NZ’s offshore mineral resources worth billions, scientists say

In a joint paper to the recent AusIMM minerals conference in Wellington, Ray Wood of GNS Science and Ian Wright of the UK’s National Oceanography Centre (and formerly of NIWA) say that a number of large mineral deposits of different types were known to exist on New Zealand’s continental shelf sea floor.

Shortly after the conference, the Government announced that a special United Nations Commission has officially confirmed a claim to an Extended Continental Shelf area totalling 1.7 million sq km, increasing the size of New Zealand’s continental shelf rights over the sea floor by 42% to 5.7 million sq km.

The new continental shelf rights include a small additional area of the Kermadec Arc near the border with Tonga.

The Extended Continental Shelf area recognises New Zealand’s rights where the shelf goes outside the 200 nautical mile EEZ area and includes resources such as minerals and petroleum on and beneath the seafloor, though the water column above is still regarded as international waters.

Mr Wood said polymetallic sulfides formed by submarine volcanic activity on the Kermadec Arc containing gold, silver, copper and zinc could be worth tens of billions of dollars.

Ferromanganese nodule deposits occur on the seafloor of the Campbell Plateau south west of the South Island. In-ground value was of the order of $450 million at current prices.

In another conference paper on this ferromanganese resource Dr Ian Graham of GNS Science said this resource was conservatively estimated at 280 million tonnes, containing 1.5 million tonnes of nickel, copper and cobalt. The nodules, which formed from precipitation from seawater, were found at greatest density 4,000 m down on the deep sea floor beneath the Deep Water Boundary Current which flows north from the Antarctic.

Mr Wood said phosphorite nodules formed on the Chathams Rise seafloor, between Chatham Islands and the South Island in a much similar manner to ferromanganese nodules. These were extensively studied in the 1980s by New Zealand and German scientists. The in-ground value of these deposits at current phosphate rock prices is of the order of $1 billion.

Marine placer deposits of ironsand, gold and aggregates also existed in shallow coastal waters. Ironsand exploration companies were currently looking for resources potentially worth $5-10 billion.