Ivanhoe Mines and sinking contractor Aveng Mining have reached a new milestone at its Platreef PGM-nickel-copper-gold project in South Africa with Shaft 1 now at the top of the ‘Flatreef’ deposit, 780 m below surface.
At the Shaft 1 intersection, the flat-to-gently-dipping deposit is an estimated 26 m thick, making it amenable to the sort of bulk-scale mechanised mining most PGM operators would dream of.
This is the first time Platreef, in the Northern Limb of South Africa’s renowned Bushveld complex, has been intercepted by underground mining activity, according to Ivanhoe Mines.
The mining team has now delivered first ore from the underground mine development to a surface stockpile for metallurgical sampling. “The estimated thickness of the mineralised reef (T1 and T2 mineralised zones) at Shaft 1 is 26 m, with grades of platinum-group metals ranging up to 11 g/t 3PE (platinum, palladium and rhodium) plus gold, as well as significant quantities of nickel and copper,” the company said.
The 26 m intersection is expected to yield some 3,000 t of ore, estimated to contain more than 400 oz of PGMs.
The 750 m station on Shaft 1 will provide initial, underground access to the orebody, enabling mine development to proceed during the construction of Shaft 2 – the mine’s main production shaft.
The mining zones in the current Platreef mine plan occur at depths ranging from approximately 700 m to 1,200 m below surface.
Shaft 1’s 750 m station will also allow access for the first raisebore shaft, which will have an internal diameter of 6 m, to provide ventilation to the underground workings during the mine’s ramp-up phase.
As shaft-sinking advances, two additional shaft stations will be developed at mine-working depths of 850 m and 950 m. Shaft 1 is expected to reach its projected, final depth of 980 m below surface, complete with the stations, in early 2020.
Excavation of the Shaft 2 box cut to a depth of approximately 29 m below surface is progressing well, according to Ivanhoe.
Completion of the box cut will allow for the construction of the concrete hitch (foundation) for the 103 m-tall concrete headframe that will house the shaft’s permanent hoisting facilities and support the shaft collar.
Shaft 2, around 100 m northeast of Shaft 1, will have an internal diameter of 10 m, will be lined with concrete and sunk to a planned, final depth of 1,104 m below surface. It will be equipped with two 40 t rock-hoisting skips with a capacity to hoist a total of 6 Mt/y of ore. This is the single largest hoisting capacity at any mine in Africa, according to Ivanhoe.
Headgear for the permanent hoisting facility was designed by South Africa-based Murray & Roberts Cementation.
In July 2017, Ivanhoe issued an independent, definitive feasibility study (DFS) for Platreef covering the first phase of production at an initial mining rate of 4 Mt/y. The DFS estimated Platreef’s initial, average annual production rate would be 476,000 oz of platinum, palladium, rhodium and gold, plus 21 MIb (9,525 t) of nickel and 13 MIb (5,897 t) of copper.