Offshore ironsands explorer TransTasman Resources says it has confirmed "inferred" and "indicated" resources of around 200 million tonnes to the internationally recognised JORC code standard in its southern Taranaki exploration zone.
The company announced a resource of at least 102 million tonnes earlier this year in the zone off the coast of Patea, within the New Zealand 12 mile nautical limit, and has since been granted further exploration rights in an adjoining 3,134 square kilometre licence in the Exclusive Economic Zone.
The find doubles the size of the potential resource so far discovered, although the JORC code "inferred" and "indicated" standards are still short of a proven resource.
The latest JORC-compliant estimate is based on ironsands yielding titano-magnetite iron ore at a 60 per cent concentration. Some 70 million tonnes is at the "inferred" level, and a further 130 million tonnes is "indicated".
Chairman Bill Berend says further exploration is expected to "increase very substantially" the size of the mineral resource so far uncovered.
TTR has been examining offshore ironsands mining since 2007, and believes the combination of booming Asian steel demand and the relatively low cost and high quality of NZ offshore sands may make NZ a highly competitive source of ore for Asian steel mills, despite the fact the NZ resource is the less-used titano-magentite ore.
It has yet to seek resource consents, and has been conducting extensive marine biology and environmental studies, and extensive onshore community consultations in readiness for applications.
Marine studies so far suggest minor impacts on marine life, as the ironsands - created when ancient rivers washed volcanic debris to the sea - have themselves have produced a relatively barren marine environment