Seafloor mineral exploration update

The world’s largest seafloor massive sulphide explorer Nautilus Minerals has located 10 multi-mineral deposits in Tongan waters just north of New Zealand at the northern end of the 2500 kilometre long Kermadec-Tonga Arc.   By LINDSAY CLARK

The zinc dominated deposits – some samples were almost solid metal with zinc grades over 40 percent – also contained high grades of copper, gold, silver and lead.

The seafloor discoveries are part of the Western Pacific’s ‘volcanic ring of fire’ where mineral-rich deposits lie on the seafloor above underwater volcanoes. The minerals are leached from the oceanic crust by acidic superhot water. When this stream hits the cold seawater the minerals instantly precipitate at the “black smoker” vents.

Both Nautilus and the smaller Sydney-based Neptune Minerals have both pegged out extensive areas of ground in New Zealand’s exclusive economic zone from offshore Bay of Plenty north to near the Tongan boundary.

Canadian-based Nautilus has also applied to prospect in New Zealand waters at the southern end of the arc. Nautilus is a much bigger and financially well-endowed company with experience in developing underwater mining techniques in waters off Papua-New Guinea.

Nautilus originally applied for a huge area of 180,000 square kilometres long New Zealand’s Kermadec Arc – but has reduced this to 48,200 square kilometres. However, the prospecting licence has not yet been granted by Crown Minerals.

Another seafloor massive sulphide explorer Neptune Minerals has focused mainly on offshore New Zealand, though it holds acreage in number of Pacific island countries as far north as Japan.

Neptune’s three Kiwi continental shelf licences cover over 50,000 square kilometres on the Kermadec Arc including one that stretches north towards the boundary with Tonga.

The Sydney-based Neptune is concentrating on developing its New Zealand acreage and applied last year to Crown Minerals for a mining licence over the Rumble West III seamount. This also has yet to be granted.

Nautilus’ first commercial deepwater exploration program in the Kingdom of Tonga’s exclusive economic zone was completed by MV Norsky in mid December 2008.

In earlier Tongan exploration, Nautilus and partner Teck Cominco – the big Canadian-based base metals company – found seafloor deposits containing a higher proportion of gold and less zinc.

Nautilus the latest targets sampled were in a 100 kilometre segment of its total 1500 kilometre-long Tongan tenements.

With financial difficulties in the current world recession, Teck Cominco has elected not to participate further in exploration in Tonga and Papua New Guinea, but says it wishes to retain the right to joint venture with Nautilus in New Zealand, subject to grant of titles.