australia's identified mineral resources 2005 - Geoscience Australia

AUSTRALIA’S IDENTIFIED MINERAL RESOURCES 2005
LEAD
Lead EDR of 23 Mt is about 40% of total lead resources and over 30% of world EDR, making Australia
the leading inventory country. Queensland has over 60% of EDR, mainly at Cannington and Mt Isa,
with other holdings in the Northern Territory, New South Wales, Western Australia and Tasmania.
Total identified resources increased from 55.2 Mt in 2003 to 56.8 Mt in 2004. EDR increased by 18%
to 22.9 Mt of contained lead, which comprised 40% of total identified resources. Queensland retained
first ranking with EDR increasing from 10.2 Mt to 14.1 Mt, over 60% of total EDR. The increase was
due to additional resource definition and reclassification at Mt Isa. The Northern Territory decreased
slightly from 5.53 Mt to 5.25 Mt EDR, 23% of the total. New South Wales declined further from 1.7 Mt
in 2003 to 1.6 Mt in 2004, through production at Broken Hill and Elura. EDR in Western Australia
static at 1.8 Mt, while in Tasmania it rose by 0.02 Mt (22%) to 0.11 Mt due to a small increase in
resources at Rosebery.
Of Australia’s EDR of lead, 43% is in JORC ore reserves categories (down from 54% in 2003).
The national EDR/production ratio is 35 and ore reserves/production ratio 15.
Paramarginal demonstrated resources of lead are 2.9 Mt (2 Mt in 2003), which is 5.1% of total
identified resources. Submarginal demonstrated resources totalled 9.3 Mt (9.2 in 2003) or just over
16% of total identified resources. These changes are attributed to relatively small adjustments in most
states and the Northern Territory in both categories.
Total inferred lead resources fell by over 13% to 21.6 Mt following reclassifications of resources,
in particular the Mt Isa and George Fisher resources.
SILVER
EDR for silver are 50 000 t, which is 18% of world EDR. Queensland has 78% of EDR mainly in the
Mt Isa, Cannington, Century and Hilton deposits. Other holdings are in the Northern Territory, South
Australia, New South Wales and Western Australia.
EDR decreased marginally to 41.4 kt in 2004. Queensland remained the major holder, although its
EDR went from 32.2 to 30.1 kt (less than 73%) as a result of resource depletion at Cannington.
The Northern Territory at 4.5 kt had the second largest EDR and its share of the total was marginally
down to 11%. South Australia had the third largest EDR with 2.5 kt (2.4 kt in 2003) followed by
New South Wales at 2.3 kt (2.2 kt in 2003), with minor increases at Broken Hill and Elura offsetting
decreases at Tritton. Western Australia was next with 1.2 kt (0.8 in 2003), followed by Tasmania with
0.41 Mt (0.31 kt in 2003), due to minor increases at Rosebery, with Victoria unchanged at 0.28 kt.
Of Australia’s EDR of silver, 63% is in JORC ore reserve categories. EDR/production ratio is 19 and
ore reserves/production 12.
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Paramarginal demonstrated resources of silver increased from 9.82 kt in 2003 to 17.6 kt in 2004 and
submarginal demonstrated resources increased from 11.8 kt to 16.9 kt over the year. These changes
result from increases at Mt Isa and George Fisher mines and Bowdens deposit in New South Wales.
Total inferred silver resources decrease slightly to 41.4 kt in 2004 following an increase of resources
at Mt Isa’s open pit mine.
Exploration
In 2004, expenditure on zinc-lead-silver exploration was $33.4 million, 12% higher than in 2003,
and about 16% of total base metal expenditure of $207.3 million. In the March quarter 2005 spending
on zinc-lead-silver exploration was $7.0 million, slightly higher than the preceding March quarter.