The gold deposits of the Tabakoto project are dominantly hosted in the Birimian, turbiditic sedimentary rocks of the Kofi Formation. These rocks have been intruded by multiple generations of dikes and sills ranging from felsic to mafic composition. The entire package of rocks have been deformed and metamorphosed during the Eburnean orogeny. While individual structures associated each of the deformational events can host mineable deposits, multiple generations of structure enhances the probability of mineable ore.

The deposits can be further divided into three broad types as follows:
- Shear Zone hosted (Ségala and Ségala NW);
- Fracture and cross structure hosted (Dar Salam, Tabakoto, Dioulafoundou and Kofi C), and;
- Intrusive hosted (Djambaye II).

SHEAR ZONE HOSTED DEPOSITS

The Ségala and Ségala NW deposits are considered to be part of a structurally controlled alteration and mineralization system that is hosted by the core of an isoclinal anticline whose axial trace trends ESE (approx. 110°) and dips steeply to the south at approximately -80°. The anticline is made up of somewhat deformed and altered meta-sediments (greywacke and argillite) that display variable intensities of alteration of chlorite, carbonate, sericite, sulphide and silica. A series of quartz stringers and veins intrude this package.

BRITTLE FRACTURE ZONE HOSTED DEPOSITS

At the Dar Salam, Tabakoto and Dioulafoundou and Kofi C Deposits, a geological model for gold mineralization proposed by Nielsen (2004) favours the emplacement of gold-bearing mineralization along structures developed during north-northeast directed isoclinal folding. Mineralization is associated with pervasive silicification and sericite + quartz + Fe-carbonate alteration within and adjacent to dikes and along intersecting north-east, north-west and easterly trending structures. Gold is preferentially hosted within silicified felsic to intermediate dikes and adjacent sedimentary strata along the axial trace of the north-northeast trending Tabakoto anticline.

Veining at Tabakoto displays a protracted history of development with the dominant vein orientations compatible with the development within pre-existing extensional and shear structures formed during NNE directed folding. There is development of moderate to steeply southeast plunging mineralized zones (“ore shoots”) coincident with the intersection of north trending and subsidiary north-east, north-west and easterly trending mineralized corridors. Late reactivation of these structures has facilitated the emplacement of intermediate, mafic and lamprophyre dikes.

INTRUSIVE HOSTED

Most of the gold mineralization at Djambaye II is stockwork-style, hosted within the intrusion, which is different from Tabakoto where the mineralization is predominantly associated with more discrete veining. From previous work (Standing, 2004), including thin section data, the dominant alteration type at Djambaye II was identified as albitization with lesser amounts of silicification (quartz veining) and sulphidation (pyrite and subordinate arsenopyrite).

Mineralization at Tabakoto, Ségala and Kofi is typically associated with disseminated to massive sulphides; pyrite, pyrrhotite, arsenopyrite and in rare instances chalcopyrite and sphalerite. The gold is either associated with quartz veining or moderate to intense silicification and/or albitization. In addition to the silicification, there is evidence of potassic (sericite and biotite), propylitic (chlorite), and carbonate (dolomite to ankerite).

The deposits, identified to date at Tabakoto and Kofi, occur in a number of different environments and exhibit different styles of mineralization.

Tabakoto mine operations currently consist of two underground operations (Tabakoto and Ségala) and open pit (Kofi C) with gravity/CIL processing facilities. During 2015, mining operations at Tabakoto concentrated on the Kofi C open-pit, Tabakoto and Ségala underground from which a total of 10.66Mt of material were mined to deliver 1.37Mt of ore at an average grade of 3.34g/t Au containing 147,500oz to the ROM pad.

The Tabakoto and Ségala underground mines constitute the majority of the ore production at Tabakoto and open pit mining is now essentially used to augment the underground as mill feed.

The Ségala Deposit consists of the Ségala Main and the Ségala North West zones. Open pit mining has taken place at both of these deposits previously. Production is currently planned from underground mining of the Ségala Main zone only. This zone consists of several parallel mineralized structures which run along the length of the ore body and contains the bulk of the currently defined mineralization. The spacing and the thickness of these structures vary. Individual veins, which can be less than a metre thick, are grouped into ore zones which can collectively be up to 25m thick.

