What are Intrusion-related Gold Systems?

What is an oxidized intrusion-related gold deposit?

Oxidized intrusion-related gold deposits are hosted in a stockwork of quartz veinlets occurring within oxidized porphyry stocks in magmatic arcs. Copper-rich skarns and high-sulfidation epithermal systems are also found near these porphyry intrusions.

“The oxidized intrusion-related gold systems are all directly associated with porphyry copper systems in one way or another, so their tectonic settings are the same,” according to Chris Ralph, mining engineer and associate editor at the ICMJ Prospecting and Mining Journal. The gold-copper ratios in intrusion-related gold deposits can vary widely.

These polymetallic deposit types are found in gold-rich zones in the Australian provinces of Victoria, Queensland and New South Wales, as well as Canada’s Abitibi Greenstone Belt, which crosses the provinces of Ontario and Quebec. As for mines and projects in these zones, Australian examples include the former Kidston and Red Dome gold mines in Queensland, and Abitibi examples include IAMGOLD’s (TSX:IMG,NYSE:IAG) Côté gold-copper deposit and Agnico Eagle's (NYSE:AEM,TSX:AEM) Macassa gold mine. Both demonstrate that these systems can host economically significant gold mineralization.

Oxidized intrusion-related gold exploration projects

• Antler Gold (TSXV:ANTL) is targeting intrusion-related gold systems in Namibia at its Paresis and Onkoshi South-East gold projects. Paresis is located within the gold corridor in the northern region of the country that hosts B2Gold’s (TSX:BTO,NYSEAMERICAN:BTG) Otjikoto gold deposit, as well as Osino Resources’ (TSXV:OSI,OTCQX:OSIIF) Ondundu and recently discovered Eureka gold deposits.

• Kenorland Minerals' (TSXV:KLD,OTCQX:KLDCF) project portfolio includes four early stage properties in Quebec’s Abitibi region that are highly prospective for intrusion-related gold systems. One is its flagship Frolet project, where the company began drilling in September 2023.

• Many Peaks Gold’s (ASX:MPG) Mount Steadman gold project in the New England orogenic province in Queensland hosts intrusion-related gold mineralization. In August 2023, the company completed soil sampling in preparation for drill work on the property.

• PJX Resources (TSXV:PJX,OTCQB:PJXRF)believes its Dewdney Trail property in the Sullivan mining district of Southeast British Columbia “has potential to host intrusion related copper-gold-silver and possibly molybdenum deposits."

• Red Pine Exploration's (TSXV:RPX,OTCQB:RDEXF) Ontario-based Wawa gold project hosts a large intrustion-related gold system, which the company has been exploring. In June 2023, Red Pine released a geological interpretation of the system, which it said has "well-developed pathways for fluid flow, a critical ingredient for mineral deposition." The mineralization associated with this intrusion-related gold system can be traced over 1 kilometer.

What is a reduced intrusion-related gold deposit?

The terms “reduced” and “intrusion” in this deposit type’s moniker relate to the existence of “reduced granitic intrusions ... characterized by large zones of parallel, sheeted, gold-bearing quartz veins and veinlets,” as per ICMJ's Ralph.

It’s the size of this sheeted zone that determines whether or not a bulk-tonnage, low-grade gold deposit will form. Such a deposit can be mined by open-pit methods. The sheeted vein systems typically host coarse gold, which when eroded by local streams can generate placer deposits. In addition, tin and tungsten deposits may be found in the same geological setting.

The Tintina Gold Belt that covers the northern portion of the North American Cordillera is a favorable geological address for reduced intrusion-related gold deposits. Ralph pointed to Barrick Gold (NYSE:GOLD,TSX:ABX) and NovaGold’s (TSXV:NG,NYSEAMERICAN:NG) Donlin asset, Kinross Gold's (TSX:K,NYSE:KGC) Fort Knox property in Alaska and the Dublin Gulch intrusion in the Yukon as prime examples. “The huge Donlin Creek deposit in Alaska was a small, moderately productive placer area until the huge hard rock deposits adjoining them were recognized,” he stated.

Within Dublin Gulch, Victoria Gold's (TSX:VGCX,OTC Pink:VITFF) Eagle mine is the Yukon’s newest gold mine. The company describes the property's geology as a “large-tonnage reduced intrusion-related gold systems associated with Cretaceous Tombstone and Mayo suite granodiorite intrusions and structurally-controlled high-grade gold-sulfide veins." Northern Star Resources’ (ASX:NST,OTC Pink:NESRF) Pogo deposit in Alaska, which commenced production in 2006, is another example and is proof that this deposit type can be high grade.

Reduced intrusion-related gold exploration projects

• Fireweed Metals (TSXV:FWZ,OTCQB:FWEDF) has recently identified numerous gold targets at its Macmillan Pass project that are highly prospective for reduced intrusion-related gold mineralization. The project is located in the Yukon’s Tombstone Gold Belt. In July 2023, the company launched a field program to further investigate this potential.

• Rackla Metals (TSXV:RAK) is also exploring for reduced intrusion-related gold systems in the Yukon’s Tombstone region. The company says gold anomalies at its flagship Astro project resemble other reduced intrusion-related gold deposits in Tombstone, including Victoria Gold’s Eagle gold mine.

• Sitka Gold’s (CSE:SIG,OTCQB:SITKF)RC gold project in the Yukon’s Tombstone Gold Belt has multiple intrusion-related gold deposit targets, including the Blackjack deposit, which has an inferred resource of 900,000 ounces of gold grading 0.83 grams per metric ton gold with a cut-off grade of 0.25 grams per metric ton gold.

• Snowline Gold (CSE:SGD,OTCQB:SNWGF) has a number of Yukon-based projects with reduced intrusion-related gold systems, including its Rogue gold project in the Mayo Mining District. The company has said its recently discovered bulk-tonnage-style Valley target shares geological similarities to Kinross' Fort Knox mine and Victoria Gold's Eagle mine.

• Trailbreaker Resources (TSXV:TBK,OTC Pink:APRAF) recently added the Sheldon property in the Yukon’s Tombstone Gold Belt to its portfolio; it hosts what the company calls "reduced intrusion-related gold system style mineralization." Trailbreaker is also exploring intrusion-related gold systems at its Eakin Creek and Gold Sable properties.