Semafo, which operates three gold operations in West Africa including the Mana gold mine commissioned in 2008, has completed phase one of the Mana plant expansion.
This expansion program was aimed at increasing plant capacity to up to 6,000 tonnes a day (tpd) in saprolite ore (soft rock). This phase of the expansion involved enhancements to the plant’s carbon-in-leach (CIL) circuit. The milling circuit was modified to allow the two ball mills to operate sequentially, thereby increasing milling capacity.
“With the successful completion of phase I, we are now focused on completing phases II and III of the Mana plant expansion,” Semafo COO Benoit Desormeaux says. “Phase II, which is aimed at increasing plant capacity to 6,000 tpd for the treatment of the hard rock portion of the deposit is scheduled for completion at the end of the second quarter of 2010. The benefits of the plant expansion are further enhanced with underground mineral resources discovered in 2009.”
Phase III will extend the leach time to accommodate the increased throughput and optimise gold recovery. The addition of two CIL tanks will increase leach time from 22 to 29 hours when processing 6,000 tpd. Completion of this phase will assure optimal gold recovery. Based on a gold price of US$1,000 per ounce, a 1% increase in recovery rate would generate an additional US$1.5 million in operating revenue.
Based on extensive metallurgical tests realised in 2009, the improvement in leach time will increase recovery by 1% to 2%. Phase III commissioning is scheduled for the end of 2010.
As of the end of 2009, Mana’s measured and indicated mineral resources were 21.6 million tonnes at an average grade of 2.3 g/t of gold for just less than 1.6 million ounces. This is an increase of 55% over the resource of just over one million ounces announced in December 2008. Inferred resources increased by 79% to 12,745,000 tonnes at 2.2 g/t for some 900,000 ounces compared to some 500,000 ounces in December 2008.
As at December 31st, 2009, the Mana mine’s mineral reserves and resources totalled 2.35 million ounces of gold, representing a 30% increase relative to the 2008 reserves and resources estimate.
“Mana’s 2009 exploration program, which began in April, added more than one million ounces to our resources estimate at a discovery cost of US$7 per ounce,” La Salle says.
Intensive exploration and definition drilling was conducted throughout 2009 exclusively proximal to the Wona pit, and particularly on the Wona Deep structure. A total of 35,011 meters of core drilling was completed on the Wona.
“When we launched the two-year exploration program in April 2009, our objective was to add between one and 1.5 million ounces to our resources,” Michel Crevier, Semafo’s geology manager and Qualified Person says.
Semafo estimates that its 2010 production at Mana will be between 170,000 and 175,000 ounces at a cash operating cost of between US$380 and US$425/oz.