Harmony Gold Mining and Newcrest Mining are set to invest $2.3bn in developing their Golpu deposit in Papua New Guinea.
Harmony and Newcrest each own 50% of the Golpu project through the Wafi-Golpu Joint Venture (WGJV).
The companies will advance the project to feasibility study stage, which covers the first stage of Golpu's development.
Targeting the upper higher value portion of the ore-body, work during stage one will continue on optimising a second stage mine development (stage two), which will encompass the rest of the ore reserves.
The feasibility study for the first stage, as well as the updated pre-feasibility study (PFS) for the second stage of the project, is slated for completion by the end of calendar year 2015.
Harmony Gold Mining CEO Graham Briggs said: "The updated pre-feasibility study supports our view that Golpu is a spectacular ore body with a large copper component, affordable and mineable.
"The conclusion of the updated PFS is a major project milestone and has demonstrated the significant potential of this world-class orebody, which contains mineral resources of 20 million ounces of gold and 9.4 million tonnes (Mt) of copper."
With the assistance of WorleyParsons as project consultant, the Golpu project team has incorporated a total of 52,000 new drill core samples into the updated study.
The two proposed block caves in stage one have been designed to access about 40% of the contained metal (gold and copper) of the Golpu reserve with the remaining 60% of reserve being extracted by a future deeper block cave (stage two).
Later, the mining and processing infrastructure of stage one will be used to support development of the second part.
Stage one extracts 146Mt at an average grade of 1.02g/t gold and 1.6% copper, and the proposed start-up production rate is 3Mt as year mined from Block Cave 1 (BC1) and 6Mt a year from the deeper Block Cave 2 (BC2).
BC2 is situated about 1,050m below surface whereas BC1 is only around 425m below surface and will produce 12Mt of cave ore over a five year period.
Image: Schematic cross section of Golpu porphyry deposit 2012 compared with 2014. Photo: courtesy of Harmony Gold Mining Company Limited.