Mineral power

Materials World magazine
,
2 Mar 2010
Map showing the Crosshair Exploration and Mining site

Michael Forrest reports on the activities of Crosshair Exploration and Mining, which is exploring for uranium and vanadium in Labrador, Canada.

 

Canadian company, Crosshair Exploration and Mining has mounted extensive exploration programmes in the Central Mineral Belt (CMB) of Labrador, a province of complex geology and few inhabitants. Crosshair CEO Mark Morabito states his objective is to develop an energy company appropriate for today’s environmental and economic climate.

 

‘The company is focusing on clean energy components, including uranium and vanadium. The latter may come as a surprise, but one of the difficulties with alternative energy sources (for example wind and solar) is that their intermittency prevents base-load generation. The technology associated with vanadium redox batteries and their ability to rapidly charge and discharge without deterioration is ideal in this application.’

 

The principal energy project in Canada is in the CMB of Labrador, an area underlain by Archean granitic rocks. Regionally, the CMB is hosted in overlying middle Proterozoic sediments, volcanics and granitoid intrusions that have been deformed by three metamorphic episodes that extend from one to 1.7Ga. Structurally the basement is the Nain Archean craton overlain by the early Proterozoic submarine volcanics and sediments of the Moran Lake Group. These two provinces were overlain by the Bruce River Group, forming a distinct unconformity that is marked by a basal conglomerate, followed by a tuffaceous sandstone.

 

This regional geology defines the mineralisation of the CMB – there are three regional faults that mark the division between Nain, Makkovik and Grenville, a granitic basement and later intrusions that are possible sources of uranium and vanadium. These unconformities channel mineralising fluids, porous sandstones and breccias.

 

Its potential has been recognised for nearly 100 years. From the 1920s exploration, including uranium airborne surveys, took place at decade intervals but failed to pick up known surface radioactive zones associated with volcanic breccia units. In 1978, Shell Canada drilled three holes in the Moran Lake area (now the C Zone) following up boulder anomalies of two per cent uranium oxide (U3O8) found by previous explorers, and described the several uranium-bearing horizons as quartzite.

 

Morabito states, ‘We understood from all the previous exploration that there was undoubtedly large-scale uranium mineralisation in the district as attested by surface values of up to two per cent but the past piecemeal exploration, and its different objectives, required a new model. In 2004, we began systematic exploration with the objective of assessing uranium potential and proving the multiple deposit potential of the area. The main areas of interest were the Northstar licence areas that included the Armstrong, Moran Heights, Zone C and B, and Areas 1 and 51’.

 

Good grades

Extensive drilling over the C Zone, where the local geology is dominated by mafic volcanics and cherts overlain by sandstone, has revealed that the uranium mineralisation is generally fracture controlled and associated with silicification and iron oxide, and pyrite and chalcopyrite mineralisation. Some of this was measured by geochemical analysis of the core that the shallow Shell Canada drill holes (<75m) had recovered.

 

Spurred on by the good grades, Crosshair drilled 155 holes in 2007 with a composite depth of 28,612m to focus on expanding the resource at C Zone, it also tested Area 1, Armstrong and Croteau Lake. Crosshair proved its theory that the C Zone, Area 1 and Armstrong make up part of a 4.5km-long corridor, as seen in the map (above, right). The following year another 15,558m was drilled that enabled a 43-101 indicated uranium resource estimate of 6.92Mt grading 340g/t, and an inferred resource of 8.17Mt at 320g/t.

 

Sample analysis also reported concentrations of vanadium. Vanadium mineralisation is hosted mainly by hematised and brecciated mafic volcanic rocks. In many areas, its concentration is directly proportional to the intensity of these formations. The vanadium appears to be associated with an earlier mineralising event overprinted, in part, by a later event during which the uranium was deposited. Drill intersections of vanadium-rich mineralisation include drill hole C-14, which returned 62.6m averaging 0.237% vanadium oxide (V2O5).

 

‘The anomalous vanadium envelope extends beyond the uranium mineralisation, supporting a much larger deposit,’ says Morabito. In December 2009, the company began the Vanadium Resource Expansion Programme that includes re-sampling roughly 4,000m of core that formed the basis of the uranium resource definition. It is projected that

this will more than double the current vanadium resource of 27Mlb as previous low uranium logs that contained vanadium were not included in the resource. Vanadium has been intersected as far as 165m away from the existing resource envelope, demonstrating the project’s possibility for expansion.

 

According to Morabito, ‘Exploration is continuing across the company’s properties in the CMB’, and recent results within the area indicate large-scale mineralisation. However, it is the markets for these commodities that will support the conversion from prospect to mine.

 

Morabito points to the coming demand for non-carbon energy that can maintain a base load that intermittent wind and wave cannot fulfil. Nuclear new build is growing globally and uranium oxide spot prices are four times higher than a decade ago, six if the direct contract price is considered. Looking at vanadium, its use in high strength steel has reduced the weight of vehicles, pipelines and construction, with demand for these steels outpacing that of carbon steel.

 

Perhaps the most innovative use is in redox-vanadium batteries, which have the potential for large-scale power grid use due to their lifespan of tens of thousands of cycles, as well as the ability to absorb or release large amounts of electricity at a moment’s notice. The technology is well proven and is most suitable for static sites where the large volume-to-power ratio can be accommodated. Another strength is the ability to scale up by adding more cells that suffer no harm in either constant charge or a completely discharged state over long periods.

 

They are ideal, says Moratibo, for bridging the continuity energy gap in wind turbines, solar cells and wave power.

 

Further information: Crosshair Exploration and Mining Corporation