Fireweed targets Gayna River minerals

On the heels of its successful Macmillan Pass zinc-lead exploration play in eastern Yukon Territory, Fireweed Metals Corp. is making a bid to expand its project portfolio in what may be an astute move.

Studying the region's geology, the junior jumped territorial boundaries to stake nearly 129 square kilometers (50 square miles) of lapsed claims covering all historic showings and anomalies of the historical Gayna River zinc-lead-gallium-germanium project in Northwest Territories.

"The acquisition of the Gayna River project by staking is a low-cost way for Fireweed to expand our portfolio of Critical Metals projects and add some exciting exploration potential," said Fireweed Metals CEO Brandon Macdonald, in a statement reporting the action last spring. "While our focus remains on our flagship Macmillan Pass project, we are keen to explore Gayna River where we see the potential for high-grade massive sulfide mineralization.

"I see a similar story unfolding at Gayna River as MacPass, where Fireweed can build upon historic exploration and use modern scientific understanding of deposit genesis to unlock a potentially world-class district," Macdonald explained.

Situated 180 kilometers (112 miles) directly to the north of Macmillan Pass, the Gayna River project is in the Mackenzie Mountains on First Nations traditional territory 150 kilometers (93 miles) southwest of the winter road between Fort Good Hope and Norman Wells, NWT.

Explorers discovered abundant zinc-lead-silver mineralization at Gayna River in the 1970s, and Rio Tinto drilled more than 28,000 meters in the late 1970s, resulting in a large tonnage exploration target.

However, Rio Tinto concluded that there was low potential for a high-grade deposit at Gayna River and allowed the claims to lapse.

Gayna River geology

Fireweed said a new idea gleaned from recent academic studies indicates potential for very-high-grade massive sulfide targets at Gayna River not recognized by previous owners.

This shift in thinking behind the geological model for Gayna River indicates potential for high-grade massive sulfide zones within areas that Rio Tinto did not evaluate, the company said.

Mineralization at Gayna River occurs in veins and breccias in carbonate rocks like Mississippi-Valley-Type mineralization, or Irish-type zinc-lead mineralization. Sphalerite and minor galena occur as infill within veins, vugs, and breccias, along with dolomite-calcite-quartz-pyrite. Historic grab samples also contain elevated concentrations of the critical metals gallium (up to 68 parts per million) and germanium (up to 15.6 ppm).

The geological environment of Gayna River is remarkably like host rocks at the high-grade Kipushi zinc-copper-lead-silver-germanium mine in the Democratic Republic of Congo in southern Africa. At the Kipushi Mine, operators produced about 60 million metric tons grading 11% zinc and 7% copper between 1924 and 1993 before placing the mine under care and maintenance. Miners also produced more than 12,600t of lead and approximately 278t of germanium between 1956 and 1978.

Previous explorers of Gayna River, including Rio Tinto, developed non-compliant mineral resource estimates for the property. Fireweed, however, considers these historical estimates to be relevant only because they demonstrate the large-size potential of the hydrothermal system present on the property and conformed to accepted practices at the time. The historical estimates are not reliable determinations of potential tonnage because they do not conform to modern Canadian standards and methodology.

At both Kipushi and Gayna River, zinc mineralization is located around large Neoproterozoic carbonate reefs – geology believed to be unique to only these two locations worldwide. At Kipushi, high-grade lenses of massive sulfides are located around the margins and tops of the carbonate reefs, including the "Big Zinc" zone.

Using Kipushi as an exploration analog, Fireweed sees the potential for massive sulfide mineralization at Gayna River in similar reef-margin and reef-top positions that remain largely untested by historical drilling, which occurred on a wide-spaced grid drilling approach. The extensive mineralization discovered to date on the Gayna River project is believed to represent a large zinc system that may have higher-grade centers of massive sulfide.

Fireweed cautions that the geological comparison to the Kipushi mine is conceptual in nature, and the company is uncertain if further exploration at Gayna River will result in the definition of mineral resources or mineral reserves.

"We are excited to put the exploration methods we have honed so successfully at Macmillan Pass to use in a whole new search space at Gayna River," Fireweed Chief Geologist Jack Milton said in May. "Leveraging our experience with gravity surveys, muon-tomography, and innovative inversions, we can enable exploration for what has been previously difficult to find – the high-grade centers of large zinc systems.

"With this new technology we expect to target high-grade massive sulfides with better precision and at relatively low-cost, enabling a new wave of zinc exploration and revitalizing activity at this well-renowned zinc district," he added.

First season results

Fireweed's initial exploration program this summer at Gayna River included a ground gravity survey, rock and soil sampling and mapping, and a lidar survey.

The junior completed a 52.7 line-kilometer ground gravity survey over two areas identified as geologically favorable based on their proximity to carbonate reef rocks and possible buried reef margins. Ground gravity has been a successful tool in Fireweed's exploration of the Boundary Zone area at Macmillan Pass. There, gravity anomalies have provided targets for new discoveries and step-out drill holes that have intersected multiple styles and thicknesses of sulfide mineralization within 100-200 meters of surface. Gravity anomalies identified at Gayna River may similarly be associated with potential sulfide bodies close to surface.

Fireweed used relatively tight station spacing of 50 meters since the project is being explored for a potential Kipushi-style target, which is high-grade mineralization on the steeply dipping sides of Neoproterozoic carbonate reefs. Fireweed said previous exploration programs that used wider-spaced vertical drill holes may have missed such steeply dipping massive sulfide lenses.

In all three survey areas, gravity highs align with areas the company has identified as having high potential for buried reef margins. Due to rheological and permeability contrasts, these margins may have served as conduits for mineralizing fluids and therefore have greater potential for hosting sulfide mineralization.

The lidar survey was flown over the entire Gayna River property (455 line-kilometers) to generate a very high-resolution topographic surface that will provide a base map for future exploration. The primary function of the survey this season was to enable high-resolution terrain corrections for the ground gravity survey. The LiDAR survey also acquired high-resolution orthophotos that will assist in planning future work.

The small program of rock sampling at Gayna River served to ground truth the geology and record mineral occurrences and showings on the property, Fireweed said. Samples confirmed the presence of high-grade zinc and lead sulfide mineralization at surface, as well as elevated concentrations of the critical minerals gallium and germanium.

Eight grab samples, including dolostones, dolostone breccias, limestones, and veins. All had grades of greater than 7% zinc, including one sample with 73.7 % lead, 9.2% zinc and 40.5 ppm silver. The highest zinc grade was 51.2% in a sample that also contained 42 ppm gallium and 39 ppm germanium.

Fireweed conducted a small soil sampling program across the Jaws anomaly on the property to verify its location and magnitude. Jaws is a strong lead- and zinc-in-soil anomaly that spans an area of more than 4,000 by 1,000 meters

All 10 soil samples exceeded 4,000 ppm lead, including seven samples over 1% lead, one sample of 27.5% lead and 176 ppm silver, and another with 0.75% zinc, confirming the presence of a strong soil anomaly and validating the high lead- and zinc-in-soil values in the rest of the historical soil geochemical dataset, Fireweed said.

Historical soil anomalies on the property are spatially coincident with some potential reef margin target areas identified geologically, as well as with new ground gravity anomalies. Combined, these geochemical, geological, and geophysical anomalies form tantalizing targets for future drill programs, the company added.

Fireweed won a mining incentive grant from the Northwest Territories government to assist with exploration at Gayna River. The grant of C$132,000 significantly reduced the cost of its 2022 exploration program, the company said.