Mining exploration on the rebound at new, old prospects

  • The Alaska Industrial Development and Export Authority is leading development of a 211-mile industrial road to access the Ambler mining district. Trilogy Metals intends to start the permitting process next year on its Arctic prospect and the Sun deposit is the latest to see major exploration activity. (Map/Courtesy/Alaska Industrial Development and Export Authority)

A recent resurgence in oil exploration in Alaska has been a topic of much discussion for the potential revenue it could eventually generate for state coffers, but there is ample exploration activity in the state’s mining sector as well.

At existing mines, Teck Resources Ltd., which operates the Red Dog zinc mine near Kotzebue in Northwest Alaska, has been exploring the Aktigiruq prospect about seven miles north of the mine facilities.

Teck CEO Don Lindsay has said it could end up being “one of the best undeveloped zinc deposits in the world” if initial drilling results are proven up. Red Dog is already one of the largest zinc-producing mines on Earth.

Earlier this year Kinross Gold Corp. announced it would start work on a $100 million expansion to the Fort Knox gold mine just northeast of Fairbanks that is expected to keep the mine open for another 10 years through 2030.

The Gilmore project, as it is known, could yield up to another 1.5 million ounces of gold for the open-pit mine that opened in 1996, according to a feasibility study Kinross conducted on the prospect.

Production from Gilmore could start in early 2020, the company estimates.

Geologist Bonnie Broman told a gathering at the Alaska Miners Association in Anchorage Nov. 6 that the newly formed private Alaska exploration firm Valhalla Metals Inc. has acquired 230 mining claims covering 36,000 acres in the Ambler mining district farther north of Fairbanks and west of the Dalton Highway.

Valhalla’s claims include the Sun copper and zinc prospect that the company plans to advance in the coming years.

The easternmost deposit in the Ambler district, the Sun prospect was first discovered in 1974 by Sunshine Mining Co. and has changed hands frequently since. Valhalla is the 10th company to control the claims since Sunshine made the initial discovery, according to Broman.

The Sun prospect was regularly drilled in the years immediately following its discovery, but the work mostly stopped in the 1980s and 1990s following the passage of the Alaska National Interest Lands Conservation Act in 1980, as did much of the mining exploration activity going on in the state at the time, Broman said.

The area was most recently explored from 2007-12 by Canadian Andover Mining Corp., which went bankrupt in 2014.

Overall, more than 19,100 meters of drilling has been done at Sun since it was first discovered.

“This area has had quite a bit of work done to-date. There’s quite a lot of known prospectivity in the region,” Broman said.

The Sun deposit sits east of the Arctic and Bornite multi-metal prospects currently being advanced by Trilogy Metals. Trilogy plans to begin permitting Arctic early next year but development of the remote Ambler prospects is dependent upon construction of the roughly 211-mile Ambler industrial access road.

The Alaska Industrial Development and Export Authority is leading development of the industrial road to access the mining district. The Bureau of Land Management is in the midst of writing an environmental impact statement for the road and the first draft of that document is expected in March 2019, with a final EIS following late next year, based on the current schedule.

AIDEA officials believe the access the road would provide could spark further exploration activity in the region, as well.

Specifically to Sun, Broman said mineralization has been intersected over a 3.5 kilometer strike.

So far it’s estimated the deposit holds 10.7 million metric tonnes of indicated and inferred resources of 4.2 percent zinc, 1.5 percent copper and 1.4 percent lead. It also has prospectivity for silver and small amounts of gold, she added.

Broman said unlike the Arctic and Bornite prospects, Sun would likely be an underground mine and it’s not uncommon for mineralization in similar sulfide deposits to continue to depths of 1,000 meters.

“There is potential to add resources at Sun by drilling the down dip portion,” she said, as it has not been explored at depth.

Valhalla expects to continue exploration drilling at Sun in the coming years and will also be looking for new deposits elsewhere in its claims area, she said.

Icy Cape progress

Along Alaska’s south coast the Alaska Mental Health Trust Land Office continues to advance its unique heavy industrial minerals prospect in the beach sediments of Icy Cape.

About 75 miles northwest of Yakutat, the roughly 30-mile long, 50,000-acre Mental Health Trust property is approximately half covered by sediments containing heavy industrial minerals, according to Trust Land Office Minerals and Energy Chief Karsten Eden.

The Trust Land Office manages roughly 1 million acres of land across Alaska for real estate and resource development purposes, the proceeds of which go to fund the Alaska Mental Health Trust Authority’s work to benefit Alaskans with mental health and addiction challenges.

“It’s a totally different kind of geology and it’s a totally different kind of exploration, but it’s exciting,” Eden said during a presentation at the AMA convention Nov. 6.

The eastern portion of the large property contains sediments from the glaciers of Icy Bay, while the river deposits on the coastal plain influence the area to the west.

All of the sediments contain heavy minerals, according to Eden.

The heavy minerals are often used in industrial applications in which hard, abrasive materials are required, such as sandpaper and sandblasting.

The sediments also contain ilmenite, which is highly magnetic and is a common industrial mineral often used as white pigment feedstock in paints and plastics, he said.

The Trust Land Office has been investigating the prospect for four years; drilling started in 2017 and continued last summer.

During the 2018 work season the TLO spent roughly $3 million, had a crew of 24 working at the Icy Cape camp and built a 60-foot by 40-foot sample processing facility — a shed — to further evaluate the drilling samples.

Eden said the office has had to use sonic drilling to bore through the sediments.

“The drilling conditions are really challenging. Those are abrasive sands,” he commented.

The multiple sources mean the sediments are separated into two distinct layers, which provide different mineral grain sizes, an important benefit to the project, according to Eden.

“Particle size is very important because it has an impact on recovery,” he said.

“Out there we have mineable and recoverable particle sizes including platinum group minerals. It’s a poly-mineralic and poly-metallic deposit. It’s very, very interesting.

If developed, the Trust property would be the only source for some heavy minerals such as garnets on the West Coast, Land Office officials have said.

There is currently a global shortage of garnets, another abrasive, as India, the world’s longtime primary supplier has stopped exporting mineral sands altogether in an effort to halt illegal private exports, Eden added.

The Trust Land Office plans to continue exploring the area in the coming years, he said.

Elwood Brehmer can be reached at [email protected].

Updated: 
11/07/2018 - 11:48am

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