Summer testing for Seafield gold project

Seafloor goldminer Seafield Resources, which has offshore seabed permits stretching 500km from Karamea to Jacksons Bay on the West Coast, hopes to begin a full test programme next summer.

Seafield has been held up for almost 18 months as it designs and develops a range of new drilling systems, including a continous 10m core sampler, a stronger drill launch and recovery system and a buoyancy compensation system to keep the drilling ship stable - all understood to have cost several million.

South African mining dynasty the Oppenheimers are the majority shareholders of Seafield, whose partner in the venture is marine diamond-mining specialist De Beers Marine, a subsidiary of De Beers Group.

Dunedin geoscientist John Youngson, whose company Placer Solutions floated the undersea gold project to De Beers Marine and is a consultant to Seafield, said three onshore tests of the Wellington-made drilling system had gone well.

A sea trial is planned off Nelson's coast next summer, ideally followed by the first 40-60 day sampling programme within the permitted West Coast area.

"The drilling system has been refined [since the onshore tests] but is otherwise working well," Mr Youngson said.

Because of the high cost of operating the test rig from a ship, its operation had to run "like a finely tuned Formula 1 pit crew", he said.

Aside from designing the launch and recovery and buoyancy systems, the test drill design incorporates seven-inch and 13th-inch-sized bits, for taking geological samples and then changing to the larger bit for mineral sampling.

"The systems' designs and testing is what has been the holdup for the past 18 months," Mr Youngson said.

Seafield's combined two prospecting and licensed areas, granted in October 2006 until October 2010, cover a total of more than 10,000sq km offshore to beyond the 12-mile limit, which includes drilling in depths up to 120m.

It is targeting gold swept into the sea by glaciers and rivers over thousands of years, but now trapped in the seafloor in sand and gravel. Seafield has carried out 4000km of airborne magnetic surveys and two ship-based geophysical surveys totalling 2400km off the West Coast and commissioned several independent environmental studies, including of marine mammals.

About 10 million ounces of alluvial, or loose placer gold, have been recovered in the past 145 years from West Coast beaches and rivers. Mr Youngson said the results from the earlier airborne and geophysical surveys provided a large number of initial target areas to explore, including post-glacial channels, submerged shorelines and glacial outwash deposits.

"There's no shortage of targets and we won't get to them all," he said of the proposed summer drilling programme.

The four-year exploration permits and licences held by Seafield, which are due to expire in 15 months, could be extended with an application made three months before they end in October.

- OTAGO DAILY TIMES