The Institute of Geological and Nuclear
Sciences Ltd has carried out a mineral resource assessment of the Coromandel
region, one of the most mineral-rich regions of New Zealand. The
assessment focussed on metallic minerals and clays, because these are the main
commodities that have potential for increased production and export from the region (and from New
Zealand).

Three steps were used in the assessment:
1) development of mineral deposit models,
2) comparison of the models with regional
geology, structure, geochemistry and past mineral production to estimate the
number of undiscovered mineral deposits, and
3) application of grade-tonnage models to
determine the quantity and value of the known and undiscovered resources.
In step 1, descriptive and grade-tonnage
mineral deposit models were developed for 11 different types of mineral
deposits:
Low-sulphidation
andesite-hosted epithermal Au-Ag
Low-sulphidation
rhyolite-hosted epithermal Au-Ag
High-sulphidation
quartz-alunite epithermal Au
Porphyry
Cu-Au-Mo
Andesite-hosted polymetallic
veins adjacent to mineralised porphyry stocks
Zn-Pb-Ag
skarn
Cu-Ag
skarn
Hot spring
Hg
Shoreline placer
Ti
Rhyolite-hosted halloysite
clay
Volcanic-related kaolinite
clay

Step 2 was aided by a geographic information
system (GIS) assembled from a number of digital spatial data sets including: a
digital elevation model, an aeromagnetic map (from open file mining company
data), a geological map (from the GNS QMAP project), location of areas of
hydrothermal alteration, locations of mineral deposits (from the GERM database), stream sediment
geochemical analyses (from the REGCHEM database), and a lineament map derived
from satellite remote sensing data and the digital elevation model.

Based on May 2001 commodity prices, potential
resources estimated for the 11 mineral deposit and grade-tonnage models total
NZ$22 806 million for the metallic minerals, NZ$1000 million for halloysite clay
deposits and NZ$57 million for kaolinite clay deposits.