AFRICA SPECIAL — Nevsun Resources leads pack of junior explorers in Africa

Among the most active junior companies exploring for gold in West Africa is Vancouver-based Nevsun Resources (NSU-T), which has several key projects under way.

Aggressive drilling at the Kubi concession in Ghana and the Tabakoto East concession in Mali has culminated in preliminary resource estimates in excess of 1 million oz. for each of the projects.

Nevsun ventured into West Africa in the latter part of 1993, initially optioning a 90% interest in the Kubi Village concession and a 51% interest in Tabakoto. The company’s entry into the region came after it reviewed potential acquisitions in Venezuela, which, at the time, was the focus of an extensive area play centred on the Kilometre 88 district and fueled by Placer Dome’s Las Cristinas discovery.

Nevsun instead looked to West Africa’s prolific greenstone belt, which had a proven history of gold production. The company believed the region offered much more exploration potential and a lot less competition than Venezuela.

A large portion of West Africa is underlain by metamorphosed volcano-sedimentary belts of the Birimian Supergroup, which is Early Proterozoic in age and characterized by greenstone belts of tholeiitic to calc-alkaline volcanic rocks separated by basins containing volcaniclastics, greywackes and argillic sediments.

Isoclinal folding and regional faulting are widespread. Major faults and associated shear zones often mark the transition between sedimentary and volcanic rocks. The most significant gold deposits in the Birimian are hosted by shear structures in the transition zone along the flanks of the volcanic belts.

Gold mineralization occurs as either quartz-vein type or

disseminated-sulphide type.

In Ghana, the Birimian Supergroup comprises five parallel, northeast-trending volcanic belts measuring several hundred kilometres in length.

Kubi concession

The Kubi concession covers 44 sq. km directly south, and along strike, of the Ashanti Obuasi mine concession in the Ashanti belt. BHP Minerals spent US$400,000 in 1991 on a grassroots program searching for a potentially large oxide gold deposit. One of several potential oxide and sulphide targets was drilled with 12 widely spaced holes along a strike length of 750 metres.

Based on the limited drilling, BHP estimated a preliminary oxide resource of 300,000 tonnes grading 3.3 grams gold per tonne to a depth of 55 metres. An additional sulphide resource was calculated at 122,000 tonnes grading 14.8 grams gold to a depth of 150 metres.

Nevsun felt there was potential for significant sulphide reserve expansion to depth based on other operations within the belt — in particular the Ashanti Obuasi mine, where mining is carried out at depths of up to 1,500 metres.

The first phase of drilling in 1995 initially confirmed that the mineralized zone extends over a strike length of 700 metres and to a vertical depth of 300 metres. Drilling has since intersected mineralization along a strike length of 1,800 metres and to a vertical depth from surface of 600 metres.

At the end of 1996, the zone was estimated to have a sulphide resource of 5.2 million tonnes grading 7.6 grams, based on 72 drill holes and a 3-gram cutoff. The calculation was based on a strike length of 1,300 metres, a downdip of 500 metres and an average thickness of 5 metres. Also, the estimate assumes that gold mineralization continues to a depth of 1,000 metres.

When an additional, oxide resource is taken into account (about 3.4 million tonnes grading 2.14 grams gold to a depth of 50 metres), the Kubi project is estimated to contain 1.5 million oz. of the yellow metal. It remains open in all directions, and preliminary metallurgical tests indicate that recoveries in excess of 90% are possible using simple grinding and leaching techniques.

Tabakoto property

In western Mali, Nevsun initially acquired an option to earn a 51% interest in the Tabakoto concession in the Kenieba district. The 8-sq.-km property covered a host package of Birimian metasediments with later-stage felsic intrusives. Higher-grade gold mineralization was identified in structurally controlled quartz veins.

In 1994, Nevsun completed a $400,000 program of prospecting, geological mapping, geochemical sampling and geophysical surveys.

A preliminary program of reconnaissance drilling included three holes that tested the southern end of a series of artisanal mine workings extending to the northeast onto the adjoining concession for a distance of 2 km.

The workings date to at least the early 1980s and extend to a depth of 15-20 metres, which was apparently limited by the water table.

Collared 50 metres from the property boundary, the first hole intersected 5.3 metres of 4.6 grams at a vertical depth of 40 metres and 3.5 metres of 3.7 grams at an 82-metre depth. A 50-metre stepout to the east hit 12.8 metres of 3 grams at a depth of 35 metres, including 7.2 metres grading 5.4 grams.

Nevsun acquired an option to earn an initial 51% interest in the adjoining Tabakoto East concession, which covers 8 sq. km of ground over the strike extension of this zone.

In 1995, the company increased its interest in Tabakoto East to 90% and drill-tested 1,100 metres of the 2,200-metre-long zone. The zone was identified as a north-south-trending, fault-controlled, silicified porphyritic monzonite dyke, varying in width from 5 to 40 metres. Gold mineralization occurs in native form and is associated with pyrite and arsenopyrite.

During 1996, an aggressive drill program tested the system over a strike length of 1,850 metres and to a vertical depth of 275 metres. Several high-grade, crosscutting shear structures were encountered, and preliminary drilling suggests the potential for increased grade where the structures cut across the Main zone. Further delineation drilling is planned.

Geophysical work suggests the main structure extends farther to the south and at depth. Several other crosscutting shear structures are also interpreted.

Tabakoto will soon receive a second drill rig, which will be capable of drilling to depths of 600 metres.

1.2 million oz.

The Tabakoto deposit is estimated to contain a combined, measured and indicated resource of 4.4 million tonnes grading 7.2 grams gold, based on 91 drill holes. High-grade intercepts have been cut to 60 grams, and a cutoff grade of 3 grams has been used. The measured resource is defined to a depth of 200 metres, while the indicated resource is projected to a 400-metre depth below surface.

An additional inferred resource is calculated at 2.9 million tonnes grading 2.17 grams, based on material grading between 1 and 3 grams down to 200 metres. The total contained gold at the Tabakoto project is estimated at 1.2 million oz.

Nevsun anticipates it will spend $10 million each in exploration at Kubi and Tabakoto during 1997 as it continues to advance the projects and build on the reserves.

A further $2 million is budgeted for exploration on the Gemap project in Ghana and the Kakadian project in Mali.

Nevsun holds a 75% interest in the 110-sq.-km Gemap (or Juabo) concession, situated 40 km west of Kubi in the Asankrangwa-Manso Nkwanta belt.

Geochemical sampling and shallow reverse-circulation drilling have been carried out in an attempt to test the potential of several large, coincident gold-arsenic soil and geophysical anomalies.

A preliminary program of mapping, sampling and geophysics is planned for Kakadian. In late 1995, Nevsun acquired an 80% interest in the 200-sq.-km concession, which lies 20 km west of Anglo American’s Sadiola Hill gold deposit and 70 km north-northwest of Tabakoto.

The property covers Birimian metavolcanics cut by felsic and mafic intrusives. Preliminary work has a central gold-in-soil anomaly associated with a regional, north-south-trending fault structure.

Nevsun has 22.5 million shares outstanding (or 25.1 million fully diluted) and working capital of $35 million.