The mining newspaper for Alaska and Canada's North
The mining newspaper for Alaska and Canada's North
Growing deposit could bolster economics of world-class mine North of 60 Mining News – December 14, 2018
In addition to resource expansion drilling at Iron Cap, Seabridge completed geotechnical drilling at the other KSM deposits, including this hole being logged from Mitchell.
Exceptional widths of higher grade gold and copper mineralization tapped during this year's drilling continues to support the idea that the Iron Cap deposit deserves to be queued up earlier in the plan for a future mine at Seabridge Gold Inc.'s KSM project copper-gold in northwestern British Columbia.
The four deposits that make up the KSM project – Kerr, Sulphurets, Mitchell and Iron Cap – encompass 2.2 billion metric tons of proven and probable reserves averaging 0.55 grams per metric ton (38.8 million ounces) gold, 0.21 percent (10.2 billion pounds) copper, 2.6 g/t (183 million oz) silver, and 42.6 parts per million (207 million lb) molybdenum.
These reserves support a 53-year mine that would average 540,000 oz gold, 156 million lb copper, 2.2 million oz silver, and 1.2 million lb molybdenum per year, according to a 2016 prefeasibility study.
At the time of the PEA, the potential of Iron Cap was not fully understood, and this deposit wasn't slated to be mined until about 32 years into the life of a proposed operation for KSM.
Since that time, however, Seabridge identified Iron Cap as a potentially much larger deposit and has taken strides to fully understand that potential.
A resource published for Iron Cap in February of this year outlines 370 million metric tons of indicated resource averaging 0.43 grams per metric ton (5.1 million oz) gold; 0.23 percent (1.9 billion lb) copper; 4.2 g/t (49.9 million oz) silver; and 48 parts per million (39 million lb) molybdenum. Plus, 1.3 billion tons of inferred resource averaging 0.48 g/t (20 million oz) gold; 0.3 percent (8.6 billion lb) copper; 2.9 g/t (121 million oz) silver; and 34 ppm (34 million lb) molybdenum.
In addition to emerging as a world-class deposit in its own right, Iron Cap enjoys an advantageous location and geometry, which has prompted Seabridge to investigate the viability of mining this deposit much earlier in the life of a future mine at KSM.
"Iron Cap has clearly become one of the best deposits in the KSM cluster, not only for its superior grade but also due to its proximity to infrastructure, which we expect will require less capital to develop than the Kerr and Sulphurets deposits, and also its size and orientation which favor efficient, cost-effective underground block cave mining," said Seabridge Gold Chairman and CEO Rudi Fronk.
With this idea, the 2018 drill program targeted the expansion of a high-grade core zone at Iron Cap, first identified by Seabridge in 2016.
This drilling targeted three areas – the northwestern down-plunge projection of the high-grade core zone; the northeastern up-dip projection of the core zone; and the potential for a southern extension.
Challenging Northwest Plunge
Northwest Plunge provides the most promise for expanding the high-grade core at Iron Cap. This expansion area, however, is challenging to drill due to a broad zone of intensely sheared intrusive rocks. Due to this very poor rock quality, several holes targeting this deep expansion area were lost before reaching their target.
The first hole to encounter this shatter zone, IC-18-74, had to be abandoned due to technical problems in the shatter zone. This hole, however, did cut 52.9 meters of 0.7 g/t gold, 0.34 percent copper and 3.7 g/t gold from 802.5 meters to the bottom of the hole.
Hole IC-18-74B, which was wedged off IC-18-74, was able to get through the sheered intrusive rocks and hit the targeted high-grade plunge of Iron Cap. This hole cut four mineralized zones: 34.6 meters of 0.46 g/t gold, 0.43 percent copper and 11.2 g/t silver from 837.5 meters; 232.2 meters of 0.3 g/t gold, 0.25 percent copper and 1 g/t silver from 967.1 meters; 83.8 meters of 0.42 g/t gold, 0.29 percent copper and 1.1 g/t silver from 1,270.3 meters; and 95.9 meters of 0.38 g/t gold, 0.35 percent copper and 1.3 g/t silver from 1,412.2 meters.
