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

Trilogy Metals Inc. June 8 provided details of the planned US$26.2 million exploration program slated for this year at the Upper Kobuk Mineral Projects in the Ambler Mining District of Northwest Alaska.

Ambler Metals LLC, a joint venture company equally owned by Trilogy and South32 Ltd., has begun mobilizing equipment and crews for a summer field program that is expected to include at least 10,000 meters of diamond drilling, with additional meters contingent on drill performance, weather, and approval of supplementary budgets.

This drilling is slated to include infill and geotechnical drilling at the Arctic deposit, exploration drilling focused on discovering copper-rich satellite deposits near Arctic, as well as testing copper-rich targets in the Cosmos Hills and the Ambler Lowlands along strike from the Bornite deposit.

"I am very excited that we will soon be opening camp for the 2022 exploration program. We expect to commence drilling by early June with first assay results being available in early fall," said Trilogy Metals President and CEO Tony Giardini. "The proposed exploration program will be one of the largest programs in the history of drilling within the Ambler Mining District and we expect that it will allow us to expand our geological knowledge of this emerging world-class mining district."

Upgrading Arctic

At least 6,000 meters of this year's drilling will be carried out at Arctic, the most advanced of the UKMP projects.

According to the most recent calculation Arctic hosts 36 million metric tons of indicated resource averaging 3.07% (2.44 billion pounds) copper, 4.23% (3.36 billion lb) zinc, 0.73% (541 million lb) lead, 0.63 grams per metric ton (730,000 oz) gold, and 47.6 g/t (55 million oz) silver.

A 2020 feasibility study for developing a mine at Arctic details a financially robust operation that would produce 1.9 billion lb of copper, 2.3 billion lb of zinc, 388 million lb of lead, 386,000 oz of gold, and 40.6 million oz of silver over an initial 12-year mine life.

Last year, Ambler Metals completed 4,131 meters of drilling focused on upgrading a portion of the indicated resources at Arctic to the higher confidence measured category, as well as provide material for metallurgical testing and geotechnical information.

Details and highlights from this successful drilling at Arctic can be read at Even more high grade assays from Arctic in the April 22, 2022 edition of North of 60 Mining News.

Following up on the 2021 program, Ambler Metals plans to complete 27 infill holes targeting areas of the mineral resource that would be mined during the first four years of mining outlined in the feasibility study.

An additional three to five holes will be drilled for geotechnical and hydrogeological study purposes.

Exploring the Ambler Belt

The upcoming program is also expected to include drilling to test three targets – Riley Ridge, 98-9, and East Dead Creek – prospective for shallow VMS mineralization similar to Arctic.

Located about two kilometers (1.2 miles) northwest of Arctic, Riley Ridge hosts a discrete conductor identified by geophysics about 100 to 200 meters below the surface. This conductor is the easternmost in a string of versatile time domain electromagnetic (VTEM) anomalies that trends for six kilometers (3.7 miles) across a target area mapped by Ambler Metals last year.

Situated about three kilometers (1.9 miles) northeast of Arctic, the 98-9 prospect was discovered by Kennecott in 1998 but has never been drilled. Outcropping copper oxide mineralization occurs within a 50-meter vertical thickness of folded and altered Ambler sequence rocks in two narrow gullies over 100 meters. Along strike to the south is a moderate airborne electromagnetic anomaly that is more than 500 meters long. Kennecott completed a small soil sampling program over the anomaly, which produced a moderately strong copper-zinc-lead geochemical anomaly. Further work was recommended, but Kennecott ceased exploration in the Ambler Belt later that year.

