Mining_Methods_UnderGround_Mining - Mining and Blasting

garPenBerg, Sweden
Simba M7 C production drill rig at Garpenberg.
mine led to the progressive extension
of a 1:7 ramp down to the 910 m level.
In 1998-9, it was extended to the 1,000
m level, increasing the overall length to
8.7 km.
To increase hoisting capacity at the
Garpenberg mine, the new Gruvsjö production
shaft was completed in 1997
and the original shaft was converted
for personnel and materials hoisting.
With a hoisting capacity of 450,000
t/y, the newer shaft connects with a
ramp accessing the Kanal and Strand
orebodies.
The present operating area extends
approximately 4.5 km SW to NE from
the original shaft to the Gransjön mining
section.
Concentrate production
Upgraded in the early 1990s, the concentrator
yields separate zinc, lead,
copper and precious metals concentrates.
The zinc and lead concentrates
are trucked to Gävle harbour and ship-
ped either to Kokkola in Finland or Odda
in Norway. Copper and precious metals
concentrates are railed to the Rönnskär
smelter in Sweden. Since 1957, Boliden
has milled over 20 million tonnes of ore
at Garpenberg.
While the new shaft raised hoisting
capacity, and ramp extension accessed
new ore in the North mine, metals production
rose to record levels in 1998.
However, this improvement could not
be maintained. Zinc concentrate output
fell from 69,051 t in 1998 to 61,126 t in
2001, despite a rise in ore production.
And proven plus probable ore reserves
declined from 5.7 Mt in 1998 to 2.2 Mt
at 4.0% Zn in 2003, putting a question
mark on the future of the mine.
However, Boliden continued to make
investments in technology for the long
term at Garpenberg. The mine, the company
and the market are now benefiting.
And the geologists are very popular.
new reserves
Probably the most significant event at
Garpenberg during the period of decline
was the discovery in 1998 of a new orebody
between Garpenberg North and
Dammsjön, named Lappberget. This
encouraged the company to start development
in 2000 of an approximately
3.0 km-long drift to connect the 900 m
level at Garpenberg North, first to Lapp-
berget for exploration access, and thence
to the ramp at the 800 m level at Garpen-
berg. During 2001, Boliden started core
drilling at the 800 m and 1,000 m levels
in Lappberget, and by February, 2003
was able to start mining ore from the
new source. Zinc concentrate production
in the year increased to 80,748 t.
In March, 2004 the connecting drift
was completed, and the formerly separate
mines have since been regarded and
managed as a single operation. The drift
allows access and infrastructure deve-
lopment of new mineable areas, and
Garpenberg quickly boosted mine output.
The main focus has been on Lappberget,
including driving a ramp close to the ore-
body from the 350 m level, with connection
to the surface scheduled for 2007.
The Tyskgården mineralization, discovered
in the early 1980s, also became
accessible, and mining started there in
2003-4. In 2004 Boliden discovered an
extension of the Dammsjön mineralization
around the 800 m level, and during
2005 a new discovery was made, the
reportedly large and potentially highgrade
Kvarnberget deposit.
Higher output
In 2005, the mine produced 1,102,000 t
ore grading 5.75% Zn, 2.28% Pb, 0.09%
Cu and 117 g/t Ag. Approximately 40%
of the ore came from Lappberget. The
mill yielded 101,000 t of 55.3% zinc
concentrate; 29,000 t of 72% lead concentrate
with 1,800 g/t silver; 2,800 t
of 15% copper concentrate with 40,000
g/t; and 120 t of precious metal concentrate
grading 65% lead, 40,000 g/t
silver and 400 g/t gold. Some 967,000
t of tailings retained 0.34% Zn, 0.29%
Pb, 0.02% Cu and 25.5 g/t Ag. By end-
2005 Boliden employed 280 people at
Garpenberg, with a further 70 working
for contractors at the site.
The operation works around the
clock 7 days/week in both the concentrator
and the mine, with mining
carried out by four production teams
supported by a development crew and
a charging crew. Garpenberg is the
Hedemora Community’s largest private
sector employer.
Since the start of 2005 exploration
has continued, not only adding tonnes,
but also raising average grade. Thanks
to the exploration effort, Garpenberg
also started 2006 with proven reserves
of 4.73 Mt grading 6.0% Zn, 2.5% Pb,
48 underground mining methods