Hole IC-18-75, also targeting the northwestern plunge projection of the high-grade core, cut two zones: 36.1 meters of 0.54 g/t gold, 0.39 percent copper and 1.3 g/t silver from 878.3 meters; and 582.7 meters of 0.59 g/t gold, 0.41 percent copper and 1.4 g/t silver from 991.6 meters.
Similar thicknesses but higher grades were encountered in IC-18-83. This hole cut 547.6 meters of 0.63 g/t gold, 0.44 percent copper and 2.4 g/t silver from 818.4 meters.
The widest intercept in the northwest plunge area came in IC-18-82, which cut 1,018.2 meters of 0.44 g/t gold, 0.37 percent copper and 1.6 g/t silver from a depth of 428 meters.
In all, nine holes of the 2018 program successfully encountered gold-copper-silver mineralization in the northwest plunge area.
In addition to expanding the Iron Cap resource, drilling in this area was targeted in a way to address a potential conflict between the projection of the Iron Cap deposit and the Mitchell-Treaty tunnel (MTT), which is a critical piece of the infrastructure that would be used to haul ore to the mill at KSM.
While this drilling may find that the tunnel needs to be realigned to avoid a potential future ore body at Iron Cap, this potential re-engineering is a good problem.
"Due to its proximity to the MTT and its higher grade, Iron Cap could potentially improve KSM's economics by mining it before the Kerr deposit," Seabridge Gold penned in its Dec. 12 press release.
Impact of Iron Cap
While Iron Cap remains open down-dip to the Northwest, this year's drilling closed the expansion potential to the northeast and to the south
Hole IC-18-84, drilled to define the up-dip continuity of the ore zone on the northeastern side of Iron Cap, confirms that the ore zone reaches the surface below glacial ice thereby limiting the potential in the northeast direction.
This hole, however, did cut four zones of mineralization: 31.2 meters of 0.2 g/t gold, 0.36 percent copper and 5.1 g/t silver from 170 meters; 34 meters of 0.36 g/t gold, 0.78 percent copper and 35.4 g/t silver from 223 meters; 14 meters of 2.53 g/t gold, 0.03 percent copper and 1.8 g/t silver from 281 meters; and 27 meters of 0.4 g/t gold, 0.24 percent copper and 4.7 g/t silver from 344 meters.
The drill holes targeting the southwestern plunge projection were focused on defining the extent of zones encountered in IC-17-72, a hole drilled last year that cut 858.1 meters of 0.86 g/t gold and 0.51 percent copper, including 113.4 meters of 2.98 g/t gold and 1.56 percent copper; and IC-14-58, a 2014 hole that cut two gold-copper intercepts.
Seabridge said this year's drill found that the intrusive rocks in this area are less altered, less mineralized and have been intruded by younger igneous rocks. Effectively, the limits to the south for the Iron Cap central core zone have been defined. Those limits are defined both by a decrease in mineralization and the impact of a younger intrusion.
These results provide an interpreted strike for the Iron Cap high-grade zone of about 800 meters from the North Iron Cap Fault to the southern limit.
With the 2018 drill results in, Seabridge is having a new resource calculated for Iron Cap. This larger resource could provide the push needed for Seabridge to reach its ultimate goal at KSM – bring on a partner with the financial wherewithal to develop a mine at this world-class gold-copper project in northwestern British Columbia.
"We believe the impact of Iron Cap on the economic potential of KSM will help us conclude a joint venture partnership on positive terms," Fronk said.
Over his more than 16 years of covering mining and mineral exploration, Shane has become renowned for his ability to report on the sector in a way that is technically sound enough to inform industry insiders while being easy to understand by a wider audience.
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