Summary

Deposit type

• Vein / narrow vein
• Orogenic

Summary:

lization. Gold occurs primarily in pyrite and secondarily as native gold in quartz veins.

Two distinct deposit styles are recognized within the Ahafo Operations. Kenyasi-style deposits, comprising Apensu, Awonsu, and Amoma, are associated with the Kenyasi Thrust Fault, along a sheared thrust contact between Dixcove Suite granitoids and footwall volcano-sedimentary units. Subika-style mineralization comprises gold that is entirely hosted in Dixcove granitoids, in the hanging wall of the Kenyasi Thrust Fault. To date, the only recognized deposit of the style is Subika.

Gold typically occurs as native gold, associated with pyrite. Alteration associated with the deposits includes silicification, albitization, pyritization, and carbonation.

Mineralization in Kenyasi-style deposits is associated with mixed (meta)-pelitic sedimentary rocks and (meta)-mafic volcanic units along the footwall of the Kenyasi Thrust Fault. Dixcove Suite granitoids form the hanging wall to the thrust, and

Mining

• Truck & Shovel / Loader
• Longhole open stoping
• Sub-level shrinkage

Summary:

k in November 2019.

Open pit mining is conducted using conventional techniques and an Owner-operated conventional truck and shovel fleet. Underground mining is currently conducted using conventional stoping methods, and conventional mechanized equipment. Underground mining is conducted by a contractor.

Open pit
Subika mining is in the final stage with limited potential to grow at depth because of the underground crown pillar. No changes were made to the Phase 4 pit design for Subika. The minimum mining width between the Subika Phase 4 and the mined-out third phase is 50 m. All operating pits are mined on 8 m benches. Mining dilution and recovery are included in the block model, based on historic reconciliation.

Open pit design uses defined geotechnical domains together with rock mass quality ratings for the principal lithologies and appropriate pit design criteria that reflect expected conditions and risk. Inter-ramp angles vary by deposit and pit wall lithology, and range from 30–55º.

The active pits are currently mining below the water table. Pit dewatering uses a combination of perimeter and in-pit dewatering wells, in-pit sumps, and horizontal drains. A network of monitoring piezometers is installed around all of the operating pits.

The LOM plan currently envisages mining at an average rate of approximately 26 Mt/a for nine years and peaking at 32.2 Mt/a in 2022 with a maximum rate of advance by pit stage of eight benches per annum and an average of six benches (48 m) per year. The mine life will extend to 2030 with material mined from the open pit. Milling will cease in 2032 after treatment of stockpiled ore.

Ore Loss and Dilution
All operating pits at Ahafo South are mined on 8 m benches. The Subika model is a 24 x 12 x 8 m model to account for the 8 m mining. Block models for Awonsu, however, are produced using a 12 x 12 x 8 m block dimension to reflect the increased selectivity in ore zones

Pit design assumptions include haul road widths for two-way travel of 30 m, maximum ramp grades of 10% and minimum pit-bottom widths of 30 m in deep pits as a safety measure. For the last couple of benches to the pit bottom where good grades are located, the haul road widths are reduced to a 21 m one-way traffic to allow for maximum ore mining recovery.

Production drilling and blasting for the open pits is conducted on 8 m benches with a subdrill of 1.2 m, using a 165 mm diameter bit. The pattern for production drilling is 4 x 4.5 m in both ore and waste, with powder factors varying by material type and geological conditions. Bulk emulsion is loaded into both production and buffer holes; the stemming length varies according to rock type and other geologic conditions but it is generally at 3.3 m. Pre-splitting is conducted on all pit wall areas with power-split explosives supplied by the explosives provider, Orica. The powder factor for open pits is 0.92kg/m .

Underground
Mining levels are based on the mining method to

Comminution

Crushers and Mills

Summary:

allation of a new crusher, a single stage SAG mill and two leach tanks.

Crushing Circuit
ROM ore is dumped from haul trucks or a front-end loader into a feed hopper which feeds a 54- inch x 75-inch gyratory crusher. Primary crushed material is discharged into a surge hopper directly underneath the crusher. From the surge hopper, the primary crushed material is withdrawn to a reclaim stockpile via an apron feeder, conveyors and a transfer station. Where oxide ore is available, the oxide ore is loaded onto the tail end of the SAG mill feed conveyer. Primary ore from the reclaim stockpile is discharged to the SAG mill feed conveyor through apron feeders. A regulated amount of lime from a lime silo is also added to the SAG mill feed conveyor.

