Overview
Stage | Pre-Feasibility |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
|
Processing |
- Filter press plant
- Flotation
|
Mine Life | 10.5 years (as of Jan 1, 2021) |
Ore Reserve confirms A4 as a high-grade source of additional ore feed for the Motheo Copper Mine, underpinning an expanded long-life 5.2Mtpa Production Hub.
Sandfire will now move directly to a Definitive Feasibility Study (DFS) for the 5.2Mtpa Motheo Expansion, with the DFS expected to be completed in Q3 of FY2022. |
Source:
p. 17
Sandfire, through their 100% ownership of Botswanan company Tshukudu Metals Botswana (Pty) Ltd, hold prospecting license PL190/2008 as part of a larger tenement package. This licence, on which A4 occurs, was renewed on 1st October 2020 and is valid till 30th September 2022.
Royalty covers the area subject to the historical Tshukudu joint venture with MOD Resources Ltd and includes PL190/2008, which hosts the A4 resource area.
Deposit Type
- Sediment-hosted
- Breccia pipe / Stockwork
- Vein / narrow vein
Summary:
The A4 deposit is located within the Ghanzi-Chobe belt in western Botswana. The stratigraphy in this belt comprises the basal Kgwebe volcanics which are unconformably overlain by Ghanzi Group sediments. The Ghanzi Group is a meta-sedimentary group comprising (in successively higher stratigraphic order) the Kuke, Ngwako Pan, D’Kar and Mamuno Formations.
A4 occupies a similar structural and stratigraphic position to that of the T3 deposit in that it occurs within a NE-SW trending periclinal anticline (“Dome”) with a core of Ngwako Pan Formation sandstone, overlain by a succession of D’Kar Formation shale, sandstone, siltstone and carbonates. All mineralisation modelled and incorporated in the Mineral Resource estimate occurs within the D’Kar Formation.
Second order (parasitic) upright to overturned folds are developed within the axial region of the periclinal anticline. The second order folds are cross-cut and displaced by moderately north-west dipping brittle-ductile, thrust-sense shear zones. These shear zones are characterised by zones of heterogeneous foliation of variable width and intensity. High strain zones have been recognised along which different sedimentary units have been juxtaposed by brittle displacement.
Flat lying to shallow dipping zones of extensional fracture and veining are developed in the footwall of the main shear zone. These extensional zones are interpreted to have formed as shear related extensional structures during thrust movement. The extensional structures are preferentially developed within a sandstone dominated package but also penetrate the overlying carbonate and siltstone dominated units.
Cu-Ag mineralisation that forms the focus of A4 is developed along both the shear zones and the extensional zones. Within the shear zones copper sulphides (bornite, chalcocite, chalcopyrite) are associated with quartz-carbonate veins developed sub-parallel to the shear foliation. Within the extensional zones copper sulphides are associated with either quartz-carbonate veins or as sulphide fill to in-situ fragmentation zones (breccias) within the host sediments.
Cu-Ag mineralisation that forms the focus of the A4 study extends from approximately 5m – 220m below surface. Mineralisation extends for 1,200m along strike and the cumulative total true width of mineralisation ranges from 10m – 80m.
Mineralisation extends over a strike length of approximately 900m and 270m down-dip and remains open at depth and along strike. Wireframes were developed using the high strain zones and extensional structures to guide interpretation of hosted mineralisation. A nominal 0.3% Cu cut-off grade was used to determine the external boundary of the mineralised zones. Immediately above the mineralised zone, soil/sand and calcrete extends to a depth ranging from 3 – 8m below surface. Saprolite (>25% oxidation) extends from 25 – 60m below surface and saprock (1 – 25% oxidation) from 55 – 85m below surface. Where oxidised, primary copper sulphides are altered to malachite, chrysocolla or covellite.
Summary:
Preliminary mining studies for the A4 deposit have shown that the currently defined Mineral Resource could potentially be economically mined using open-cut methods at the currently reported average Cu grade.
Conventional open pit mining method using backhoe excavators and rigid dump trucks was adopted in line with the mining method at T3. 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 was optimal for mining at A4. A split shell approach for staging of the pit was selected as the preferred option for managing pre-stripping requirements and continuity of ore supply. The mine design used minimum mining width of 20 m and 100 m respectively for pit floor and cutbacks.
The majority of site facilities such as accommodation and other camp facilities, sewerage plant, ROM pad, processing plant, maintenance facilities, tailings storage and Contractor built/supplied workshops were already required for the T3 pit. For the satellite operation at A4, the infrastructure requirements for the open pit operation include dewatering bores, water storage dams, haul roads, satellite workshop for minor servicing and office facilities.
Flow Sheet:
Crusher / Mill Type | Model | Size | Power | Quantity |
Ball mill
|
|
|
|
1
|
Summary:
Designed to be rapidly scalable to 5.2Mtpa with only the addition of a Ball Mill and expanded Concentrate Storage.
Processing
- Filter press plant
- Flotation
Flow Sheet:
Summary:
The A4 PFS outlines the first additional satellite deposit to the Motheo Copper Mine, expanding plant production from 3.2Mtpa to 5.2Mtpa over its five-year mine life.
The metallurgical testwork program to support development of the A4 Deposit commenced in July 2020 which initially targeted 6 samples from selected drill core within the proposed A4 pit shell. The initial results were encouraging with the samples tested exhibiting similar metallurgical characteristics (ore competency and copper recovery to concentrate) as the T3 deposit.
The results provided confidence that the copper ore from the A4 deposit will respond well when processed through the proposed T3 process flowsheet. As a result, the second stage of the A4 testwork program was developed on the basis that the A4 ore will be treated in the T3 plant.
The T3 testwork flowsheet and conditions were adopted for all flotation testing during the A4 test program, a flotation feed mass P80 grind size ........

Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Copper
|
Recovery Rate, %
| 92.3 |
Copper
|
Head Grade, %
| 0.96 |
Copper
|
Concentrate Grade, %
| 30 |
Projected Production:
Commodity | Units | LOM |
Copper
|
kt
| 437 |
All production numbers are expressed as metal in concentrate.
Operational Metrics:
Metrics | |
Stripping / waste ratio
| ......  |
Plant annual capacity
| ......  |
* According to 2021 study.
- Subscription is required.
Reserves at July 21, 2021:
The Mineral Resource and Ore Reserve had been reported above a cut-off of 0.5% Cu.
Category | Tonnage | Commodity | Grade | Contained Metal |
Probable
|
9.7 Mt
|
Copper
|
1.2 %
|
114 kt
|
Probable
|
9.7 Mt
|
Silver
|
18 g/t
|
5.7 M oz
|
Indicated
|
8.9 Mt
|
Copper
|
1.4 %
|
124 kt
|
Indicated
|
8.9 Mt
|
Silver
|
22 g/t
|
6.2 M oz
|
Inferred
|
0.9 Mt
|
Copper
|
1 %
|
9 kt
|
Inferred
|
0.9 Mt
|
Silver
|
15 g/t
|
0.4 M oz
|
Total Resource
|
9.8 Mt
|
Copper
|
1.4 %
|
134 kt
|
Total Resource
|
9.8 Mt
|
Silver
|
21 g/t
|
6.6 M oz
|
Corporate Filings & Presentations:
Document | Year |
...................................
|
2021
|
...................................
|
2020
|
...................................
|
2019
|
- Subscription is required.
- Subscription is required.