Exploring under the landscape

Pilar Villamor explains why the Canterbury earthquake was a surprise. Photo by Ross Louthean.
Pilar Villamor explains why the Canterbury earthquake was a surprise. Photo by Ross Louthean.
A diverse range of subjects was introduced at the annual New Zealand branch of the Australasian Institute of Mining and Metallurgy (AusIMM) conference yesterday, as a geoscience conference finished and the mining sector stepped in.

Several hundred GeoNZ delegates were joined by about 300 in the mining industry, with the last of several dozen presentations on geothermal issues being concluded as the first on the mining sector began; including offshore West Coast gold sampling from the sea floor and an update on data gleaned from the Canterbury earthquake on September 4.

However, high in every delegate's mind was the Pike River Coal mine disaster and fate of the 29 miners.

Speakers expressed sympathy for the missing men and their families, and AusIMM New Zealand branch chairman Cam Wylie asked all delegates to refrain from talking to the media attending the conference, as it would be "inappropriate" to comment as the media "search for stories" as the situation unfolded.

Arguably of most interest to southern mining sector was an update on the West Coast continental shelf gold sampling programme undertaken by AuruMar, on behalf of Seafield Resources and joint-venture partners De Beers Marine and AngloGold Ashanti.

More than 75% of recent samples returned shows of gold.

AuruMar had developed a New Zealand-designed core sampling system, which is hung from the stern of a ship in up to 130m of water, to take up to 10m-long sea-bed samples.

In its quest for gold washed down from the Southern Alps and out to sea where it has settled on the continental shelf, AuruMar works within an 8000sq km block, running from Karamea to Big Bay and up to 12 nautical miles offshore.

Neil Fraser, of AuruMar, said during 2009 there a 55-day sampling programme was completed, with 55 cores taken and 933 samples analysed.

He said gold was found on 20% of the samples and 76% of the cores, but the gold grades were "disappointing".

He declined to reveal the grades, but said more evaluation of data during the year would determine prospective "leads", then a decision would be made on more sampling programmes.

A popular session yesterday was an update on data gleaned from the Canterbury earthquake.

Dr Pilar Villamor, from GNS science, said the Darfield-centred earthquake, the worst since that in the Wairarapa in 1942 and the first of the internet age, caused $4 billion damage, and the cost was still rising.

She noted the fault that caused major liquefaction in the area had not been mapped by scientists, as it was covered by hundreds of metres of sediment and gravel. It did not show up topographically; being "obscured by the landscape".

She compared the Canterbury quake to the San Andreas earthquake in 1989 and the Haiti quake this year, where adjacent faults had not been previously mapped.

• Reporter Simon Hartley is a guest of AusIMM.

 

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