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The Great Barrier Island Charitable Trust
is opposed to the government’s proposal to facilitate mining on
Conservation land at Te Ahumata on Great Barrier Island.
Schedule 4 lands – a social and ethical
issue.
Land covered in native ecosystems,
uninhabited and largely untouched by man, is an increasingly rare
commodity worldwide. In the 1980’s the government of New Zealand, with
much popular support, chose to place certain land areas, mainly in
National Parks, into a special category – Schedule 4. The point of this
Schedule was to protect the land from inappropriate developments,
especially those having large environmental impacts, such as mining.
This was in recognition of mankind’s dependence on a healthy planet in
which at least some areas remained as examples of the natural order and
beauty of the world. These places link us as a nation and as individuals
to our past, both Maori and Pakeha, in ways that cannot be achieved in
highly modified landscapes. There was also an understanding of the
growing role of tourism in the New Zealand economy, and the role such
places played in the furtherance of this, and in propagating a
‘clean-green’ international image.
Land was not put into Schedule 4 as some
sort of land-bank, which could be exploited once the price was right. We
do not believe that facilitating mining in Schedule 4 lands is
appropriate or important for New Zealand’s economic well-being. On the
contrary, we believe it could have serious negative repercussions on out
tourist industry and on our agricultural exports.
Clearly there is an intention to mine in
Schedule 4 lands. It is not logical to imply that the current exercise
is merely a stock-take, solely to find out what is present in these
areas, unless there is the possibility of mining. Such a cynical
approach would be hugely wasteful of many people’s time and money.
The environmental case against mining
on Te Ahumata.
Great Barrier Island is promoted to
Aucklander’s and overseas tourists alike as “the jewel in the crown” of
the Hauraki Gulf. The Gulf is a Marine Park, and mining is not permitted
under the District Plan.
The island includes the largest area of
Conservation Land within the Auckland Conservancy, and is regarded as
significant for its high biodiversity values (endangered birds, reptiles
and plants) and the absence of some significant mammalian pests (eg
possums, deer).
It is inconceivable to us that the
Minister of Conservation, Hon. Kate Wilkinson, should countenance the
removal of any part of this island from Schedule 4. The Mayor of
Auckland, John Banks, the National MP for Auckland Central, Nikki Kaye,
and the chairperson of the local Community Board, Paul Downie, have all
expressed strong opposition to any mining on Te Ahumata.
There will be strong opposition to this
proposal from lobby groups such as the Enironmental Defence Society, The
Royal Forest and Bird Society and Coromandel Watchdogs. The Great
Barrier Island Charitable Trust can offer support to such groups in the
form of information in its recently completed “Great Barrier Island
State of the Environment Report”.
The area in question is crossed by the
central portion of ‘The Great Walk’, which is being developed to
encourage tourism on the island.
Te Ahumata is highly prominent feature of
the central part of the island, visible from many points, including the
administrative centre (Claris), and the airport. It is the most
conspicuous feature seen by tourists as they approach the island from
the air. In his 1980 report (Ministry of Development #372) Rabone noted
that: “The scars of mining would tend to be obvious, both to the local
population and to visitors by air”.
Rabone (1980) also notes: “In the event of
open-pit mining, a suitable area for spoil/tailings is the adjacent
Kaitoke swamp …. which would also provide soil material suitable for
post-mining rehabilitation.”
He indicates that the vegetation of the Te
Ahumata area is of no consequence, and suggests that hydrothermal power
might be tapped at the hot springs.
While these views are now historic, and
hopefully do not reflect current thinking, the points they raise, namely
high visibility, the problems of an adequate power source, what to do
with vast quantities of toxic tailings, and how to rehabilitate the
site, remain pertinent.
The casual disregard of the local
community by mining companies, as demonstrated in the above quotations,
should not be furthered by the government, whose role is to serve the
best interests of all New Zealanders; in our view, to create a large
industrial site in this setting is totally inappropriate for the future
long-term sustainable development of the island’s economy, and is likely
to be resented and resisted by a significant proportion of the
population.
The environmental case against mining on
Great Barrier Island is very strong, and is backed by legal precedents,
which demonstrate the high biodiversity, environmental and social values
of the island.
The economic case against mining on Te
Ahumata.
The economic case for mining on Great
Barrier is very weak, and backed by a history of resource exploitation
which has left no appreciable be nefits
for the local community.
