Integra Gold issues million-dollar challenge

VANCOUVER — Integra Gold’s (TSXV: ICG; US-OTC: ICGQF) historical dataset for the former Sigma-Lamaque gold mines — in the town of Val-d’Or, Que. — has been cast open to the masses, and the rush is on for challengers across the globe to data-mine their way to discovery in exchange for a total of $1 million in cash prizes.

The Northern Miner visited Integra at its corporate office in Vancouver, and spoke with chairman George Salamis about the challenge and what makes the property’s geology unique. 

 “We’re looking to unlock the value of these historic datasets,” Salamis said. “We’re hoping it will serve as a conceptual guide towards finding another multi-million ounce gold deposit elsewhere on our property, because the potential is there, now we’re just after the best ideas on where to dig.”

Salamis, who cut his teeth as a geologist working for Placer Dome in 1988 at the Sigma mine, said he was spoiled in his early career by the “gangbuster” grades and the deposit’s intriguing geology.

 “The main focus back then was structure, drilling and that’s it,” he said. “Drill for structure, drift for grade — that’s what you do in this district.”

He notes the Sigma-Lamaque property lies along the eastern end of the Abitibi Greenstone Belt — a 2.8-billion-year-old, Archean-age volcanic arc that spans 750 km long and 250 km wide across the Ontario-Quebec border. 

The belt shares geological similarities with other world-class camps, he added, such as Kalgoorlie, Granny-Wallaby and Sunrise Dam in Australia’s Yilgarn Craton. 

“They’re not so different from each other, except perhaps it’s much colder here in Canada,” he joked. 

Since 1901, the Abitibi belt has produced 156 million oz. gold from camps that include Kirkland Lake (24 million oz.), Timmins (71 million oz.) and Val-d’Or (14 million oz.). Most of the gold deposits cluster around an easterly trending deformation zone called the “Cadillac fault.”

 “The Cadillac is the big kahuna in the district,” he said. “It’s the major crustal suture zone that formed during the accretion of what is now North America onto an Archean core.”

And the deformation it imposed was extensive. The impacted volcanics were tilted onto their side, shot through with countless shear zones, flushed green from metamorphism, and folded so extensively into an east–west grain that it would be impossible to trace their folds from its peak to trough. 

During the waning stages of its tumultuous history, gold seeped its way up from great crustal depths, onwards through the Cadillac fault and smeared its yellow mark within the surrounding branches of fractures and shears. 

After the big endowment, tectonism ceased and the gold-rich veins have been undisturbed ever since — at least up until the turn of the 20th century, when miners stumbled upon the bounty of its low-hanging fruit.

At the Val-d’Or district — French for the “Valley of Gold” — Teck Cominco  dug out 4.6 million oz. gold within 24.2 million tonnes at grades of 5.9 grams gold per tonne between 1935 to 1985. 

At the adjacent Sigma mine, Placer Dome mined most of the 4.5 million oz. gold from 23.9 million tonnes at 5.8 grams gold down to 1,830 metres deep from 1937 to 1997. Another 488,293 oz. gold were produced until the mine was placed on care and maintenance in 2012.

During these years, inquisitive geologists joined the miners in the march underground to map rock tunnels, collect samples and study veins to unravel the enigmatic formation of the deposits.

Integra inherited 6 terabytes of data — including a drill hole database and underground workings — after acquiring the property out of bankruptcy in 2014. 

Over the past century, geologists have found that most mineralization at Sigma-Lamaque is within either elliptical-shaped intrusive plugs, or a network of dykes and sills “punching” up through the volcanics — all of which are cut by large-scale and steep, southern-dipping shear zones.

“Rocks are certainly not homogenous, and they will shift, bend or break differently when subjected to strain,” Salamis said, adding that the intrusives were more prone to “shattering” than folding like the volcanics, “and that is a big control on how gold is distributed within the system.”

Mineralized veins within the intrusives are shallowly dipping and run oblique to the large-trending shear zones, forming what’s called a classic “riedel” fracture pattern.

Gold and quartz were also trapped and deposited along irregularities within the shear zones, as fluids made their way through the system — though Salamis says the most “phenomenal” grades are seen where the two structures intersect.

“When we were mining at Sigma, the intersections between the shears and the riedels were like jewellery boxes — there would be gold hanging off the walls underground,” he said. “There’s no way to know they were there until you drifted into them, because they have limited strike and volume. When we drifted into one, the mine captain would come down, seal it off, put up a big padlock door and lock off the stope. You can literally make up a month’s work of production just from one of these stopes by sending a guy in there with a bucket and a hammer.”

In more recent years, operators at the mines struggled with low grades as they battled against dilution and trying to profitably mine via open pits the upper reaches of the underground deposits. 

But Integra is focusing on the larger mineralized shears at its Triangle zone deposit, 3 km south of the Lamaque mill. 

“The shear zones have been a real game-changer at the property — they’re a single structure with better continuity, and are well mineralized,” he said. “They’re beautiful from a mine perspective because you can long-hole stope it, whereas the riedel veins are more labour intensive because they’re flat.”

Since starting exploration at Triangle, the company has outlined at least five parallel-trending mineralized shears that extend for 625 metres outside a northern-dipping intrusive plug to vertical depths of 900 metres. 

Recent drill results on the C4 shear have returned 12.86 grams gold over 6 metres on a 125-metre step-out from a1.3-million tonne indicated resource at 10.4 grams gold per tonne for 441,580 oz. gold, and a 429,300-tonne inferred resource at 11 grams gold for 152,370 oz. gold (using a 5-gram gold cut-off).

But what George finds peculiar is the gold distribution along subvertical shear zones. 

“The shears are well mineralized before they hit the intrusive, but above that they’re sort of average,” he said, tracing his finger along a map. “It’s kind of like a weather system that hits a mountain range — on the lee side the air has been stripped of its moisture, whereas here the gold was fed into the intrusive by the shears.” 

He says another exploration strategy will be to follow the mineralized shears to where they intersect more intrusive bodies, in the hopes of finding more deposits like Sigma-Lamaque. Fortunately, he said, that kind of intrusive pops up in a geophysical survey like a bullseye. 

“Magnetics is pr
oving to be one of the few useful tools for exploration on the property,” he said. “Induced polarization doesn’t work because there’s little to no sulphide, and resistivity doesn’t work either, because there’s not enough quartz to show up as an anomaly.”

He added that geochemistry is also a struggle, considering that any alteration associated with gold is mostly limited to the veins themselves.

“There’s no massive alteration zone leading up to the vein … you only know you’re at the veins when you’ve literally hit them,” he said. “If you could use by-product elements as a vector it’d be great, but it’s really tough.”

He underscored that what happens in one place doesn’t necessarily happen in another.

“It’s a large property and there’s a lot of data that contradicts itself, so there’s potential to find targeting criteria,” he said. “We’re casting open the dataset because it’ll get some fresh eyes on the science.”

Participants can submit a “high-conviction” exploration plan to Integra by Dec. 1. After this, a panel of judges will determine the winners and the results will be presented at the Prospectors & Developers Association of Canada convention held next March  in Toronto.

Salamis says contestants should “stick with submitting an idea.”

“When Goldcorp did a similar challenge in 2000, there were just a few submissions,” he said. “The odds could be in your favour — so give us your best ideas.”