Mexivada Mining Corporation has reported the discovery of a new area of potentially large volume, disseminated gold mineralisation at Ngouaka, on the company’s Malambani concession in the Mayoko greenstone belt in the Republic of Congo (Brazzaville).
The area was mined for coarse alluvial gold during the 1950s and local miners are washing 0.5 – 1.0 g/m3 recovered grades of gold from residual bedrock exposures. Medium-size gold (0.2 -1.3 mm), approximately equivalent in grade to 1.22 g/t gold, was recovered from 45 to 410 litre bulk samples from five sites at Ngouaka, and soil geochemistry reveals that the strongest anomaly occurs 140 m west of the prospect, defining a large target area. The Ngouaka area could be ready for drilling later this year. A new drilling contractor has contacted Mexivada and has drill rigs available in the Republic of Congo.
Mexivada, through its wholly-owned subsidiary in the Republic of Congo, Compagnie Minière du Chaillu, was awarded four Phase 1 prospecting permits covering 9,156 km2 and three exclusive, Phase 2 concessions for raw diamonds, gold and connected substances within a 2,970 km2 area in the Chaillu Massif, centred on the Mayoko greenstone belt, a past producer of alluvial gold and gem diamonds. The three-year exclusive permits were signed on April 3, 2008 by the president of the Republic of Congo, Denis Sassou N’Guesso.
The Mexivada properties are located in the south-western part of the Republic of Congo, adjacent to and near the border with Gabon, 280 kilometres northeast of the oil port city of Pointe Noire and 370 kilometres northwest of the capital city of Brazzaville. The permit areas lie in the Chaillu Massif, an uplifted domal area that contains a sheared, mineralised, eight by greater than 23 kilometre long, north-easterlytrending Mayoko greenstone belt enclosed by younger Archean granitic rocks.
Alluvial gold and diamonds were produced from four regions in the permit areas. The Mayoko target area yielded mine production of 1,047 kilograms of gold between 1945 and 1962, mined by the Avoine company. The largest gold nugget found in the operation was approximately one kilogram in weight, with others mined ranging in weight between 10 and 70 grams, according to Avoine’s production superintendent who Mexivada interviewed in 1995. Such large nuggets could be indicative of a lode gold deposit at depth, such as occurred at Boddington, Australia. Artisanal mining of gold continues in the Mayoko area today, with upwards of 50 orpailleurs extracting alluvial gold from the area. Local very rich accumulations of alluvial gold are present here, including the ‘Coke Bottle Zone’, where local prospectors filled up Coca Cola bottles with alluvial gold particles. Mexivada’s geologists have told management that a substantial resource of highgrade alluvial gold appears to be present at Mayoko, despite the mining by Avoine.
At least four types of lode gold deposits have been recognised to date by Mexivada in the greenstone belt sequence at Mayoko. These include shear zone hosted gold-quartz veins, BIF-hosted gold systems, Archean age Witwatersrand-type metaconglomerate gold-hosted alluvial gold-diamond mineralisation, and bismuth-rich gold mineralisation that potentially could be of intrusiverelated gold. These gold deposit types may be superimposed atop of each other in the core of the greenstone belt, opening the possibility for discovery of openpittable, hybrid, higher-grade gold systems of world class size at Mayoko.