Mining_Methods_UnderGround_Mining - Mining and Blasting

Ore processing
MOunT iSa, auSTralia
Mount isa mines – the company
Scooptram loader at Mount Isa.
Wholly owned by MIM Holdings,
Mount Isa Mines (MIM) has 2,000
permanent employees at its Mount Isa
and Townsville operations, and over
Lead-zinc-silver ore from Mount Isa
and George Fischer mines is ground to
a fine powder at the Mount Isa facility,
after which a flotation process is used
to separate waste, and produce lead-rich
and zinc-rich concentrates.
Lead concentrate from Mount Isa
contains 50-60% lead, and around 1
kg of silver/t. After smelting to remove
further impurities, blocks of material,
each containing approximately 3,984 kg
of lead and 10 kg of silver, are transported
by rail to Townsville for shipment
to MIM’s lead/silver refinery
in England. In 2001-2002, lead-zinc
concentrator throughput and recovery
increased, and there was improved plant
reliability at the lead smelter.
Around 51% zinc concentrate is also
railed to Townsville for refining, or ship-
ment to overseas customers. MIM currently
produces approximately 190,000
t of lead bullion and 500,000 t of zinc
concentrate each year.
At the Mount Isa processing facility,
there is a chimneystack at the copper
smelter, built in 1955, which is 155 mhigh,
and at the lead smelter the stack,
5,800 employees in other operations
across Australia and overseas. In addition
to the Mount Isa complex, MIM
has copper mines at Ernest Henry in
Queensland, and a 50% interest in
the Bajo de la Alumbrera project in
Argentina. For lead-zinc-silver,
there is the George Fischer mine (incorporating
the former Hilton mine)
in Queensland, which uses the Mount
Isa and Townsville processing facilities,
and a majority interest in the
McArthur River mine in Australia’s
Northern Territories. There is a gold
mine at Ravenswood, and extensive
coal operations. The latter comprise
built in 1978, is 270 m-high. Copper is
produced electrolytically in the form
of anodes. Each weighs 375 kg and is
99.7% pure copper.
expansion plans
In the year ending June, 2002, record
copper smelter production of 233,000 t
of anode was achieved. This was up
from 207,000 t for the previous year.
A recent copper study to improve
reserves and efficiencies has resulted in
an increase in reserves to 12 years. This
has led to a planned 40% expansion in
copper production by 2006. A rate of
400,000 t/y for up to 20 years from
Mount Isa and MIM’s Ernest Henry
Mine is predicted by MIM.
MIM is planning to expand copper
production by developing the 1900 ore-
body, the Enterprise Mine 3000 and
3500 orebodies, and the surface open
pit mines in and around existing orebodies.
The aim for 2003 was to increase
Mount Isa copper production to 245,000
t, improve the recovery rate in the concentrator
following an upgrade, and
increase plant utilization by improving
maintenance practices. It is estimated
Table: Mount Isa mine life production statistics
Resource Tonnage (million t)
Total lead-zinc ore mined and processed 100
Total copper ore mined and processed 200
Total copper resource remaining 400
Total lead-zinc resource remaining 200
coking coal at Oaky Creek, steam coal
at Newlands, and steaming and coking
coal at Collinsville. There is also coal
shipping from Abbot Point and Dal-
rymple Bay, and a coking plant at
Bowen Basin. All are in Australia.
MIM’s sources of revenue from all
mines are split by products: copper
31%; by-product gold 8%; Ravenswood
mine gold 1%; zinc 18%; lead 8%;
silver 4%; coal 30%.
Markets for Mount Isa’s copper are
Australia (33%), Asia (53%); and
Europe (14%). Mining finance group
Xstrata owns MIM Holdings.
that Mount Isa has over 6 million t of
contained copper still to be mined, more
than has been extracted over the past
60 years.
In more detail, the 2002 reserves and
resource report gave a total of proved
and probable ore reserves of approximately
73 million t at 3.3% copper
(previously 47 million t at 3.6% copper).
The total underground measured, indicated
and inferred resources, including
reserves, were approximately 116 million
t at 3.3% copper (previously 88 million t
at 3.7% copper). In addition there were
a total open-cut indicated, inferred resources
of 255 million t at 1.2% copper
(previously an inferred resource of 112
million t at 1.6% copper).
The improved lead-zinc concentrator
performance and smelter reliability in
2001-2002 contributed to an increase in
production from 140,000 t to 161,000 t
and reduced operating costs. Still, MIM
is planning to reduce off-site realization
costs such as transport and smelting,
which represent up to 60% of total production
costs at present.
acknowledgements
Atlas Copco is grateful to the management
of Mount Isa Mines, and in
particular to Jim Simpson, General
Manager Mining, Lead Zinc, for writing
this article which first appeared in
Underground Mining Methods, First
Edition.
104 underground mining methods