Tulawaka Gold Mine, Tanzania
Tulawaka Gold Mine is situated 160km south-west of Mwanza in the western part of the Lake Victoria Goldfield, in the United Republic of Tanzania. The mine is owned 70% by African Barrick Gold (ABG) and 30% by Canada-based MDN Northern Mining.
ABG is the operator of the mine. The property lies in the Biharamulo district (Kagera Region) license area and has a surface area of 317km².
The mine consists of two ore bodies, which include the East and West Zones. Exploration and drilling activities at the east zone extended the mine's life from 2011 to mid 2013.
Commercial mining at the Tanzania mine
MDN commenced commercial production at the Tulawaka mine in March 2005. The mine produced 60,134oz of gold with a 93.2% recovery rate in 2010. The production in 2011 stood at 84,101oz of gold, a rise of 40% over 2010, with an overall recovery rate of 95.1% driven by high graded stockpiles and large mill recoveries.
Geology, reserves and mineralisation of the Tulawaka gold mine area
Tulawaka gold mine lies in the western Rwamagaza greenstone belt with mineralisation hosted in a regional northwesterly striking Ushirombo shear zone.
The east zone is hosted in dominantly volcanogenic tuffaceous rock and bedded terrigenous sediment with small layers of silicate iron formations. Six different mineralised areas were identified through geological studies of the mine.
Proven and probable reserves at the mine as of December 2011 stand at 237,000t graded at 12.02g/t Au, which is equivalent to 91,000oz of Au.
Gold mineralisation at the east zone occurs within quartz - tourmaline veins and minor sulphides within a 30m to 80m shear structure. The gold deposits are spread laterally at a depth of 100m. The mineralisation extends to a strike length of 1.1km. The east zone is highly mineralised compared to the west zone.
The gold deposits in the west zone are hosted within a sheared felsic intrusive. The gold is consociated with distributed sulphides, periodic quartz stringers and narrow veins. Mineralisation is open in all directions and spans to a strike length of 750m.
Mining at ABG and MDN Northern Mining's Tulawaka east and west zones
The Tulawaka gold mine was initially developed as an open-pit operation in 2005. The east zone deposit was mined by the Tanzania-based company Caspian through an open-pit method. It was converted to underground mining operation in 2008.
The mine comprises of a dessert open-pit, an underground access ramp at the rear of the pit, waste rock dumps, an ore stockpile area, crushing plant, a processing plant and wastewater treatment and appurtenant facilities. The infrastructure being used for mining includes Komatsu shovels, loaders, dozers and haul trucks.
Drilling is continuing to further extend mineralisation. As of July 2012, around 73 holes were drilled to a total depth of 9,251m. A second underground portal is being built to improve accessibility for mining and drilling platforms.
Processing plant and methods at the United Republic of Tanzania gold mine
The processing plant at the Tulawaka mine can process 1,480 tons a day (tpd) of ore.
The run of mine (ROM) ore stockpiled is crushed to high degree of fineness by using a primary jaw crusher. The crushed ore is transferred to a single stage semi autogeneous grinder (SAG) mill for grinding.
The ground ore is fed to the FFE liners, Knelson concentrators, a Gekko intensive leach reactor and electrowinning circuit to retrieve approximately 50% to 70% of the gold. The remaining gold is treated through carbon-in-leach (CIL) technology.
In the CIL method, the ground ore is transferred to cyanide leach tanks to generate pregnant solution. The solution is fed to a series of carbon adsorption agitated tanks where the gold sticks to the surface of the carbon. The gold bearing carbon is poured into a heated sodium hydroxide-cyanide-water solution to detach the gold precipitates from carbon.
The gold precipitates are washed with high pressure sprays, dried and melted at the smelter or refinery to produce pure gold dore bars or ingots for export. The solution is transferred to the tails thickener to recycle water for the processing plant.