Some impressive results from a pair of advanced copper projects in Botswana have seen shares in London-based explorer
Delineation drilling at the company’s flagship Dukwe copper project, 130 km northwest of Francistown, recently yielded some high-grade copper values from the Mapanipani North lens footwall.
The northernmost hole in the recent 12-hole program yielded 9.33 metres running 3.54% copper. The company says it coincides with previously sunk hole 46BD2, which cut 9.33 metres of 6.44% copper.
The new footwall zone extends along 200 metres of strike, 300 metres vertically, and ranges between 10-30 metres in true thickness. It remains open to the north and at depth.
Meanwhile, drilling on the hanging wall returned a 14.5-metre interval of 3.49% copper. Other intersections include 2.95 metres of 6.73% copper and 3.52 metres of 5.7% copper; both are contained in a 86.6-metre section of 0.92% copper. Another 38.9-metre interval averaging 1.18% copper includes 3.05 metres of 4.57% copper.
The drilling generally tested at depths between 140 metres and 625 metres. The intervals do not represent true widths.
Drilling at the northern (69.3 metres of 1% copper) and southern (37.4 metres of 1.08% copper) ends of the lens (600 metres apart) also indicates a continuous high-grade zone surrounded by a halo of lower-grade material.
“The deepest hole in the current program cut the deposit at a depth of approximately 475 metres below surface, providing the company an opportunity to expand the Mapanipani lens,” says African Copper chief executive David Jones.
A resource estimate for the Mapanipani North zone, which measures 600 metres by 2 km, is expected shortly.
Mapanipani North is one of five continuous sections that make up the 4.4-km-long Dukwe deposit. The sections are slightly displaced along post-mineral faults. The deposit is home to an oxide reserve totalling 5.1 million tonnes grading 1.85% copper to a maximum depth of 175 metres. This reserve overlies another 13 million tonnes of inferred sulphide resources averaging 3.85% copper. The estimates employ a cutoff grade of 1.5% copper and a minimum mining width of 2 metres.
The Dukwe deposit is situated in a metamorphosed belt of Matsitama group sedimentary rocks. The steeply dipping stratabound mineralization thins toward the south. Sulphide mineralization is primarily chalcopyrite with minor pyrite. That is overlain by a chalcocite blanket measuring up to 150 metres at its thickest point. Copper oxide mineralization extends from surface to around 70 metres.
Dukwe was initially envisaged as an open pit followed by underground mining. The company is now looking at underground mining only via a twin ramp system — one ramp for a conveyor, the other for men and materials. During the initial years of operation, supergene material would be hauled to surface by truck from above the 125-metre level.
Ore would be sent to a 350-tonne-per-hour, 3-stage crushing circuit feeding a 3,000-tonne-per-day ball mill and sequential sulphide and oxide flotation circuits. The circuit is expected to spit out around 22,680 tonnes of copper-in-concentrate annually. Metallurgical testing on sulphide material indicates recoveries between 88% and 93%, yielding concentrates containing 27% to 30% copper. The recoveries exceed those expected via an originally planned heap-leach, solvent extraction-electrowinning (SX-EW).
The new plan carries an estimated price tag of around US$37.7 million. Preliminary operating costs for crushing, grinding and flotation ring in at US$10 per tonne, with another US$5 per tonne for general and administration costs. Cash costs are pegged at US65 per lb.
African Copper chief executive David Jones says the switch to underground mining and flotation concentration instead of the original open-pit, SX-EW operation would see cash flow accelerated and working capital shrink. The result would be both a quicker capital payback and higher internal rate of return.
African Copper expects all mine permits to be granted by the end of February; construction could follow as soon as the second quarter.
Dukwe produced some 100,000 tonnes of ore grading between 8% and 30% copper between 1908 and 1918. The production was derived from 12 shafts that sank to depths of 80 metres.
African Copper’s six drill rigs have now turned their attention to tracing the copper horizon at the Mapanipani and Bushman lenses to the south. A previous resource estimate at Bushman totals 2.7 million tonnes running 2.2% copper; Mapanipani contains an estimated 6.4 million tonnes averaging 2.4% copper. The global estimates were calculated in 1997 and do not employ a cutoff grade.
Meanwhile, some 70 km to the southeast, a pair of holes on the Matsitama Schist belt returned some impressive grades from the advanced Thakadu and Makala deposits. Late last year, a single hole was sunk into each deposit to confirm geology, mineralization, and copper and silver grades.
Drilling at Thakadu yielded 4.45% copper and 1.97 oz. silver per tonne over a true width of 12.74 metres, beginning 32.8 metres down-hole. Makala surrendered a 6.24-metre interval running 2.64% copper and 2.52 oz. silver, from 144.2 metres down-hole.
The results have prompted the company to update feasibility studies of the pair, which sit around 2 km apart. Historical in situ resources total 4.85 million tonnes running 2.71% copper at Thakadu-Makala. A third deposit, which saw more limited drilling, Nakalakwana, was previously estimated to contain an oxide resource amounting to 11 million tonnes grading 0.63% copper.
The primary disseminated-to-massive copper sulphide mineralization is chalcopyrite, zoning out to chalcopyrite-bornite-chalcocite to pyrite, with secondary supergene enrichment in malachite, cuprite-tenorite, chrysocolla and azurite.
Both Thakadu and Makala were tested by some 39,000 metres worth of percussion and diamond drilling in 156 holes by majors
The work resulted in the completion of four feasibility studies at various times; a fully permitted mining licence was granted over the concession in the early 1990s. A mine was never built owing to low throughput rates dictated by a lack of power, water and workers. The resulting proposed mine life ran about 20 years.
African Copper says the infrastructure and availability of workers in the area has since improved. The company plans a 3-rig drill program on the 4-km strike length of favourable stratigraphy over the next eight months, in anticipation of a new feasibility study.
Previous drilling to a vertical depth of around 550 metres returned well-mineralized material, suggesting downdip potential. Limited geophysical and geochemical surveying, trenching and mapping suggests the favourable folded stratigraphy is probably continuous between the two deposits, and that mineralization may extend up to 2 km west of Makala.
Looking ahead, the 4,000-sq.-km Matsitama licence also contains at least four large mineralized targets stretching tens of kilometres in strike length, and more than 170 untested copper and zinc anomalies.
Shares in African Copper continued their recent strong run, finishing 24, or 14% better at $1.94 in Toronto following the latest drill results on Jan. 30. The shares have more than do
ubled since the beginning of the year, and are up 85% since being listed for trade in Toronto on July 19.
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