Although best known for its Tabakoto-Segala gold projects in the Kenieba district of Mali,
Plans call for at least 20,000 metres of diamond drilling on the gold-copper-zinc volcanogenic massive sulphide deposit. Two diamond drills are turning and will be joined soon by a reverse-circulation rig that will bring the combined drill program to a total of 30,000 metres.
Nevsun’s main focus is infill drilling of the Bisha Main and NW zone deposits for the purpose of completing an independent resource estimate this spring. Several exploration targets in the Bisha project area will also be drill-tested, and some work is planned for the nearby Okreb and Augaro projects.
Nevsun began assembling properties in Eritrea in 1997, after the resource-rich, yet under-explored, East African nation made efforts to attract mining investment with a competitive mining code.
The Bisha project is owned 90% by Nevsun and 10% by the Eritrean government. An underlying 1.5% net smelter return royalty is also payable upon production.
Nevsun President John Clarke says the company is pleased by its progress at Bisha. “The overall aim of the current program is to bring the property to commercial production in as short a time frame as possible,” he says.
Clarke expects the first stages of production to come from the surface gold-bearing oxides and underlying, near-surface supergene copper sulphides of the Bisha Main deposit.
“These could in turn provide future funding for the mining of the copper and zinc-bearing primary sulphides,” Clarke adds.
To date, 146 diamond drill holes totaling 19,181 metres have been drilled at Bisha. The Bisha Main zone has been tested over a strike length of 1,100 metres, with massive sulphide mineralization intersected to a vertical depth of 225 metres.
Oxidation of the primary massive sulphides has developed a gold-enriched oxide layer that extends from surface to a typical depth of 35 metres. This overlies a further 30 metres of supergene copper-enriched massive sulphides. Nevsun says “very significant copper and high-grade zinc zones” have been recognized within the underlying primary massive sulphides.
The company is encouraged by several recent drill holes that indicate the base metal component of the southern portion of the Bisha Main deposit is increasing in width and is open at depths beyond 200 metres vertical.
Hole B-121, for example, returned 66.6 metres averaging 9.1% zinc and 0.94% copper, whereas Hole B-117 returned 81.9 metres averaging 1.62% copper and 3.05% zinc. Both intersections also returned significant precious metal credits. No surprise, then, that some of this year’s drilling will test the downdip extent of the deposit.
Previous drilling of the NW zone revealed the presence of significant gold values associated with disseminated sulphides that are proximal to the main NW massive sulphide zones. Results from this work include Hole B-75, which returned 14 grams gold per tonne over 15 metres, and hole B-70, which averaged 14.3 grams over 3 metres. Another mineralized zone, to the west, returned 7.3 grams over 4.3 metres and 6.7 grams over 4.5 metres. More drilling is planned for these zones.
Preliminary metallurgical tests are being carried out on the primary massive-sulphide mineralization to determine if it is amenable to conventional processing methods. Past metallurgical work focused only on the oxide gold and supergene copper mineralized zones.
While crews advance the main targets at Bisha, Nevsun sees potential for additional significant discoveries at its surrounding land package in Eritrea.
The results of geophysical surveys (gravity and electromagnetic) and soil sampling on the southern end of the Bisha Main deposit reveal coincident anomalies for at least 2 km from the last drilling in this area.
The gravity survey will be extended farther south to cover the continuing EM anomaly. Exploration drilling will also test these anomalies, with a view toward expanding the mineralized zone to the south.
Nevsun’s structural interpretations suggest the southern portion of the Bisha Main and NW zones may be directly related though displaced by later faulting. A newly defined anomaly, 1.6 km southeast of the Bisha Main zone, appears to be related to a portion of the Bisha Main deposit.
Meanwhile, in Mali, Nevsun has acquired rights to explore for diamonds on a permit that surrounds and includes its Tabakoto and Segala permits. Large alluvial diamonds of up to 232 carats have been found in the region, which is known to host 24 kimberlite occurrences.
Nevsun says initial heavy-mineral indicator work has returned “encouraging results,” with one microdiamond found in stream sediments.
Nevsun is also continuing work at the Tabakoto gold project with the intention of starting production in 2005. At year-end, the Vancouver-based mining company had 73.8 million shares outstanding and $80.5 million in its treasury.
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