Modern Mining May 2017

MINING News

The Tschudi project is an open-pit, heap leach, SX/EW copper mine located near Tsumeb (photo: Weatherly).

Slow leaching hits Tschudi’s first quarter production

Weatherly International, whose shares are quoted on AIM, reports that its Tschudi copper project in northern Namibia pro- duced 3 236 tonnes of copper cathode in the March quarter. This was 24 % below nameplate capacity due to slower than anticipated leach rates for mixed oxide/ sulphide ore stacked in the later months of 2016 and in early 2017. It says that it was unable to compensate for the shortfall due to above average seasonal rainfall during the quarter which prevented short-term acceleration of mining and stacking. Mixed oxide/sulphide ore stacked earlier in 2016 had leached at rates as predicted in the 2012 Bankable Feasibility Study (BFS). However mixed ore stacked later in 2016 showed slower leaching char- acteristics over time, leading to the current production shortfalls. Investigations are continuing with appropriate external assistance and advice

to produce a JORC-compliant Code (2012) maiden resource for Nkuluwisi. Total resources declared for Nkuluwisi amount to 3,97 Mt at 1,1 g/t for 140 894 ounces of gold. The measured resources total 224 000 t at 1,29 g/t for 9 266 oz of gold while the indicated resources total 2,3 Mt at 1,13 g/t for 83 888 oz of gold. In addition, the deposit has inferred resources of 1,44 Mt at 1,03 g/t for 47 761 oz of gold. Toby Bradbury, Shanta’s CEO, com- mented: “The significant scale of Nkuluwisi to determine how site operating param- eters may be changed to ensure that optimal conditions for bacterial leaching of sulphide minerals are maintained in the heap in order to maximise leach rates and ultimate overall recoveries of copper from stacked ore. The changes currently under investiga- tion include changes to solution chemistry, potential for forced aeration of the heap, modified irrigation strategies, and possible changes to lift heights. In the meantime, capital construction of the stage two heap leach pad area has commenced to provide additional time for the leaching of copper from mixed ore currently under irrigation, and also for implementation of changed operating parameters for this ore prior to sealing and over-stacking. Groundwater in the open pits had no adverse effect on mining during the quar-

opens the door to possible expansion options at our flagship New Luika Gold Mine to target lower grade orebodies which could increase production levels and add to mine life. The NLGM already has resources of 9,47 million tonnes at 2,24 g/t for 683 000 oz that sit outside the recently updated Revised Mine Plan and the Nkuluwisi maiden resource adds signifi- cantly to that. Further upside remains along strike at Nkuluwisi and also at a series of highly prospective and proximate targets in the Lupa goldfield identified through our focused exploration programme.”  Full financial year production to June 2017, as previously advised byWeatherly, is now forecast to be 14 500 to 15 000 tonnes. The poor production result in the March quarter has caused C1 quarterly operating costs to increase to US$5 907/t. Full finan- cial year C1 costs are now forecast to be US$5 250 to US$5 350 per tonne.  ter, with groundwater inflows managed using the in-pit pumping systems. Detailed investigations continue into opportunities to reduce operating costs and produc- tion delay risks via capital expenditure to enable removal of groundwater before it enters the pits. During April, says Weatherly, rates of stacking contained copper metal tonnes onto the heap have improved and the rate of leaching copper metal tonnes into solution is expected to improve during the June quarter. However April’s cathode pro- duction tonnage will remain weak.

Nkuluwisi adds to the potential of New Luika Shanta Gold, listed on AIM, has provided an update from its ongoing exploration programme within, and surrounding, the New Luika Gold Mine (NLGM), located in the Lupa goldfield of south-west Tanzania. In March this year, Shanta released encouraging drilling results from the Nkuluwisi mineralised target, located approximately 12 km north-west of the NLGM’s central processing hub. Since March, the company and its indepen- dent resource consultants have worked

14  MODERN MINING  May 2017