The geology of the host rocks and the mineralisation is exposed in the open pit mines in the Chatree leases and the area has been the subject of a number of geological investigations commissioned by Akara.

In the mine area, the host volcanic sequence comprises four main units. The basal unit is dominated by andesite lavas and breccias, containing dacite dome complexes. This is followed by a thick sequence dominated by andesitic breccia. Overlying this is a largely sedimentary package with interfingering rhyolitic breccias. The uppermost unit in the mine area is a lithic rich fiamme breccia. As the lithologies interfinger, the locations of some unit boundaries in core, and especially in chips, are not always clear. All units are cut by dykes, predominantly andesitic, and typically less than 10 metres wide.

Epithermal gold deposits, such as those at Chatree, are generally formed in areas of active volcanism around the margins of continents, and may be associated with “bonanza” or high grade style mineralisation. Mineralisation in such deposits is deposited from hot fluids which are estimated to range in temperatures from less than 100 degrees centigrade to approximately 300 degrees centigrade. The mineralisation contained in these fluids is deposited as they rise to elevated crustal settings and boil, cool or mix with evolved nearsurface waters which oxidise the fluids to promote high grade gold deposition. The fluids usually travel toward the surface via fractures in the rocks and the resulting mineralisation often occurs at the intersection of these fractures and brittle host rocks in layered volcanic sequences.

The gold mineralisation is closely associated with a variety of types of quartz carbonate veins, some of which contain sulphides. They vary in width from millimetres to tens of metres. Significant amounts of silver and very minor amounts of zinc and lead are also associated with the mineralisation. The deposit is classed as low sulphidation epithermal, and sulphides tend to comprise less than 3% of the ore mass (Cumming, et al). Visible gold is rare within the system. Chlorite is common both in the veins and as alteration in the host rock.

The style of quartz carbonate gold mineralisation found at Chatree is common to a number of the most prolific gold producers in the Pacific rim, including Porgera and Misima in Papua New Guinea, Kelian and Mount Muro in Indonesia (Corbett). The variety of low sulphidation epithermal gold deposits all display controls dominated by structure, competent host rocks and efficient mechanisms of Au deposition.

All mining operations at Chatree are currently open pit. Recent activity has been focused on A and Q Pits.

Of the excavations, A Pit will be the largest, providing more than 50% of the future plant feed, as currently planned. The pattern of mineralisation and intrusive dykes, shown with the superseded outline of A Pit based on ore reserves previously estimated at a projected gold price of US$750 per ounce, is illustrated in. The zone was initially developed by two starter pits, which will eventually merge.

The open pit operations are conventional, and involve drilling and blasting of all materials except topsoil. The pits were previously blasted as 6-metre high benches, although 9-metre high benches are being established in A Pit. All benches are then excavated as 3-metre high flitches. Eleven drill rigs are employed, providing 102 mm to 115 mm diameter blast holes.

Chatree employs conventional CIL processing in two semi-parallel plants. CIL is a well proven method of extracting gold, along with silver and is now used in most modern gold plants throughout the world. The two plants each comprise separate crushing and grinding circuits followed by leaching and CIL tanks. Gold and silver are taken into solution by a dilute cyanide leach and adsorbed onto activated carbon.

The original plant consisted of 12 tanks, each of 720 m3 capacity. Plant 2 consists of 11 tanks, each of 2,500 m3 capacity. It was built such that the first 4 tanks were dedicated leach tanks with the remaining 7 tanks as CIL tanks. Tanks 2 to 4 have now been converted to CIL tanks.

Residence time in the integrated CIL circuit is achieved by directing the flow from the last CIL tank from Plant 1 to tank 4 of Plant 2. Loaded carbon is directed to AARL stripping circuits. Gold and silver from each plant are removed from the carbon, recovered from the eluted solution by electrowinning. The resultant gold and silver electrowon sludge from each plant is then smelted in separate furnaces to produce doré bullion in a new and expanded single gold room. Eluted carbon is regenerated in kilns and returned to the CIL circuits.