My Explaining Exploration series is embarking on a world tour over the next few weeks to look at some of the ‘juicy’ exploration and mining jurisdictions across the globe. Often, these jurisdictions correspond with states or provinces, but they can also be entire countries, or several countries where a geological zone extends across borders.
Today, we look at my home province of British Columbia. This jurisdiction has a long mining history that reliably ranks well in the Fraser Institute Annual Survey of Mining Companies.
I spoke with geologist Charles Greig, vice-president exploration at GT Gold, who has spent his career exploring in B.C. and beyond. He started his geology journey sampling soils in the highly prospective Toodoggone district in northeast B.C. in 1981. Almost 30 years later, he believes, “there’s no better place to work than B.C. in terms of potential, the ability to develop, the (rock) exposure, the variety of the geology – it is a fantastic place and hard to beat.”
Greig is currently working in northwest B.C.’s Golden Triangle, but has explored all corners of the province with the B.C. Geological Survey and at projects such as Brucejack Lake (Pretivm), Red 2 Mountain (Lac Minerals, IDM), Silbak Premier (Westmin, Ascot), and IKE (HDI-Amarc). He helped create GT Gold and has guided their exploration programs since they listed in 2016.
Lots Of Land, Lots Of Options
As an exploration and mining jurisdiction B..C has a lot going for it, but the number one feature is its size. “B.C. is huge,” says Greig.
Mountains cover 75% of the province. Rock exposure is great in the mountains and, as Greig points out, if we stretch and flatten out the mountainous land surface, we are left with a lot of surface area to explore.
There are also the valleys and plateaus of central B.C., such as the Chilcotin and Cariboo areas, which are less rugged. But these valleys tend to be thickly forested at the surface; below the trees, the rocks are covered in thick layers of glacial sediments smeared across the province in the last ice age or covered by young volcanic rocks just tens of thousands of years old.
For explorers, this means it is easier to drive and walk around in the valleys and on the plateaus but the sought-after rock may be obscured. On the flip side, it is harder to get around in the mountains but the rock is better exposed.
Mountain exploration programs are more expensive, incurring the costs of hiring a helicopter to move people, drills and mining equipment. But at the same time, Greig says, “at least you know fewer people have been out there looking in the same place, so chances of finding something new and different are increased.”
Copper, Gold And Other Stuff!
B.C. has a wide range of mineral deposit types. “Certainly, there are some great gold deposits but then there’s the optionality provided by the copper-gold-silver or copper-moly porphyry deposits,” Greig says.
In a nutshell, the geology of B.C. is shaped by its position on the eastern rim of the Pacific Ocean. It is an active plate boundary, where the massive tectonic plates that cover the globe are being pushed against each other and the ocean plate is being subducted under the continental plate.
The upper plate resists and becomes wrinkled forming new mountains while the lower plate melts below, like adding wood to a fire. Geologists familiar with B.C. talk excitedly about plate collisions, orogenic (mountain building) phases, voluminous arcs (lines of active volcanoes producing lots and lots of lava), and accreted terranes (huge packages of rock with a specific geologic history).
Bottom line: All this tectonic activity generates the heat and metal-rich (hydrothermal) fluids to form a wide range of mineral deposit types.
B.C. is particularly well known for its giant porphyry copper deposits. Porphyry deposits form when a volume of magma rises through the earth and, as it cools, forms a core of igneous rock with a distinct ‘porphyritic’ coarsely crystalline texture.
As the system cools further, hydrothermal fluids escape into the surrounding rock carrying dissolved metals. These fluids bleach the surrounding rocks, changing the chemistry and the minerals in them, forming the discrete, often mineralized, alteration zones porphyry systems are known for.
Porphyries tend to be low grade but they make sense to mine when they offer scale and are accessible. There have been dozens of successful porphyry mines in B.C., especially in the southern half of the province, and many are still operating. And the B.C. porphyry story is still very much going strong: GT Gold’s Saddle North discovery is the latest major gold-rich copper porphyry discovery in three the province and Newcrest acquired 70% of the Red Chris mine for US$804 million last year to form a partnership with Imperial Metals on a relatively new mine tapping another large – and this time rich – B.C. porphyry.
Porphyries are also important as ‘engines’, by which I mean the huge amounts of heat and fluid involved in the intrusion can also create other deposit types, including epithermal, skarn and breccia deposits. The Saddle South zone at GT’s project is a good example: it’s a high-grade epithermal gold system peripheral to a major gold-copper porphyry.