Grinding Circuit
The grinding circuit consists of a single 10.36 m diameter (Ø) x 5.00 m effective grinding length (EGL) SAG mill followed by a ball mill in closed circuit with hydrocyclones. The SAG mill and two MP800™ pebble crushers are in a closed circuit. The SAG mill discharge is classified via a pebble dewatering screen. The oversize from the screen is crushed via the pebble crushing circuit and returned to the SAG mill.

The Line 2 was commissioned in September 2019. The process route commences with one single-stage primary crushing fed by direct truck dump or front-end loader for crushing of primary ores onto a live crushed stockpile. This material is fed from the live crushed stockpile directly onto the Line 2 SAG mill feed conveyor by apron feeder. SAG milling is in closed circuit with pebble crusher for scats or pebble crushing. Crushed pebbles scats return to the SAG mill feed conveyor. This is followed by closed-circuit cycloning to a P80 size of 106 µm for Line 2.

Beneficiation

• Carbon re-activation kiln
• Smelting
• Reverse osmosis
• Crush & Screen plant
• Counter current decantation (CCD)
• Agitated tank (VAT) leaching
• Carbon in leach (CIL)
• AARL elution
• Carbon adsorption-desorption-recovery (ADR)
• Solvent Extraction & Electrowinning
• Cyanide (reagent)

Summary:

ion tonnes per year. The current processing plant consists of two crushing plants, two grinding circuits, carbon-in-leach circuits, elution circuit, counter current decantation circuit, a tailings disposal facility, a reverse osmosis water treatment plant, and an analytical laboratory managed by a third-party

The Ahafo Mill Expansion which was completed in October 2019, expanded the plant capacity to process approximately 11 million tonnes per year through the installation of a new crusher, a single stage SAG mill and two leach tanks.

Wet Circuit
The undersize of the trash screens reports to the 42 m Ø pre-leach thickener with the thickener overflow recycled to the milling circuit as process water. The pre-leach thickener underflow is pumped to CIL leach and adsorption tanks in series. Carbon is added to the CIL tanks and flow countercurrent to the process slurry. The CIL tailings is discharge onto the carbon safety screens before being pumped to the countercurrent decantation (CCD) circuit.

The CCD circuit consist of two 42 m Ø thickeners. The overflow from the thickeners is recycled back to the process as process water while the underflow is pumped to the tailings disposal tank. Tailings are discharged via a spigot system into the TSF.

Stripping and Dore Production
The loaded carbon is recovered via a carbon recovery screen and treated in the elution and electrowinning circuit. Loaded carbon is acid washed with dilute hydrochloric acid in an 18 t acid wash column prior to transfer into an elution column where it is presoaked in a cyanide/caustic solution for 30 minutes to elute gold. The pregnant eluate is then rinsed from the carbon by as many as 10 bed volumes of water heated to 130º C. The resultant pregnant solution is pumped to electrowinning cells in which the gold is deposited on cathodes. The gold sludge on the cathodes is washed, dried and smelted in a furnace to produce doré. Doré is shipped to Switzerland to be refined to bullion at Valcambi.

A CCD circuit was commissioned in 2008 to recover cyanide from CIL tailings prior to discharge to the TSF. Recovered cyanide is effectively re-used in the CIL circuit and weakly acid-dissociable cyanide (CNWAD) levels in the plant tailings are effectively controlled to ensure the discharge limit of 50 ppm CNWAD is not exceeded.

A gravity circuit that was initially included in the plant was decommissioned in 2010.

Water Supply

Summary:

ed. Potable water for the mining operations and camps is produced from bore fields.

Water supplies are sufficient for current and planned development needs. The Ahafo mine operates with an excess water balance resulting from the accumulation of seasonal rainfall contacting the mining operation. The excess is stored in the mined-out Apensu pit, which has an area of 350,000 m.

Water management infrastructure at Ahafo South for mine operations include the following:
• Surface water management infrastructure: diversion channels around the pits and collection systems downstream of the WRSFs and stockpiles;
• Pit runoff management infrastructure: in-pit and ex-pit sumps with a system centrifugal pumps and high- density polyethylene (HDPE) pipelines dewatering to holding and transfer ponds;
• Groundwater management infrastructure: hybrid system of ex-pit dewatering wells and installations of arrays of horizontal drain holes.

A reverse osmosis water treatment plant with a 50 L/s (feed) capacity was commissioned in August 2017. A second reverse osmosis water treatment plant is planned for execution in 2024, based on the current business plan BP22 and will have an additional 50 L/s (feed) capacity.

Commodity Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
General Manager	Alex Kofi Annin		Apr 8, 2024