Modern Mining

Reporting on its Platreef project near Mokopane in its financial results for the year ended 31 December 2017, TSX-listed Ivanhoe Mines says sinking of the project’s Shaft 1 had reached a depth of 584 m at the end of December 2017 and had further advanced to 711 m by 19 March this year.

Platreef project powers ahead

Excavation of a boxcut is now underway for Shaft 2 (photo: Ivanhoe).

The shaft is expected to intersect the upper contact of the Flatreef deposit (T1 mineralised zone), at an approximate shaft depth of 783 m, during the third quarter of this year. The grade for the T1 mineralised zone at this location is 4,83 g/t of 3PE (platinum, palladium and rhodium) plus gold, 0,33 % nickel and 0,15 % copper over a vertical thickness of 12 m.

Shaft 1, with an internal diameter of 7,25 m, will provide access to the Flatreef deposit and enable the initial underground development to take place during the development of Shaft 2. Ultimately, Shaft 1 will become the primary ventilation intake shaft during the project’s initial 4 Mt/a production case.

The average sinking rate has ranged between 40 to 50 m a month. The shaft includes a 300-mm-thick, concrete-lined shaft wall. The main sinking phase is expected to reach its projected final depth of 980 m below surface in 2019.

Shaft stations to provide access to horizontal mine workings for personnel, materials, pump stations and services will be developed at depths of 450 m, 750 m, 850 m and 950 m.

The first off-shaft lateral development on the 450-m level, which will serve as an intermediate water-pumping and shaft cable-termination station, was successfully completed in September 2017. The next off-shaft lateral development will be at the 750-m level and will serve as the first mine-working level. The 750-m-level station development is expected to be completed by September 2018.

Shaft 2, to be located approximately 100 m north-east of Shaft 1, will have an internal diameter of 10 m, will be lined with concrete and sunk to a planned, final depth of more than 1 100 m below surface.

The headgear for the permanent hoisting facility was designed by South Africa-based Murray & Roberts Cementation. The early-works for Shaft 2 include the excavation of a surface boxcut to a depth of approximately 29 m below surface and the construction of the concrete hitch (foundation) for the 103-m-tall concrete headgear (headframe) that will house the shaft’s permanent hoisting facilities and support the shaft collar. Excavation of the boxcut commenced in January 2018 and is expected to be completed by the end of 2018.

Shaft 2 will be equipped with two 40-tonne, rock-hoisting skips capable of hoisting a total of 6 Mt/a of ore – the single largest hoisting capacity at any mine in Africa. This will allow a relatively quick and capital-efficient first expansion of the Platreef project to 6 Mt/a by increasing underground development and commissioning a third 2 Mt/a processing module and associated surface infrastructure as required.

A further expansion to more than 8 Mt/a would entail converting Shaft 1 from a ventilation shaft into a hoisting shaft. This would require additional ventilation exhaust raises, as well as a further increase of underground development, commissioning of a fourth 2 Mt/a processing module and associated surface infrastructure, described in the Platreef preliminary economic assessment as Phase 2 of the project.

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Title: Editor
Name: Arthur Tassell
Email: mining@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

Title: Advertising Manager
Name: Bennie Venter
Email: benniev@crown.co.za
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