Primary uranium mineralisation in the Etango-8 Project area is related to uraniferous leucogranites, locally referred to as alaskites. The alaskites are often sheet-like, and occur both as cross-cutting dykes and as bedding and/or foliation-parallel sills, which can amalgamate to form larger, composite granite plutons or granite stockworks, made up of closely-spaced dykes and sills. These alaskite intrusions can be in the form of thin cm-wide stringers or thick bodies up to 200 m in width.

The alaskite bodies have intruded into the metasediments of the Nosib and Swakop Groups of the Damara Supergroup. These metasediments and alaskite intrusions flank the Palmenhorst Dome which is cored by Mesoproterozoic (1.7 2.0 Ga) gneisses, intrusive rocks and meta-sediments of the Abbabis Metamorphic Complex.

Uranium mineralisation in the Etango-8 Project area occurs almost exclusively in the alaskite intrusives. Minor uranium mineralisation is also found in the metasedimentary sequences close to the alaskite contacts, probably from metasomatic alteration and in minor thin alaskite stringers within the metasediments.

The dominant primary uranium mineral is uraninite (UO2), with minor primary uranothorite ((Th,U)SiO4) and some uranium in solid solution in thorite (ThO2). The uraninite is commonly associated with chloritised biotite in the alaskites and with ilmenite and magnetite within foliated alaskites. The primary uranium mineralisation occurs as microscopic disseminations throughout the alaskite, at crystal interfaces, and as inclusion within other minerals. Secondary uranium minerals such as coffinite (U(SiO4)(OH)4) and betauranophane (Ca(UO2)2(SiO3OH)2 5H2O) occur as replacements of the primary minerals or as coatings along fractures.

QEMSCAN analysis indicates that about 81% of the uranium present is in primary uraninite, while 13% is in secondary coffinite and 5% is in secondary betauranophane (Freemantle, 2009). The remaining 1% of the uranium occurs in various minor phases including brannerite, betafite and thorite. Very minor amounts of uranium are also present in solid solution in monazite, xenotime and zircon. A very minor amount of primary betafite (Ca,U)2(Ti,Nb,Ta)2O6(OH) is also present.

The deposit is a large, shallow uranium deposit that is amenable to bulk open pit mining, followed by crushing, heap leaching, ion-exchange, nano-filtration and uranium recovery. The heap leaching operation can treat approximately 8Mtpa dry ROM feed material to produce on average 3.5 million pounds of triuranium octoxide (U3O8) per annum to be drummed and shipped.

For the purpose of the Etango-8 PFS, it was assumed that mining would take place by conventional open pit methods and that the whole mining operation, except for the mine technical services function, will be outsourced to a reputable mining contractor company. This includes drilling, blasting, loading and hauling of ore and waste.

Drilling and blasting would be performed on 12 m high benches. Waste benches will be excavated in a bulk mining fashion with shovels on a single 12 m bench while mineralised benches will be selectively loaded in three 4m flitches using backhoe excavators to minimise ore loss and dilution. The truck and shovel match on the ore and waste benches have been considered by the reputable mining contractor as follows:
• A 130-t hydraulic backhoe shovel would be employed for selective loading purposes;
• The waste benches would be mined in a bulk mining approach where a 250-t hydraulic face shovels will be utilised to load the full 12 m bench;
• In both cases 100-t capacity, off-highway rigid haul truck would be used and standard open-cut drilling and auxiliary equipment will be required.

Radiometric truck scanning (discrimination) and downhole gamma probing will be employed as the definitive grade control process as is common practise in large scale open pit uranium mines. The objective of the pit design process was to transform the pit shells obtained from the optimisation into a practical pit, with the inclusion of ramps, bench and berm configurations by taking all the required inputs into account. The practical pit design forms part of a critical input for the scheduling and reserving processes.

Etango-8 PFS ultimate pit design was designed with a dual pit access strategy along the eastern and western pit highwalls. The ultimate pit will be mined in eight pushbacks, which represent areas that the optimisation process considers to be of high value.

Mass balance modelling for the comminution and agglomeration circuits included a combination of excel and supplier specific simulation software. This included Bruno, Metso’s comminution simulation software, to mimic the steady state solution based on the selected equipment configuration. The comminution circuit was also modelled utilising the appropriate Sandvik software allowing for preliminary comparative costing. Both the Sandvik and Metso circuits are constrained to 8 Mtpa capacity by the secondary crushers. Expansion above this would require a second production line. The selected primary gyratory crusher operates at 60% of capacity, so 13 Mtpa is possible through the selected unit.

The metallurgical process comprise of three stages of crushing, agglomeration, followed by sulfuric acid heap leaching on an industry standard on/off heap leach pad followed by ion-exchange and nano-filtration extraction and calcination.

Key metallurgical assumptions include:
- Plant throughput of 8 Mt per annum;
- Metallurgical Recovery of 87.8%;
- Total Sulphuric Acid consumption of 18.01 kg/t ore leached.

Heap Leach Pad
The stacking system comprises a fixed stacking feed conveyor with tripper along the length of the pad. A wing conveyor facilitates transfer of ore to a mobile stacking system consisting of 8 (maximum) grasshoppers and 2 stackers in line. The reclaim system is similar to the stacking system. A time in motion study confirms that two CAT 980 H Front End Loader’s (FEL’s) are required for reclaim of the leached ore. Seven (maximum) grasshopper conveyors are required – transferring the ripios to a heap leach reclaim conveyor, a fix ........