Overview
| Stage | Production |
| Mine Type | Open Pit & Underground |
| Commodities |
|
| Mining Method |
- Truck & Shovel / Loader
- Longhole open stoping
- Cemented backfill
|
| Processing |
- Gravity separation
- ACACIA reactor
- Carbon re-activation kiln
- Centrifugal concentrator
- Smelting
- Concentrate leach
- Agitated tank (VAT) leaching
- Counter current decantation (CCD)
- Carbon in leach (CIL)
- AARL elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
| Production Start | 2002 |
| Mine Life | 10 years (as of Jan 1, 2020) |
The North Mara mine consists of an underground operation (Gokona) and Nyabirama open pit. |
| Latest News | Barrick Gold Corporation: Twiga a Triumph of Partnership October 23, 2020 |
Source:
p. 19-20
| Company | Interest | Ownership |
|
Government of Tanzania
|
16 %
|
Indirect
|
|
Barrick Gold Corp.
|
84 %
|
Indirect
|
|
Twiga Minerals Corporation Ltd.
(operator)
|
100 %
|
Direct
|
On September 17, 2019, Barrick acquired all of the Acacia Mining plc. Acacia became a wholly-owned subsidiary of Barrick called Barrick TZ Limited.
On January 24, 2020, Barrick announced that the Company had ratified the creation of Twiga Minerals Corporation, formalizing the establishment of a joint venture between Barrick and the GoT and resolution of all outstanding disputes between Barrick and the GoT. The Government of Tanzania will receive a free carried shareholding of 16% in each of the former Acacia mines (Bulyanhulu, Buzwagi and North Mara). The GoT’s 16% free-carried interest was made effective on January 1, 2020.
Twiga Minerals Corporation (“Twiga”), the operating company formed to manage the Tanzania mines (Bulyanhulu, Buzwagi and North Mara).
Contractors
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Summary:
The North Mara Mine is situated within the Mara Greenstone Belt. The underlying geology comprises felsic and mafic volcanics intercalated with sediments which are intruded by various granitoid and gabbroic plutonic rocks. Tertiary volcanic lava flows partially cover the underlying Archaean geology and the ore bodies are structurally controlled, shear-hosted lode gold deposits. There are several types of gold mineralisation including shear-zone-related quartz vein and disseminated gold.
Mining Methods
- Truck & Shovel / Loader
- Longhole open stoping
- Cemented backfill
Summary:
The North Mara mine consists of an underground operation (Gokona) and Nyabirama open pit.
At Gokona, Acacia utilizes an existing exploration decline for initial access to the planned underground mine. Two major declines are included in the mine plan.
The mining method utilised in the operation is Long Hole Open Stoping (“LHOS”) with Cemented Aggregate Fill (“CAF”).
In the second quarter of 2022, North Mara has seen the successful ramp-up at the Nyabirama open pit.
A successful ramp-up in opencast mining and similar improvement is expected in underground mining when new equipment arrives in the second half of 2022.
Source:
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Processing
- Gravity separation
- ACACIA reactor
- Carbon re-activation kiln
- Centrifugal concentrator
- Smelting
- Concentrate leach
- Agitated tank (VAT) leaching
- Counter current decantation (CCD)
- Carbon in leach (CIL)
- AARL elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Source:
Summary:
Both oxide and sulphide reserves are mined and processed by conventional carbon-in-leach (CIL) technology.
The concentrate from the Knelson Concentrators is fed to the Acacia reactor in the gold room for gold recovery by intensive cyanidation. Acacia tailings are returned to the ball mill circuit and pregnant solution is pumped to electrowinning cells.
The trash screen overflow falls into a bunker whilst the underflow is fed to two thickeners. Thickened slurry is pumped to the CIL circuit and water recovered from the thickeners is pumped back to the mill circuit as process water. The CIL circuit consists of three pre-leach tanks and nine adsorption tanks. Carbon is transferred counter current to slurry flow by means of air lifts and is pumped from Tank 4 over the loaded carbon screen before being transferred to the acid wash section.
Residue from the CIL section is pumped to a cyanide detoxification circuit where Weak Acid Dissociable (WAD) cyanide con ........
Recoveries & Grades:
| Commodity | Parameter | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
|
Gold
|
Recovery Rate, %
| ...... | ...... | ...... | 92.7 | 92 | 92 | 88.2 |
|
Gold
|
Head Grade, g/t
| ...... | ...... | ...... | 4 | 3.9 | 4.5 | 3.6 |
Production:
| Commodity | Units | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
|
Gold
|
koz
| ...... ^ | ...... | ...... | ...... | 336 | 324 | 378 |
All production numbers are expressed as metal in doré.
^ Guidance / Forecast.
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Operational Metrics:
| Metrics | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
|
Total tonnes mined
| ...... | ...... | 14,263 kt | 16,935 kt | 15,953 kt | 15,996 kt |
|
Ore tonnes mined
| ...... | ...... | 6,333 kt | 3,657 kt | 3,801 kt | 3,192 kt |
|
Waste
| ...... | ...... | 7,930 kt | 9,783 kt | | |
|
Stripping / waste ratio
| ...... | ...... | 1.39 | 4.47 | | |
|
Tonnes processed
| ...... | ...... | 2,459 kt | 2,847 kt | 2,841 kt | 2,830 kt |
|
Annual processing capacity
| ...... | ...... | 8,000 t | 2.8 Mt | 2.8 Mt | |
|
Daily processing capacity
| ...... | ...... | | 8,000 t | 8,000 t | |
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Reserves at December 31, 2021:
| Category | OreType | Tonnage | Commodity | Grade | Contained Metal |
|
Proven & Probable
|
In-Situ (OP)
|
45 Mt
|
Gold
|
1.73 g/t
|
2.5 M oz
|
|
Proven & Probable
|
In-Situ (UG)
|
8 Mt
|
Gold
|
3.44 g/t
|
0.89 M oz
|
|
Proven & Probable
|
Total
|
52 Mt
|
Gold
|
1.99 g/t
|
3.3 M oz
|
|
Measured
|
In-Situ (OP)
|
15.5 Mt
|
Gold
|
2.54 g/t
|
1.2 M oz
|
|
Measured
|
In-Situ (UG)
|
0.76 Mt
|
Gold
|
3.56 g/t
|
0.087 M oz
|
|
Measured
|
Total
|
15.5 Mt
|
Gold
|
2.59 g/t
|
1.3 M oz
|
|
Indicated
|
In-Situ (OP)
|
48 Mt
|
Gold
|
1.41 g/t
|
2.1 M oz
|
|
Indicated
|
In-Situ (UG)
|
21 Mt
|
Gold
|
2.04 g/t
|
1.4 M oz
|
|
Indicated
|
Total
|
69 Mt
|
Gold
|
1.61 g/t
|
3.6 M oz
|
|
Inferred
|
In-Situ (OP)
|
6 Mt
|
Gold
|
1.1 g/t
|
0.21 M oz
|
|
Inferred
|
In-Situ (UG)
|
9.3 Mt
|
Gold
|
1.8 g/t
|
0.55 M oz
|
|
Inferred
|
Total
|
15.5 Mt
|
Gold
|
1.6 g/t
|
0.77 M oz
|
Aerial view:
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