Nevsun expands gold deposit in Mali

Nevsun Resources (NSU-T) has boosted its resource estimate by 29% at the Tabakoto gold project in western Mali.

The estimate is based on 250 diamond drill holes and 382 reverse-circulation holes. A cutoff grade of 0.5 gram gold was used for surface oxide material; 3 grams for the sulphide portion. The primary mineralization weighs in at 5.6 million tonnes grading 7.46 grams gold per tonne, equivalent to 1.3 million contained ounces. The oxide portion contains 500,000 tonnes of material grading 1.84 grams, equivalent to 32,000 contained ounces.

The total indicated resource, which includes oxide and primary material, is reported to be 6.1 million tonnes grading 6.99 grams gold, or 1.4 million contained ounces.

An additional inferred resource is pegged at 2.1 million tonnes grading 7.64 grams gold, or 505,000 contained ounces.

Mineralization has been tested to a depth of about 700 metres, though the resource estimates are based on drilling to a depth of only 380 metres. The deposit remains open at depth and along strike to the north.

Metallurgical tests indicate the gold is non-refractory, with high recoveries. “We expect our milling operation will get 50-60% recovery by gravity methods, and we will be in the 90-plus percentile when it comes to gravity plus cyanidation,” says Nevsun’s president, John Clark.

The deposit, which occupies the 8-sq.-km Tabakoto East concession, strikes in a north-south direction. Exploration has delineated a mineralized structure with a strike length of 2,200 metres.

The gold is hosted in a narrow swarm of sub-vertical, feldspar porphyry dykes that have invaded a sequence of greywacke and shale. Mineralization occurs in tensional fractures and in fault gouge within, and along, the margins of the porphyry dykes.

Occasionally, silicified sediments near the intrusions are also mineralized. The dyke zones are crosscut by high-grade quartz stringers; the gold is found as coarse free grains and in the sulphide minerals.

Weathering has produced a 50-to-70-metre-thick laterite zone. On top of the laterite, an alluvial cap, about 10-to-12 metres deep, stretches over the entire length of the Tabakoto deposit. Clark says the alluvial cap is difficult to model and was not included in the resource estimate.

In related news, Nevsun has delayed the closing of a deal with Trillion Resources (TLQ-T) and Oliver Gold (OGO-V) to acquire the adjacent Segala property.

Nevsun has 23.4 million shares outstanding and working capital of $10 million.