And a further $185 million will be spent in the planned second stage of the expansion.

The announcement is set to provide a major boost to the Orange economy with demand for housing for the additional staff and flow-on effects for retail shops.

Cadia will start a major international, national and local recruitment campaign to seek workers across a range of skills to fill its requirements.

The expansion will involve the development of a mining area known as PC 2-3, materials handling system upgrades, associated infrastructure and the initial works to increase the plant capacity.

The expansion plan has improved on a pre-feasibility study announced last year and is expected to add 1.8 million ounces of gold output and 67,000 tonnes of copper, with an estimated $800 million increase in projected free cash flow generation by Cadia over the life of the mine.

Newcrest Managing Director and Chief Executive Officer, Sandeep Biswas said it was a significant boost for the mine.

"The capital investment has an estimated 21.5 per cent rate of return and ensures Cadia remains a Tier One asset for many years to come," he said.

Cadia Valley Operations general manager Peter Sharpe said it was a windfall for the Orange region.

"This is great news for Cadia and for the region, and testament to the hard work and commitment by everyone involved from across Cadia, Newcrest, the local community and our local government stakeholders," he said.

"Recruitment for more workers to support the project is underway, with approximately 100 new positions for early works filled to date, and hundreds more required for the construction phase."

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