Australian miner Newcrest has approved the $280-million expansion of the Lihir mine, in Papua New Guinea, announcing on Wednesday that the board had endorsed the Phase 14A feasibility study.

Ore mined from Phase 14A will displace lower grade ore feed to the processing plant, with about 13-million tonnes of high and medium grade ore from Phase 14A expected to be fed through to the 2026 financial to produce an incremental 400 000 oz of gold.

Lower grade material will be stockpiled and fed progressively over the remaining mine life.

“The development of Phase 14A is another innovative step forward in realising the full potential of Lihir. The findings of the study are expected to deliver gold production from an additional high-grade ore source, which would have otherwise been inaccessible through standard mining techniques,” said interim CEO Sherry Duhe.

“The Phase 14A ore zone is now well informed by geotechnical drilling that underpins the design and stability of the cutback and we expect Phase 14A to be delivering higher grade ore from FY24,” she added.

The study demonstrates an internal rate of return of 48% and a net present value of $202-million with a payback of 2.9 years.

The study outlines an updated life-of-mine plan, with upside potential.

“The application of steep wall technologies, together with an alternative, lower cost and simpler seepage barrier design have the potential to enable access to additional high-grade zones outside the current ore reserve and extend the elevated production profile beyond FY31,” said Duhe.

Further application of the civil steep slope technology used in Phase 14A is being assessed to potentially unlock additional high-grade mineralisation outside the current ore reserve in the northern and eastern extents of the Kapit orebody. This work has the potential to improve the production profile beyond the 2031 financial year, before the high-grade ore from Kapit declines. The design optimisation and associated impact on the longer term production profile is expected to be completed in the second half of 2023.

In addition, following completion of the seepage barrier feasibility study in October 2021, an alternative seepage barrier design, the nearshore soil barrier (NSB) option, is currently being studied. The NSB would sit between the No Coffer Dam limit and the existing shoreline of the Inner Harbour, about 500 m west of the proposed Kapit seepage barrier (KSB). Initial work indicates that the NSB would be a simpler solution, faster to construct and less costly.

A prefeasibility study level assessment of the NSB option is currently under way and is expected to be completed in 2023.