The Kobada Gold Project is based on one mining permit (Kobada, No. PE 15/22) and two exploration permits (Kobada-Est, No. PR 18/957 and Faraba, No. PR 17/921), wholly owned by AGG Mali SARL, the local Malian Company, which is a 100 % owned subsidiary of AGG.
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Summary:
DEPOSIT TYPES
Three types of gold occurrences may be expected at Kobada:
• Primary lode gold mineralisation, associated with quartz veins and fault zones related to one or several Eburnean deformation phases (orogenic gold, shear zone gold or mesothermal gold deposits). Deposits of this typeoccur in the surrounding area.
• Lateritic deposits, resulting from the climatic weathering and alteration of primary deposits with diffusion of the gold into mushroom-shaped red oxidation zones (saprolite).
• Placer deposits, where the gold is associated with large angular fragments of quartz and intensely silicified pyritic rocks in alluvial sand and gravel horizons usually several metres in thickness. These fragments are derived from proximal lode deposits.
Placers are present on the Project and have been worked by artisanal miners for a long time.
The Kobada gold deposit is a quartz-carbonate veined mesothermal, orogenic gold deposit hosted within a greenstone belt. It is located in arenites affected by a geological structure that is oriented northeast along the border of an intermediate intrusive that has basic components. Mesothermal veins are formed at moderate temperature and pressure, in and along fissures or fractures in rocks. They are known for their large size and continuation to depth and, therefore, are a major source of the world’s gold production. Veins are usually less than 2 m wide and often occur in parallel sets. Typical mineralisation includes the sulphides chalcopyrite, sphalerite, galena, tetrahedrite, bornite and chalcocite. Gangue includes quartz, carbonates and pyrite.
MINERALISATION
Gold at Kobada is present in the laterite, saprolite, unaltered rock as sulphides and in quartz veins. There are also placer-style deposits in the region, although these have largely been exploited by artisanal miners. Gold mineralisation was coeval with the hydrothermal events that introduced the regionally common quartz veins. The 20° NE structures are the only regional structures that have been identified on the property, the east-west and low angle features seem to be confined to the mineralised zone in between the discrete shear zones.
Mineralisation at Kobada extends for a minimum strike of 4 km and is associated with narrow, irregular, high-angle quartz veins and with disseminated sulphides in the wall rock and vein selvages. Mineralisation occurs as free gold, whereas in sulphides mineralisation includes the occurrence of arsenopyrite, pyrite and rarely chalcopyrite. Visible gold is not common. Arsenopyrite (up to 5 mm) is localised near vein selvages and as fine-grained disseminated patches within the host rock. Pyrite occurs in finely disseminated patches within the host rocks and as euhedral crystals in the black shale, generally as traces up to 3 % by volume with up to 10 % locally in the wall rock at centimetre-scale intervals adjacent to the quartz veins.
Veins have a milky white colour and are generally discordant, with a thickness ranging from millimetric to sub-metric. Mineralised veins are narrow, high-angle quartz veins that either cross-cut another vein or the main fabric. This indicates that more than one generation of quartz veining is present, with a later phase resulting from remobilisation of gold mineralisation from an earlier hydrothermal event.
The quartz veins at the Project Area strike and dip at various orientations and angles, and three broad populations have been identified:
• 20° NE population parallel to the regional foliation: These veins are consistent between 10° NE and 35° NE, dipping between 60° and 90° E and ranging from 5 mm to 1 m in width. They are often sheared (crack and seal), strongly brecciated and cemented with iron and manganese oxides, and mylonatised in places. They are associated with lowgrade mineralisation (0 to 1 ppm Au).
• E-W population: These include strikes 45° NE to 135 °NE and are concentrated between 80° NE and 110° NE, mainly dipping at 60°to 90° N, with some dipping steeply south. They are 1 mm to 50 cm in width, pinch and swell, are relatively discontinuous and can be sigmoidal. Stockwork zones up to 3 m in width can be formed. These veins display a fracture cleavage, which is commonly stained with red iron oxides. They are often surrounded by 5 mm to 10 cm wide limonitic alteration zones that are often wider than the veins themselves. Locally, they are folded in open folds. The veins cross-cut the foliation-parallel veins and are not as intensely deformed as the latter. They are well mineralised (1 ppm Au to 17 ppm Au within the mineralised envelope). These veins may have formed as extensional fractures and/or Riedel shears in the Kobada Shear Zone, with a possible dextral (right lateral) shear sense.
• Sub-horizontal population: These veins display dips ranging from 0° to 30°, with varying strike directions. The veins vary from 1 mm to 10 cm in thickness and often occur as stockworks and ladder vein systems. They can form long continuous crosscutting features and are moderately mineralised (1 ppm to 2 ppm Au within the mineralised envelope) with barren stockwork zones.
Production
The Kobada Gold Project, when completed, will produce 100 000 oz/a of gold via a conventional gravity carbon-in-leach (CIL) process designed to treat 3 Mt/a of run of mine (ROM) for the first 10 years of production, followed by low gold production as a result of treating low grade ore.
| Commodity | Product | Units | Avg. Annual | LOM |
|
Gold
|
Payable metal
|
koz
| | 1,201 |
|
Gold
|
Metal in doré
|
koz
| 100 | 1,202 |