Using results based on a 0.5% copper cut off, one of the 85 new diamond coreholes intersected 140 metres at 1.11% copper and 1.04 grams per tonne gold at 60m depth.

Another hole intersected 110m at 1% copper with 0.6gpt gold just 8m from the surface.

A third hole intersected 108m at 1.10% copper and 0.2gpt gold at a depth of 82m.

A separate hit of 126m at 0.81% copper and 0.65gpt gold was 120m downhole.

Located about 175 kilometres northwest of Barrick Gold's major Porgera mine, more than $US250 million has been spent on exploration at the Xstrata-operated project (81.82%) which has spanned more than 1300 holes and 270km.

"These drilling results again highlight the fabulous Frieda deposit as a special copper porphyry giant," Highlands Pacific managing director John Gooding said.

"Past drilling from surface to 1000 metres has also highlighted the depths of the deposit. The feature of this more recent in-fill drilling is the quality of grade for the early year starter pits."

Gooding said the updated mineral resource estimate is expected to push even more of the current 8.6 million tonnes of contained copper inventory into the higher confidence measured and indicated resource categories.

The prefeasibility study last year indicated the project could have a multi-decade mine life and process 60Mt per annum of ore over the first eight years for an average of 246,000tpa of copper and 379,000 ounces per annum gold.

The study revealed that cash costs could be in the lowest 30th percentile of world copper mines, while Frieda River could be one of the top 15 producing copper mines around the globe.

The bankable feasibility study is due in January.

Highlands Pacific owns 18.8% of the project and its shares closed down 5.3% to 27c this afternoon.