Журнал геологии и геофизики
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Evaluation of Placer Gold Deposit in Kenieba District, Kaye Region, Mali: A Case Study from West-Sanoukou Village

Elzien M Siddig*, S Osama, EM Abdelrhman, MB Osman, T Mohamed, F Sadig, AB Elhag

The upper crust of the Sanoukou area, Kenieba district in the southwest parts of Mali are well known for the placer gold occurrences. The extraction of the gold by using primitive tools has been practiced since long period in the region. However, mining of placer gold in Mali has not been given due consideration so far. The study of the placer deposit of Sanoukou stream terrace has, therefore, been carried out to determine the mineralogy their texture, size and shape of these placer deposits, which help in investigation the source rock for gold and also to design methods for the extraction of placer gold in more economic manner. Placer deposits result from weathering and release of the gold from lode deposits, transportation of the gold, and concentration of the gold dominantly in stream gravels which composed mainly of laterite-gravels with clay cemented. Unless preserved by burial, a placer subsequently may be eroded, and either dispersed or re-concentrated.

The estimation of mineral resources/reserves together with a quantification of the distribution of metallurgical attributes provide strong evaluation of the large alluvial gold deposits within west Sanoukou and its surrounding, which occurs along the flank of the stream. This reduces the risk arising from uncertainties within the ore body as far as geological and metallurgical information are concern and also improve decision making processing during the production stage of the mining project.

Hand-dug pits data formed the basis for the estimation of the source as well as the determination of the spatial distribution of the metallurgical parameters of the west Sanoukou gold deposits. A typical grid density of 50 m × 50 m was used for the pitting between 2 m to 7 m depth. Detailed logging of pit samples together with processing provided first-hand information concerning the metallurgical behaviour of the gold bearing gravels and subsequent distribution of these parameters. The estimation of the mineral sources have been based on an initial estimation of the gold grade and gravel section using the Inverse Distance Weighting (IDW) technique and subsequent estimation of the sources using the volume and mean grade of the ore. A total volume of 448,672 m³/717875 tones gold bearing gravels were estimated at average grade of 0.1675 g/t and 120,244 grams of the alluvial gold within the area of 600 m × 300 m. With 92% purity of gold so the estimate resource will be 110,624.538 g equal 3,539.71439 oz.

The gold within the study area are usually fine in nature with majority of the fine to medium gold occurring at the upstream of the drainage in the area. Clayey materials also represent large portion of the gold bearing gravels in almost all the sampled area.