The TauTona gold mine in South Africa was extended to a depth of 3.9km in 2008, making it the world’s deepest mine at that time. The name TauTona means ‘great lion’ in Setswana.
The TauTona mine exists within the West Witts area, near the town of Carletonville. TauTona neighbours the Mponeng and Savukamines, and TauTona and Savuka share processing facilities. All three are owned by AngloGold Ashanti.
Production at TauTona fell to 409,000oz in 2007, down from 474,000oz in 2006, due to increased seismic activity.
This required a review of the practice of mining of shaft pillars and high-grade remnant and delays to the build-up in volume caused by opening up of the sequential grid. Capital expenditure in Siguiri was R2.5bn ($71m) in 2007, with 56% committed to the development of ore reserve. TauTona accounted for 7% of AngloGold Ashanti’s total 2007 gold production.
The TauTona mine was put under orderly closure in 2017 and ore reserve was transferred to Mponeng mine, the infrastructure of which will access the carbon leader reef (CLR) orebody from 109 to 120 levels of TauTona’s current network as of 2020.
TauTona mine background
The mine was originally built by the Anglo-American corporation with its 2km-deep main shaft being sunk in 1957, with operations starting in 1962.
Since its construction two secondary shafts were added bringing the mine to its current depth. The mine had 800km of tunnels and employed up to 5,600 miners. It is an extremely dangerous environment, with five workers losing their lives in 2007.
The mine was so deep that temperatures in the mine can rise to dangerous levels. Air-conditioning equipment was used to cool the mine from 55°C down to a more tolerable 28°C.
The journey to the rock face required one hour from the surface level. The lift cage that transports the workers from the surface to the bottom travels at 16m a second. The mine was also featured on the MegaStructures programme produced by National Geographic.
Geology and reserves
The TauTona mine was located within the West Witts area slightly south-west of Johannesburg in the north-west of South Africa.
Two reef horizons were exploited at the West Wits operations: the Ventersdorp Contact Reef (VCR), located at the top of the Central Rand Group, and the CLR near the base. Owing to nonconformity in the VCR, the separation between the two reefs increased from east to west, from 400m to 900m. TauTona and Savuka exploit both reefs while Mponeng only mines the VCR. The structure is relatively simple with rare instances of faults greater than 70m.
The CLR consists of one or more conglomerate units and varies from several centimetres to more than 3m in thickness. Regionally, the VCR dips at approximately 21° but may vary between 5° and 50°, accompanied by changes in the thickness of the conglomerate units. Where the conglomerate has the attitude of the regional dip, it tends to be thick, well-developed and accompanied by higher gold accumulations.
The CLR, previously mined at TauTona and Savuka mines, is located within the Witwatersrand Supergroup and lies 800m below the Mponeng VCR.
Where the attitude departs significantly from the regional dip, the reef is thin, varying from several centimetres to more than 3m in thickness.
The measured resources at TauTona CLR Eastern block were 1.33Mt at 23.38g/t containing 31.09t of gold (1Moz) as of 2019. The indicated mineral resources were 1.79Mt at 22.39g/t containing 40.16t of gold (1.29Moz).
The total proved and proven ore reserves at TauTona CLR Eastern block were 1.58Mt at 8.1g/t containing 12.8t of gold (0.41Moz).
Mining and processing at TauTona
Mining operations are conducted at depths ranging from 1.8km down to 3.9km following the recent expansion.
The mine consists of the main shaft system supported by secondary and tertiary shafts. The main mining method is longwall. TauTona shares a processing plant with Savuka. The plant uses conventional milling to crush the ore and a CIP (carbon in the plant) to further treat the ore. Once the carbon has been added to the ore, it is transported to the plant at Mponeng for electro-winning, smelting and the final recovery of the gold.
Approximately 0.4Mt of total attributable tonnes treated or milled and 6.56g/t of average grade of gold was recovered in 2017.
Gold production declined by 14% to 12,714kg (409,000oz) (2006: 14,736kg (474,000oz)), owing to a higher-than-expected fall in the volumes of ore mined. This was due to increased seismic activity in the vicinity of the CLR shaft pillar, which is being mined, and at several high-grade production panels, where production was halted for limited periods during the year. Both face length and face advance were negatively affected by seismicity during the year. The increased geological risk from this seismic activity necessitated replanning regarding mine layout and mining methods.