The 2012 measured and indicated resources average grade increased by 15% to 1.89 g/t Au for a total 4.2 million ounces as compared to 4.7 million ounces in 2011. The decrease in resources is due to the Samira Hill revision as well as the removal of most of the refractory sulphide material from the south sector deposits (Yaho, Fofina and Fobiri), which was uneconomical according to various metallurgical tests conducted during the year. The 2012 measured, indicated and inferred resources in Mana's south sector are mainly composed of oxide and transitional mineralization and are not refractory.
Total inferred resources amounted to 36.3 million tonnes at an average grade of 2.57 g/t Au for 3.0 million ounces as compared to 61.4 million tonnes at 1.51 g/t Au for 3.0 million ounces in 2011. A slight gain in inferred resource ounces and the 89% increase in grade, despite the removal of the majority of the refractory sulphide material from the 2012 inferred resources are due to the inclusion of the initial in-pit inferred resources from the high-grade Siou Zone. Discovered in August 2012, Siou hosts 6.7 million tonnes at 4.62 g/t Au for close to one million ounces.
Our Flagship Mana Mine, Burkina Faso
-- Mana's reserves totalled 1.9 million ounces-- Mana's measured and indicated resources increased by 8% to 3.0 million ounces and the average grade increased by 14% to 1.93 g/t Au-- The Wona-Kona super pit reserves stand at 1.6 million ounces at an average grade of 2.21 g/t Au-- Mana's inferred resources' average grade increased by 89% to 3.18 g/t Au resulting from the addition of the Siou Zone initial in-pit inferred resources of 999,200 ounces, bringing total inferred resources to 18.3 million tonnes at an average grade of 3.18 g/t Au for 1.9 million ounces.
Mana's mineral reserves total 25.1 million tonnes at an average grade of 2.31 g/t Au at year-end 2012 compared to 25.7 million tonnes at an average grade of 2.40 g/t Au in 2011.
Total measured and indicated mineral resources at Mana increased by 8% in 2012 to 48.6 million tonnes at an average grade of 1.93 g/t Au, representing 3.0 million ounces. This compares to 51.4 million tonnes at an average grade of 1.69 g/t Au for 2.8 million ounces at the end of 2011. The slight increase in ounces, despite the removal of the majority of the refractory sulphide material in the south sector is due to the higher grade material at Kona at depth and the inclusion of the high-grade mineralization from the Fofina Zone.
Mana's 2012 inferred resources totalled 18.3 million tonnes at a grade of 3.18 g/t Au, representing 1.9 million ounces as at December 31, 2012. The higher grade is due to the inclusion of the initial in-pit resources of our high-grade Siou Sector discovered in August 2012, representing 6.7 million tonnes at a grade of 4.62 g/t Au. The decrease of the overall inferred tonnage, despite of a higher resource grade is due to the removal of most of the inferred refractory sulphide resources from the south sector deposits (Yaho, Fofina and Fobiri).
In 2012, metallurgical tests showed that the sulphide portions for the Fofina, Fobiri and Yaho deposits had low recoveries (20% to 48%) with CIL treatment. Consequently, SEMAFO decided to investigate other process routes such as sulphide flotation, sulphide concentrate regrinding and ultimately oxidation to seek better gold recoveries. Although a combination of ultrafine grinding followed by oxidation at Fofina significantly improved recoveries to 88%, the tests also indicate that the capital expenditures and consumable costs required to achieve optimal results are not justified at current gold prices.