The “core” of the Canadian Shield consists of three Archean (pre-2300 my) “provinces” or proto-continents, of which the largest is the Superior province; it extends from the Saskatchewan-Manitoba border in the west to western Labrador in the east, and from Lake Huron in the south almost to the northern extremity of Québec. Around the edges of the Superior province are a series of elongated sedimentary basins (or “troughs”) that developed at various times from 2200 my to 1800 my, and have themselves been folded, metamorphosed and accreted into the expanding Canadian Shield. These fold belts contain a remarkable mineral endowment which makes up a large part of the mineral wealth of the Shield. In the south is the “Huronian fold belt” and its Elliot Lake uranium deposits. In the northwest is the well known Thompson nickel belt. In the northeast is the “Cape Smith-Wakeham Bay fold belt” with its exceptionally rich nickel-copper-PGE deposits. In the southwest is the clumsily named “Minnesota River Valley Terrane” which hosts the iron deposits of northern Minnesota and Wisconsin. And in the east is the much larger and much more prolifically iron-bearing Labrador Trough.
The Labrador Trough (alternatively known as Labrador Fold Belt or Labrador geosyncline) is a belt of Proterozoic (i.e. post-2300 my) sedimentary rocks and associated igneous intrusions that extends for almost 1,500 kilometres from south to north and is up to 100 kilometres wide. At its western margin, the Labrador Trough is structurally simple, with sediments resting on Archean basement and dipping gently to the east. Towards the centre of the trough the structure becomes more complex with at least two generations of folding and a series of east-dipping thrust faults.
Iron ore was discovered in the Labrador Trough by the Geological Survey of Canada in 1894, although there is little doubt that the indigenous Cree and Innu populations, who valued hematite as a pigment, were well aware of the deposits long before that. However, because of the relative remoteness of the area, there was no serious attempt to develop the iron deposits until after the second world war. Exploration outlined a large body of DSO at Knob Lake, which led to the development of the town of Schefferville and the construction of the 565-kilometre QNS&L rail line to the deep-water port of Sept-Iles on the St. Lawrence north shore in Québec. Production by Iron Ore Company of Canada (IOC) commenced in 1954 and continued until 1982, and 350 million tons were mined and shipped. This was the first phase of iron mining in the Labrador Trough.
The second phase of iron mining in the Labrador Trough started in the early 1960s and soon came to outstrip IOC’s DSO production from Schefferville. The southern end of the Labrador Trough extends into the Grenville Province where a much higher grade of metamorphism has recrystallized the taconite into an ore with a coarser grain size, hence easier and cheaper beneficiation. These iron ores are referred to as “metataconites”. Similar rocks in Brazil are referred to as “itabirite”. Production of metataconite began at IOC’s Carol Lake mine in 1962, and at Wabush Mines (now Cliffs Natural Resources) Wabush/Scully mine in 1965. In adjacent parts of Québec, Quebec Cartier Mining (now ArcelorMittal) commenced mining at Lac Jeanine in 1963, then moved north to much larger deposits, starting to produce at Fire Lake in 1973 and Mont Wright in 1975. Consolidated Thompson Iron Mines commenced production at Bloom Lake in 2010. Complex folding, which is typical of the Grenville province, has often caused thickening of iron formations, and this has made delineation of large orebodies much easier.
The third phase of iron mining in the Labrador Trough is just commencing. Driven by higher prices for iron, and the fact that world reserves of DSO are being rapidly depleted, interest is focusing on developing plain taconite deposits. There is nothing unusual or innovative about this. Taconite mining commenced in Ontario and Minnesota in the late 1950s. These areas of course had a more developed infrastructure and were closer to markets, so development was easier. Further developments in Labrador were restricted in those years because the QNS&L railway was operating at full capacity until the Schefferville mines closed in 1982 (while it formerly operated trains of 100 cars carrying 100 tons of pellets or ore each, it can now operate trains of 240 100-ton cars). Also the Cartier Railway was wholly owned by Quebec Cartier Mining and was not accessible to other users.
While the metataconites of the southern Labrador Trough can develop large tonnages by repetitive folding, the somewhat simpler structures of the northern Labrador Trough lead to taconite deposits with more lateral consistency. Hence it is often possible to delimit large resources with widely spaced drilling.
In the current phase of development of the northern Labrador Trough, the main players are as follows:Labrador Iron Mines Holdings Ltd. has acquired IOC’s residual DSO deposits near Schefferville, which total 150 million tons at about 55% Fe. This project benefits from existing infrastructure and is expected to commence production shortly. New Millenium Capital Corp. holds a 20% interest (Tata Steel of Singapore 80%) in a series of DSO deposits near Schefferville with a total measured+indicated resource of 56 million tons at 59% Fe and an inferred resource of 6 million tons at 56.7% Fe. New Millenium also has two taconite deposits – Labmag, with measured+indicated resources of 3.66 billion tons at 29.6% Fe (plus inferred resource of 1.47 billion tons also at 29.6% Fe) and the Kemag deposit with measured+indicated resources of 2.45 billion tons at 31.3% Fe (plus inferred resource of 1.01 billion tons at 31.1% Fe). New Millenium and Tata Steel are planning production with the use of a slurry pipeline to transport product to the coast. They appear to be hedging their bets and negotiating for use of the rail line as well.
Adriana Resources Inc.’s Lac Otelnuk taconite deposit has been drilled off and has an indicated resource of 4.29 billion tons at 29.08% Fe plus inferred resource of 1.97 billion tons at 29.24% Fe. Champion Minerals Inc.’s Attikamagen project has deposits of DSO and taconite that are currently having resource estimates prepared. Grand Century Iron has the option to earn 60% in the project. Cap-Ex Ventures Inc. has a property at Lac Connelly only 20 km southwest of Zone Resources Inc.’s Girard Lake project. The Lac Connelly property has reported zones of DSO and taconite mineralization.
- Canada: Innu Forced to Protest Cap-Ex Ventures’ Exploration Activities (yubanet.com)
- Rio Tinto plans to double Labrador mine output (cbc.ca)
- More student housing needed in western Labrador: Jones (cbc.ca)
- Goldman Sachs Says Yes On Metals & Mining: Growth Vs. Value (FCX, AA, CENX, RS, WOR, XME, COPX) (247wallst.com)