Mining Plus visited the site on 6 and 7 June 2022 and can confirm the deposit type as described in Woodman and van Osta (Woodman, 2007). They describe the principal deposit at Diba and Diba NW as analogous to the Sadiola Gold Mine, located 20km north of the Diba & Lakanfla project. However, the Sadiola deposit occurs in rocks assigned to the Kofi Formation, whereas the Diba discovery occurs in rocks assigned to the Kéniébandi Formation. Until the discovery at Diba, no significant gold deposits had been recognized in the Kéniébandi Formation of western Mali.

Common features of the orogenic gold deposits in the Kéniéba-Kédougou inlier are their shear-hosted character, the intimate association of the gold mineralization with permeable lithologies and fractured host rocks, producing stratabound mineralized bodies, and the link between gold mineralization and carbonatisation and Fe-rich alteration.

The source of orogenic gold has been strongly debated. In particular, the composition and source of hydrothermal fluids that sourced the gold mineralizationin Mali had been poorly studied until very recently. Simon and Pizarro (Simon, 2013)reviewed a detailed geological study at Loulo, which included fluid-inclusion investigations, and determined that low-salinity, reduced, CO2-rich metamorphic fluids were associated with gold mineralization at Loulo, which is consistent with many orogenic gold fluid studies worldwide. The geological study considered the hyper-saline fluid as being related to a magmatic source, and its presence points to the potential role of multi-fluid sources in the formation of orogenic gold deposits. Gold precipitation may be, therefore, linked to fluid mixing between metamorphic and magmatic fluids, thus increasing metal fertility and leading to the formation of world-class orogenic gold deposits

Diba
Gold mineralisation modelled at Diba extends over an area measuring 700m x 700m. Anomalous gold at theDiba / Korali Sud property extends over 2.5km north –south (Woodman, 2007), and is defined as auger sample values >0.1g/t Au.

No sulphide or gold mineralisation has been intersected in the Lower Calcareous Sequence (LCS). Gold mineralisation is strata-bound and constrained to the Upper Calcareous Sequence (UCS). The sulphide content of the mineralised lenses is typically less than 10% by volume, and commonly as little as 1%. Disseminated sulphides are fine-to very-fine grained, and consist dominantly of pyrite, with a minor amount of arsenopyrite, chalcopyrite, tellurides and native gold.

Calcite is a ubiquitous constituent of the rocks at Diba, typically 5 -20% of the overall mineralogical composition. The mineralized dark-grey siltstone is strongly reactive to hydrochloric acid. Calcite also often occurs in veinlets and irregular pockets. The distribution of pyrite relative to calcite is inconsistent, but sometimes pyrite develops marginal to calcite crystals. Associated veinlets consist of millimetre-thick bedding-parallel veinlets of pyrite with subordinate amounts of calcite-quartz-biotite.

According to the report by Simon and Pizarro (2013), gold mineralisation in the Property is represented by native gold and calaverite within graphite, biotite and quartz-bearing silicates, and by native gold as inclusions in carbonates. Grain sizes vary between 3 -100 µm, and all are believed to have formed during hydrothermal processes. The absence of silver in calaverite would suggest moderate to high temperature of crystallization.

Simon and Pizarro (2013)also reported native gold in biotite-altered domains that contain aggregates of fine-grained titanite and rutile, as a rim on epidote, as minute inclusions in recrystallized feldspars of a sericite+biotite-altered siltstone. The strong association of gold with biotite, sericite and carbonate suggests its mobilisation and concentration during hydrothermal processes. No visual guides for determining the presence of mineralisation in the drill holes have been identified. The depositis characterized by an Au+Ag+As+Te±Sb geochemical signature.

Based on the continuity of mineralised zones >0.3g/t Au, and the interpretation of the mineralisation as sediment-hosted, disseminated epigenetic deposit, Mining Plus modelled the zones of the deposit as a series of 8 stacked lenses. These were given restricted continuity along strike and at depth.

The mineralised units extend horizontally over a 700m x 700m area, and the mineralised bodies are usually shallow-dipping (30 degrees east –ESE) and generally 20 –40m thick. The spatial distribution of the gold grades dipping approx. 30oESE supports the interpretation of the stacked lenses modelled with the grade shells.

Lakanfla
Most of the Lakanfla property is underlain by a tightly-folded sequence of (a) calcareous metapelites, meta-arenites and meta-greywacke and (b) impure carbonate rocks (marble) interbedded with carbonaceous meta-argillite and minor metasiltstone/wacke. A 2 km2, composite granite- granodiorite intrusion, elongated NE-SW, lies roughly at the centre of the explored area.

