North of 60 Mining News - The mining newspaper for Alaska and Canada's North

Newcrest Mining Ltd. Jan. 25 reported a drop in gold and copper production at its two mines in Northern British Columbia during the fourth quarter of calendar year 2022.

Newcrest's BC assets include a 70% operating ownership of the Red Chris copper-gold mine, Imperial Metals Corp. owns the remaining 30% interest and full ownership of the Brucejack gold mine.

The drop in gold production at Brucejack was anticipated due to a fatality during the quarter that resulted in a 21-day shutdown of operations to support the investigation and those impacted by the fatal incident.

"We were deeply saddened by the tragic fatality at our Brucejack mine in October," said Sherry Duhe, Newcrest Mining's interim CEO. "An extensive safety review has been conducted across all activities at site to identify major hazards and corresponding critical controls and we are applying these learnings across the business as we remain steadfastly focused on the health and safety of our people."

The slump in quarterly copper and gold production at Red Chris is largely related to a transition in mill feed at the mine.

Shutdown impacts Brucejack

Brucejack produced 51,813 ounces of gold during the fourth quarter of 2022, a 38% drop from the 84,123 oz during the prior three-month period.

In addition to the 21-day shutdown, production at this Northern BC underground mine was impacted by lower-grade ore being fed into the mill. During the fourth quarter, the mill head grade at Brucejack averaged 6.72 grams per metric ton gold, a roughly 11% drop from the 7.59 g/t gold ore fed into the mill during the third quarter.

Due to the lower output during the final three months of 2022, Brucejack is anticipated to deliver at the lower end of its production guidance range of 320,000 to 370,000 oz of gold during the Australian mining company's fiscal year 2023, which ends June 30.

Newcrest continues to implement a three-phase strategy to unlock the full potential of Brucejack and the district-scale property this high-grade gold property is located on. This included expanding the mill throughput to 4,500 to 5,000 metric tons per day, which is a roughly 18% to 32% boost to the current 3,800 t/d processing rate.

Newcrest believes that much of this mill throughput increase can be achieved by simply eliminating bottlenecks in the current process, making this a potentially low-cost, high-reward gold production initiative.

This expansion has now reached the prefeasibility level, and the company plans to file for permits in the next couple of months.

The company is also implementing ore sorting that is expected to upgrade the already high-grade Brucejack ore by removing any unmineralized material ahead of the mill.

High-grade exploration

While a new reserve estimate has not yet been calculated since Newcrest's 2022 acquisition of Brucejack, the operation hosted 11.5 million metric tons of proven and probable reserves averaging 8.7 g/t (3.2 million oz) gold and 9.8 g/t (3.6 million oz) silver at the onset of 2021.

Extensive exploration carried out at Brucejack over the past two years, including roughly 89,000 meters of drilling carried out by Newcrest in 2022, has identified several intriguing expansion targets immediately surrounding Valley of the Kings and a 2.5-mile- (four kilometers) trend of high-grade gold zones that runs across the property.

Roughly 54,000 meters of Newcrest's 2022 drilling at Brucejack focused on expansion of the Valley of Kings deposit that hosts the current resources at the operation.

During the fourth quarter, Newcrest completed 7,665 meters of resource expansion drilling from underground at Brucejack. Highlights from this drilling in zone 1080 HBx on the south side of Valley of the Kings include:

• 10.5 meters averaging 917 g/t (29.5 ounces per metric ton) gold in hole VU-4624, including one meter of 9,618 g/t (309.2 oz/t) gold.

• 11 meters averaging 269 g/t (8.6 oz/t) gold in hole VU-4626, including one meter of 2,954 g/t (95 oz/t) gold.

During the final three months of 2022, Newcrest also drilled 22 holes at Golden Marmot, an exciting exploration target about 3,500 meters north of Valley of the Kings. Highlights from the Golden Marmot drilling include:

• 18 meters averaging 12 g/t gold in hole SU-893, including one meter of 184 g/t (5.9 oz/t) gold.

• 1.5 meters averaging 113 g/t (3.6 oz/t) gold in hole SU-896.

