Since acquiring a 70% interest in Imperial Metals Corp.'s Red Chris Mine in 2019, Newcrest Mining Ltd. has envisioned establishing an underground block cave mine to unlock the full potential of this porphyry copper-gold asset at the northern end of British Columbia's Golden Triangle.

The Australian miner took a major step toward this vision with the start of construction on the box cut for the underground decline at Red Chris. Roughly C$12 million has already been approved for this surface work, as well as related infrastructure, in preparation for the underground development needed for more detailed exploration and eventually mining.

"The commencement of construction of the box cut is a significant milestone in the objective of having a block cave in operation at Red Chris in the next five to six years," said Newcrest Mining CEO Sandeep Biswas.

Block cave is a bulk tonnage underground mining technique that involves starting at the bottom of the orebody and allowing the deposit to progressively collapse under its own weight.

Newcrest has been successful with this technique at Cadia, an Australia mine similar to Red Chris.

Since taking over as operator at Red Chris, Newcrest has focused on optimizing the current open-pit operation by eliminating bottlenecks and improving processing plant recoveries.

With these improvements, the mine produced 88.3 million pounds of copper and 73,787 ounces of gold during 2020, this marks a 23% increase over the 71.9 million lb of copper and 103% jump over the 36,471 oz gold produced in 2019.

While Newcrest is happy with the significantly increased metals output, the Australia-based miner is even more excited about the continued success of drilling a pod of high-grade mineralization that will likely enhance the second stage of its Red Chris plan – block cave mining.

Imperial Metals, which owns the remaining 30% interest in the Red Chris joint venture, first encountered this high-grade pod in the East Zone with a 2009 hole that cut 432.5 meters of 2% copper and 3.8 g/t gold.

Newcrest's 2020 drilling cut additional wide sections with impressive grades at East Zone. Hole RC634 in particular demonstrates the high-grade pods within wide sections of porphyry mineralization at East Zone. This hole cut 532 meters averaging 0.82% copper and 1.3 g/t gold, including 166 meters averaging 1.5% copper and 3 g/t gold.

"Drilling results at Red Chris have returned 166 meters grading 3 g/t gold and 1.5% copper, which is significantly higher than we would expect to find in porphyry systems," said Biswas.

Newcrest and Imperial are investigating the potential of mining these high-grade pods via more conventional underground methods ahead of block caving.

"With drilling confirming the presence of even higher-grade pods within the deep East zone, a number of options are being studied to mine this higher-grade material before block caving operations begin," said Imperial Metals President Brian Kynoch. "The aim of this smaller scale underground mining would be to increase cash flow prior to the start of the block cave operations."

In preparation for targeted high-grade underground mining and the ultimate goal of a block cave operation, Red Chris Joint Venture has approved C$135 million to fund the underground development, which is expected to begin after the completion of the box cut and receipt of requisite regulatory approvals.

According to their ownership, Newcrest will pay 70% of the underground development costs and Imperial will pay the 30% balance.

Newcrest Mining Ltd.

After spending 2020 optimizing open pit operations at Red Chris, Newcrest and Imperial are preparing to begin advancing underground development and eventual block cave mining at the porphyry copper-gold operation.

"Together with the support of our stakeholders, we are excited by the potential to transform Red Chris into a tier-1 asset through the application of our industry-leading block caving technology," said Biswas.

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Shane Lasley, Publisher

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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