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The purpose of mineral exploration is to find new mineral deposits so that the supply of all of the minerals we use every day can continue. Certainty of access to land for minerals exploration is the issue critical to enabling the build of this essential knowledge base. Exploration for New Zealand’s mineral resources began with Maori discoveries of greenstone (pounamu), and other rocks and minerals suitable for making weapons, tools and ornaments. Mineral exploration intensified when European settlers arrived in numbers in the mid-19th century.
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As the world’s population has grown along with the amount and range of minerals being used, exploration has changed. Most exploration is now carried out by companies, which may be independent exploration companies or divisions of mining companies. Several thousand exploration companies are now active throughout the world.
Finding new mineral deposits
In the past prospectors used simple methods and had to rely mainly on what they could see to find mineral deposits.Today a wide range of methods is used. They include satellite images, airborne methods using various types of sensors, and ground methods that can help to find buried deposits that are not visible at the surface. The prospectors’ traditional methods are still used by geologists, helped by their much better understanding of where mineral deposits might be found.
Geological research has explained how mineral deposits form and where they can be expected to be found. They have been divided into types which are found in regions with a particular geological history. The deposits themselves are often small, lying under an area of a few hectares, but they may be surrounded by geological features that can be recognised, making mineral deposits easier to find. These features are used to set up 'models' of particular types of deposits that are used to select areas to be explored. New Zealand has been a world leader in research into mineral deposits that form from hot water (hydrothermal deposits) based on many years of research into geothermal energy in the North Island’s active Taupo Volcanic Zone.
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Airborne geophysical survey
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An exploration drill rig
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Gold panning |
Mineral exploration is being carried out throughout New Zealand, particularly in the Waikato Region of the North Island, and the West Coast and Otago regions of the South Island. Offshore mineral deposits on the sea floor to the northeast of the North Island between the Bay of Plenty and the Kermadec Islands are being investigated by companies working alongside New Zealand and international research agencies. New Zealand is a leader in this research too.
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| Geologists target their search for mineral deposits by collecting and analysing information. Computer software can help to narrow the search by highlighting areas where favourable factors defined by the geologist coincide. Source: GNS Science |
Exploration can be divided into stages ranging from reconnaissance, which covers large areas (hundreds or thousands of square kilometres), through to detailed studies of smaller areas (up to only a few square kilometres). These methods find and define prospects that are tested by drilling holes to obtain samples. Drilling is expensive and explorers take care to ensure that holes are drilled in the best locations. In spite of this, for metallic minerals, only one exploratory drill hole for every thousand drilled finds a new mineral deposit that becomes a mine. For every 1000 prospects investigated only one will result in a new mining operation.
The success rate is much higher for more common, lower value materials such as sand and quarry rocks. Flat-lying coal seams are easier to find than metallic mineral deposits as horizontal coal seams can be tested with widely spaced vertical drill holes.
The role of the Government
Like almost every other country, most minerals in the ground in New Zealand are owned by the Government. Exploration is carried out under permits granted by the Crown Minerals Group of the Ministry of Economic Development.Information on exploration activities is filed by permit holders and is held by the Crown Minerals Group. This information becomes available to the public after five years and allows mineral explorers to build on past results. Exploration companies have spent more than $100 million looking for mineral and coal deposits in New Zealand since 2000. Data is progressively becoming available via the Ministry’s website – www.crownminerals.govt.nz.
The Government (through GNS Science, a Government owned geological research company, and other research agencies) carries out geological research into mineral deposits, producing technical information and maps while universities and their students also carry out research that helps exploration. This student research is often sponsored by mining and exploration companies.
Will mineral resources run out?
Mineral resources are usually defined as being 'non-renewable', suggesting they could one day one run out. Predictions of crises due to the depletion of minerals and oil have been made frequently over the last 200 years. In the 1850s an eminent English economist warned of the collapse of British industry through depletion of coal resources. Today known coal resources are much larger than they were in the 19th century.
Over the last century numerous studies of mineral and oil resources have predicted industrial collapse through their depletion, the most recent being the 'peak oil' scare. In every case these fears have proved to be unjustified.
A New Zealand example suggests an explanation for this. In 1974 Gordon Williams, an eminent economic geologist and Dean of the Faculty of Technology at Otago University wrote: 'In the general area of the former Hauraki Goldfields, it is not likely that mines will be re-opened for their gold content, or that new vein deposits will be found.' Few would have disagreed with him at the time. Since then, the Martha mine at Waihi has been reopened for its gold content and new vein deposits have been found in the district at Golden Cross and Favona, containing a total of several million ounces of gold.
The expansion of resources results from:
- continuing exploration which has discovered new resources
- changes in the economics of mining that allows rocks with a much lower mineral content to be worked
- developing new technology for exploration, mining and mineral processing.
The efficiency of mining and processing continues to improve. Advances in science and technology have allowed new methods to be developed, and growing knowledge of mineral deposits is being used to help in the search for new resources throughout the world, and in New Zealand.
Mineral exploration and the public
Mineral exploration activities are usually short term and localised. Airborne geophysical surveys usually mean a low flying aircraft will fly back and forth over the area, and it is standard practise to notify the pubic in advance, and provide contact details so potential problems can be minimised. Entry onto private land is by agreement with the landowner. Most Crown land is managed by the Department of Conservation. Access is by negotiation with the regional (Conservancy) office. Further information is available at
www.doc.govt.nz/templates/page.aspx?id=43634
An outline of the system of mineral ownership, access and permits is available on this site at:
www.minerals.co.nz/html/main_topics/overview/mining_legislation.html
Environmental approvals are generally not required for exploration except for access track-making and drilling. Core drilling needs relatively small quantities of water so consents to take and discharge water can be required.
Mineral exploration information sources
Crown Minerals www.crownminerals.govt.nz
Web map of permits, downloadable reports and maps
GNS Science: www.gns.cri.nz
Mineral, coal and petroleum information and geology
Companies active in New Zealand
Onshore exploration
Glass Earth Gold Ltd: www.glassearthlimited.com
Heritage Mining: www.heritagegold.co.nz
Auzex Resources: www.auzex.com
Newmont Waihi Gold: www.marthamine.co.nz/06_03_07.htm
Details of a geophysical survey of the Waihi district.
Offshore exploration
Neptune Resources New Zealand Ltd: http://www.neptuneminerals.com/
Australian “Catalyst” TV documentary (10 minutes) on offshore geological research by GNS Science that includes White Island, seafloor volcanoes and new animal life.
www.abc.net.au/catalyst/stories/2008/02/14/2160790.htm
Mining companies
Newmont Waihi Gold: www.marthamine.co.nz
OceanaGold: www.oceanagold.com
Solid Energy NZ Ltd: www.coalnz.com
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photo courtesy of Newmont Waihi Gold
middle: A track-mounted drill rig.
bottom: A 'bird' ready to be flown below a helicopter in a geophysical survey.
photos courtesy of Glass Earth Gold