The first two holes drilled by Coventry at Caribou Dome (at the Lense 6 area) produced immediate success, with intersections of 10.1m at 7.1% Cu from 39.0m and 12.2m at 3.2% Cu from 39.8m respectively. These results confirmed that substantial thicknesses of shallow, high grade copper mineralisation are present at Caribou Dome. The results were comparable with previous adjacent drilling results, providing confidence in the reliability of the historic data.
- 18.1m at 9.34% copper from 22.7m (DH9)
- 18.4m at 6.25% copper from 31.4m (DH39)
- 15.4m at 7.01% copper (DH93U)
- 13.1m at 7.20% copper from 15.8m (DH40)
- 11.0m at 8.20% copper from 29.0m (DH41)
- 10.4m at 7.94% copper from 14.0m (DH37)
- 12.8m at 5.78% copper (DH51U)
- 13.0m at 4.94% copper (DH91U)
- 9.1m at 6.97% copper from 28.7m (DH43)
- 10.2m at 6.23% copper from 46.6m (DH32)
- 12.2m at 5.04% copper from27.1m (DH32)
- 10.7m at 4.99% copper from 18.0m (DH15)
- 10.2m at 4.96% copper (DH70U)
- 8.3m at 6.07% copper from 77.7m (DH44)
Thick copper mineralisation was intersected in the first two exploration holes drilled to test primary mineralisation beneath 200m of mineralised outcrop at Lense 2. Assay results included 8.7m at 1.7% Cu from 54.3m and 10m at 1.6% Cu from 62.5m. New IP data showed that these holes were drilled directly above a strong IP anomaly that was to be drill-tested.
A further hole drilled deep enough to begin evaluation of the 250m-long strong IP anomaly at Lense 2 intersected high-grade copper mineralisation including 3.4m at 4.8% Cu and 3.5m at 1.9% Cu.
A hole drilled at Lense 4 produced a spectacular intersection of thick, shallow, primary high-grade copper mineralisation, in total comprising 51.1m (estimated true thickness of ~25m) at 5.3% Cu from 4.4m. This result included 2.3m at 17.1% Cu from 4.4m, 14.1m at 10.6% Cu from 10.7m, 3.3m at 9.0% Cu from 39.8m and 3.2m at 9.6% Cu from 52.3m.
Mineral Resources
On 5 April 2017, Coventry announced a maiden JORC Mineral Resource estimate for the high-grade Caribou Dome Project. The total mineral resource is 2.8mt at 3.1% Cu (using a 0.5% lower cut-off) containing 86,000t of copper. Significantly, approximately 60% of the Mineral Resource (1.6Mt at 3.0% Cu) lies within 150m of surface. The Mineral Resource remains open at depth and along strike both at surface and depth.
- JORC mineral resource estimate of 2.8Mt at 3.1% copper (at 0.5% lower-cut) for 86,000t of contained Copper
- 60% in the top 150m including 935,000t @ 4.4% copper
- High grade, sediment-hosted copper
- Drill intersections over > 800m strike-length
- Open in all directions
- Structural re-interpretation underway targeting additional tonnages
A grade-tonnage curve for the Mineral Resource was also published. The curve clearly indicates the flexibility to further increase grades at higher cut-off levels should this be deemed to be appropriate. For example, at a 2% Cu cut-off grade, the head grade increases from 3.1% Cu to 4.6% Cu, and despite tonnage falling from 2.8Mt to 1.6Mt, the contained metal drops by only 16% to 72,000t of copper.
A strong indicator of the depth potential is that the second deepest hole drilled to date, which reached a depth of 280m from surface, recorded an intersection (not true width) of 15.4m at 7% Cu.
Background to the Project
Copper mineralisation was first discovered at Caribou Dome in 1963. Almost all the exploration was undertaken at the Project between 1964 and 1970. Nine lenses of outcropping mineralisation were delineated over approximately 750 metres of strike. However, virtually all work was focused on only three of these lenses with a view to developing a small high-grade underground mine. Approximately 1,000 metres of underground workings were developed on two levels (an adit and a decline). In addition, more than 6,000m of diamond drilling (43 diamond core holes drilled from surface and 48 diamond core holes drilled from underground) were completed, together with 3,282m of underground percussion drilling.
The top 14 intersections produced copper grades ranging from 4.9% to 9.3% over intersected widths ranging from 8.3m to 18.4m. Cross sections and longitudinal sections indicate that mineralisation is mainly confined to sub-vertical lenses of good thickness. The drilling did not constrain the extents of mineralisation at any of the known lenses.
Little additional work has been undertaken since 1970. A further 17 surface diamond holes were drilled; nine shallow holes were drilled in 2011 to evaluate lenses 7 and 9, six of which intersected copper sulphide mineralisation. A 225kg bulk sample for metallurgical test work was collected in 2008.
Geology
Copper mineralisation at the Caribou Dome Project is predominantly stratiform. Historically, nine outcropping lenses of high-grade pyrite-chalcopyrite mineralisation were delineated over approximately 750m of strike. These are predominantly located in argillites at an interface with a sequence of volcanic rocks. Interbedded limestones appear to have exerted an important control on the location of mineralisation.
Metallurgy
