Overview
Stage | Production |
Mine Type | Open Pit / Underground |
Commodities |
|
Mining Method |
- Truck & Shovel / Loader
- Bench stoping
- Avoca
- Cemented backfill
|
Processing |
- Gravity separation
- Smelting
- Concentrate leach
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
Mine Life | 11 years (as of Jan 1, 2018) |
The mine will be operated by a mining contractor. The mining contractor will provide all labour, plant and materials to develop and produce from the mine. Contractor oversight and technical direction will be provided by WAF. |
Latest News | First gold poured at West Africa’s ‘next Tier 1 gold asset’ March 20, 2020 |
Source:
p. 15
Underground mining contract awarded to Byrnecut Q4 2018.
Deposit Type
- Vein / narrow vein
- Orogenic
Summary:
Gold mineralisation at the Mankarga deposits is associated with sheared and boudinaged quartz vein and veinlet arrays exhibiting silicification with sulphide, carbonate-albite and tourmaline-biotite alteration assemblages consistent with an orogenic gold deposit.
Gold mineralisation is associated with quartz vein and veinlet arrays, silica, sulphide and carbonate-albite, tourmaline-biotite alteration. Gold is visible and is mainly associated with minor pyrite, chalcopyrite and arsenopyrite disseminations and stringers. The currently defined economic mineralisation is sub-vertical with a strike length of up to 120m, widths of up to 50m over two discrete lenses and remains open at depth.
Mining Methods
- Truck & Shovel / Loader
- Bench stoping
- Avoca
- Cemented backfill
Summary:
The majority of the defined mineral resources at the Project are within 200m depth from the surface and of a lode style mineralisation. The material to be excavated will be predominantly free dig from surface with blasting required deeper in the oxidation profile. Given these conditions, conventional open pit mining techniques using drill and blast with material movement by hydraulic excavator and trucks will be employed. The project scale suits 120t – 200t class excavators in a backhoe configuration matched to 95t class mine haul trucks.
In addition to the open pit resources, the steeply dipping, high grade zone at M1 South will be exploited by underground methods. The open pit has been limited to a depth of 120m from surface as optimisation of the mine schedule and project cashflow indicated that this provided the best interface with the underground mine. The underground mine will be accessed via a portal constructed in the south east wall of the open pit.
Open pit:
The main M5 pit is 2km long and averages 430m wide and 205m deep at the southern end. The pit has been designed so the southern higher grade portion can be mined independently of the northern portion of the pit. Both the northern and southern pits will be mined in two stages, an initial starter pit and then a cutback to final limits, in order to target higher grade earlier in the schedule and defer waste. The M1 deposit will be mined in two pits, a north and a south pit. The M1 South pit has been limited to a depth of 120m from surface, as optimisation of the mine schedule and project cashflow indicated that this provided the best interface with the underground mine. The M1 South pit design incorporates an underground portal in the south east wall. To enable the earliest possible development of the underground workings, the southern section of the pit will be mined to a depth of 30m to enable the portal to be developed in fresh rock. The final M1 South pit is 570m long by 290 wide and 120m deep. The M1 North pit is 350m long by 240m wide and 90m deep. The M3 deposit also has two small, predominately oxide, pits less than 40m deep.
Production schedules were completed with the primary aim of providing the highest value ore to the mill as early as possible in order to maximise the value to the Project. In order to provide the highest value ore to the process plant in the earlier years of the schedule the development of the M1 South underground mine has been prioritised. In addition, the higher grade and higher strip ratio material from the M1 South pit and the southern part of M5 are mined. This results in a total material movement of 20.7Mt in the first production year and 17.3Mt in the second reducing approximately to 8Mt/yr for the remainder of the mine life. For the initial high production period a mining fleet of 1 x 200 tonne class excavator and 2 x 120 tonne class excavators and matching truck fleet (95t class) has sufficient capacity for these production rates. The 200t sized excavator and associated fleet will be demobilised after year 2 with the combined smaller fleet having sufficient capacity for the remainder of the mine life.
Underground:
The most appropriate underground mining method of Modified Avoca was chosen in the feasibilty study and as the fundamentals underpinning this choice have not changed it is still the preferred option.
The stope recovery is assumed at 95%, with underground dilution averaging 9%.based on an estimated skin of waste being incorporated in the ore production. The M1Sth deposit averages 4,500 tonnes per vertical metre of resource at a 3.5g/t Au cutoff. A standard rule of thumb is that mining rates of up to 60m vertically per year are reasonable; this equates to a production rate of 350,000tpa.
The following describes the design approach:
• The mine is planned to be developed using conventional two boom jumbos capable of face advance and installation of ground support.
• Access is by decline, commencing from a portal the M1 South starter pit.
• The planned mining method is uphole retreat bench stoping with loose rock fill and cemented fill where necessary.
All mine development is in fresh rock and geotechnical assessment indicates that ground conditions are expected to be generally good. The portal and start of decline may be in transitional material.
Decline 1:7, 5.5mH x 5.5mW, crosscuts and stockpiles will be 5.0mH x 5.0mW and ore drives 4.5mH x 4.5mW.
The escape way will be equipped as services raise with high voltage power cable and rising main and will form part of the ventilation system. Main ventilation raise dimensions of 3.5m diameter. Ore production levels on 20 vertical metre intervals. The geotechnical assessment indicates stope strike lengths of approximately 20m to 25m.
It is proposed to use a combination of cemented rockfill and loose rockfill for backfilling stope voids, to allow high stope recovery and ensure ground stability. Cemented fill will be necessary where there is a need to expose fill. However, the mine sequence is designed to be predominantly bottom up to maximise the use of loose fill. Approximately half of the required stope backfill will come from mine development waste, with the balance being sourced from open pit waste. Backfill will be placed with loaders, with cemented fill being cement slurry.
Processing
- Gravity separation
- Smelting
- Concentrate leach
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
The Sanbrado process plant will have a nameplate throughput of 2Mtpa, with an availability of 8,000 hours per annum and a nominal capacity of 250 tonnes per hour (tph).
The plant will be located southeast of the M5 pit, adjacent to the WSF and TSF. The plant is to be fed predominantly from the M1 and M5 deposits, with only small volumes of material supplied by the M3 pit. The process flow diagrams were developed from the process design criteria prepared by Mintrex.
The plant design proposed is simple but robust and broadly comprises the following:
• Primary Jaw Crushing;
• Crushed Ore Stockpile and Reclaim System;
• SABC Mill Grinding, Pebble Crusher and Classification;
• Gravity Recovery;
• Leaching and Adsorption;
Leach Feed Thickening;
• Elution;
• Electrowinning; and
• Smelting.
Ore will be placed in stockpiles on the ROM pad located to the north of the process plant and will be fed by front ........

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Production:
Commodity | Units | Avg. Annual (Projected) | LOM (Projected) |
Gold
|
koz
| 133 | 1,462 |
All production numbers are expressed as metal in doré.
Reserves at June 22, 2018:
Category | Tonnage | Commodity | Grade | Contained Metal |
Probable
|
20,386 kt
|
Gold
|
2.4 g/t
|
1,573,000 oz
|
Indicated
|
39,600 kt
|
Gold
|
1.8 g/t
|
2,350,100 oz
|
Inferred
|
13,850 kt
|
Gold
|
1.2 g/t
|
550,000 oz
|
Corporate Filings & Presentations:
Document | Year |
...................................
|
2018
|
...................................
|
2018
|
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