The general fabric of the sedimentary rocks (S0/S2) is steep and strikes in a north- to NNE direction; attitude varies locally however, particularly near the granite contact. Minor intrusive rocks observed at Lakanfla include pre-mineral metadiorite dykes associated with gold bearing structures such as Lakanfla West Prospect, and post-mineral microdiorite and fine-grained “volcanic” or aplite dykes that crosscut Lakanfla Central. Dolerite dykes striking 015°are the youngest rocks on the project. The southwestern edge of the extensive Taoudenni Basin, comprising Neo-Proterozoic to Phanerozoic sedimentary rocks, lies 6 km east of the Lakanfla licence boundary.

Lakanfla Central is hosted exclusively in massive, medium- to coarse-grained granite and granodiorite. Mineralisation occurs in two styles; firstly, in a wide, NE striking, steeply-dipping body of disseminated mineralisation. This orderly, disseminated orebody has a strike length of approximately 650 m and an approximate width of 140 m, with consistent lower grade typically between 0.5 g/t Au to 1 g/t Au. Mineralisation is thought to be controlled by subvertical, NE- striking brittle-ductile faults and barren dykes. In some instances, the faults are mineralised (with quartz-sulphide veinlets) and are characterized by higher gold grades, typically above 3g/t Au over 1-2 metres.

The pit optimisation was completed based on a selling price of USD$1,750/oz Au.

Pit shell selection was performed for mine design and planning. At Diba Pit 99 with a profit factor of 100% was selected. At Lakanfla Pit 57 was chosen with a profit factor of 83%.

Tonnage of PMI content inside the selected Diba pit shell includes 6,080 kt of PMI with an average grade of 1.22 g/t of Au and includes a stripping ratio (waste:PMI) of 1.04. Lakanfla pit shell includes 3,420 kt of PMI with an average grade of 0.70 g/t of Au and includes a stripping ratio (waste:PMI) of 0.99.

A conceptual mine design has been completed based on the optimal pit shell generated, assuming the use of rigid off road trucks with ~100t tray capacity. The pit design was prepared using a minimum mining width of 30m with a ramp width of 16m single lane; 25m dual lane and 10% gradient. Face angles used are 50° for the oxide zone, 60° for the transitional and 65° for the fresh rock zone.

The mining plan requires limited initial waste stripping using a PC1250-8 and a CAT365 excavator. Mining would be via conventional open-pit methods (drilling, blasting, loading, haulage and ancillary services). It is expected that oxide material is free dig and will not require blasting, however a blasting cost has been applied to 15% of oxide tonnage in case of any difficult ground. The use of a mining contractor for earth movement has been assumed for both mine plans

Mine Scheduling targets the mining of PMI with the highest grade in the first months with the aim being to maximize the NPV for the project.

The life of mine (LOM) is 56 months or 4.7 years.

Considering the anticipated production rates the use of Komatsu HD785-7 (or similar) trucks has been forecast.

The parameters used for drill and blast consider different blast patterns depending on the rock characteristics. Blast patterns of 3.2m x 4.3m for the oxide zone, 3.2m x 3.7m for the transitional zone and for the fresh zone a blast pattern of 2.8m x 3.2m were assumed.

For loading waste material a PC1250SP-8 excavator (or similar) will load 91t rigid dump trucks. With a 6.7m3 bucket capacity, ten passes are required to fill each truck. For loading ore material a CAT 365 excavator (or similar) will load 91t rigid dump trucks. With a 4.6m3 bucket capacity, 16 passes are required to fill each truck.

Conceptual mine design, production planning, operating and capital cost estimates have been developed for an open-pit operation.

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The proposed conceptual heap leaching system is similar to existing and operating heap leach mines processing similar material under comparable conditions. The processing facilities proposed for the Diba project include:
• Two-stage crushing, screening, and agglomeration;
• Heap stacking and leaching;
• Gold recovery by Carbon-in-Column processing.

The processing plant concept is based on a typical metallurgical flowsheet for the production of gold doré at optimum recovery while minimizing initial capital expenditure and operating costs.

The heap leach concept envisages processing of 2.0 million tpa of oxide material, equivalent to a throughput rate of approximately 4,100 t/d. The crushing, leaching and gold recovery will operate 24 hours per day, seven days per week. The stacked material on the heap leach pad will be leached continuously all year-round.

The process for the extraction of gold from the Diba & Lakanfla project oxide materia ........