East Dead Creek, which lies about six kilometers (3.7 miles) northwest of Arctic, was also discovered by Kennecott in 1998. At the time, alteration at East Dead Creek was noted to be the most intense in the district outside of Arctic and a soil survey outlined a 1,400- by 1,000-meter area of anomalous base metal geochemistry. Due to weather and safety, Kennecott drilled only one of five planned drill targets at East Dead Creek – hole 98-3-01 cut three 1 to 4.5-meter-thick zones of semi-massive sulfides with copper and zinc mineralization in the top 40 meters of the hole. Conductor plate modeling of the VTEM data defined several strong shallow conductors above a weakly conductive horizon interpreted to be the graphitic schist intersected in the lower part of hole 98-3-01. Ambler Metals' first hole will be directed toward the strongest of these shallow conductors.

In addition to the drilling, Ambler Metals plans to carry out additional geological mapping and soil sampling at several other VMS prospects in the Ambler Belt, including Ambler, Dead Creek, Sunshine and COU, as well as at high-priority VTEM anomalies.

Bornite-Cosmos Hill trend

In addition to exploring for VMS exploration similar to Arctic, Ambler Metals intends to carry out drilling, mapping, and sampling in the Bornite-Cosmos Hills-Ambler Lowlands area of UKMP.

Located about 16 miles (26 kilometers) southwest of Arctic, Bornite hosts 6.4 billion lb of copper and 77 million lb of cobalt in near-surface and underground deposits.

At a cut-off grade of 0.5%, the open pit portion of Bornite hosts 40.5 million metric tons of inferred resource averaging 1.02% (913 million pounds) copper; and 84.1 million metric tons of indicated resource averaging 0.95% (1.77 billion lb) copper.

At the same cut-off grade, the Bornite open pit also hosts 124.6 million metric tons of inferred resource averaging 0.017% (45 million lb) cobalt.

The below-pit portion of Bornite, at a cut-off grade of 1.5%, hosts 57.8 million metric tons of inferred resource averaging 2.89% (3.68 billion lb) copper and 0.025% (32 million lb) cobalt.

Outside of Bornite itself, this area has not been systematically explored for similar carbonate-hosted copper mineralization since historical work was carried out by Kennecott in the 1990s.

Last year, crews began investigating this area with soil sampling, detailed structural mapping, relogging historical core, trenching, and two drill holes. Trilogy says this work has outlined four areas for drilling – Bornite West, Pardner Hill, Pardner Hill North, and Ambler Lowlands.

This year, in addition to drilling, which is expected to total about 2,400 meters, further detailed mapping and soil sampling and a minimum of 2,000 meters of trenching are planned around Pardner Hill and the Bornite East target area.

A 2021 scout hole drilled about 2 kilometers (1.2 miles) west of the Bornite deposit encountered low-grade copper in Bornite sequence carbonates. The intersection is encouraging as the hole was sited about one kilometer along the projected NE trend of mineralization at Pardner Hill, a three-kilometer (1.9 miles) copper soil and rock geochemical anomaly. Follow-up holes at Bornite West are planned for this year.

At Pardner Hill itself, Kennecott defined a five- to 35-meter-thick zone of shallow stratabound copper mineralization over a roughly 150- by 400-meter area. This zone – which is open to the northwest, west and southwest – will be tested with three holes this summer.

Another two scout holes are expected to be completed at Pardner Hill North, which is located 250 to 500 meters northeast of the Pardner Hill mineralized zone. These holes are contingent on the results of a trenching program that will begin in June.

Trilogy Metals Inc.

The second hole Ambler Metals drilled last year to test for carbonate-hosted copper similar to Bornite was completed in the Ambler Lowlands, a 10-kilometer- (six miles) wide glaciated valley separating Arctic and Bornite that is virtually unexplored despite its proximity to these deposits. Hole ALL21-001 was designed to redrill one of the only two holes ever drilled in the valley – NANA-1, a 1974 hole that historical drill logs show intersected dolomitized carbonate and carbonate breccia similar to the carbonates that host the Bornite deposit. Unfortunately, the hole last year was lost at a depth of 300 meters, above the expected depth of the Bornite sequence.

Ambler Metals proposes to re-enter and complete the hole this summer, contingent on drill production and weather.

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.

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