Mowana Mine moves to increase production

| Monday March 1, 2010 00:00

Newswire Bloomberg reports that African Copper will install a mobile crushing unit and amend its environmental management plan at its Mowana mine to remove bottlenecks hampering the ramp-up to full capacity.

African Copper reopened its Mowana mine in August 2009, following a bail-out by JSE-listed company Zambia Copper Investments. With the bail-out, the company reached encouraging levels of production in October and November 2009, but lower plant availability affected output in December and January.

Copper and processed ore recoveries increased in October and November 2009, reaching 57,3 percent in November, in line with the company's targeted recovery rate of 57 percent, before declining again. This was caused by high crusher liner wear and heavy rain that adversely affected the consistency of the ore and hindered the flow of material from stockpiles.

The plant produced 4,3 t of concentrate, at an average grade of 1,30% copper for 1,19 t of copper contained in concentrate, from the time it was recommissioned in late August, 2009.

The Mowana mine lies within a palaeoproterozoic sedimentary basin of the Southern African shield. The Dukwe deposit is an epigenetic quartz-carbonate vein-hosted copper deposit. The mineralisation lies within a near vertically dipping, extensive belt of the early proterozoic matsitama supergroup metasedimentary rocks and is enclosed by sheared granite gneisses and granites within the broader structural domain of the Bushman lineament.

The primary sulphide consists of chalcopyrite mineralisation within a complex assembly of quartz-calcite veins, breccias and carbonaceous calcareous sedi- ments developed within a limestone horizon of the matsitama group sediments. The near-surface parts of this zone have been enriched in a supergene blanket, while the parts closest to surface have been oxidised with the development of copper-carbonates and copper-oxide minerals.

The near-surface tenor of the orebody at Mowana is characterised by the mixed nature of oxide and supergene enrichment extending from the surface to a maximum depth of about 70 m. With increasing depth, supergene chalcocite mineralisation continues and dominates with a nominal transition to chalcopyrite-bearing hypogene mineralisation at about 150 m below the surface.

The process plant at Mowana is standard flotation process technology and has been designed to produce saleable copper concentrates from the treatment of about one-million tons a year of oxide, supergene and sulphide ores.

The process plant has two flotation circuits. Sulphide minerals are separated first and tailings from the sulphide roughers are sent to an oxide circuit. Most other mineral species are recovered in the oxide flotation pro-cess.

Concentrates are filtered to recover excess process water, as are tailings, where they are dry-stacked. The water recovered in the dewatering stages will be recycled to the various parts of the plant as process water.-(Miningweekly)