PERTH (miningweekly.com) – The board of gold miner Regis Resources has approved a A$29.4-million investment to develop an underground mining operation beneath the current Rosemont openpit mine, in Western Australia.
Regis on Friday said that the underground component of the expanded operation would exploit a mineral resource of some 1.4-million tonnes, grading 5.1 g/t for 230 000 oz of gold, at a 2 g/t cutoff grade.
The combined openpit and underground mine will deliver some 10.3-million tonnes of ore, at 1.72 g/t for 570 000 oz over the current five-year mine life. The expanded operation will continue at a rate of 2.1-million tonnes a year, with the underground mine contributing between 480 000 t/y and 600 000 t/y.
At the life-of-mine grades of the openpit and underground operation, the combined Rosemont project will produce at a run rate of between 120 000 oz/y and 130 000 oz/y, an increase of between 35 000 oz/y and 45 000 oz/y from the openpit-only operation.
“The decision to approve the first development of an underground mine in one of our Duketon operations is a very exciting step for Regis,” said chairperson Mark Clark.
“We believe that the approved Rosemont underground operation is a robust business in its own right but just as importantly will see the infrastructure in place to grow that mine through exploration from an established underground footprint.”
Clark said that the growth opportunity will be targeted both laterally between the two mining zones and at depth, and along strike.
“There is also a very strong opportunity to replicate this development path at Garden Well in the near term, and then at other Duketon satellite pits in due course.”
The operating cost for the combined openpit and underground operation is estimated at A$1 015/oz, with the operating cost of the underground component expected to be in the order of A$1 154/oz.
Development work for the underground operation will start in the current quarter with permitting, the ordering of long-lead capital items, and underground mining contract tendering processing.
The start of portal development in the southern end of Rosemont Main is expected in the March quarter of next year, with the processing of underground material expected to start in the December quarter.