AFRICA SPECIAL — Ghana’s Asankrangwa belt offers gold mining potential

Well to the west of Ghana’s principal gold region, the Asankrangwa greenstone belt is often overshadowed by its neighbors. Although the area has limited placer production and only one hard-rock mine, small-scale mining could yet lead to quality gold prospects.

The regional setting of these prospects differs from large gold deposits such as Ashanti, Prestea and Bibiani, all of which are clustered near major, northeast-striking structural breaks that form the boundary between the Lower and Upper Birimian greenstones. A similar fault zone has not been mapped in the Asankrangwa belt, and the rocks are all believed to belong to the older series of greenstones.

The belt’s gold showings, however, occur along a northeast-trending line that conceivably marks a similar feature, and some grassroots properties there are starting to show potential.

The Stenpad property, held by Golden Rule Resources (GNU-T) and Hixon Gold Resources (HXG-V), has attracted the most attention. While results are in hand from five trenches, it is nonetheless too soon to start talking about ounces.

Quartz veins

Stenpad is 70 km west of Obuasi, site of Ashanti Goldfields’ (AHD.U-T) main Ashanti mine. That operation is near the middle of the Asankrangwa belt, a Lower Birimian greenstone belt about 2 billion years old. Gold deposits in the area are in quartz vein structures that have typically developed in shear zones.

Stenpad, however, does have an inviting surface; and Golden Rule and Hixon have trenched two prospects, called Agykra and Seidu. At Agykra, the two initial trenches were hand-dug across the vein structure about 31 metres apart along strike. The trenches returned 27.5 grams gold per tonne over 12.4 metres, and 16 grams over 13.6 metres.

Golden Rule has now dug an extension of the first trench, which has an average grade of 8.8 grams over 100 metres. The mineralization remains open: samples taken from each end of the trench grade 20.9 grams and 19 grams.

The first two trenches at the Seidu prospect, about 2 km to the southwest, were dug 200 metres apart and returned average grades of 54.4 grams over 19.3 metres and 7.3 grams over 14.3 metres. A third trench, 87 metres long, was dug halfway between the first two and averaged 15.9 grams over its length.

The gold values in any one trench, however, vary greatly from sample to sample — from fractions of a gram to as high as 51 grams (over 1 metre) at Agykra and 107 grams (over 1.5 metres) at Seidu.

Golden Rule’s next move will be to use a backhoe for quicker trenching. A reconnaissance-scale soil survey, with 50-metre sample intervals on lines 400 metres apart, is already complete. Once additional trenching is complete, Golden Rule expects to select a series of drill targets.

Both prospects on the property are gold-bearing quartz veins exposed at surface. At Agykra, soil geochemistry around old prospect pits revealed a 40-by-350-metre zone of high gold content, and, at Seidu, a vein about 5 metres wide and 150 metres along strike is surrounded by a zone of geochemically anomalous soils 200 metres long.

Exploration strategy

Hixon started investigating property acquisitions in Ghana in early 1996, ultimately making a series of deals with privately owned Ghanam Resources in April and May of that year. Golden Rule fronted the money to acquire the ground and is acting as operator. The companies are concentrating on identifying exploration concessions with past prospecting activity and small-scale mining. With a number of old workings on site, combined with recent small-scale operations, the Stenpad concession fits this mold.

Hixon and Golden Rule have also begun exploring the 83-sq.-km Fredag concession, about 6 km from Stenpad, where similar small-scale mining has been conducted. The two companies also hold the Tinso prospecting concession in the Tarkwa area, about 110 km southwest of Obuasi. The 5-sq.-km concession covers a contact zone

between Upper Birimian phyllite and younger Tarkwaian quartzite. The property’s Essaman mine was in production from 1889 to 1915, during which time it produced more than 200,000 oz. gold.

South of Stenpad, Opawica Explorations (OPW-T) holds the 373-sq.-km Asankrangwa concession, where Ashanti recently finished a 12-hole program of reverse-circulation drilling. Assays for only four holes have been released, the highest grade being 1.4 grams over 2 metres. The company is awaiting more results from Ashanti, which needs to complete the program to earn a 60% interest. If Ashanti drops out of the project, Opawica will retain a 100% interest.

On the Gemap concession, east of Stenpad and north of Asankrangwa, Nevsun Resources (NSU-V) has drilled some shallow reverse-circulation holes for a reconnaissance soil geochemistry survey, and is interpreting the results to select targets for detailed exploration.