Background Research
Three main quartz veins or reefs, the
Iona, Sunbeam and Barrier reefs, have been worked in the past. The
quartz in these veins carries on average about 3.6g/tonne of gold, and
from 140 to 1100g/tonne of silver, but the grades vary greatly from
sample to sample. When the mines closed (c. 1920) the Barrier reef was
considered to be ‘worked out’.
Waihi's Martha Mine - open pit extraction
of similar
epithermal gold deposits to GBI. Photo: Ugotravel blog
Since the old mines closed, very extensive
exploratory investigations, drilling and sampling has been carried out
on Te Ahumata (Quennell 1963, Quennell et al. 1973, d’Auvergne 1974,
Rabone, 1980, 1981, Canyon Resources 1984).
In addition, according to Barker (2010)
“over the last ten years, reviews and assessments of the mineral
potential of the goldfields have been made”. However, no further
reference is made to these additional, more recent, data.
Thus, the nature of the underlying
geology, and the possibility of further gold and silver deposits, have
both been very thoroughly investigated already.
Ten drill holes have been bored through
the plateau, initially with the intention of intersecting the known
reefs, and subsequently to investigate the potential for a larger
stratified diffuse ore-body beneath the mountain. The latter was not
found: “a large tonnage of ore-grade mineralisation within the rhyolitic
tuffs is now virtually excluded” (Rabone 1981).
Referring to the Iona reef Rabone (1981)
notes that some potential remains: “as a relatively small-scale
quarrying proposition for a small mining company”. But he also notes
that : “ At deeper levels, where intersected in drill holes, it (the
Iona vein) was found to be much narrower and weaker than at the surface,
and was not significantly mineralised”.
Canyon Resources (1984) reinterpreted the
drill hole results, and assumed that the most significant drill hole
(DDH2) did not in fact reach the main Iona vein, rather it sampled small
veins penetrating the rock above the main vein.
Confusingly, Canyon Resources (1984) claim
that (by analogy with similar veins on the Coromandel Peninsula): “..it
is likely that ….. mineralisation would reduce sharply with depth to the
underlying andesites”, and also (without any drill-hole based evidence)
that there is “good potential for significant grade improvement and
increased gold/silver ratio in the deeper levels” (i.e. in quartz vein
where it penetrates the underlying andesites).
The Tailings.
To realise the supposed value of the
gold/silver in the Iona and Sunbeam reefs would involve the removal of
4.317 million tons of quartz rock. This then would be crushed and
treated with cyanide before electrolytic separation and smelting. The
resultant tailings are acidic and toxic for plant growth.
Depending on the thickness of the pile,
this quantity of tailings could cover up to 400 ha. It would certainly
require an area of tens of hectares.
A cover of new top-soil to at least 1m
depth, and extensive planting of the area with native vegetation would
be required.
Value of resource.
Inexplicably, the current value of the
gold/silver resource on Te Ahumata has been stated as $NZ4.3 billion by
the Ministry of Economic Development. This figure is not substantiated
by Ministry’s own review (Barker 2010), which gives an estimate of
$NZ1.28 billion (but concludes with the figure of “more than $NZ1
billion”). This much lower estimate supposes that average gold and
silver concentrations (which vary widely in different samples) in the
quartz are maintained throughout the reef, and that the reef thickness
and lateral extent has been correctly estimated and is maintained in the
underlying geological structure (andesite). Finally, it also assumes
that all the quartz is removed, and all the metal extracted from it,
from the surface to sea-level.
Moreover, Barker’s (2010) report also
stresses the “substantial investment in exploration, feasibility
investigations and development”, which would be needed to realise any
potential economic benefits.
Rabone’s (1981) statement about the
thinning of the reef with depth, calls into question even Barker’s
(2010) lower estimated value, as he assumed that the Iona reef
maintained both its thickness and mineralisation to sea level. Canyon
Resources (1984) statements appear to be based on an optimistic
assessment of drill hole 2 (DDH2) and analogy with supposedly similar
situations on Coromandel.
Thus, while there is clearly some
gold-silver mineralisation in the quartz veins and associated rock, we
are left with no convincing evidence that an economic gold/silver ore
body, or economic quartz reefs, lie under Te Ahumata.
We conclude that the value of the resource
estimated by Barker (2010) is based on assumptions for which there is
rather weak supporting evidence. The three-fold higher value given by
the Ministry of Economic Development cannot be substantiated from any of
the published reports referred to, and seems to be a wildly optimistic
speculation.
The References used in the Trust’s
submission can be viewed here. |