• One meter averaging 8,000 g/t (257.2 oz/t) gold in hole SU-899.

• One meter averaging 1,740 g/t (55.9 oz/t) gold in hole SU-903.

Future drilling at Golden Marmot will test the extent of the mineralization, which remains open to the south and at depth.

Updated ore resources and reserves are expected to be calculated for Brucejack early this year.

Red Chris transitions

Both gold and copper output at Red Chris were down due to lower recovery following the transition of mill feed from Phase 5 to Phase 7 ore during the quarter, as well as decreased mill throughput due to lower mining rates and unscheduled maintenance on an overland conveyor belt.

Red Chris produced 10,163 oz of gold during the final three months of 2022, which is about 17% lower than the 12,259 oz produced during the previous quarter. Likewise, the Northern BC mine produced 4,162 metric tons of copper during the fourth quarter, which is nearly 32% less than the 6,090 metric tons produced during the prior period.

Despite this lower output, Red Chris remains on pace to achieve Newcrest's guidance of 30,000 oz of gold and 20,000 metric tons of copper for fiscal year 2023.

Newcrest continued the development required to transition Red Chris from an open pit mine to a bulk tonnage underground block cave operation.

A prefeasibility study completed in 2021 details an underground block cave mining operation forecast to produce 4.9 million oz of gold and 1.5 million metric tons of copper from 406 million metric tons of ore over roughly 31 years of mining.

In preparation for this bulk tonnage underground mine, Newcrest is advancing an exploration decline that will provide a platform for underground drilling, as well as to potentially mine higher grade pods ahead of full-scale block caving.

As of Jan. 18, this decline had been advanced to 2,685 meters, and installation of the first ventilation raise bore is progressing in line with expectations.

A feasibility study for the block cave mine at Red Chris has been pushed into the second half of this year to allow optimization opportunities to be evaluated and defined. Inflation and global supply chain interruptions are also being assessed as part of the feasibility study, and value engineering is underway with the objective to offset inflationary cost pressures.

Newcrest says the roughly six months of extra time spent on the feasibility study is not expected to impact the project development timeline expected.

Eastward expansion

Newcrest has completed 300,154 meters of drilling in 291 holes since it acquired a 70% stake in Red Chris in August 2019, including 13,854 meters of drilling in 18 holes during the fourth quarter of 2022.

As of June 30, the open pit portion of Red Chris hosted 240 million metric tons of measured and indicated resources averaging 0.3 g/t (2.4 million oz) gold and 0.36% (880,000 metric tons) copper; plus 8.5 million metric tons of inferred resource averaging 0.25 g/t (69,000 oz) gold and 0.30% (26,000 metric tons) copper.

The underground portion of Red Chris hosts another 670 million metric tons of measured and indicated resources averaging 0.46 g/t (10 million oz) gold and 0.40% (2.7 million metric tons) copper; plus 180 million metric tons of inferred resource averaging 0.32 g/t (1.8 million oz) gold and 0.3% (540,000 metric tons) copper.

Newcrest's recent drilling has focused largely on East Ridge, a zone not included in Newcrest's current mineral resource for Red Chris. So far, the company has drilled 71 holes and five more are being completed at this exciting expansion target east of the resource.

During the fourth quarter, Newcrest received assays from five East Ridge holes; highlights include:

Newcrest Mining Ltd.

Click on image for larger Red Chris exploration map.

• 202 meters averaging 0.47 g/t gold and 0.64% copper in hole RC843.

• 248 meters averaging 0.33 g/t gold and 0.46% copper in hole RC848.

• 266 meters averaging 0.43 g/t gold and 0.57% copper in hole RC857.

Newcrest says holes RC848 and RC857 extend the higher-grade mineralization a further 100 meters deeper to a depth of more than 700 meters. The result from RC857 is the deepest significant higher-grade intercept at the project to date. All holes remain open at depth.

The East Ridge mineralized corridor is 900 meters long, more than 700 meters thick, and 125 meters wide, with several smaller pods with higher-grade mineralization.

Author Bio

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.

• Email: [email protected]
• Phone: (907) 726-1095
• https://www.linkedin.com/in/shane-lasley-ab073b12/