Reporting on its Platreef project near Mokopane in Limpopo Province in its recently released 2018 full-year results and review of exploration and development activities, TSX-listed Ivanhoe Mines says that Shaft 1 reached the top of the high-grade Flatreef deposit (T1 mineralised zone) at a depth of 780,2 m below surface in Q3-2018 and has since been extended to the 850-m level with the 850-metre-level station development underway.
Construction in progress on the foundation that will support Shaft 2’s 103-m tall concrete headframe (photo: Ivanhoe).
The thickness of the mineralised reef (T1 & T2 mineralised zones) at Shaft 1 is 29 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 29-m intersection yielded approximately 3 000 tonnes of ore, estimated to contain more than 400 ounces of platinum group metals. The ore is stockpiled on surface for metallurgical sampling.
The 750-metre-level station, including the steelwork and concrete construction, was successfully completed in Q4-2018. The 750-metre-level and 850-metre-level stations will provide initial underground access to the high-grade orebody, enabling mine development to proceed during the construction of Shaft 2.
As sinking of Shaft 1 advances, one more station will be developed at a mine working depth of 950 m. Shaft 1 is expected to reach its projected final depth of 982 m below surface in early 2020. Shaft 1 ultimately will become the primary ventilation shaft during the project’s initial 4 Mt/a production case.
The Platreef’s second major shaft, Shaft 2, is to be located approximately 100 m north-east of Shaft 1. It will have an internal diameter of 10 m and will be lined with concrete and sunk to a planned, final depth of more than 1 104 m below surface. It will be equipped with two 40-tonne rock-hoisting skips capable of hoisting a total of 6 Mt/a – the single largest hoisting capacity at any mine in Africa.
The headgear for the permanent hoisting facility was designed by Murray & Roberts Cementation. Nine blasts were successfully completed in 2018 enabling the excavation of Shaft 2’s boxcut to a depth of approximately 29 m below surface and the construction of the concrete hitch (shaft collar foundation) for the 103-m tall concrete headgear that will house the shaft’s permanent hoisting facilities and support the shaft collar.
Excavation of the boxcut and construction of the hitch foundation are expected to be completed in Q2-2019, enabling the beginning of the pre-sink that will
extend 84 m below surface.
Ivanhoe plans to develop the Platreef mine in phases. The initial annual production rate of 4 Mt/a is designed to establish an operating platform to support future expansions. This is expected to be followed by a potential doubling of production to 8 Mt/a, and then a third expansion phase to a steady-state 12 Mt/a, which would establish Platreef among the largest PGM mines in the world.
The mining zones in the current Platreef mine plan occur at depths ranging from approximately 700 m to 1 200 m below surface. Shaft 2 will provide primary access to the mining zones; secondary access will be via Shaft 1. During mine production, both shafts will also serve as ventilation intakes. Three additional ventilation exhaust raises are planned to achieve steady-state production.
Planned mining methods will use highly productive, mechanised methods, including long-hole stoping and drift-and-fill mining. Each method will utilise cemented backfill for maximum ore extraction. The ore will be hauled from the stopes to a series of internal ore passes and fed to the bottom of Shaft 2, where it will be crushed and hoisted to surface.
The Platreef project is owned by Ivanplats (Pty) Ltd, which is 64 %-owned by Ivanhoe Mines. A 26 % interest is held by Ivanplats’ historically-disadvantaged, B-BBEE partners, which include 20 local host communities with approximately 150 000 people, project employees and local entrepreneurs. A Japanese consortium of ITOCHU Corporation, Japan Oil, Gas and Metals National Corporation and Japan Gas Corporation owns a 10 % interest in Ivanplats, which it acquired in two tranches for a total investment of US$290 million.