Australia's most lucrative gold mine is out of action indefinitely after a "large seismic event" damaged parts of Newcrest's Cadia operation and put a cloud over the company's ability to meet its full-year gold production target.
The seismic event rocked the mine early on April 14 and while none of the workers were killed nor injured, the event has been deemed serious enough for New South Wales safety regulators to issue a "prohibition notice" over the mine.
That means the mine, which is Newcrest's flagship asset, has ceased operating indefinitely despite the fact the surface infrastructure is unharmed and able to continue processing stockpiled ore.
The incident sparked a 4.5 per cent slide in Newcrest shares, with the stock closing $1.15 lower at $23.98 on Tuesday.
Newcrest stressed that no "major damage" to mine and infrastructure had been observed, but minor damaged had occurred in some areas and inspections of the mine were continuing.
In the short term, the interruption is expected to stop Cadia from achieving its gold production target of between 730,000 and 820,000 ounces in fiscal 2017.
The mine was already on track to hit the lower end of that guidance after a first half that delivered 374,474 ounces of gold and 38,158 tonnes of copper.
Newcrest left open the possibility that its company-wide gold production target could also be in jeopardy.
"Cadia is not expected to meet its production guidance for the 2017 financial year. It is too early to be definitive about the impact on the group's production guidance for the 2017 financial year," said the miner in a statement to the ASX.
Newcrest was ahead of the pace required to achieve its guidance target, having produced 1.23 million ounces in the first half of fiscal 2017.
The full-year production target is between 2.35 million and 2.6 million ounces of gold.
RBC analyst Paul Hissey said Cadia accounted for 30 per cent of Newcrest's gold production and 65 per cent of the company's valuation, but he said the company's other assets may be able to temporarily fill the void left by Cadia.
"Should Cadia's production be lowered by about 50,000 ounces for 2016-17, we expect that other assets within the portfolio could step up to temporarily fill the void [as has been done in the past] and therefore expect the financial impact to be somewhat muted," he said.
"We expect the market may be concerned around risks to what is clearly a marque asset in Newcrest's portfolio."
Newcrest said the outage is not expected to affect Cadia's production target for 2017-18.
Longer term, the focus will be on whether the incident has caused permanent damage, particularly to the two underground "panel caves" at Cadia.
The larger and more important "Panel Cave 2" has only suffered minor damage, but it is not yet known whether "Panel Cave 1" has been so fortunate.
"PC1 appears to have sustained some damage to the access ways. A cautious approach is being taken to assess any damage to the PC1 extraction level by using a remote-operated camera prior to personnel being permitted into that area," said Newcrest in the statement.
Newcrest's other major mines include Lihir in Papua New Guinea and Telfer in Western Australia.
The seismic event is the second major interruption to Cadia within the past 20 months, after a mill outage slowed output in September 2015.
Newcrest was not the only gold miner to suffer a share price fall on Tuesday, with Resolute, Regis and Saracen suffering falls of more than 12 per cent, five per cent and four per cent respectively.
Gold was fetching $US1283 per ounce on Tuesday.
