Marine Mineral Potential in New Zealand's Exclusive Economic Zone

Abstract

ABSTRACT Marine minerals recovered from the New Zealand Exclusive Economic Zone include salt, silica sand and minor aggregate. Irons and gold placers are known but of no commercial interest. Potentially, the most important mineral is the Chatham Rise phosphoresce. With the present depressed agricultural economy, exploitation of this deposit in the near future appears unlikely. Future work is likely to concentrate on manganese crusts and nodules and on hydrothermal mineral deposits associated with the Australian/Pacific plate boundary. INTRODUCTION The islands of New Zealand represent an isolated landmass which forms part of a largely submerged sub-continent, the New Zealand Platform. The presently emergent part of this subcontinent represents only a minor portion (-14%) of the total area (2.07 × 106 km2) above the 2000 m isobathic. This platform area initially resulted from the splitting of this sub-continent from Gondwanaland about 80 m. yrs ago. Its development has been associated with an active plate boundary since that time. This has led to the complex morphology and geological history of the area. In addition, late Cenozoic glacial history has played a dominant role in the oceanography and associated phenomena such as sea level and sedimentary regime in the region. The New Zealand 200-mile Exclusive Economic Zone (EEZ), declared in 1978, extends over most of the submerged sub-continent and significant areas of the surrounding deeper ocean basins. As a result of the occurrence of a number of small, isolated islands (Kermadec, Chatham, Bounty, Antipodes, Campbell, Auckland and The Snares Islands) on the New Zealand Platform, the New Zealand EEZ covers some 4.05 × 106 km 2 making it the world's fourth largest. It has a large latitudinal spread (from 26°S - 56°8). Major bathymetric features of the region include the Lord Howe Rise and Challenger Plateau to the west, and the Chatham Rise and Campbell Plateau to the east of New Zealand, respectively. The Kermadec and Colville Ridges, Havre Trough and Kermadec Trench in the north, and Macquarie Ridge in the south form part of the presently tectonically and volcanically active Australian-Pacific plate boundary. Most of the presently known marine mineral potential of the New Zealand EEZ can be related either to the effects of past climate change and New Zealand's position across a number of major oceanographic boundaries or to volcanism associated with the active plate boundary. Examples of the former include nearly all of the relict placer deposits on the continental shelf (including iron sand, gold, and aggregate) and the phosphoresces of the Chatham Rise, whilst hydrothermal deposits are related to volcanism.