Modern Mining January 2016

COPPER

Yet another lease on life for

of blasted ore and later the subsidence of the pit’s north-west wall – the lifespan of Lift I was shorter than expected, and a base-case pre-fea- sibility study was therefore conducted for Lift II and approved in June 2012. A bankable feasibility study followed in May 2014, providing a positive business case to pro- ceed, based on a grade of 0,64 per cent copper and an orebody very similar in size, shape and grade to the one exploited by Lift I. “Key to the confidence underlying the Lift II project has been the geological certainty around the deposit,” said Nick Fouche, General Manager for Palabora’s Growth Division, responsible for Lift II. “We had the benefit of all the initial drilling results for the opencast pit, followed by about 26 000 m of drilling for Lift I, and then another extensive programme totalling 72 000 m of core drilling data, more recently for Lift II.” This, he said, gave them a better understand- ing of how the cave would develop and how the ore grades would transfer to the produc- tion level, giving more certainty about what ore values would report to the drawbells at every stage. By the time the go-ahead for the project was given in November 2014, shareholders had allowed about R2 billion to be invested in the

Taking over where its Lift I project left off, Palabora Copper’s R9 billion Lift II expansion is giving the well- known South African mine another two decades of life – by developing one of the world’s deepest and largest block-cave operations. Modern Mining contributor Paul Crankshaw reports on the project.

H aving gained experience from its initial transition to underground mining nearly 20 years ago, Palabora is taking advantage of similar conditions and grades to forge a 33 500 tonne per day (t/d) operation from a production level at 1 650 m below sur- face. The aim is produce ore by late 2017. Plans to mine underneath Africa’s widest open pit – some 2 000 m in diameter at sur- face and over 800 m deep – were first put into action in 1997, when shaft construction began on the Lift I project at 1 200 m deep. First ore was drawn from Lift I in 2001, well-timed to overlap with the open pit’s closure in 2002, although it took until May 2005 to reach target production of 30 000 t/d. Mainly due to the competence of the rock mass – leading to insufficient fragmentation

Celebrating a new record at Palabora. The machine in the background is Master Drilling’s 120-ton RD8 raise borer. The brand newmachine – the largest manufactured by Master Drilling to date and one of the biggest in the world – is being used to bore two 6,1 m diameter ventilation shafts for the Lift II project to a depth 1,2 km.

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62  MODERN MINING  January 2016