PERTH (miningweekly.com) – ASX-listed Venturex Resources is considering openpit mining at its Pilbara copper/zinc project, in Western Australia, following an optimised study.

The company reported on Thursday that a review of the mining plan identified that the upper part of the mineralisation could be more economically mined using openpit methods, rather than the underground methods proposed in a 2012 feasibility study.

The feasibility study estimated that the project could deliver 16 500 t/y of copper, 30 000 t/y of zinc and 200 000 t/y of silver, with a mine life of eight-and-a-half years, based on a processing rate of one-million tonnes a year.

C1 cash costs for the project were estimated at $1.57/lb, after by-product credits, while preproduction captial had been estimated at A$279-million.

Venturex said on Thursday that a preliminary assessment had indicated that some 50-million tonnes of ore could be obtained through openpit mining, which could provide feed to the one-million-tonne-a-year processing plant for the first four to five years of operation.

The company argued that openpit mining would be more economical than underground mining and would achieve better recovery of the resource within the openpit shell.

There would also be significant reductions in the amount of development required to establish an underground mine, as the portal of the decline and entries to the ventilation shafts could be located within the openpit.

As a result, the expected capital costs of the underground mine would be lower and would be deferred until the fourth year of production.

It was expected that an improved recovery from the Sulphur Springs resource, combined with mining inventory anticipated from the Kangaroo Caves resource, could extend the mine life beyond the initial eight-and-a-half years.

“Openpit mining of the upper section of the Sulphur Springs deposit represents a paradigm shift for the project. It will significantly simplify it and reduce the implementation and start-up risk,” said Venturex interim CEO and nonexecutive director John Nitschke.

Opportunities have also been identified for capital savings in the process plant and site infrastructure proposed in the initial feasibility study, but Venturex was yet to quantify these savings.

The optimisation study on the Pilbara project would likely be completed by the end of October.

Venturex had previously tried to divest of the Pilbara project in a A$14-million transaction; however, the deal fell through after the buyer was unable to complete a due diligence.