Porphyries are essential in the world of mining for their scale…but explorers, and the investors who buy exploration companies, often prefer grade. B.C. also has that to offer.
Pretivm’s Brucejack mine is a good example. According to the 2020 technical reports, Brucejack has 4.2 million ounces of gold (15.7 million tonnes grading 8.4 grams of gold per tonne) and a 13-year mine life. That’s a good amount of gold – but it’s the grade that catches attention. Some of the early underground drilling intersected zones grading greater than 1,000 grams per tonne gold.
Those hits came from an area called Valley of the Kings, which joined a list of zones or deposits in B.C. that have, over time, offered up phenomenally high gold grades. That, my friends, is why explorers and investors flock to the Golden Triangle.
Of the ‘other’ deposit types, Greig says, “There’s also some potential in nickel, for example, and very large zinc, lead, silver deposits like the Sullivan [a SEDEX deposit near Kimberley in the southeast of the province]. People are still looking for the next one.”
“There are also some big resources farther up in the north, north-central B.C., north of McKenzie in the Kechika belt, that haven’t been exploited. They’ve been discovered and I think there are probably more discoveries to make there,” Greig
B.C. also has potential for the more obscure minerals, such as the rare earth elements. Greig says, “People haven’t looked for the more obscure things as hard as they’ve looked for say the copper and gold porphyries in BC.”
The Golden Triangle Draws A Crowd
I said that explorers and investors like grade and the data on who’s exploring where in B.C. backs that up. In 2019, northwest B.C.’s Golden Triangle accounted for 55% of total mining and exploration expenditure for the province. It’s a proportion that has been rising every year over the last decade or so.
Why is the Golden Triangle so popular? After all, it’s a rugged and ice-covered area where you can only work your projects for a few months each year. But those challenges are worth it considering the potential prize, which is to discover another Valley of the Kings (super rich gold vein system) or Saddle North (big, rich gold-copper porphyry) or Eskay Creek (rich gold-silver-copper-zinc VMS deposit).
And importantly – new roads and power lines have made the area far more functional than it was even 10 years ago, while receding glaciers keep exposing more rock.
Access
The Golden Triangle used to be isolated but not any more. In 2012-14, B.C. Hydro built the 344-kilometre Northwest Transmission Line into the northwest. The power utility also drove several new roads into the heart of the area to build and service several new run-of-river hydro projects, which made big areas for more accessible for explorers. And Highway 37 is paved and port facilities are available in Stewart.
“This kind of infrastructure is a huge boost for mining,” Greig notes, particularly for big, low grade deposits that need a lot of power to mine.
“With those roads in there and the addition of nearby power, it can really make the difference to developing a mineral deposit and gives incentive to people to explore,” says Greig.
Glaciers
Glaciers in the north of B.C., particularly on the coastal mountain range, are receding quickly. At the Red Mountain project, for example, ice has retreated significantly since Charlie worked there in the early 1990s.
“If you look back at the oldest geologic maps say around the Stewart area, from the 1910s and that era, you can really see how much ice has been lost,” Greig says. On one hand, this exposes fresh rock outcrop for companies to explore, but on the other it is a stark reminder of a changing climate.
Communities
In B.C., community, particularly local First Nations, acceptance has the power to make or break a project.
Explorers in B.C. apply for a mineral claim with the provincial government and a permit to carry out mechanized exploration activities. Traditional land holders are informed by the government of the activity to take place and the responsibility is on the explorers to build a relationship with the relevant First Nations.
“Companies understand – for the most part now – that you have to start relationships very early on,” says Greig, “Most (First Nations) have a resource person. There’s an education process that has to go on, they learn from experience, like we all do.”
The Golden Triangle is in the traditional territory of the Tahltan First Nation, and partly in the Nisga'a and Gitxsan territories. On the whole, these communities are savvy to the resource sector and willing to work with exploration and mining companies.
One approach that has worked for Greig is to try to employ First Nations people during exploration and to build individual relationships at every level, not just at the top. “It’s real people working together on the ground from day one,” he says.
Greig points to Pretium’s Brucejack gold mine as evidence that: “you can get into these tough areas and actually make something happen.”
Where Next?
The remote Toodoggone mineral district to the east of the Golden Triangle in northeast B.C. is Greig's pick. The district hosts different gold, silver and copper mineral deposit types and is close to Centerra Gold’s Kemess copper and gold project.
“That’s a great area for exploration and for potential deposit to be developed. There’s power up to that area and I think it has a bright future,” he says, of the area he started working in almost 40 years ago.
His advice to explorers is: “The way you find mineral deposits is boots on the ground.”