recovery to 99% and also results in carbonate reduction and thus reduces acid consumption for the two stage acid leach step.

The two stage leaching circuit consists of primary and secondary agitated leach tanks in recirculation with a leach thickener after the first stage and a belt filter after the second stage leach. In the first stage solution from the second stage belt filters is recirculated to leach the fresh feed after which the slurry is thickened with the thickener overflow routed to the uranium recovery circuit as pregnant leach solution (“PLS”). The thickener underflow is routed to the second stage leach, which uses fresh acid to further leach the milled solids. After the second stage the slurry is filtered and the filtered solids residue is washed with fresh solution and discarded to the tailings disposal system.

Leach tanks are agitated and aerated to allow the milled ore to react with sulfuric acid allowing dissolution of the contained uranium. The acid consumption (per ton of feed to the leach) in this case is forecast to be lower because of the rejection of the acid consuming constituents of the feed during flotation. The solution from leach (thickener overflow) is routed to uranium recovery.

Uranium Recovery:

Based on laboratory testwork solvent extraction (“SX”) has been selected as the mos appropriate method for uranium recovery. Cytec has developed a new SX reagent that canallow recovery and separation of uranium and molybdenum from acidic solutions termed CYANEX® 600 extractant. CYANEX 600 is a highly selective, stable phosphinic acid based reagent and allows molybdenum and uranium recovery from acidic solutions by the same solvent. Based on the test results, the use of 10 Vol% CYANEX 600 could be used to selectively extract and separate Molybdenum and Uranium while achieving recoveries greater than 98 % for Mo and 99 % for U.

The overall circuit configuration would consist of two extraction steps, one stripping step for iron, two stripping steps for molybdenum, an ammonia washing step and two uranium stripping steps. A wash stage will be used after the Uranium strip to prevent phosphoric acid transfer. Phosphoric acid will be recovered through an evaporation step in order to reduce reagent requirements. Additional uranium recovery will come from this step through a bleed stream that would feed back into the solvent extraction process.