The Tabakoto Deposit is accessed from the bottom of an open pit where mining was previously conducted. Underground mine access uses a northern portal to exploit the northwest-trending (“NW”) zones and a southern portal for both the northeast-trending (“NE”) zones and the South zones.

There are five veins being exploited by means of underground mining methods. These are:
- The Ségala Main Zone, where transverse long hole stoping is preferred and either cemented rock fill (“CRF”) or unconsolidated rock fill is utilized to enhance local and overall ground stability;
- The Ségala Footwall Zone, where longitudinal long-hole stoping is the design together with cemented rock fill or unconsolidated rock fill;
-The Tabakoto North West veins where there are more than five closely spaced veins. Selective longitudinal long-hole stoping is used to extract ore from the top down without using fill;
-The Tabakoto North East veins where two main veins are separated by about 10m and long hole stoping is also used to extract ore from the top down without fill, and;
- The Tabakoto South vein, which is relatively long and narrow with better grades. Long-hole stoping moves from the bottom upwards as opposed to a top down approach. Waste fill is also used in this instance.

The Tabakoto Deposit is accessed from the bottom of an open pit where mining was previously conducted. Underground mine access uses a northern portal to exploit the northwest-trending (“NW”) zones and a southern portal for both the northeast-trending (“NE”) zones and the South zones.

Tabakoto is at full production producing just over 40ktpm from underground. The various sub vertical veins are accessed using decline ramps from a North and a South portal both located at the bottom of the Tabakoto open pit.

Development support consists of split sets and mesh. In the main ramps and accesses the split sets are installed from scissor lifts and a bolting crew using hand held equipment to ensure that the proper bolting patterns are achieved. Where required waste fill is drawn from waste development headings or surface waste dumps and trucked down the south decline and placed with the use of LHD.

Ségala is at full production producing just over 40ktpm from underground. Decline access is from a portal located 25 m above the Ségala open pit floor in the eastern corner of the Ségala open pit.

Cross cuts are used to access the ore zone from a footwall drift along the full length of the ore zone. They will link with ore drives at the centre of the ore body to minimise waste development and primary stopes access development. Stoping will start from the centre of the ore zone and progress east and west along strike, away from the centre and opening from hanging-wall to footwall.

Production will start from the bottom of a production block and move upwards. Primary and secondary stopes have been designed. The primary stopes will be filled with cemented rock fill and the secondary stopes will be blasted after the appropriate curing time has elapsed. The cement will bind the primary waste fill and minimise dilution of the secondary stopes.

All Tabakoto open pits are conventional open pit mining operation involving the mining of Saprolite, Transition and Fresh rock. Every pit was developed and operated as a combination of contract and owner mining operation. To supplement underground production 1,000tpd currently trucked from Kofi C to the Tabakoto processing plant located 38km to the southeast. The production rate was determined by considering the size of the available resource and the required mining fleet. An office and a small shop facility located near the Kofi C pit exit. A 20,000 litre fuel tank and dispensing station also located in this vicinity. A small generating plant provides power for lighting, tools, pumps and related facilities and equipment. Mining at Kofi C commenced by the beginning of 2015.

The primary objective of the production schedule has been to maximize ore production to supplement the underground mill feed and generate enough cash flow to optimize the mine operations.

A combination of Endeavour and SFTP contactor fleet is used for current mining operations in Kofi C. Blasting on the ore zone is mainly on 5m benches while for bulk waste stripping is 10 m benches. The blasting on the ore is more controlled to minimize dilution. Excavation of the blasted material is mainly on 2.5m high flitches. Gold ore transported to Tabakoto process plant by tip trucks (contractor).

The process plant is designed to treat 4,000tpd, following the plant expansion completed in 2013.

The process design criteria consist of crushing, ore stockpiling, milling and classification, gravity and in-line leach reactor (“ILR”), CIL, tailings disposal, acid wash, elution, electro-winning and gold room.

