Primary uranium mineralisation is related to uraniferous leucogranites, locally referred to as alaskites. These 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 200m in width.

The alaskite bodies have intruded into the metasediments of the Nosib and Swakop Groups of the Neoproterozoic (pre-550Ma) to early Palaeozoic (c500Ma) Damara Supergroup. These metasediments and alaskite intrusions flank the Palmenhorst Dome, which is cored by Mesoproterozoic (1.7-2.0Ga) gneisses, intrusive rocks and meta-sediments of the Abbabis Metamorphic Complex.

During the Damara Orogenic event, the metasedimentary cover was subjected to multiple phases of deformation, resulting in overturning of the succession and development of a prominent gneissosity and lineation which is generally sub concordant with original bedding. This gneissosity was further deformed leading to the formation of elongate basement-cored domes. Uraniferous alaskite sills and bodies that wrap around the Palmenhorst Dome are confined to dilatational sites in high-strain zones, with the alaskite sills generally striking from north northwest to north-northeast and dipping to the west.

The localised geological setting is depicted in, and the uranium occurrences at the contiguous Anomaly A, Oshiveli and Onkelo Prospects can be seen to wrap around the western edge of the Palmenhorst Dome. Uranium mineralisation occurs almost exclusively in the alaskite, although minor uranium mineralisation can be found in metasediments close to the alaskite contacts, probably from metasomatic alteration and in minor thin alaskite stringers within the metasediments.

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

The mining method preferred for the Etango open pit will be a high tonnage (100Mtpa), low cost, traditional open pit truck and backhoe operation employing 550t diesel hydraulic excavators, off road 220t haul trucks and 203mm down the hole (DTH) hammer diesel drills.

The pit will be mined in a series of cutbacks to deliver 20Mtpa of ore to the heap leach operation and lower the amount of waste movement required during the early years of the project. Selective mining for the Etango Project consists of drilling and blasting on a 12m bench, with loading out in three flitches of equal height, which will nominally be 4.5m high, after allowing for swell from blasting. The mining selectivity recommended should minimise ore loss and dilution but, at the same time, allow the 100Mtpa mining rate to be achieved cost efficiently. There is also a clear advantage from a safety point ofview for loading in 4.5m flitch heights.

The process flowsheet (Figure 1.2) comprises a crushing circuit, reusable (on-off) heap leach pad for sulphuric acid leaching of the ore, and a uranium SX and recovery circuit to produce U3O8 yellowcake.

The ore is stacked in modules (52 in total), where each module represents one day of stacking. The first three modules are designed for stacking, ore rest and dripper installation. The next 15 modules are irrigated with intermediate leach solution (ILS). The liquor from these modules produces the PLS, which is pumped to the SX circuit for uranium recovery. The subsequent 15 modules are irrigated with raffinate solution, which drains to the ILS pond and is recirculated to the heap to build up uranium tenor. Thereafter there are 12 modules for draining and rinsing. Solution from these modules is recirculated to the rinse modules and also to the ILS and raffinate as water make-up. The remaining modules are spares and used for dripper removal and reclaiming.

PLS is pumped to a single train SX circuit which consists of two extraction, two scrubbing, four stripping, one organic regeneration and one crud removal stage. Bateman pulsed columns are used for extraction and conventional mixer/settlers are used for all other contacting duties.