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Big gold and silver find in Tonga

Published: 10:26AM Wednesday November 07, 2012 Source: Fairfax

  • Tongan flag (Source: ONE News)
    Tongan flag - Source: ONE News

An international mining company says it has discovered two rich gold and silver deposits in deep waters in Tonga's exclusive economic zone.

In a statement to the London and Toronto stock exchanges, Nautilus Minerals said the finds, in waters between Samoa and Tonga, continued a trend of finding "high precious metal grades" in the area.

The company, which also planned to prospect in New Zealand's EEZ, sent a remote-operated vehicle down to around 1000 metres to sample rocks on hydrothermal systems known as seafloor massive sulfide (SMS) deposits.

The samples were rich in copper and zinc, and contained 28.6g per metric ton (g/t) of gold and 673 g/t silver. By comparison, prospectors on land in New Zealand's Waihi area report results of around 38 g/t gold and 49 g/t silver.

Nautilus, which is working to get the world's first under-sea mining operation underway in waters around Papua New Guinea, said that despite the depth it would be able to easily mine SMS, which are towering rock systems also known as ''black smokers''.

The latest discovery in the north eastern Lau Basin, is in the area of the massive Tonga Trench and near the epicentres of two massive earthquakes that generated the lethal Samoan tsunami in 2009. It is an area of extreme seismic activity.

Nautilus CEO Mike Johnston said the finds highlighted the potential of the company's Tongan prospects.

At one site, Fonualei South, they discovered two separate chimney fields tightly packed in clusters.

At another site they sampled two 30m-high chimneys and found ''exceptional zinc and gold values''.

At another site, North Mata, they sampled fields of chimneys, including active black smokers. Although rich in minerals, they were much deeper at 2360m.