Extreme exploration - Uranium in the Arctic Circle

Materials World magazine
,
2 Oct 2012

What prompts a company to set up a base perched on the edge of the Arctic Circle, more than 200km from the nearest town? Michael Forrest talks to Jim Paterson of Kivalliq Energy Corp to find out.    

Harsh climate and remote locations add to the challenges of exploration, and Canadian company Kivalliq Energy Corp knows all about them. The company’s exploration camp at Angilak is in the centre of what is known as the barren lands that in the short Arctic summer is a treeless tundra only accessible by aircraft. In winter, caterpillar tractors and sleds can traverse the icy ground and frozen lakes are used as temporary landing strips.    

So what leads a company to be here? Uranium. Demand for it is growing and currently stands at 68,000t per year, fuelling a global generating capacity of 375GWe. According to a recent study by the Ux Consulting Company, the gap between uranium supply and demand shows no sign of diminishing, despite reviews undertaken by many countries following the events at Fukushima. The majority of resources are in Australia, with Kazakhstan in second place, followed by Russia. However, when measured by a price of under US$80/kg or US$35.5/lb (current price US$49.50/lb, US$136/kg), Australia and Canada account for more than half of global resources.    

Geological grading    
Although uranium is not a rare metal – it is similar in concentration to zinc or tin in Earth’s crust – there is a huge variation between rock types in the concentration of uranium, and even in uranium mines. For example, the Rössing granite-hosted mine in Namibia is around 270ppm, while very high grade ore associated with the Athabasca Basin mines in Canada is in excess of 20,000ppm. This variation reflects the local geology and its metallogenic history. Principal targets for high grade deposits are those formed at unconformities between rock groupings of Archean Eon (fewer than 2.5 billion years old) and lower Proterozoic (2.5–1.5 billion years old) in basin environments, the Athabasca deposits being typical.    

In Nunavut, Kivalliq is exploring in a similar environment. In terms of regional geology, its Lac Cinquante uranium deposit (LCUD) is located adjacent to Proterozoic basins that formed during the structural deformation of the Churchill province. It is thought these were the result of compression between the Superior and Slave provinces causing crustal shortening, thickening, uplift and then collapse. The entire Angilak property is located between two very large shear systems resulting from this deformation, the Snowbird zone to the northwest and the Tyrrel shear zone to the southeast. These zones were formed during the Archean and reactivated periodically by Proterozoic tectonic activity and especially in the mid-Proterozic when extensional movements defined basin development in a northeasterly trend. The outcome was a series of fault-bound rift basins, accompanied by voluminous alkali magmas related to these reactivated Archean structures, collectively known as the Baker Lake basin and its sub-basins.    

The LCUD is structurally and stratigraphically controlled and the majority of the mineralisation is vein-hosted, occurring within or near to a graphite and sulphide-bearing tuffaceous horizon. It is located at the eastern margin of the Angikuni basin (a sub-basin of the Baker Lake basin) and is situated in Archean volcanics next to the unconformable contact with Proterozoic metamorphosed sedimentary and volcanic rocks that are approximately 1.8 billion years old. Basin lithologies at the contact are coarse-grained sandstones and conglomerates resting on an unconformity represented by a paleo surface breccia comprised of the weathered Archean basement of mainly mafic volcanics and rarer gneiss. Although the breccia tends to have higher background radioactivity than the overlying basin, it is essentially unmineralised. Above the basal sequence are finer gained sediments intercalated by volcanic lavas and clastics. As there are no volcanic fragments within the finer-grained sediments it is postulated that the sedimentation occurred between volcanic outpourings.    

Jim Paterson, CEO of Kivalliq, explains the company has been drilling extensively on its Angilak property since 2009. Historical data from exploration in the Angikuni basin identified significant uranium mineralisation, but the lack of technical data on past drilling programs prevented inclusion in a National Instrument 43-101 compliant resource statement. Paterson continues, ‘In 2009 and 2010, we extended drilling to a depth of 275 metres to test the mineralisation in the main zone of the LCUD and to the east and west along strike length’. In these two years, 18,350 metres of core from 139 holes was recovered. This enabled Kivalliq to produce a compliant inferred resource estimate of 810,000 tonnes at an average grade of 0.792% (7,920ppm).    

In 2011, Kivalliq drilled an additional 23,849 metres, and based on those results an update to the mineral resource base was obtained. This update, based on a lower cut-off grade of 0.2%, estimates an inferred resource of 1,779,000 tonnes at an average grade of 0.692% U3O8. Last year a number of samples were collected from the radioactive ore-bearing intersections within the LCUD. The most abundant uranium mineral was uraninite (pitchblende) with trace amounts of brannerite and uranophane. The gangue minerals are dolomite and calcite, quartz and feldspar and a number of sulphides with pyrite being the most common. Preliminary tests on a 65kg composite sample returned recovery rates in excess of 90% with both acid and alkaline circuits. Due to the high carbonate content of the ore, acid consumption is high. Saskatchewan Research Council (SRC) is refining metallurgical processes to minimise acid consumption and maximise recoveries.    

The project has developed significantly over the past three years and has almost doubled the inferred resources. Work on characterising the uranium and other metal mineralisation has shown that samples from the tuffaceous horizon differ significantly from surrounding lithologies. Within the mean is 0.68% U3O8 and 12.2ppm silver, 0.17% copper and 0.22% molybdenum. Outside the uranium mean falls to 0.02% while the other metals are approximately 10% of those within tuffaceous horizon. There are, however, high values outwith, resulting from samples taken within fault zones that are interpreted as feeders to the main mineralisation. It is possible that these zones may add to the resource base but at present they are not included in the inferred resource statement.    

Paterson continues, ‘We have also explored proximal targets to the LCUD with some success. Both 2011 and 2012 have been great years for discoveries of new zones.’ The Blaze area, approximately two kilometres west of the LCUD, has been drilled across a strike length of 100 metres with significant mineralisation recorded 30–126 metres below surface. An exceptional value 1.01% U3O8 was recorded over a 25-metre interval, having an estimated true width of four metres. The principal mineral is uraninite with disseminated and patchy zones of sulphide mineralisation in quartz carbonate veins and fractures. At Pulse 600 metres northeast of LCUD mineralisation similar to the western zone was identified following a geophysical conductive trend, while at Spark, 500 metres west of the high grade Blaze zone, a single drillhole intercepted radioactivity at 47 and 80 metres. Perhaps the most promising are high-grade U-Cu-Mo and Ag values found at the BIF zone 10 kilometres from LCUD. Here values up to 30.30% U3O8, 22.9% Pb, 5.2% Cu and 163ppm silver were found in grab samples from boulders and a series of narrow shears in sparse outcrop. The BIF occurrence is associated with a 3km long magnetic response and possible reactivated shear zone.    

As Paterson explains, ‘Exploration at the Lac Cinquante uranium deposit and the rest of the Angilak Property continues to illustrate the exceptional uranium resources of the region by providing some of the highest uranium values outside the Athabasca Basin, the world’s richest uranium province’.