Overview
North American Palladium Ltd. Is one of the world's only two
primary palladium producers. The Lac Des Iles (LDI) mine is located 85
kilometres northwest of Thunder Bay in northern Ontario. There is no nearby
community and accommodations are provided at the mine camp.
The Lac des Iles deposit contains one of the largest bulk mineable
palladium reserves in the world. The mine has been in operation since 1993;
underground mining commenced in 2006 to access higher grade material.
The mine is an underground mining operation and open pit operations. The
mining methods used are longitudinal and transverse long-hole open toping.
There were 196 employees at the Lac des Iles mine.
The ore crushing system includes a gyratory crusher, and secondary
crushers. The crushed ore is processed in a standard flotation circuit. A
palladium rich sulfide concentrate is produced and shipped off-site for
final processing.
Payable palladium production for the year ended December 31, 2011
was 146,600 ounces.
In 2004 a final feasibility study confirmed the economic viability of
the Roby zone located directly underneath the existing open pit, initiating
the planning for the underground operations. Commercial production of the
underground mine commenced in 2006. On August 16th, 2010 the
company announced the results of preliminary economic assessment on the
offset zone, which was discovered in 2001. The existing open pit and
underground resources, particularly at the Offset Zone, represent potential
to extend the current mine life.
The company is expanding the underground mine and intends to transform
it into a long life asset that is also a low cost producer. The expansion
is underway and it makes a transition from mining via ramp access to
mining via shaft while utilizing a high volume bulk mining method.
Commercial production from the shaft is targeted for the end of 2012.
Palladium represents approximately 59% of
revenues generated from the operation. The remaining 41% are comprised of
platinum, nickel, gold and copper.
Location
Lac des Iles is located 85 kilometers northwest of Thunder Bay, Ontario
and Lake Superior. This is northwestern Ontario on the Canadian Shield, a
vast rocky plateau, bordered to the south by Minnesota, to the west by
Manitoba, and to the east by Thunder Bay. The Shield regions of northern
Ontario are largely lakes, rocks and trees. Large parts of the region are
monotonous, and the landscape rarely rises more than 100 meters.
Geology
The 1,465 ha property consists of 6 Crown Mining Leases comprising
3416.3 ha. Contiguous with these leases are 54 mineral claims consisting of
331 claim units covering 5,119.1 ha, for a total property area of 8,535.3
ha.
All of the known PGM reserves occur within a gabbro intrusion that is
approximately 10 sq km in size and is part of the Lac des Iles intrusive
complex. PGM and base metal mineralization in the Lac des Iles intrusion
occurs in both primary and secondary situations within sulphide and
silicate minerals. Mineralization appears to be dominantly stratabound
along the contact between the East Gabbro and the mineralized Heterolithic
Gabbro Breccia. Within the Heterolithic Gabbro Breccia, there is a high
grade core typically constrained to an easily recognized ultramafic unit
know as the Pyroxenite.
The Roby Zone Deposit is hosted within an Archean aged suite of
mafic/ultramafic intrusives called the Lac des Iles Intrusive Complex. The
Roby Zone Ore Body is dominated by varitextured gabbro containing pipes and
pods of breccia. The breccia contains blocks up to (~60 m across) of
varying lithology. Mineralization at Lac des Iles occurs as: (1) PGE-Ni-Cu
rich breccias (breccia ore); (2) mineralized dikes or sills (North Roby
Zone); and (3) within a 15 m to 25 m thick unit of high grade Pd
mineralization located along the eastern portion of the Roby Zone in
contact with the barren East Gabbro that forms the hangingwall of the
deposit.
The Roby Zone is currently being exploited by means of underground
mining methods. Mineralization to date at the Roby Zone has been outlined
by surface trenching and diamond drilling over a 900 m long by 850 m wide
area, and has been traced to a vertical depth of 1220 m.
The Offset High Grade zone (OHGZ) is believed to be the fault displaced
continuation of the Roby Zone mineralization and is located below and
approximately 250 meters to the west of the Roby Zone. 2011 drill results
were positive and also indicated that the mineralized zone is still
open in several directions.
The ongoing underground mine expansion is based on the Offset Zone.
Mining & Operation
The Company began mining the Roby Zone in 1993 using open pit mining
methods. Ore and waste from the open pit is mined using conventional
hydraulic 27 cubic meter and 23 cubic meter shovels, 190 tonne trucks, 187
millimeter blast hole drills and a fleet of conventional ancillary
equipment. Mine waste is stockpiled outside of design pit limits.
Development of the underground mine commenced in the second quarter of
2004 in order to access the higher grade portion of the Roby Zone. The
underground deposit lies below the ultimate pit bottom of the open pit and
extends to a depth of approximately 660 meters below the surface where it
is truncated by an offset fault. Commercial production from the underground
mine commenced on April 1, 2006..
The chosen mining method for the underground mine is sublevel retreat
longitudinal longhole stoping with no fill. The mining block interval is 70
meters floor to floor including a 15 meter to 25 meter sill pillar below
each haulage level. Stopes are 45 meters to 55 meters high by the width of
the ore body. Total intake ventilation for the mine is designed to be 205
cubic meters per minute. There is one intake ventilation raise/secondary
egress situated outside the ultimate open pit limits and air exhausts up
the main ramp.
At the rate of production prior to being placed on temporary care and
maintenance on October 29, 2008, open pit ore reserves would have been
exhausted during the first half of 2009 and the current underground mining
operation would have continued until late 2010 or early 2011. Management
currently anticipates that high grade ore at the pit bottom will be
accessed from the Roby underground mine.
It is envisaged that the Roby underground mine will support production
at lower tonnage levels but higher grade than historical production. The
Roby underground has identified reserves and resources for at least two
more years. During this period, development work on the Offset Zone will
continue with the objective of achieving a seamless changeover from the
Roby underground to the Offset Zone.
The company is expanding the underground mine and intends to transform
it into a long life asset that is also a low cost producer. The expansion
is underway and it makes a transition from mining via ramp access to mining
via shaft while utilizing a high volume bulk mining method. Commercial
production from the shaft is targeted for the end of 2012.
The mine was placed on temporary care & maintenance in the period
October 2008 - December 2009.
Processing
In 2001, a new mill facility was commissioned with a nominal design
capacity of 15,000 tonnes per day. The processing operation utilizes a
conventional flotation technology to produce a palladium-rich concentrate
that also contains platinum, nickel, gold and copper.
Ore is first crushed in a gyratory crusher and conveyed to a coarse ore
stockpile. With the commissioning of the secondary crusher in 2004, the
coarse ore stream can be split so that a portion is crushed in the
secondary crusher producing a fine material feed which is then combined
with the coarse feed. This mixture of coarse and fine material feeds the
SAG mill to increase mill throughput. In 2005, modifications were made to
the secondary crusher, including the installation of a slide gate and
better control feed distribution.
The ore is ground to a nominal P80 (the size of an opening through which
80% of the product will pass) of 74 microns in a conventional
semi-autogenous mill/ball mill/pebble crusher (SABC) circuit. The ground
ore then feeds a flotation circuit that is comprised of rougher/scavengers
and four stages of cleaning. The flotation circuit in the old concentrator
is currently connected to the new concentrator to provide additional
cleaner flotation capacity. The final concentrate is thickened and
dewatered using two pressure filters.
