OZ Minerals Extends Prominent Hill Mine Life

Bolstered by recent increases in reserves, OZ Minerals’ Prominent Hill
copper/ gold mine will now stay in operation at least until 2028, with the
majority of overall production gradually shifting to underground operations.
(Photo: OZ Minerals)
OZ Minerals reported in mid-November that its Prominent Hill mine in northern South Australia will continue to operate until at least 2028, underpinned by a new mine strategy and an updated mineral resource and ore reserve estimate. Prominent Hill mineral resources are now estimated at 148 million mt of copper mineralization grading 1.2% copper, 0.6 g/mt gold, and 2.9 g/mt silver, and 25 million mt of gold mineralization grading 1.3 g/mt gold and 1.6 g/mt silver. These resources occur in the Prominent Hill open pit, Prominent Hill underground and surface stockpiles. The mineral resources are inclusive of ore reserves.

Underground proven and probable ore reserves stand at 33 million mt, grading 1.5% copper, 0.6 g/mt gold, and 3.5 g/ mt silver, containing 480,000 mt of copper, 600,000 oz of gold, and 3.5 million oz of silver. A significant recent increase in the underground reserve has been driven by a combination of ongoing drill programs targeting increased volumes of higher-confidence mineral resource; mine planning initiatives that have seen the deepening of the underground mine by 150 m, along with lateral extensions; and reduction in cut-off grade driven by successful cost-saving initiatives.

Current underground production of 2 million to 2.2 million mt/y is forecast to increase to 3.5 million to 4 million mt/y by 2019, with mining costs projected to be in the bottom half of the cost curve. The Prominent Hill processing plant will continue to operate at its current capacity until mid-2023 by processing stockpile and underground ore, prior to running full time at a milling capacity of about 3.5 million to 4 million mt/y to 2028.

OZ Minerals CEO Andrew Cole said, “While the open pit will ramp down, the ore stockpiles that we continue to build and the growth in the company’s underground mining operations will see Prominent Hill remain one of Australia’s largest sources of copper.”

Carrapateena Progress: In other news from OZ Minerals, the company has reported the results of a prefeasibility study of its proposed A$980 million Carrapateena underground copper mine and concentrate treatment plant project. Carrapateena is located about 250 km southeast of Prominent Hill. The concentrate treatment plant will be located at the port of Whyalla on the Spencer Gulf, about 200 km south of the Carrapateena project site.

Key production and financial highlights from the Carrapateena prefeasibility study include a 4-million-mt/y, sublevel- cave mining operation and production of more than 100,000 dry mt/y of concentrate after treatment in the concentrate treatment plant. Contained metal production is estimated at 61,000 mt/y of copper and 63,000 oz/y of gold. Mine life is projected at more than 20 years at the proposed operating rate. Pre-production capital cost to develop the mine is estimated at A$830 million, excluding the concentrate treatment plant but including owner’s cost and contingency

The OZ Minerals board of directors has approved development of a project feasibility study. The concentrate treatment plant is undergoing a parallel study that the company expects to release with the feasibility study.

As featured in Womp 2016 Vol 12 - www.womp-int.com