By Hilary Mare
THE management at AIM-listed Weatherly International’s Tschudi open pit copper mine has expressed huge disappointment at how high groundwater has rampantly affected their third quarter throughput spoiling the company’s record of beating its own guidance.
The company delivered 3 641t of copper cathode in the quarter ended September 30, in line with expectations informed by the excessive rates of groundwater inflow into the open pit.
“After recording such a strong performance in the March quarter, we are disappointed that we were unable to anticipate such high groundwater inflow rates at Tschudi, and have consequently spoiled the company’s record of beating our guidance,” Weatherly CEO Craig Thomas said.
He noted, however, that the operating team was fully focused on meeting, or exceeding, the revised guidance and on again demonstrating the capabilities of the Tschudi operation.
The mine had produced 4 442 t of copper cathode in the quarter ended March 31 – 4% above its nameplate production rate of 17 000 t/y.
The company, however, reported in July that open pit mining operations had encountered groundwater inflow rates that exceeded the highest rates indicated in hydrogeological studies conducted as part of the bankable feasibility study.
These excessive inflow rates had caused delays in mining the scheduled ore volumes to deliver to the heap leach operation, which, in turn, resulted in lower copper output.
As a result of the decreased production in the September quarter, additional costs to manage the groundwater inflow and adverse exchange rate movements, C1 costs for the quarter increased to US$5 073/t.
Upgraded in-pit groundwater management systems and infrastructure have been commissioned as planned, and mining is proceeding according to the revised schedule, the company reported on Thursday.
The focus is now on long-term groundwater management systems including the introduction of dewatering boreholes within and/or outside the pits, the company stated, adding that it was confident in its ability to manage groundwater in the long term. bAlthough output for the first quarter of the 2016 financial year was 14.3% below the nameplate rate of 1 417 t/m, as expected, the company still expects to achieve the nameplate copper output rate by the end of the December quarter.
Tschudi is a low-cost open-pit mine extracting oxidised copper ore to be treated through heap-leach, solvent extraction and electro-winning. Environmental approval for the Tschudi mine was granted in April 2013 and ground-breaking was held in November that year. Civil construction works at the mine site began in April 2014 and the first copper was produced in October 2015. Tschudi is expected to produce an average of 17 000t of copper per annum during its 11-year life period. The deposit is expected to create more than 500 jobs.
The ore body of the Tschudi mine is located in the basal sandstones and minor conglomerates of the Malden Group. The deposit is open-ended at the south-west and has a strike length of approximately 2 500m.
Oxide mineralisation at Tschudi occurs up to a depth of 70m below surface. Beyond the 70m level, a transitional zone of mixed sulphide-oxide mineralisation then extends to a depth of approximately 110m, followed by a sulphide zone.
Copper mineralisation in the oxide zone is mainly composed of malachite and minor chalcocite. The mineralisation is disseminated through a sandstone and conglomerate unit lying above a dolomite unit. The sulphide zone contains chalcocite and bornite, while the transitional zone contains a combination of chalcocite and bornite.As of December 2015, the mine was estimated to contain reserves of 24.4Mt of ore grading at 0.85 percent copper containing 207 000t of copper.
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