A front-end loader is used to feed ROM to the crushing circuit from the ROM PAD, via a grizzly of aperture 800mm x 800mm with a ROM Bin live capacity of 150t The primary crushing circuit consists of a 1250mm x 950mm single toggle SANDVIK jaw crusher and is fed by a 1.8m x 6m primary apron feeder. The design closed side setting is 120mm but currently operating at 110mm. The primary crusher operates at a maximum throughput of 400 tonnes per hour.

The crushed product is dumped onto a new stockpile ahead of the SAG mill. The stockpile is fitted with three underneath apron feeders and conveyor systems, including a weightometer. The feeders are linked with feeder loop controls and instrumentation which ensure regulated feed rates to the SAG mill.

The Tabakoto grinding circuit was upgraded to include a 6.1m x 8.46m SAG Polyseus mill, in series with the existing ball mill. It operates on a 5MW motor, while the 4.75m X 7.92m ball mill is driven by a 2.4MW motor. The SAG mill has a design capacity of 4,200tpd but with the possibility of feeding above name plate upon optimisation. The SAG mill is in close circuit with a scalping screen to handle 50-150% circulating load. The grinding circuit was also upgraded to include a cluster of ten 15” Krebs hydro cyclones in close circuit with the ball mill. A target P80 of 75 micron is fed to the leach circuit.

Current configuration and optimisation allows 28% of the cyclone underflow to be fed to the Gemini shaking table via the scalping screen and one Falcon concentrator and 44% to the Gekko ILR via scalping screen and the other two Falcons concentrators. The balance of the under flow reports directly to the Ball mill for regrinding.

The plant has an active gravity concentration circuit consisting of three SB 2500 model Falcon concentrators, a Gemini shaking table and a Gekko ILR (2000BA). 72% of the cyclone underflow is subjected to gravity treatment. The performance of the gravity unit is highly sensitive to feed grade and contributes about 48% to the mine’s gold production. A dedicated electro-winning cell was installed to handle the ILR concentrate.

The current trash screen had enough capacity to accommodate a 5,000tpd flow rate. Modifications were made to this screen to feed two thickeners

Tabakoto operates on a pre-leach thickening system with thickener feed of 22% solids. An additional 86tph thickener was constructed with the plant expansion which operates in parallel with the old 86tph thickener feeding the leach circuit with 50% solids at 118m3 /h each.

Three additional 2,155m3 leach tanks were installed with the plant extension. These run in series with one 785m3 tank and seven of the old 785m3 tanks to bring the current configuration to 11 tanks. This expansion of the leaching tanks and CIL system was necessary to maintain a 48 hour retention time. Each adsorption tank is fitted with a 4m2 Kemix MPS400P inter-stage screen and carbon transfer pump. There is a Multotec online automatic sampler that samples the head feed. Plant air is injected into the tanks through the agitators to aid the leach kinetics.

The old elution system was not capable of handling the increased production. Required carbon movement is about 3.5tpd. In order to accommodate this movement, the current two tonne carbon stripping circuit was left as a standalone unit and a new three tonne standalone elution column was installed.

The two columns will use the current boiler system as a common system. Desorption is done at 130°C using 3% caustic solution. The elution circuit has two Ansac thermic oil boilers operating independently but support each other to generate an oil temperature of 300°C. Primary and secondary heat exchangers regulate the required temperatures for the elution process. The circuit currently is capable of treating two batches per day with elution efficiencies currently averaging at 96%. Elution contributes about 52% of the total gold production.

An Ansac diesel powered regeneration kiln is also installed to re-activate carbon treated in the elution circuit at 11hrs per batch, 200kg/h and at a temperature of 700° – 800°C.

Tabakoto mine currently do not do cyanide recovery. However, UV light destroys about 90% of cyanide that goes to the tailings facility.

Gold room upgrade saw the addition of two electro-winning cells to the existing two, to handle ILR pregnant solution, a new diesel powered furnace and filter machine for the ILR concentrate. A Gemini concentrate table handling the old gravity circuit product, diesel furnace and an electric powered calcine oven. Conventional calcining and smelting procedures are practiced using fluxes like borax, nitre, silica, soda ash and others required. New ventilation and cooling systems have been modified to provide healthier working conditions.