VANCOUVER (miningweekly.com) – Africa-focused explorer and project developer Ivanhoe Mines has reported further intercepts of greater than 10% copper, at a 3% cutoff, highlighting the high-grade nature of the thick, flat-lying, shallow, chalcocite-rich core of the Kakula Discovery zone, near the Kamoa copper project in the Democratic Republic of Congo (DRC).

"The consistent frequency of thick intersections of exceptionally high-grade copper mineralisation from both infill and step-out drill holes enhances our absolute confidence that Kakula is a game-changing discovery for the Kamoa project," stated executive chairperson Robert Friedland.

Among the recent drill holes is DD1016, which intersected 8.75 m (true width) of 9.84% copper at a 3% copper cutoff, beginning at a downhole depth of 362 m; 9.27 m (true width) of 9.11% copper at a 2.5% copper cutoff; 10.22 m (true width) of 8.49% copper at a 2% copper cutoff; and 18.78 m (true width) of 5.32% copper at a 1% copper cutoff.

Similarly, DD1026 intersected 14.66 m (true width) of 7.66% copper at a 3% copper cutoff, beginning at a downhole depth of 333.8 m; 15.48 m (true width) of 7.39% copper at a 2.5% copper cutoff; 16.97 m (true width) of 6.94% copper at a 2% copper cutoff; and 18.57 m (true width) of 6.49% copper at a 1% copper cutoff.

Ivanhoe advised that the Kakula Discovery remained open along a north-westerly/south-easterly strike, with high-grade copper mineralisation outlined along a corridor that is now more than 3 km in length. The high-grade copper zone starts less than 300 m below surface in the north-west section and gently dips to a depth of about 525 m in the south-east.

The drill work has shown that Kakula copper mineralisation displays vertical mineral zonation from chalcopyrite (containing about 35% copper), to bornite (about 63% copper) and to chalcocite (about 80% copper), with the highest copper grades associated with the siltstone unit consistently characterised by chalcocite-dominant mineralisation, the company said.

According to Ivanhoe, chalcocite is a high-tenor mineral that is opaque and dark-grey to black with a metallic lustre. Chalcocite is considered to be the most valuable copper mineral because of its very high percentage of contained copper by weight. Its tenor – or the percentage of the mineral that is actual metal to be extracted – is 80% copper by weight, while it is also coveted for its capacity to produce an exceptionally clean, high-grade concentrate.

Meanwhile, work on expanding the known mineralised zones is proceeding apace, with two drill rigs currently drilling step-out holes to the south-east of Kakula's currently defined high-grade core, looking to extend the high-grade mineralisation beyond the current 3 km strike length. Two more rigs are drilling step-out holes further to the north-west to test the extension of the high-grade core in that direction.

Two other rigs are busy drilling in-fill holes and one is drilling a large-diameter core hole for the second phase of metallurgical testwork.

Ivanhoe noted that initial metallurgical test results received in July from a sample of drill core from the Kakula Discovery zone achieved copper recoveries of 86% and produced a copper concentrate with an extremely high grade of 53% copper. Importantly, the July results also indicated that material from Kamoa's Kakula and Kansoko zones could be processed through the same concentrator plant, which would yield significant operational and economic efficiencies, the company advised.

GOING UNDERGROUND
Since the drilling programme started at the project earlier this year, Ivanhoe has drilled about 21 000 m. It plans to continue to drill a total of about 34 000 m this year, although expansion plans are being developed.

The main objective of the current drilling programme at Kakula, using seven rigs, is to confirm and expand a thick, flat-lying, bottom-loaded zone of very high-grade, stratabound copper mineralisation at the southern part of the Kakula Discovery area, which has the potential to be amenable to bulk, mechanised mining and, therefore, could have a significant, positive impact on the Kamoa project's future development plans.

The 60 km² Kakula exploration area is about 10 km south-west of Kamoa's planned initial mining area at Kansoko Sud, where mine construction is advancing ahead of plan.

To help advance the ongoing evaluation of Kakula, the Kamoa technical team is proceeding with engineering and preparing tender documents to construct a box cut at Kakula to accommodate decline ramps that will provide underground access to the deposit. Several possible box cut sites at Kakula have been identified and geotechnical drilling will be undertaken to determine the best location, Ivanhoe said.

KANSOKO SUD
Ivanhoe advised that underground mine development at Kamoa's planned initial mining area at Kansoko Sud is progressing ahead of plan and within budgeted costs. The twin declines, incorporating both a service and a conveyor tunnel,  have each advanced more than 160 m since the first excavation blast was conducted in May.

Development of the underground mine is designed to reach the high-grade copper mineralisation during the first quarter of 2017. The project is a joint venture between Ivanhoe Mines and Zijin Mining.

A dewatering system, including pumps, pipes and valves, is being installed in both declines before the onset of the rainy season in October.

Further, the construction of 20 km of high-voltage, 120 kV power lines linking the Kamoa site to the national electricity grid near the Kisenge mine is nearing completion.

A contract has been awarded to a local company for the supply and construction of  8 km of 11 kV overhead lines, cabling reticulation and five mini-substations for the distribution of electricity to the mine, camps, offices and dewatering boreholes.

Ivanhoe Mines Energy, a subsidiary of Kamoa Holding Limited, is also set to begin supplying 11 MW of power into the national grid from the first of six generating units to be upgraded at the existing Mwadingusha hydroelectric power station, the company advised.

An important DRC rail link to Angola had also been upgraded and reactivated recently, providing links through Angola and other locations in Southern Africa through which the Kamoa concentrates will be exported to market.