The T3 deposit occurs within the Ghanzi-Chobe belt in Western Botswana. The stratigraphy in this belt comprises the basal Kgwebe Formation volcanic lithofacies unconformably overlain by the Ghanzi Group sedimentary lithofacies.

The Ghanzi Group is a dominantly siliciclastic marine sedimentary group comprising (in successively higher stratigraphic order) the Kuke, N’gwako Pan, D’Kar and Mamuno Formation sedimentary lithofacies. The Ghanzi Group is an overall fining-upwards succession of sedimentary lithofacies, with sandstone and conglomerates of the Kuke Formation overlain by arkose, siltstone, shale and limestone of the N’Gwako Pan, D’Kar and Mamuno Formations.

The T3 deposit is focused on a NE-SW trending periclinal anticline with a core of N’Gwako Pan Formation that is overlain by a succession of D’Kar Formation sediments. The axial region of the anticline has been breached along a moderately northwest dipping brittle-ductile thrust zone such that moderately northwest dipping D’Kar Formation lithofacies in the hanging-wall of the thrust zone rest with angular contact upon sub-horizontal lithofacies in the footwall.

The T3 Mineral Resource has been defined along an approximate 2km long strike length and 720m downdip and mineralisation remains open at depth. Mineralisation strikes and dips parallel to a 20 30 degree north-west dipping thrust zone, and is considered to be a structurally hosted, epigenetic deposit that formed synchronous with regional deformation.

Cu-Ag mineralisation that forms the focus of the T3 deposit extends from approximately 25m – 300m below surface. The mineralisation strikes and dips parallel to the thrust zone and is considered to be a structurally hosted, epigenetic deposit that formed synchronous with deformation during Damara orogenesis. Mineralisation extends for 1940m along strike and the cumulative total true width of mineralisation within the thrust zone ranges from 10m – 80m.

Numerous, sub-parallel zones of mineralisation are developed within the thrust zone with high-grade mineralisation focused on master dislocation planes and associated foliated zones. Cumulative total true width of mineralisation within the thrust zone ranges from 10-80m, with primary sulphide Cu mineralisation hosted within quartz-carbonate veins and disseminations.

Primary sulphide copper mineralisation is hosted by one or more of chalcopyrite, bornite and chalcocite. Vein-hosted chalcopyrite and bornite are dominant, whilst disseminated chalcocite occurs in lesser amounts throughout the deposit.

Where oxidised, primary copper sulphides are altered to malachite, chrysocolla or covellite. Mineralisation starts at shallow depth below surface (~25m depth) and extends beyond the limit of the planned open pit at ~250m depth.

Host rocks include limestone, marl, shale, black shale, siltstone and sandstone within a 300m wide sequence of interbedded sediments within the lower part of the D’Kar Formation. The contact between D’Kar Formation and the Ngwako Pan Formation is approximately 150-200m below the base of the T3 deposit.

It is proposed that T3 will be mined by a mining contractor, utilising a conventional truck and shovel (excavator) method with Sandfire maintaining orebody definition, quality control and medium to long-term mine planning functions and management.

The bench heights and equipment selection were reviewed in parallel with the dilution modelling and confirmed the 2.5 m flitch height for ore mining with blasting on 10 m benches.

Grade control drilling is proposed from 20 m vertical intervals in advance of mining with angled holes perpendicular to the orebody using RC drilling methods to minimise contamination.

In general terms, the mining method is:
• Clearing and stripping of suitable material from all disturbed areas into discrete stockpiles for later use in rehabilitation activities;
• Grade control drilling and systematic pit mapping to demarcate ore boundaries;
• Drilling and blasting of ore and waste on 10m benches using choked or semi-choked blasting methods to reduce dilution;
• Load and Haul utilising 250-tonne excavators and 140-tonne class haul trucks mining on ~2.5m high flitches in ore zones and ~3.5m high flitches in bulk waste zones;
• Direct dump of run-of-mine (RoM) ore delivered to the crusher or placed on stockpiles for future rehandle as required;
• Pit dewatering will be managed by a collection of internal and external dewatering and de pressurising bores and in-pit sumps for use within the mining operation; and
• Reverse Circulation (RC) grade control drilling will be used on a predominantly 12.5m by 12.5m angled drill pattern and is campaigned during the mine life.

The selected open pit mining method, design and extraction sequence suit the orebody characteristics. The open pit design allows mining to be undertaken in a safe manner and minimises dilution and ore loss while meeting the planned process plant capacity and feed grades.

The open pit will be developed in four stages, each based on Whittle™ pit shell progression and practical mining width. A key driver in the staging logic was to minimise the capitalised pre-strip and variability in total material movement while maintaining process plant throughput and managing feed grades.

A minimum mining width (MMW) was applied to the stages when cutting back on high walls of 100m to ensure full production rates can be maintained safely. The stage designs were focused on reducing the impact of narrow mining areas between stages and, as a result of the practical considerations, the final design captured 0.6% less copper from 0.8% additional ore at a cost of 2.0% additional waste relative to the optimised shells.

The primary objective of the schedule was to keep the mill consistently fed with a secondary objective to produce ~30,000t of copper per year. The waste mined until the commencement of ore feed is classified as capitalised pre-strip. The Total Material Movement (TMM) per annum was also targeted to be maintained at a consistent, as low as possible level, while also minimising capitalised pre-strip.

• SAG mill
• Primary crusher
• Pebble crusher
• The single-stage SAG (SSSAG) circuit
• Coarse grind size (P80 212 µm)
• Typical flotation scale-up factors
• Simple rougher flotation circuit
• Coarse regrind size (P80 90 µm)

The start-up nameplate plant capacity is based on 3.2Mtpa (dry) of ore at plant availability of 92%. Some of the plant equipment has been sized with a capacity large enough to sustain a future plant throughput expansion, namely: the primary crusher, the concentrate trash screen, the flotation cells, the concentrate thickener and the concentrate filter. Other areas of the plant will require additional equipment to meet the expanded (future) capacity. Space allowance in the layout has been provided for that future additional equipment (e.g. ball mill, etc.).

The process plant for the T3 (Motheo) Project is based on a simple and robust metallurgical flowsheet designed for optimum recovery with minimum operating costs. The flowsheet has been constructed from unit operations that are well proven in the industry. The key criteria for equipment selection were the suitability for duty and the projected mine life of the operation without unnecessarily compromising reliability and eas ........